JPS59116669A - Developing device - Google Patents

Abstract

PURPOSE:To prevent the degradation and the scattering of a developer to improve the capacity, by supplying the developer to upper and lower developing rolls with a rotating member which is provided in a lower developer storing part and agitating the developer and a supply toner with an agitating member provided in an upper developer storing part. CONSTITUTION:Two, upper and lower developer storing parts 36 and 40 are provided adjacently to upper and lower developing rolls 34 and 35 which are arranged to face a photosensitive drum 31 and are rotated in directions opposite to each other. The developer recovered from the first developing roll 34 and the toner supplied from a toner supply device 44 are agitated and mixed in the first developer storing part 40 and are supplied to the second developer storing part 36, and the developer recovered from the second developing roll 35 and the developer which is dropped from the first developer storing part 40 by the rotation of an agitating member 37 are agitated and mixed in the second developer storing part 36 and are carried toward the first developing roll 34 and the second developing roll 35 again.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improvement in a developing device in an electrostatic recording device, such as an electrophotographic copying machine.More specifically,
The present invention relates to a magnetic brush type developing device composed of a plurality of developing rolls having magnetic absorption power.

Prior art In electrostatic recording devices such as electrophotographic copying machines, electrostatic image forming devices for computer output, and electrostatic facsimiles, an electrostatic latent image of an image to be recorded is formed on a charge carrier such as a photoreceptor or a dielectric. 2. This electrostatic latent image is developed into a visible image using a developer containing toner. The device used for this development is a developing device, and although a block-type developing device is currently known, conventional magnetic brush developing devices can be roughly divided into two types.

One is a developing system that uses a single magnetic brush roll as shown in Figure 1, and the other is a developing system that uses multiple magnetic plano rolls as shown in Figure 2 to distribute the developer in one direction. This is a development system that uses multiple magnetic plan rolls that are conveyed to the printer and developed.

FIG. 1 shows an example of a conventional developing device using a single magnetic brush roll. A developing device is fitted facing the electrostatic charge carrier, for example, the photoreceptor drum 1.
27% ri is installed, and this developing device 211'
A developer reservoir consisting of Li toner and a carrier is stored, and a stirring member 3 disposed so as to be partially buried in the developer reservoir, a developing roll 4, a spike regulating plate 5, and a toner It is composed of a supply member 6. Further, the developing roller 4 includes a developing sleeve 4A and a magnetic roller including a plurality of permanent magnets 4B. When applying such a single-roll development system to a high-speed copying machine, in order to improve the reproducibility of image density and maintain good copy quality, it is necessary to (1) increase the circumferential speed of the development roll 4; 2) It has been a requirement to increase the toner content of the developer used. However, an increase in the circumferential speed of the developing roll due to force causes an increase in toner cloud and carrier scattering due to an increase in centrifugal force, which causes background stains, reduces the reliability of the copying system, and shortens the life of the developer. cause it to happen. Furthermore, an increase in the toner content of the developer results in an increase in toner cloud, which reduces the reliability of the device as a military machine for removing background dirt.

FIG. 2 shows an example of a conventional developing device using multiple nonmagnetic brush rolls. A developing device] 2 is disposed opposite to an electrostatic charge carrier, for example, a photosensitive drum 11, and this developing device 12 includes an agitating member 13, a plurality of developing rolls 14, A to 14D% spike regulating plate 15. , a toner supply member 16, and the like.

In high-speed copying machines using such multi-roll development systems, improved development performance allows the toner content of the developer used to be lowered and the number of revolutions of the development roll to be reduced. In particular, it reduces toner clouds and developer scattering, resulting in excellent copy image quality and stability. However, such a multi-roll developing system not only increases the manufacturing cost of the machine, but also poses a major problem in copying machine design in terms of the space and weight occupied by the developing device, and is also disadvantageous in terms of maintenance and maintenance of the copying machine. It has become.

