JPH1195554A - Two-component developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To move a developer to the upstream side of a developer regulating part, and in a direction perpendicular to the advancing direction of the sleeve of a developing roller as well, for reducing stress exerted on the developer, to prolong the life of the developer and further, to improve its reliability by providing a magnet roll spirally magnetized. SOLUTION: The developer supplied onto the developing roller 2 by a bucket roller 3 is carried to a napping height regulating plate 4, in accordance with the rotation of the sleeve 21. In the napping height regulating plate 4, the developer of a quantity corresponding to the space between the developing roller 2 and the napping height regulating plate 4 passes through the space, to be carried to the developing region of an adjacent photoreceptor drum 1. On the other hand, the developer failed in passing through the space remains on the upstream side of the regulating part of the napping height regulating plate 4. But, the regulating plate 4 faces the spiral magnetized part 24 of the magnet roll 23, so that the residual developer is carried in the axial direction of the roller 2 on the upstream side of the regulating part of the developer regulating plate 4, with an attracting magnetic field exerted between spiral magnetic poles and carrying force by the rotation of the sleeve 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component developing apparatus which is used in an image forming apparatus such as a copying machine, a printer, and a facsimile and performs development using a two-component developer containing a toner and a magnetic carrier.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, a two-component developing device that performs development using a two-component developer containing a toner and a magnetic carrier has been used. ing.

[0003] In a general two-component developing device, a developer tank for storing a two-component developer, a developer carried on the surface, and the developer rubbed against the image carrier are rubbed against the electrostatic charge on the image carrier. A developing roller that develops the latent image, a bucket roller that is installed in the developer tank, agitates the developer, pumps up the developer, and supplies the developer to the developing roller; and drops toner from above the bucket roller into the developer tank. And a toner supply roller for supplying toner to the developer tank.

In the two-component developing apparatus having the above structure, the developer pumped up by the bucket roller is supplied onto the sleeve of the developing roller, and is then conveyed to the fixed magnetic pole of the developing roller with the rotation of the sleeve. . Then, the developer passes through the developer regulating plate by the attracting magnetic field acting between the fixed magnetic poles and the conveying force due to the rotation of the sleeve. The amount of developer supplied to the photosensitive drum is regulated by a developer regulating plate provided at a fixed interval with respect to the developing roller. The fixed magnet of the developing roller has several magnetic poles arranged in the rotation direction, and has the same magnetic pole in the axial direction of the sleeve.

Thereafter, the developer that has passed through the developer regulating member forms a magnetic brush by the magnetic action of the magnetic poles of the developing roller itself, and is applied to the developing roller when the magnetic brush rubs the surface of the photoreceptor. Due to the difference between the applied bias potential and the surface potential of the photoconductor, the toner is electrically attracted to and adhered to the portion of the photoconductor surface where the electrostatic latent image is formed, thereby performing development.

[0006]

However, in the conventional two-component developing device, the accumulation of the developer is large at a portion upstream of the developer regulating portion which is a portion for regulating the developer, and the following problem occurs.

1) When the developer passes through the developer regulating section, a strong stress is applied, and the rotational torque of the sleeve is increased, so that a large load is applied to the drive gear and the like.

[0008] 2) A strong stress is applied to the developer, and a phenomenon in which a substance having a small molecular weight, such as a dye or a polarity controlling agent kneaded in the toner, migrates from the toner surface to the carrier surface as a contact partner is likely to occur. Become. When such carrier deterioration occurs, the ability of the carrier to contact and charge the newly replenished toner decreases. For this reason, the charge amount of the toner used for development decreases as the deterioration of the carrier progresses, and the toner is less likely to be magnetically and electrically restrained and floats. Or the toner floats inside the copier or the like and contaminates the inside of the copier.

3) In the developer regulating portion, the developer moves only in the rotation direction of the sleeve of the developing roller, so that when foreign matter or a mass of the developer reaches the developer sleeve, they stay in the developer regulating portion. However, there is a problem that the developer is not conveyed to the portion and white streaks appear on the image.

An object of the present invention is to provide a two-component developing apparatus in which the above-mentioned problems have been solved.

[0011]

In order to achieve the above object, a two-component developing apparatus according to the present invention comprises a developer tank for storing a two-component developer containing a toner and a magnetic carrier, and a developer tank on a surface of the developer tank. And a spirally magnetized magnet roll for developing the electrostatic latent image on the image carrier by rubbing it against the image carrier.

Further, the two-component developing device of the present invention has a developer tank for storing a two-component developer containing a toner and a magnetic carrier, and carries the developer on the surface, and rubs the developer against the image carrier. A developer carrier for developing the electrostatic latent image on the image carrier;
A developer carrying the developer in the developer tank; and a helically magnetized magnet roll supplying the developer pumped by the carrier to the developer carrier. .

