JPH04343376A - Developing device - Google Patents

Abstract

PURPOSE:To form a clear toner image on an image carrier by providing a non-magnetic pole part on one part of a magnet body and also providing a non-magnetic peeling member above a stirring member. CONSTITUTION:The magnet body (magnet roller) 236 provided with plural magnetic poles is constituted of a main magnetic pole M1 facing the image carrier 21 and plural sub magnetic poles M2, and in the middle of a repulsive magnetic field of the magnetic poles having the same polarity, a non-magnetic pole part Q where the magnetic pole is omitted is arranged. The density of a magnetic flux almost becomes zero on the position of the non-magnetic pole part Q, and also, the part Q corresponds to a position where developer D which is attracted on the surface of a developer carrier, then passes through a developing area E and has finished the developing, drops by gravity. And furthermore, a non-magnetic peeling member (scraper) 235, for example, formed of an elastic thin plate is stuck on a partition panel 234 fixed between a developer stirring member 232 and a developer supplying member 233 in a developing device 23, and the leading end part of the scraper is lightly press-contact with the cylindrical surface of a developing sleeve 231. Thus, a developer layer can be uniformly formed on the developer carrier 21.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to a developing device used in an image forming apparatus such as an electrostatic recording type electrophotographic copying machine, printer, or facsimile machine. The present invention relates to a developing device that develops an electrostatic latent image formed on an image.

0002

2. Description of the Related Art A developing device of an image forming apparatus using a two-component developer includes a fixedly arranged magnet body having a plurality of magnetic poles, and a developing device having the magnet body inside and supporting the developer on the surface. A developer carrying member that rotates and is driven, a developer amount regulating member that regulates the amount of developer supported on the developer carrying member, a developer supplying member that supplies developer to the developer carrying member; 2. Description of the Related Art A developing device that includes a developer stirring member that supplies and stirs developer to a supply member has conventionally been used.

In order to obtain a good image using the above-mentioned developing device, it is necessary to develop the developed developer after it has been developed in a development area where the image carrier and the developer carrier (also referred to as a developer sleeve) are close to each other. Once removed from the surface of the agent carrier,
It is necessary to supply new developer to the surface of the developer carrier again.

0004

[Problems to be Solved by the Invention] Conventionally, a non-magnetic peeling member was brought into pressure contact with the surface of a developer carrier. In order to peel off the developer material, the peeling member must be strongly pressed against the surface of the developer carrier. However, this pressure is strong and may damage the surface of the developer carrier.
A high-torque developing device drive device that can withstand pressure loads is required.

Furthermore, the conventional structure in which a peeling member is provided in the developer reservoir in the developer tank of the developing device has the disadvantage that the developer accumulates on the peeling member, making peeling unreliable.

[0006]

[Means for Solving the Problems] The present invention provides a developing device that uses a two-component developer which has the above-mentioned problems, and is capable of reliably removing developed developer from a developer carrier under a light load. It is an object of the present invention to provide a developing device that can perform stable developer exchange and obtain good images.

The developing device of the present invention that achieves the above object includes a fixedly arranged magnet body having a plurality of magnetic poles, and a developer having the magnet body inside and carrying a developer on its surface and driven to rotate. a carrier, a developer amount regulating member that regulates the amount of developer carried on the developer carrier, a developer supply member that supplies developer to the developer carrier, and a developer supplying member that supplies developer to the developer carrier; In the developing device, the magnetic flux density is reduced to almost zero in a part of the magnet body corresponding to a position where the developed developer on the surface of the developer carrier falls under its own weight. The developer stirring member is provided with a non-magnetic pole portion and a non-magnetic peeling member having elasticity that lightly presses the surface of the developer carrier corresponding to the non-magnetic pole portion to peel off and drop the developed developer. It is characterized by being placed upward.

Further, the developing device of the present invention is characterized in that the non-magnetic peeling member is integrally provided on an upper part of a partition member that partitions the developer supplying member and the developer stirring member.

Further, the developing device is characterized in that it is the elastic non-magnetic peeling member, a stainless steel thin plate, a resin film, a rubber plate typified by a urethane blade, or a composite plate thereof. .

0010

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a main sectional view of a color printer to which the developing method of the present invention is applied, viewed from the left side. The apparatus main body 10 is surrounded by an operation panel 11, an openable and closable upper cover 12, a toner supply cover 13, a front cover 14, etc. on the front side, and inside the opening of the apparatus main body 10 is a removable process cartridge 20. A paper feed cassette 30 is provided.