In order to improve these problems, a developing method using two developing rolls, ie, Japanese Patent Application Laid-Open No. 126043/1984, is known. FIG. 3 is a diagram showing an example of this two-roll fAiM device. In the figure, a developing device 22 is disposed facing the photoreceptor 2.
, stirring member n, two developing rolls 24A, 24B, @
It is composed of a standing regulation plate section, a toner supply member 2b, and the like. In such a developing device, the developer is transported by
From the lower developer retention part to the lower developing roll 274B by stirring member B, and further to the upper developing roll 24A which is closer to the lower developing roll 274B.
Since the developing device is moved to a vertically long structure, the developing device becomes larger. Also, if a large amount of developer is put into the developing device, the developer will clog between the upper and lower developing rolls 24A and 24B, making it difficult to drive, so it is necessary to provide a developer retention section at a lower position than the lower developing roll 24B. This is also a cause of increasing the size of the developing device.

Furthermore, in the stirring system of this type of developing device, the developer is not sufficiently stirred, and unmixed developer is supplied to the developing roller, degrading the quality of the developed image. Increasing the agitation speed will shorten the life of the developer, increase toner clouding and carrier scattering, and deteriorate copying performance.

Furthermore, in order to distribute and transport the developer between the upper and lower developing rolls, these developing rolls are disposed close to each other, but because of this, the internal magnetic rollers may be bent or torqued due to mutual magnetic force. cause an increase. In addition, in this type of developing method in which developer is distributed between upper and lower developing rolls,
In particular, it is difficult to form a developer layer of uniform thickness on the upper developing roll.

As described above, even the developing system using two developing rolls has the disadvantage that sufficiently satisfactory performance cannot be obtained.

OBJECTS OF THE INVENTION The object of the present invention is to eliminate and improve the drawbacks of the prior art described above. More specifically, the present invention improves the overall performance of high-speed copying machines, such as developer deterioration, developer scattering, toner cloud, background stains, manufacturing cost, and device size. It is an object of the present invention to provide a magnetic brush developing device that achieves this and obtains excellent copy image quality.

Structure of the Invention The object of the present invention is to provide a developing roller having two upper and lower magnetic attraction forces disposed facing the surface of a latent image carrier in a developing area and rotating in opposite directions, and a developing roller adjacent to the developing roller. A device consisting of two upper and lower developer retention portions provided in the lower developer retention portion includes a rotating member for stirring the developer and supplying the developer to the upper and lower development rolls;
The upper developing roller and υ
This is achieved by a developing device characterized by having a stirring member that stirs the supplied developer and the toner replenished from the toner replenishing device.

Function: The developing device of the present invention has high developing performance due to excellent stirring and conveying ability and uniform developer layer formation.
This is effective in improving the performance of copying machines that produce good copy image quality at high speed. Further according to the present invention? Not only does it speed up copying, but it also uses a small number of developing rollers and a compact stirring member to enable a developer with a low toner ratio and a low magnetic brush roll rotation speed, resulting in compactness, lower costs, and improved reliability. A developing device that satisfies various conditions required for a copying machine is provided.

Example Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 4 is a schematic sectional view showing an embodiment of the present invention, in which a developing device 32 is disposed opposite an electrostatic charge carrier, for example a photosensitive drum 31, which moves in the direction of the arrow. This developing device 32
Inside, there is a sleeve 3 that encloses two developer strips close to the surface of the photosensitive drum 31 that holds an electrostatic latent image in the development area.
4C. 35C are moved in opposite directions by the drive mechanism [7
The developer container is rotated so that the supplied developer flows from the inside to the outside, that is, the developer flows between the sleeves toward the latent image holding surface of the photosensitive drum.

The developer in the second developer retention section 36 in the developer container is conveyed and supplied to the developer roller 35 by a rotationally driven lower stirring member 37. The lower stirring member 37 has a plurality of stirring blades 37A on the rotating shaft and a plurality of gutter-like packets 37B on the outer periphery, and stirs the developer and ensures that the developing roller 35 The developer is transported in the direction of .

