JPH0423270B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION (1) Field of the Invention The present invention relates to a magnetic brush developing device such as an electrostatic copying machine or a facsimile machine.

(2) Description of prior art Conventionally, for example, in an electrostatic copying machine, a developing device located close to a photoreceptor is used as a developing device to visualize an electrostatic latent image on a photoreceptor used as an electrostatic image holding member. A hollow developing roller with a magnetic roller inside is arranged, a magnetic brush is formed around the developing roller, and the magnetic brush rubs the photoreceptor to form an electrostatic latent image on the photoreceptor. A so-called magnetic brush developing device for developing is generally widely used. In this magnetic brush developing device, if the magnetic brush formed on the surface of the developing roller is kept in contact with the photoreceptor and the drive is stopped, the developer may mechanically adhere to the surface of the photoreceptor, that is, the surface to be developed. This makes it difficult to remove the adhered developer. This tendency is particularly strong in pressure fixing developers. Further, since the developer is a chemical substance, the surface to be developed is chemically altered and deteriorated by the developer, making it difficult to obtain desired electrical characteristics.

The present invention solves the above-mentioned technical problems and prevents the developer from changing the quality of the surface to be developed, deteriorating the electrical characteristics, or adhering the developer to the surface without complicating the structure. An object of the present invention is to provide a magnetic brush developing device.

The present invention provides a magnetic brush by supplying developer to the circumferential surface of a developing roller, which is formed by disposing a rotatably supported magnetic roller in a sleeve provided close to the surface of an electrostatic image holding member. A magnetic brush developing device for forming a magnet roller includes a drive means for rotationally driving a magnet roller disposed in the sleeve around its axis, and a drive means for transmitting rotational force from the drive means to the magnet roller, a one-way clutch that cuts off the rotational force from the magnet roller to the driving means; and an adsorption piece made of a high magnetic permeability material that is disposed close to one end in the axial direction of the magnet roller and fixed at a predetermined fixed position. The attraction piece is configured such that when the magnet roller stops, the magnetic brushes on the sleeve are brought into the developing area of the electrostatic image holding member by the magnetic attraction force between the magnetic poles of the magnet roller and the attraction piece. The magnet roller is positioned such that the rotation of the magnet roller is stopped so that the concave portion is located relative to the surface, and the development area surface of the electrostatic image holding member is separated from the bristles of the magnetic brush. This is a brush developing device.

DESCRIPTION OF PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a simplified cross-sectional view of one embodiment of the invention. A photoreceptor 2 serving as an electrostatic image holding member is provided around a drum 1 that is rotated during copying. This drum 1 is rotationally driven in the direction of arrow 3. A charging corona discharger 4, an exposure means 5, a magnetic brush developing device 6 having a cleaning function, and a copying corona discharger 7 are installed at each position close to the circumferential surface of the drum 1 in order toward the front in the rotation direction 3. , and a static elimination lamp 8 are arranged.

In this electrostatic copying machine, one printing process (that is, one copying process in the copying machine) is completed when the drum 1 rotates twice during copying and the copy paper is discharged. During the first rotation of the drum 1 and the photoreceptor 2, the photoreceptor 2 is charged by the charging corona discharger 4. The exposure means 5 irradiates the charged surface of the photoreceptor 2 with a light image corresponding to the original, thereby forming an electrostatic latent image on the surface of the photoreceptor 2 . The developing device 6 applies a one-component or two-component developer to the surface of the photoreceptor 2, whereby the electrostatic latent image is visualized. The visualized toner image is transferred onto the copy paper, which is conveyed as indicated by the dashed arrow in synchronization with the rotation of the photoreceptor 2 in the rotation direction 3, by the discharge of the transfer corona discharger 7. The copy paper on which the toner image has been transferred is conveyed to a fixing device (not shown) and fixed thereon.
be discharged.

The charge remaining on the photoreceptor 2 rotated in the rotational direction 3 from the position of the transfer corona discharger 7 is removed by the charge removal lamp 8, and then, during the second rotation of the drum 1, the charge is removed by the cleaning function of the developing device 6. The toner remaining on the photoreceptor 2 is then cleaned.