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below.

<Embodiment 1> FIG. 1 is a longitudinal sectional view of a two-component developing apparatus 100 according to an embodiment of the present invention. As shown in FIG. 1, a developing device 100 includes a casing 12, a developer tank 11 for storing a two-component developer containing a toner and a magnetic carrier, a toner hopper 40 for storing an uncharged toner, and a toner hopper 40. A supply roller 7 for supplying the toner to the developer tank 11, and a developing roller for developing the electrostatic latent image on the image carrier 1 by carrying the developer on the surface and rubbing the developer against the image carrier 1 2, a bucket roller 3 for stirring the developer in the developer tank 11 and pumping a part of the developer to supply the developer to the developing roller 2; and a developer transport roller 6 for transporting the developer away from the developing roller 2. It has. FIG. 1 illustrates a photosensitive drum 1 that rotates in the direction of arrow a in the figure as an image carrier.

The toner hopper 40 is provided above the developer tank 11. When the replenishment roller 7 rotates in the direction of arrow e in FIG. 11 is supplied with toner.

The bucket roller 3 is provided in the developer tank 11 and rotates in a direction indicated by an arrow d in FIG. The bucket roller 3 is provided with a plurality of supply blades 31 having an L-shaped cross section and extending in the longitudinal direction. Each supply blade 3
Both ends of the first unit 1 are fixed to a pair of flanges 33 connected to a shaft 34, and the openings thereof are directed outward. A space is provided between the supply blades 31, and the developer can enter the bucket roller 3 through this space. A plurality of transport blades 321 and 322 for stirring the developer are provided inside the bucket roller 3. The transport blade 322 is a plate-like member provided obliquely to the longitudinal direction of the bucket roller 3,
It is fixed between the plurality of supply blades 31.

When the bucket roller 3 rotates, the supply blade 31 and the stirring blades 321 and 322 come into contact with the developer in the developer tank 11 to stir the developer, whereby the toner in the developer is charged. At the same time, the developer in the developer tank 11 is pumped up by the supply blade 31. At the same time as the developer is pumped up by the supply blade 31, the developer tank 1
The developer in 1 is pushed by the stirring blade 322 and is conveyed from the back side in the longitudinal direction to the front side.

The developing roller 2 is provided so as to face a side portion of the bucket roller 3, and a side surface opposite to the portion facing the bucket roller 3 is close to the photosensitive drum 1. The developing roller 2 includes a sleeve 21 and a cylindrical magnet roll 22 provided in the sleeve 21. A shaft 23 is provided on the sleeve 21,
An arrow b shown in FIG.
Rotate in the direction. As shown in FIG. 1, the magnetized state of the magnet roll 23 is such that an N pole and an S pole are alternately magnetized in a clockwise order from a portion facing the bucket roller 3 to a bottom portion,
Magnetization is performed so that the same poles are arranged between the bottom and the facing portion of the bucket roller 3.

A spike height regulating plate 4 for regulating the thickness of the developer on the developing roller 2 is provided near the developing roller 2. A part of the magnet roll facing the ear height regulating plate 4 has a spiral magnetized portion 24 which is spirally magnetized as described later.

The developing roller 2 carries the developer on the surface of the sleeve 21 by the magnetic force of the magnet roll 22 to form a spike (magnetic brush) of the developer. And sleeve 2
When 1 rotates, the magnetic pole of the magnet roll 22 causes
As the developer drops, the developer is transported in the direction of arrow b, that is, in the same direction as the rotation direction of the sleeve 21.

The developer conveyed by the supply blade 31 to the portion facing the developing roller 2 by the rotation of the bucket roller 3 is attracted by the magnet 22 in the developing roller 2 and moves to the upper portion of the developing roller 2. Then, by the rotation of the developing sleeve 21, first, the amount of passage is regulated by the spike height regulating plate 4, and is conveyed to a portion (developing area) facing the adjacent photosensitive drum 1. Then, the electrostatic latent image on the photosensitive drum 1 is rubbed and rubbed by the spikes of the developer on the developing roller 2 to become a toner image. The developer on the developing roller 2 is
After passing through the developing area, the toner is conveyed to a magnetized portion having the same polarity provided between the bottom of the developing roller 2 and the portion facing the bucket roller 3. In this magnetized portion of the same polarity, the developing roller 2
Is removed, whereby the developer is separated from the developing roller 2 and collected into the developer tank 11.
As described above, the developer is circulating in the developing device 100.