In addition, a developer regulating plate is provided between the upper and lower developing rolls to maintain a predetermined slit interval at a predetermined position.
Upper and lower developing rolls are different. The developer supplied to the surface of the developer 35 is conveyed only in a fixed amount to the developing area by the developer regulating blade. In this developer regulating section, a repulsive magnetic field is formed by the sub-magnets of the upper and lower developing rolls, thereby preventing the developer from being pressed.

2 It is more preferable that the developing conditions of the developing rolls 35 and 35 are different from each other rather than being the same. In particular, effective development density and resolution can be obtained by over-developing the first developing roll at the top, and by performing bias development to remove fogging at the second developing roll at the bottom. Examples of this method include the following methods.

(1) Method using electric bias For example, when toner carrying a negative charge is attached to the photosensitive drum, a DC or AC electric bias having zero or one negative DC component is applied to the first developing roll 34. A DC or AC electric bias having a positive DC component is applied to the second developing roll to prevent fog development.

(2) Method based on development speed Normally, increasing the developer transport speed in the development area
image! 1 degree increases, but resolution decreases. Therefore, by increasing the conveying speed of the first developing roll and decreasing the conveying speed of the second developing roll, appropriate developing conditions are obtained. In this case, with respect to the moving circumferential speed of the photosensitive drum 31, the former U2~
It is recommended to increase the amount by 3 times, and the latter by 1 to 2 times.

(3) Method using development interval In general, II! The smaller the development interval (the distance between the surface of the photosensitive drum and the surface of the developing roll), the higher the image quality becomes. This tendency becomes more pronounced as a developer with a higher resistance value is used. It is preferable that the developing roll 2 is provided closer to the surface of the photosensitive drum than the developing roll 35.

(4) Method based on developer layer thickness Normally, even with the same development interval, the larger the developer layer thickness, the higher the image density obtained, but the resolution becomes lower.

For this reason, the distance between the developer regulating plates is set so that the first developing roll 34 has a thicker developer layer than the second developing roll.

(5) Method using magnetic force In general, the stronger the magnetic force of the developing roll facing the photosensitive drum, the higher and harder the spikes of developer are formed in the developing area, and the higher the image quality. Therefore, the main magnet 34A of the first developing roll is the main magnet 3 of the second developing roll 35.
It is preferable to use one with a magnetic force stronger than 5 A.

Appropriate development conditions can be obtained by using each of the above embodiments alone or in combination.

With the two developing rolls 34 and 35 configured in this way, the developer in the second developer retention section is stirred, mixed, and conveyed by the stirring member 37, passes between the developer regulating plates, and is sent to the developing roller pump. , 35, and are developed while passing through the development area, maintaining predetermined layer thicknesses, speeds, magnetic forces, spacings, and electrical biases, respectively. In FIG. 4, the sleeve is rotated with a fixed magnet, but a means for conveying the developer by rotating a magnet or a sleeve may also be used. Also, the main magnet can be single pole.
The remaining developer subjected to the 1° development is removed from the surface of the sleeve 34C by a scraping plate 39 in contact with that surface of the first developing roll, and enters the first developer retention section. The developer on the second developing roll 35 is removed from the surface of the sleeve 35c by a repelling magnetic pole or a scraping plate (not shown) and enters the second developer retention section 36.

The first developer retention section 40 mixes and stirs the developer collected from the first development roll and the toner supplied from the toner replenishment device 44, and supplies the mixture to the second developer retention section 40. It was established. The retention section 40 includes developer storage sections 41A and 41B, and a rotating stirring member 42A such as a stirring blade or a screw.

42B, and partition plates 43A and 43B with holes. Rotating body 42A, 42B t/i50~
300 R, P, M are preferred. The developer introduced from the first developing roll through the scraping plate 39 into the first developer retention section 40 is transferred to the stirring member 42 in the developer retention section on the left side.
The toner is stirred by A, mixed with toner replenished as necessary, and thrown into the developer retention section on the right side through the perforated partition plate 43A. Here, the developer is sufficiently stirred by a stirring member 42B such as a stirring blade or a screw rotating within the developer storage section 41B, and passes through the perforated partition 9 plate 43s to the second developer storage section below. It is supplied falling to. This supply position is the current 1st roll 34.
．． A location as far away from 35 as possible is best. This is the first
This is to prevent insufficient unstirred developer in the developer storage section from being directly supplied to the developing roll.