The process cartridge 20 includes an image carrier,
It consists of a developing means, a charging means, a cleaning device, etc.

The photosensitive belt 21, which is an image carrier, has a photosensitive layer such as an organic photoconductive layer (OPC) coated on the surface of a flexible belt, and includes a driving roller 22A and a driven roller 22B.
and rotated clockwise.

Around the photoreceptor belt 21, charging means,
An exposure means, a development means, a transfer means, and a cleaning device are provided.

The charging means is an existing charger 24 such as a corona charger or a scorotron charger.

The developing means uses different color developers, such as yellow, magenta, cyan, and black color toners (
A plurality of developing units 23a and 2 each containing a developer (developing agent).
3b, 23c, and 23d. Each of these developing devices 23a~
23d has a function of developing an electrostatic latent image on the photoreceptor belt 21 into a toner image using a non-contact development method.

The cleaning blade 251 of the cleaning device 25 is kept at a position apart from the surface of the photoreceptor belt 21 during the image forming process, and is pressed against the surface of the photoreceptor belt 21 only during cleaning after transferring the toner image to the transfer material P. The photoreceptor belt 21 is then cleaned.

The toner collection box 26 collects and stores the residual toner on the photoreceptor belt 21 that has been removed by the cleaning device 25.

In this embodiment, the photoreceptor belt 21, charger 24,
Each process section of the developing devices 23a to 23d containing toners of each color, the cleaning device 25, and the toner collection box 26 are housed in the integrated process cartridge 20 to form a unit, and can be attached to and detached from the apparatus main body 10 all at once. Can be done.

On the other hand, on the main body side of the image forming apparatus, when the process cartridge 20 is installed and the image formation is possible, an exposing means, a transferring means, etc. are arranged around the photosensitive belt 21.

The exposure means is a semiconductor laser writing optical system unit (hereinafter referred to as optical system unit) 40, which exposes the surface of the photoreceptor belt 21 charged by the charger 24 to form a charged latent image.

The transfer means 50 transfers the toner image formed on the photosensitive belt 21 onto the transfer material P using the transfer drum 51 and the transfer device 54.

The process of forming a color image using the color image forming apparatus having the above-mentioned configuration is carried out as follows.

First, the process cartridge 20 is loaded in a predetermined position within the image forming apparatus main body 10, and is ready for image formation. When a first color image signal output from an image reading device separate from the main body 10 of the apparatus is input to the optical system unit 40, a laser beam is generated by a semiconductor laser in the optical system unit 40. . The laser beam is rotated and scanned by a polygon mirror 42 rotated by a drive motor 41,
The light is projected through the cylindrical lens 43, the fθ lens 44, and the mirrors 45 and 46 onto the circumferential surface of the photoreceptor belt 21, which has been uniformly charged to a predetermined charge by the charger 24, to form a bright line.

On the other hand, regarding the sub-scanning method, a belt index (not shown) corresponding to a specific position of the photoreceptor belt 21 is detected, or a print command signal is received, and this detection or command signal is used as a reference. Then, the main scanning line on which modulation of the semiconductor laser by the image signal starts is determined. When scanning is started, in the main scanning direction, a laser beam is detected by an index sensor (not shown), and based on this detected signal, a semiconductor laser beam based on an image signal of the first color is directed to the photoreceptor belt. Scan over the surface of 21.

Therefore, a latent image corresponding to the first color is formed on the uniformly charged surface of the photoreceptor belt 21 by the main scanning by the laser beam and the sub-scanning by the conveyance of the photoreceptor belt 21. This latent image is developed by a developing device 23a containing yellow toner corresponding to the first color among the developing means, and a yellow toner image is formed on the surface of the photoreceptor belt 21.

Thereafter, the photoreceptor belt 21 is rotated while holding the yellow toner image on its surface.
After passing under the cleaning blade 251 which is spaced apart from the surface of the image forming apparatus, the second color image formation begins.

That is, the photoreceptor belt 21 on which the yellow toner image has been formed is uniformly charged again by the charger 24, and then the image signal of the second color is transferred to the optical system unit 4.
0, and as in the case of the first color image signal described above, writing is performed on the surface of the photoreceptor belt 21 to form a latent image. The latent image is developed by a developer 23b containing magenta toner as the second color. A magenta toner image is formed in the presence of a previously formed yellow toner image.