As shown in FIG. 1, the uncharged toner dropped and supplied from the supply roller 7 falls toward the bucket roller 3 below the supply roller 7. Therefore, when the supply blade 31 passes below the replenishing roller 7 due to the rotation of the bucket roller 3, the developer containing the uncharged toner is stacked on the developer contained in the supply blade 31. It will be a heap. Then, the supply blade 31 moves toward the developer supply position to the developing roller 2,
On the way, the heaped portion including the uncharged toner is scraped into the bucket roller 3 at a position facing the regulating plate 6. The uncharged toner scraped off is mixed with the developer in the bucket roller 3 and stirred and charged. Thereby, the uncharged toner supplied into the developing device is not directly supplied to the developing roller 2 but is supplied to the developing area after being sufficiently charged.

Next, the configuration of the magnet roller 23 will be described in detail. FIG. 2 is a schematic diagram showing a magnetized pattern of the spiral magnetized portion 24 of the magnet roller 23 constituting the developing roller 2. As shown in FIG. 2, the N pole and the S pole are magnetized alternately in a spiral manner in the longitudinal direction of the roller.

The developer supplied from the bucket roller 3 onto the developing roller 2 is conveyed to the ear height regulating plate 4 as the sleeve 21 rotates. An amount of the developer corresponding to the interval between the developing roller 2 and the ear height regulating plate 4 in the ear height regulating plate 4 passes through the interval and is conveyed to the developing area of the adjacent photosensitive drum 1. On the other hand, the developer that cannot pass through the space remains on the upstream side of the regulating portion of the spike height regulating plate 4. However, since the magnet roller 23 is opposed to the helical magnetized portion 24, the remaining developer is conveyed by the attracting magnetic field acting between the helical magnetic poles and the conveying force due to the rotation of the sleeve. Is conveyed in the axial direction of the developing roller 2.

That is, the developer is conveyed by the rotation of the sleeve 21 in the developer regulating section and the spiral magnetized section 24
Accordingly, the sheet is conveyed in both the rotation direction of the sleeve 21 and the direction orthogonal to the rotation direction.

As described above, since the developer remaining on the upstream side of the regulating portion of the developer regulating plate 4 always moves in the axial direction of the developing roller 2, the accumulation of the developer does not become unnecessarily large. The agent does not stress. Further, even if foreign matters and a lump of the developer reach the developer regulating plate 4, they do not stay on the upstream side of the regulating portion of the developer regulating plate 4 and move out of the image range together with the developer. I do.

Although the embodiment in which the fixed magnet spirally magnetized is employed as a part of the magnet roller has been described, the present invention is not limited to this, and the entire magnet roller is magnetized spirally as shown in FIG. A magnet roller may be used. With such a configuration, a magnet roller can be manufactured without attaching a helical magnet to only a part thereof, and there is an advantage that the cost is reduced.

<Embodiment 2> In the two-component developing apparatus 200 of this embodiment, the bucket roller 3, the supply roller 7, the developer tank 11, the toner hopper 40, and the casing 12
Are the same as those in the first embodiment, the same reference numerals as those in the first embodiment are used, and the detailed description is omitted.

In the present embodiment, two developing rollers similar to those described in the first embodiment are used as the developing rollers, and a supply roller 5 for supplying a developer to the developing rollers is provided. The developer pumped by the bucket roller 3 is supplied to the supply roller 5, the developer is supplied from the supply roller 5 to the first development roller 8, and the second
The developer is supplied to the developing roller 9.

The supply roller 5 is provided to face the side of the bucket roller 3, and the side surface opposite to the portion facing the bucket roller 3 is close to the first developing roller 8. The side of the first developing roller 8 opposite to the side facing the supply roller 5 is close to the photosensitive drum 1. Further, a second developing roller 9 is provided below the first developing roller 8, with its side face being close to the photosensitive drum 1.

The supply roller 5 includes a sleeve 51 and a columnar magnet roll 52 provided in the sleeve 51. The sleeve 51 is provided with a shaft, and rotates around the shaft in the direction of arrow b shown in FIG.

The first developing roller 8 includes a sleeve 81,
It is constituted by a cylindrical magnet roll 82 provided in a sleeve 81. Also, the second developing roller 9
Is composed of a sleeve roller 91 and a cylindrical magnet roll 92 provided in the sleeve 91.
Each of the sleeves 81 and 91 is provided with a shaft, and rotates around the shaft in the direction of arrow b shown in FIG.

As shown in FIG.
The magnetized states of 3, 83, and 93 are such that the N pole and the S pole are alternately magnetized in a clockwise order from the portion facing the bucket roller 3 to the bottom portion, and between the bottom portion and the portion facing the bucket roller 3. Are magnetized so that the same poles are lined up.

