JPS6022350B2 - developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to direct processing of an electrostatic latent image formed on a recording medium such as an electrophotographic copying device or an electrostatic recording device.

2. Description of the Related Art Conventionally, a developing device for a dry type electrophotographic copying machine has been provided with a developing roller that rotates around a fixed shaft in close proximity to a photoreceptor drum. This developing roller is constituted by, for example, a non-magnetic cylinder, has a magnet inside, and forms a magnetic brush of developer consisting of toner and magnetic carrier on the surface of the cylinder. Then, the static latent image was visualized by rubbing the surface of the photoreceptor drum with a magnetic brush on the developing roller. In this type of developing device using a magnetic brush, if the sliding force of the magnetic brush on the surface of the photoreceptor drum during development is not always uniform, uneven development may occur. It is known that it is greatly influenced by the height of the magnetic brush and the gap between the developing loaf and the photosensitive drum. The height of the magnetic brush can be kept constant because the amount of developer pumped up by the developing roller can be regulated by a doctor plate provided on the developing roller.

On the other hand, the distance between the surface of the developing roller and the surface of the photoreceptor drum is highly likely to vary greatly depending on the eccentricity of the developing roller or the photoreceptor drum. In particular, it is impossible to make them perfect circles due to manufacturing problems, and the above-mentioned eccentricity always occurs, albeit slightly. Due to these causes, uneven development occurs every time the developing roller rotates. In addition, in a development method that uses a one-component developer consisting only of toner instead of a two-component developer, the thickness of the magnetic brush layer or toner layer formed on the developing roller is extremely thin.
Therefore, the distance between the developing roller surface and the photosensitive drum surface is much narrower than when a two-component developer is used.

Furthermore, if there is eccentricity of the developing roller or photoreceptor drum, the above-mentioned interval changes. In particular, when the above-mentioned interval becomes smaller than a predetermined value, the toner on the development roller is pressed, and the toner on the photoreceptor surface is unrelated to the static charge. toner adhesion or toner blocking/
There was an inconvenience that a solidification phenomenon occurred. Furthermore, as the above-mentioned interval becomes narrower, the toner on the developing roller cannot pass through the nip, and a so-called toner pool is formed. The toner then forcibly tries to enter the nip space, resulting in toner blocking. Therefore, a developing bag platform as shown in FIG. 1 was proposed as a method to overcome these drawbacks.

That is, in FIG. 1, reference numeral 1 denotes a photosensitive drum, which rotates in the direction of the arrow at a speed V, on which a static latent image is formed. Reference numeral 2 denotes a developing roller, which is composed of a non-magnetic cylinder 3 that rotates in the loss direction at a faster speed than V, and a magnet 4 fixed inside the cylinder and having N and S poles alternately magnetized. has been done. A toner hopper 5 is disposed above the developing roller 2 and stores magnetic toner T therein. Toner is carried out from the toner hopper 5 by the rotation of the non-magnetic cylinder 3, and the toner is regulated to a predetermined amount by a doctor 6 formed at the lower end of the toner hopper 5, forming a magnetic brush on the cylinder 3. Coaxial with this developing roller 2, and at both ends of the developing roller 2, a subesa roller 7 having a diameter larger than the cylinder 3 is attached to the axis of the developing roller 2 (not shown).
It is rotatably supported. This subesakoro 7
is pressed against the end of the photoreceptor drum 1 and rotated as the photoreceptor drum 1 rotates. In this state, the developing roller 2 must be supported floatingly relative to the main body of the developing device, and must be biased to press the developing roller 2 toward the photosensitive drum 1 side. By providing the smoothing roller 7 in this way, even if the photosensitive drum 1 is eccentric, it is possible to always maintain a constant distance between the surface of the cylinder 3 and the surface of the photosensitive drum more accurately than the developing roller 2. However, in dry development, the problem of toner scattering is unavoidable, and the scattered toner adheres to the surface of the above-mentioned smoothing roller 7.