Similarly, after forming a latent image using the third color image signal, a cyan toner image is formed in the developing device 23c containing cyan toner, and furthermore, after forming a latent image using the fourth color image signal, a black toner image is formed. A color toner image is formed on the surface of the photoreceptor belt 21 by superimposing a black toner image on the surface of the photoreceptor belt 21 using a developing device 23d containing toner.

A direct current or even an alternating current bias is applied to the developing sleeves 231a to 231d (see FIG. 2) of each of the developing units 23a to 23d, and reverse development is performed without contact with the photoreceptor belt 21 whose base is grounded. is now being carried out. Incidentally, for this non-contact development, either a two-component developer or a one-component developer can be used. When using a one-component developer, there is no need to provide a toner hopper separate from the developing section, allowing for downsizing, but a development method using a two-component developer is superior in terms of development stability. Therefore, it is preferable in terms of color reproduction.

The color toner image formed on the surface of the photoreceptor belt 21 as described above is transferred to a transfer material P which is supplied from a paper feed cassette 30 by a paper feed roller 31 and is timed with the color toner image by a timing roller 32. transcribed into. The transfer device 50 performs transfer by applying a high-voltage power output having a polarity opposite to that of the toner.

The transfer material P to which the color toner image has been transferred in this way moves sharply (small diameter curvature) along the drive roller 22A.
They are reliably separated by the photoreceptor belt 21 which changes direction, and are conveyed upward by a conveyor belt 60 having a built-in suction means 61.

After the toner is melted and fixed on the transfer material P by heat and pressure contact between the fixing roller 71 and the pressure roller 72 of the fixing device 70, the transfer material P is transferred onto the upper surface of the upper cover 12, which also serves as a paper ejection tray, by the paper ejection roller 73. It is discharged.

FIG. 2 is a side sectional view of the process cartridge 20, and FIG. 3 is an enlarged sectional view of a main part of one developing device representative of the plurality of developing devices in the process cartridge.

The process cartridge 20 includes a developing device 23
a, 23b, 23c, 23d, a charger 24, a cleaning device 25, etc., and a drive roller 22 that rotates the photoreceptor belt (image carrier) 21 above it.
A, driven roller 22B, and spacing member 28a
, 28b, 28c, 28d, and an upper unit consisting of a back plate 28e, etc., and has a structure that can be separated and combined.

Near the bottom of the housing 27 of the lower unit are a plurality of developing units 23a, 23b, 23c, 2.
The 3d casing is a developer tank formed into a concave shape. Inside each of these developing tanks, there is a developing sleeve (developer carrier) 2.
3la, 23lb, 23lc, 23ld, and toner transport stirring screws (developer stirring members) 232a, 232b.
, 232c, 232d, and the developer stirring supply screw (
developer supply member) 233a, 233b, 233c, 23
3d is mounted on both side surfaces of the housing 27 so as to be rotatable.

[0037] The developing devices 23a, 23b, 23c, 23
d all have similar structures, and Figure 3 is representative of these.
As shown in the cross-sectional view. Hereinafter, one developing device 23 representative of the plurality of developing devices 23a to 23d will be explained using FIG. 3.

A magnet body (magnet roller) 236 having a plurality of magnetic poles is fixed to both side surfaces of the housing 27 inside the concentrically rotatable developer carrier 23l. The magnet body 236 is composed of a main magnetic pole M1 facing the image carrier 21 and a plurality of sub-magnetic poles M2 (for example, six in the figure). is provided with a non-magnetic pole portion Q in which a magnetic pole is missing. The non-magnetic pole portion Q is a position where the magnetic flux density is almost zero.

The non-magnetic pole portion Q corresponds to a position where the developed developer D, which has been attracted to the surface of the developer carrier and passed through the development area E, can fall under its own weight.

A partition plate 234 (23
4a, 234b, 234c, 234d) are fixed. The partition plate 234 is made of a non-magnetic resin material or a metal plate such as an aluminum alloy plate.