In the vicinity of the supply roller 5, a spike height regulating plate 4 for regulating the thickness of the developer on the supply roller 5 is provided. A part of the magnet roll facing the ear height regulating plate 4 has a spiral magnetized portion 54 similar to the spiral magnetized portion 24 described above.

The developing rollers 8 and 9 include a magnet roll 8
The developer is carried on the surfaces of the sleeves 81 and 91 by the magnetic forces 2 and 92 to form a magnetic brush. When the sleeves 81 and 91 rotate, the magnet rolls 82 and 92 rotate.
The ears of the developer fall down by the magnetic poles, and the developer is conveyed in the direction of arrow b, that is, the same direction as the rotation direction of the sleeves 81 and 91.

Incidentally, the developer supplied by the bucket roller 3 onto the supply roller 5 is conveyed to the ear height regulating plate 4 as the sleeve 51 rotates. An amount of developer corresponding to the interval between the supply roller 5 and the ear height regulating plate in the ear height regulating plate 4 passes through the interval and is conveyed to the adjacent developing roller 5. On the other hand, the developer that cannot pass through the space remains on the upstream side of the regulating portion of the spike height regulating plate 4. But,
Since it faces the spiral magnetized portion 54 of the magnet roll 53, the remaining developer is supplied upstream of the regulating portion of the developer regulating plate 4 by the attracting magnetic field acting between the spiral magnetic poles and the conveying force due to the rotation of the sleeve. It is transported in the axial direction of the roller 5.

As described above, since the developer remaining on the upstream side of the regulating portion of the developer regulating plate 4 always moves in the axial direction of the supply roller 5, the accumulation of the developer does not become unnecessarily large. The agent does not stress. Further, even if foreign matters and a lump of the developer reach the developer regulating plate 4, they do not stay on the upstream side of the regulating portion of the developer regulating plate 4 and move out of the image range together with the developer. I do.

In the present embodiment, the developing area can be widened, and the stress applied to the developer can be further reduced. Therefore, the present embodiment is most suitable for a developing device requiring high-speed development.

[0039]

As described above, in the present invention, the provision of the spirally magnetized magnet roll allows the developer upstream of the developer regulating section to move the developer perpendicular to the direction of travel of the sleeve of the developing roller. The developer can be moved in any direction to reduce the stress applied to the developer, thereby extending the life of the developer and improving the reliability.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a two-component developing device.

FIG. 2 is a diagram illustrating a magnetization pattern of a magnet roller.

FIG. 3 is a diagram illustrating a magnetization pattern of another magnet roller.

FIG. 4 is a longitudinal sectional view of another two-component developing device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum 2 developing roller 3 bucket roller 4 spike height regulating plate 5 supply roller 6 regulating plate 7 replenishing roller 8 first developing roller 9 second developing roller 11 developer tank 21 sleeve 22 magnet roller 24 helical magnetized part 31 supply blade 51 sleeve 52 magnet roller 54 spiral magnetized part

Claims (7)

[Claims] A developer tank for storing a two-component developer containing a toner and a magnetic carrier; and a developer carrying the developer on a surface thereof, and rubbing the developer against the image carrier to form an electrostatic latent image on the image carrier. A two-component developing apparatus, comprising: a sleeve for developing an image; and a spirally magnetized magnet roll included in the sleeve. 2. The two-component developing device according to claim 1, wherein said magnet roll is formed by helically magnetizing N poles and S poles alternately. 3. The two-component developing apparatus according to claim 1, wherein a partition plate is provided near the sleeve, and only a part of the magnet roll facing the partition plate is helically magnetized. 4. A developer tank for storing a two-component developer containing a toner and a magnetic carrier, a developer carried on the surface, and rubbing the developer against the image carrier to form an electrostatic latent on the image carrier. A developer carrier for developing an image, a transport member for pumping the developer in the developer tank, and a magnet magnetized in a spiral shape for supplying the developer pumped by the transport member to the developer carrier. A two-component developing device comprising: a roll. 5. The two-component developing device according to claim 4, wherein said magnet roll is formed by helically magnetizing N poles and S poles alternately. 6. The image forming apparatus according to claim 1, further comprising a sleeve enclosing the magnet roll, wherein the sleeve rotates to convey the developer carried on the surface of the sleeve in a rotation direction of the sleeve and a direction perpendicular to the rotation direction. Item 6. The two-component developing device according to Item 5. 7. The two-component developing device according to claim 6, wherein a partition plate is provided near the sleeve, and only a part facing the partition plate is helically magnetized.