Further, due to the formation of a toner pool, the toner on the cylinder 3 may reach a height higher than the smoothing roller 7 and reach the surface of the smoothing roller O7. When the toner adheres to the surface of the smoothing roller 7, the toner is crushed by the pressing force between the smoothing roller 7 and the photosensitive drum 1, and the toner is firmly fixed to the surface of the smoothing roller 7 or the photosensitive drum 1. As a result, since the diameters of the photoreceptor drum 1 and the roller 7 are usually not the same, the surface becomes uneven due to toner adhesion, and the distance between the surfaces of the photoreceptor drum 1 and the cylinder 3 formed by them is constant. It becomes impossible to maintain it. These adverse phenomena are especially fatal in a single-component development system that requires high precision. The present invention solves all of the above-mentioned drawbacks, and an object of the present invention is to provide a developing device in which the distance between the surface of a recording medium on which a static fin image is formed and the surface of a developing roller is always maintained. It is.

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

FIG. 2 is a perspective view of a developing device showing an embodiment of the present invention, and reference numeral 8 designates a photosensitive drum, which rotates at a constant speed in the direction of the arrow.

The photosensitive drum 8 is, for example, an aluminum conductive cylinder,
and a light guide body formed thereon. As the light guide material, for example, Z, Se, CdS, organic semiconductor (OPC), etc. are used. Of course, a three-layer photoreceptor in which a transparent insulating layer is formed on the light guide body can also be used. The photoconductor includes both ends 8a of the photoreceptor drum 8,
8b, and a part of the cylinder is exposed. These portions 8a and 8b are subjected to abrasion-resistant treatment such as hard alumite treatment, or by wrapping a wear-resistant material thereon. The developing device 9 includes a developing roller 10, a toner hopper 11, rollers 12 and 13, and cleaning members 14 and 15. Developing roller 1 consists of a non-magnetic cylinder 16 that rotates in the direction of the arrow as shown in FIG. A magnetic brush of a one-component developer made only of toner is formed on the surface of the cylinder 16. A toner hopper 11 is disposed at the upper part of the developing loft 9, and stores toner T therein, and as the cylinder 16 rotates, a predetermined amount of toner is formed from the toner hopper 11 at the lower part of the hopper 11. It is regulated by the doctor 18 and transported out. It is rotatably supported on the same axis as the roller 10a of the developing roller 10, and a subesakoro I2 is provided at both ends of the developing roller 10.
, 13 are provided. This subesakoro 12, 13
The radius R of the developing roller is set larger than the diameter r of the developing roller. This developing device 9 is pushed as a whole against the photosensitive drum 8 by appropriate means. Therefore, the sliding rollers 12 and 13 are in contact with both ends 8a and 8b of the photoreceptor drum 8, and are driven to rotate in the direction indicated by the rotation of the photoreceptor drum 8. That is, the distance between the surface of the photosensitive drum 8 and the surface of the developing roller 10 is maintained at a constant interval of (R-r).
Since the deviation of the photoreceptor drum 8, so-called eccentricity, is larger than the deviation of the developing roller 10, this method makes it possible to maintain the above-mentioned distance constant regardless of the eccentricity of the photoreceptor drum 8. Cleaning members 14 and 15 are provided in pressure contact with the surfaces of the smooth rollers 12 and 13 to remove toner adhering to the surfaces of the smooth rollers 12 and 13 and clean them.

The cleaning members 14 and 15 are made of polyurethane rubber, cowhide, etc.
The one that does not harm 3 must be selected. This material is made smooth by the leaf springs 14a and 15a.
, 13. Note that the cleaning members 14 and 15 are not limited to leaf springs, and may be pressed by other suitable pressure means. FIG. 3 shows an electrophotographic copying apparatus equipped with a developing device according to the present invention.