A peeling member (scraper) 235 is attached to each of these partition plates 234, and the tip thereof is in light pressure contact with the cylindrical surface of the developing sleeve 231. The peeling member 235 is made of a non-magnetic elastic thin plate, such as a non-magnetic stainless steel thin plate or polyethylene terephthalate (
PET) film, a rubber plate typified by a urethane blade, or a composite plate made of a non-magnetic metal thin plate with a polyfluoroethyl layer, the tip of which is in close contact with the surface of the developing sleeve 231 in a counter-like manner, Moreover, it does not damage the surface of the developing sleeve.

Near the developing sleeve 231, there are magnetic thin-layer rods 29 (29a, 29b, 29c, 29d).
are mounted on the shaft with a predetermined minute gap maintained. In addition, 23
7 (237a, 237b, 237c, 237d) are shielding plates for preventing toner scattering.

In the vicinity of the developing sleeve 231, magnetic and rigid thin layer forming rods 29 (29a, 29b, 29
c, 29d) is supported by the holder 291 and pressed by the elastic member 292, and comes into pressure contact with the developing sleeve 231, thereby forming developer layer regulating means.

The developing sleeve 231 and the photosensitive belt 2
1 is maintained at all times by a roller (not shown) coaxially provided at the shaft end of the developing sleeve 231 abutting the spacing plate 28 that slides on the photoreceptor belt 21 .
It is maintained at a constant gap of around 5 mm.

Here, E is a developing area 23 formed between the photoreceptor belt 21 and the developing sleeve 231.
8 is an AC bias power supply in which DC voltage and AC voltage are superimposed.

The toner replenished from the toner storage device (toner hopper) is sent to the toner conveyance stirring screw 232, and further stored in the developer tank in advance by the developer stirring supply screw 233 which rotates in opposite directions. The developing sleeve 231 is sufficiently stirred and mixed with the two-component developer D consisting of a magnetic carrier and toner.
sent to.

A magnet roller 236 having a fixed magnetic pole is disposed inside the developing sleeve 231 that is driven and rotated. It adheres to the top in a layer and is transported in the direction of the arrow.
A predetermined thin layer is formed by passing through the pressing position of the thin layer forming rod 29.

Thereafter, after the development of the electrostatic latent image on the developing area is completed, the remaining developer D on the developing sleeve 231 is returned into the housing 27 of the developing device 23, and the non-magnetic pole portion Q, that is, the magnetic flux When the developer D reaches a position where the density is almost zero and the developer D can fall under its own weight, the developer D is scraped off from the circumferential surface of the developing sleeve 231 by the scraper 235, and then uniformly stirred by the screws 232 and 233 again. , scattered on the developing sleeve 231,
Development is performed continuously.

FIG. 4 is a longitudinal sectional view of the process cartridge 20, and FIG. 5 is a sectional view taken along line AA of the developing device 23.

A drive roller 22A is provided on the side surface of the process cartridge 20 to rotate the photoreceptor belt 21.
A drive gear G14 connected to is provided. The drive gear G14 is connected to a drive motor (not shown) in the device main body 10 via a gear train that can be moved into and out of contact with the drive gear G14. Further, the other drive motor in the apparatus main body 10 is connected to the developer stirring member 232 drive gear G of the developing device 23 via a gear train (not shown).
12. Drive and rotate the developer carrier 231 drive gear G14, waste toner screw drive gear, etc. The drive gear G12 meshes with a drive gear G13 fixed to the shaft end of the developer supply member 233 to transmit power.

On the other hand, a housing 27 of the process cartridge 20 is located inside the process cartridge housing chamber of the apparatus main body 10.
The guide rail 201 suspends the process cartridge 20 by fitting the flange portion 276 of the guide rail 201, a plurality of motors (not shown), the drive gears G12, G13, G14 of the process cartridge 20, and the waste toner screw drive gear. A gear group is arranged.

In FIGS. 4 and 5, one shaft end of the developer stirring member 232 protrudes from one side wall (right side in the figure) of the developer tank formed in the recess of the housing 27 of the process cartridge 20. A small casing 271 is formed, the upper part of which is an opening 272 for replenishing toner.

A toner replenishing device is provided above the opening 272, which includes a connecting means 131 having a shutter, a toner replenishing pipe 132 containing a spiral screw, and a toner hopper 133 containing toner of each color.

Next, the toner replenishment process will be explained below.

(1) Upon generation of the toner replenishment signal, a certain amount of toner in the toner hopper 133 is supplied to the toner replenishment pipe 132, the connecting means 131, and the opening 272 of the developing device 23.
It is sent into the small casing part 271 through the process.