In the second developer retention section, due to the rotation of the stirring member 37, the developer falling from the first developer retention section 4o and the developer collected from the second developer roll are well stirred and mixed, and then the developer is mixed again. First developing roll and second developing roll 3
5, and repeat the development process. stirring part 37
The rotation is 50-300 RPM.

is suitable.

FIG. 5 is a sectional view showing another embodiment of the developing device according to the present invention. This is characterized by changing the magnetic pole arrangement of the second developing roll. The main magnetic pole 55A facing the photosensitive drum 31 in the second developing roll 55 is an S pole, and the other sub magnetic poles are N poles.

At this time, the developer between the first and second developing rolls 54 and 55 is compressed by the magnetic poles, so to prevent this, the developer regulating plate 58 is preferably made of a magnetic material.

In the above-described embodiment of the present invention, the first developer retention section is configured with two stirring members, but it is of course possible to improve the stirring member and use only one stirring member, or it is possible to improve the number of stirring members to accommodate even higher speed development. It is also possible to provide a third stirring member to perform mixing and stirring faster and more thoroughly.

Effect of the invention The effects of the uninvented developing device are described below.

(1) *The developing device of the invention is 4 to 4 in the conventional system.
This corresponds to the performance when using five developing rolls, and it can be seen that the developing device of the present invention has great effects in terms of machine cost, space, weight, etc.

(2) Also, compared to the conventional two-roll developing device, it is possible to make the device more compact by providing the lower second developer retention portion in the upper portion. By providing the first acupuncture agent retention section above the gap, the second acupuncture agent retention section could be made smaller.

(3) By providing the first developer retention section in the upper part of the developing device, the developer is sufficiently stirred, beaten, mixed, and homogenized, so that unmixed developer is supplied to the development area. There is no reduction in image quality. Furthermore, since the agitating sections are distributed and the developer is transported and moved, agitation efficiency is improved.

As a result, the rotational speed of each stirring member can be reduced, which improves the durability of the developer and reduces toner scattering, which is effective in improving image quality. Furthermore, since the stirring torque of these stirring members can be reduced, a power-saving design becomes possible.

(4) By arranging the second dust developer retention section in close proximity to the first developing roll, developer can be directly supplied to the first developing roll as well, ensuring uniform and uniform developer supply. Stabilized. The clogging of the developer between the first and second developing rolls was solved by the effect of the magnetic pole arrangement and the regulating plate.

Note that the developing device according to the present invention requires sufficient stirring,
Moreover, it is particularly suitable for a fine-grained developer that satisfies the requirements in the development area, such as a two-component developer consisting of a carrier of 10 to 50 μm and a toner of 1 to 10 μm. Of course, it is also effective to use a one-component developer that coagulates easily and requires sufficient beating and agitation.

[Brief explanation of the drawing]

FIG. 1 shows an example of a conventional one-roll development system, FIGS. 2 and 3 show an example of a conventional multi-roll development system with seven stems, and FIG. 4 is a sectional view of a magnetic brush development device according to the present invention. , FIG. 5 is a sectional view showing another embodiment of the developing device according to the present invention. 31...Static load carrier (photosensitive drum) 32.52...
・Developing device 34.54...First tax image roll 35.
55...Second developing roll 36...Second developer uradome part 37...Stirring gS material,
58...Developer regulation plate 39...Scraping plate 40°
Jth developer retention section 40...Toner replenishment device agent
Nahara Yoshimi Hayabusa 3 mortar

Claims (1)

[Claims] A developing roll having upper and lower magnetic attraction forces, which is disposed facing the surface of the latent image carrier in the developing area and rotates in opposite directions to each other, and an upper and lower developing roll which is provided adjacent to the developing roll.
The lower developer reservoir includes a rotating member that stirs the developer and supplies the developer to the upper and lower developing rolls; A developing device comprising: a stirring member for stirring the developer supplied from the upper developing roll and the toner replenished from the toner replenishing device.