The photosensitive drum 8 is uniformly charged by a charging device 19, and then a light image is irradiated by an exposure device (not shown).
An electrostatic bath image is formed thereon. This Shizukame molten image is 109
The toner is developed using a magnetic brush made of magnetic toner having a resistance of 0 or more, that is, a medium resistance or more. In this case, the developing device 9 is arranged to the right of the photoreceptor drum 8, is supported so as to extend clockwise around the shaft 20, and is pressed against the photoreceptor drum 8 by its own weight. . Particularly in the case of medium-resistance magnetic toner, if the distance from the surface of the photoreceptor drum 8 to the surface of the developing roller 10 is long, an edge effect will appear, making it impossible to sufficiently develop the background portion. It is better to bring it closer. The developed toner image is transferred from the paper feed cassette 21 to the paper feed roller 22.
The image is superimposed on the transfer paper fed by the corona transfer plate 23, and transferred by the corona transfer plate 23. After the transfer, the electric charge existing on the back side of the transfer paper is removed by a corona separation device 24 consisting of an AC corona or a steep charger with a polarity opposite to that of the transfer corona, thereby increasing the electrostatic adhesion between the transfer paper and the photoreceptor drum 8. The transfer paper is transferred to the photoreceptor drum 8 by using the stiffness of the transfer paper.
Peel it off. The peeled transfer paper is conveyed by a belt 25 to a fixing device (not shown), fixed thereon, and discharged. On the other hand, residual toner from the transfer remains on the photosensitive drum 8 after the transfer, and is removed from the surface by the cleaning device 26.

The cleaning plate 26 has a fibrous brush formed on a cylinder 27, and rotates in the direction of the arrow with a relative speed difference to the surface of the photoreceptor drum 8, and the magnetic toner captured in the brush is removed. is removed by a beating rod 28, collected at the bottom of the cleaning machine 26, conveyed in one direction by a conveying means 29 consisting of a spiral fin, and collected or collected to the developing machine 9 for reuse. Incidentally, in order to assist the cleaning action, a magnet 30 is provided inside the cylinder 27 to magnetically attract the magnetic toner on the photoreceptor drum 8.
is located.

The photosensitive drum 8 from which the residual toner on the surface has been removed by the cleaning device 26 has the residual charge on the surface removed by the static eliminator 31 and is reused.
FIG. 4 shows another embodiment of the present invention, showing development.

The shaft 10a of the roller 10 is rotatably supported by a support arm 33 that rotates around a shaft 32. In the middle of the support arm 33, there is a shaft 35 provided with a flat roller 34 on the support arm 33.
The photosensitive drum 8 is rotatably supported by a spring 3.
It is pressed at 6. As a result, the distance between the surfaces of the developing roller 10 and the photosensitive drum 8 is maintained constant. A cleaning member 37 is placed on the surface of the smooth surface 34.
is in contact with the toner and removes the toner attached to the surface.
Cleaning. The distance between the photosensitive drum 8 and the developing roller 10 can be adjusted by displacing the shaft 35 of the subesa roller 34 with respect to the support arm 33 or by displacing the position of the shaft 32. Note that the distance between the photoreceptor drum 8 and the developing roller 10 can be maintained in the same manner as in the method described above, even if a roller that rotates alongside both surfaces of the photoreceptor drum 8 and the developing roller 10 is used. It is possible to implement.

Next, FIG. 5 shows a modification of the cleaning section. The surface of the cleaning roller 38 is made of an elastic material such as polyurethane rubber, silicone rubber, etc.
9 are in contact with each other and rotate in opposite directions on the surface of the smooth roller 38. The cleaning roller 39 uses its own adhesive force or electrostatic attraction force such as frictional charging to attach toner and the like that have adhered to the surface of the smoothing roller, and removes the toner and the like. The toner and the like adhering to the cleaning roller 39 are scraped by the blade 4 and collected from the surface thereof in a collection container 41 provided below. 6th
The figure shows a magnetic brush developing device using a two-component developer consisting of toner and magnetic carrier.

In the case of two-component developer, compared to the case of one-component developer,
Because the carrier also plays a part as a developing electrode,
There is no need to place the developing roller extremely close to the photosensitive drum. However, in order to perform uniform development, it is necessary to keep the super-dynamic force of the magnetic brush constant at all times, and the distance between it and the developing roller must be kept constant by eccentricity of the photosensitive drum. In the figure, a non-magnetic cylindrical sleeve 42 is rotating in the direction indicated by the arrow, and inside thereof a plurality of fixed magnets 43, - 434 are installed with alternating north and south poles.