(2) The replenishment toner is supplied to the drive gear G12.
The first developer tank 27 of the developing device 23 is driven and rotated by
The developer is moved and conveyed while being mixed and stirred in the direction of the arrow shown in FIG.
It makes a U-turn at 74 and enters the second developer tank 275.

(3) The developer D carried into the second developer tank 275 is conveyed to the right as indicated by the arrow in FIG. 5 by the developer supply member (screw) 233 rotated by the drive gear G13. Ru.

(4) Next, the developer carrier 231 is driven and rotated by the recording signal, and the second developer tank 275 is driven to rotate.
The developer D is held on the surface of the developer carrier 231 and reaches the development area E, where it develops the electrostatic latent image on the photoreceptor belt 21 .

In this embodiment, as an image forming process, an image forming method was described in which a color toner image is formed on an image carrier (photoreceptor belt) and then transferred to a transfer material in one step. A color imaging method may be used in which toner images are transferred onto a transfer material on a drum in an overlapping manner. Further, it is also applicable to a normal monochrome printer using a monochrome process. Furthermore, although the non-contact development method has been described as a developing method, the present invention is not limited to this non-contact development, but can also be applied to contact development. Furthermore, the present invention is also applicable to a developing device that uses a one-component developer in addition to a two-component developer.

[0060]

Effects of the Invention As detailed above, the developing device of the present invention reliably peels the developer from the surface of the developer carrier and circulates it, so that the formation of a developer layer on the developer carrier is prevented. The toner image becomes uniform, thereby stabilizing the development process for the electrostatic latent image on the image carrier, and making it possible to form a clear toner image on the image carrier.

Furthermore, since the developer carrier contacts the peeling member with low friction and the developer falls under its own weight, it is possible to reduce the driving torque of the developer carrier.

Furthermore, since the developer stripping means consisting of the magnetic body having the non-magnetic pole portion and the stripping member has a simple structure, it is extremely effective in reducing the manufacturing cost of the developing device.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a multicolor image forming apparatus equipped with a developing device according to the present invention.

FIG. 2 is a sectional view of a process cartridge of the multicolor image forming apparatus.

FIG. 3 is an enlarged sectional view of a main part of the developing device of the present invention.

FIG. 4 is a longitudinal sectional view of the process cartridge.

FIG. 5 is a sectional view taken along line AA of the developing device.

[Explanation of symbols]

10...Device body
20... Process cartridge 21... Photoreceptor belt (image carrier) 23a, 23b, 23c, 23d... Developing device (developing device)
231 (231a, 231b, 231c, 231d)...
Developer carrier (developing sleeve) 232 (232a, 232b, 232c, 232d)...
Developer stirring member (toner transport stirring screw) 233 (233a, 233b, 233c, 233d)...
Developer supply member (developer agitation supply screw) 234 (234a, 234b, 234c, 234d)...
Partition plates 235 (235a, 235b, 235c, 23
5d)... Peeling member (scraper) 236 (236a, 2
36b, 236c, 236d)... Magnet body (magnet roller) 27... Housing 27
1...Small housing part 272...Opening part
273...First developer tank 275...Second developer tank
28a, 28b, 28c, 28d... Spacing member

Claims (3)

[Claims] Claims: 1. A magnet body having a plurality of magnetic poles and fixedly arranged; a developer carrier having the magnet body therein and carrying a developer on its surface and driven to rotate; a developer amount regulating member that regulates the amount of supported developer; a developer supplying member that supplies the developer to the developer carrier; and a developer stirring member that supplies and stirs the developer to the supplying member. In the developing device, a part of the magnet body corresponding to the position where the developed developer falls under its own weight on the surface of the developer carrier is provided with a non-magnetic pole portion that makes the magnetic flux density almost zero, and An elastic, non-magnetic peeling member is disposed above the developer stirring member, and the peeling member is an elastic non-magnetic peeling member that lightly presses the surface of the developer carrier corresponding to the magnetic pole portion to peel off and drop the developed developer. developing device. 2. The developing device according to claim 1, wherein the non-magnetic peeling member is integrally provided on an upper part of a partition member that partitions the developer supplying member and the developer stirring member. 3. The non-magnetic peeling member having elasticity is a stainless steel thin plate, a resin film, a rubber plate typified by a urethane blade, or a composite plate thereof. The developing device described in .