Then, the two-component developer D in the developing container 44 is transferred to the magnet 43,
434 is attracted to the cylindrical sleeve 42 and drawn up to form a magnetic brush. This cylindrical sleeve 42
It is rotatably supported coaxially with the cylindrical sleeve 4.
A smooth roller 45 having a diameter larger than that of 2 is provided. The flexible roller 45 is pressed against both ends of the photoreceptor drum 8 and is driven to rotate. At the outlet of the developing container 44, a doctor plate 46 for regulating the amount of developer pumped up by the cylindrical sleeve 42 is brought into contact with the flattening roller 45 by means of an imitation 47.

This keeps the distance between the doctor plate 46 and the cylindrical sleeve 42 constant. If the cylindrical sleeve 42 is floatingly supported relative to the developer container 44, the doctor plate 46 must also move together with the cylindrical sleeve 42. After development, the magnetic brush is removed from the surface of the cylindrical sleeve 42 by a scraping plate 48 and falls into the developer container 44. On the other hand, the toner or carrier adhering to the surface of the flat roller 45 is removed by the blade 49 and collected into the developer container 44.

This blade 49 is excellent in keeping the spacing constant because it removes toner or carrier attached to the surface of the photoreceptor drum 8 before the spacing roller 45 comes into contact with the photoreceptor drum 8. In the embodiments described above, if the substances attached to the surface of the subesakoro are magnetic, a magnetic force generating means may be provided to remove them from the surface using the magnetic force of the magnet. .

However, if they are not provided before the substrate roller and the photosensitive drum come into contact with each other, for example, if the magnetic toner is pressed against the toner and solidified by its adhesive force, it will not be possible to remove it by the action of the magnetic force. If they cannot be provided there due to space constraints, they must be removed from the surface of the subesakoro by mechanical frictional force as described above. In addition, although all the above examples have been described only in the case of the magnetic brush development method, the present invention can be used in cases where a developer made of only non-magnetic toner is used and where precision of the development gap is required. It is also possible to use it as is.

Of course, if the developing roller is provided floating with respect to the main body of the developing device, the doctor, cleaning member, scraping plate, etc. that are in a predetermined positional relationship with the developing roller will be displaced along with it. It has become.
Further, both ends of the photoreceptor drum supporting the surface roller may be cleaned by a cleaning device or a separately provided cleaning means. Furthermore, it goes without saying that the present invention is not limited to electrophotographic copying apparatuses, but can be similarly applied to electrostatic recording apparatuses in which a static latent image is directly formed on a dielectric material by a recorder such as a multi-stylus.

As described above, according to the present invention, since the surface of the substrate roller that maintains a constant distance between the recording medium surface and the developing roller surface is constantly cleaned, the distance can be kept constant with extremely high accuracy.

Not only can uniform development be performed, but
It has an excellent advantage of being able to prevent the occurrence of developer blocking and the like. Since the development gap can be made constant using a simple device, the device is compact and inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the secondary developing device, FIG. 2 is a perspective view of a developing device showing an embodiment of the present invention, and FIG. 3 is an electronic device equipped with the developing device shown in FIG. 4 is a cross-sectional view of a developing device showing another embodiment of the present invention; FIG. 5 is a cross-sectional view of a cleaning member showing another embodiment of the present invention; FIG. The figure is a cross-sectional view of a magnetic brush developing device showing another embodiment of the present invention. 8... Photosensitive drum, 10... Developing roller, 12
, 13, 34, 38, 45... Subesakoro, 16, 42
...Cylinder, 14,15,37...Cleaning club village, 17,43. ~434...Magnet. Kaku ``Zukage and Zukou 4 zusen 5 zusaku 5 zu rare 6 zu

Claims (1)

[Claims] 1. A developer supply roller that rotates close to a moving recording medium carrying an electrostatic latent image thereon, and a developer supply roller that rotates in contact with an end of the developer supply roller or an end of the recording medium, and a developer A developing device consisting of a spacer roller that maintains a constant gap between the supply roller and the recording medium, and a cleaning member made of an elastic material that contacts the surface of the spacer roller and rotates in the opposite direction.