FIG. 2 is an enlarged sectional view of the vicinity of the developing device 6 in FIG. 1. The developing device 6 includes a developing roller 9 having a rotational axis parallel to the axis of the drum 1;
Developer storage container 10 having an opening 11 above
including. The developing roller 9 includes a sleeve 12 fixed close to the photoreceptor 2, and a magnet roller 13 rotatably supported within the sleeve 12 with the same axis as the sleeve 12. Magnet roller 13 includes a rotating shaft 17 integral therewith. This magnet roller 13 has N poles and S poles arranged alternately at equal intervals in the circumferential direction. The magnet roller 13 may have eight poles as shown in FIG. 2, or may have twelve poles. A magnetic brush 15 is formed on the sleeve 12 by rotating the magnet roller 13 in the direction of the arrow 14 . This magnetic brush 15
The magnet roller 13 has convex portions 15a with high spikes at positions corresponding to the N and S poles of the magnet roller 13, and has concave portions 15b with low spikes between the protrusions 15a in the circumferential direction. , are formed continuously in the circumferential direction of the sleeve 12. The magnetic brush 15 rotates on the sleeve 12 in the direction opposite to the direction of the arrow 14 as the magnet roller 13 rotates in the direction of the arrow 14.
Then, at the development position 16, the electrostatic latent image on the photoreceptor 2 is rubbed by the magnetic brush 15 and visualized.

FIG. 3 is a simplified perspective view of the vicinity of the developing roller 9 seen from the rear side of the electrostatic copying machine. A gear 19 is provided at the end of the rotating shaft 17 of the magnet roller 13 via a one-way clutch 18 . The gear 19 is connected via a gear 20 to a drive source (not shown) for advancing the copying process of the electrostatic copying machine. Therefore, when the drive source is in operation, the rotating shaft 17 is rotated in the direction indicated by the arrow 14. When the drive source stops operating, the rotating shaft 17 stops rotating. Further, due to the movement of the one-way clutch 18, the rotational torque of the gear 19 is transmitted to the rotation shaft 17, but the rotation torque from the rotation shaft 17 is transmitted to the gear 1.
9 is not transmitted. An iron piece 21 made of a high magnetic permeability material and serving as an adsorption piece is fixed to the body of the copying machine (not shown) at a predetermined fixed position in the vicinity of one end of the magnet roller 13 in the axial direction.

Figure 4 shows the developing device 6 seen from the rear side of the copying machine.
It is a sectional view of the vicinity. Here, it is assumed that the copying process of the copying machine is completed, the operation of the drive source is stopped, and the rotational drive of the drum 1 and the gears 19 and 20 is stopped. In this case, the magnet roller 13
is moved by the arrow 14 by the action of the one-way clutch 18.
It can be freely rotated in the direction of. Therefore, the north pole or south pole of the magnet roller 13 is attracted to the iron piece 21, and the magnet roller 13 is rotated to a rotation angle at which the north pole or south pole is located at the position of the iron piece 21 and then stopped. At this time, the fixed position of the iron piece 21 is determined so that the concave portion 15b of the magnetic brush 15 is positioned at the developing position 16. By doing so, it is possible to prevent the spikes of the magnetic brush 15 from remaining in contact with the photoreceptor 2 when the rotation of the magnet roller 13 is stopped.

The iron piece 21 may be placed close to the circumferential surface of the sleeve 12. Further, instead of the iron piece 21, a magnet piece having a magnetic force that does not adversely affect the developer may be used.

Instead of the cylindrical drum 1 as in each of the above-described embodiments, the present invention can also be implemented in connection with an endless belt-like element having a photoreceptor on its outer surface. Further, the present invention can be practiced in connection with a developing roller configured such that the sleeve 12 and the magnet roller 13 are both rotationally driven. Furthermore, the present invention can be implemented not only in electrostatic copying machines as in the above-mentioned embodiments, but also in relation to machines that form an electrostatic image on recording paper as an electrostatic image holding member, such as a facsimile machine. You can also.

Effects of the Invention As described above, according to the present invention, when the magnet roller stops, the magnet roller is rotated at such a rotation angle that the spikes of the magnetic brush on the sleeve are lowered toward the surface of the electrostatic image holding member. This prevents the spikes of the magnetic brush from remaining in contact with the electrostatic image holding member, and accordingly prevents deterioration of the developed surface of the electrostatic image holding member by the developer and electrical damage. Deterioration of characteristics can be prevented, and developer can be prevented from adhering to the surface to be developed.

Further, according to the present invention, in order to stop the rotation of the magnet roller, an adsorption piece made of a high magnetic permeability material is provided close to one end in the axial direction of the magnet roller, so the structure is simple. Therefore, the present invention can be easily implemented in connection with an existing developing device such as a copying machine. Moreover, since the suction piece is simply provided at a predetermined fixed position, a large occupied space is not required in the relatively narrow space near the developing device of a copying machine, etc., and the structure does not become large or complicated.

[Brief explanation of drawings]

FIG. 1 is a simplified sectional view of one embodiment of the present invention, FIG. 2 is an enlarged sectional view of the vicinity of the developing device 6, and FIG.
The figure is a simplified perspective view of the vicinity of the developing roller 9 seen from the rear side of the copying machine, and FIG. 4 is a sectional view of the vicinity of the developing device 6 seen from the rear side of the copying machine. 2...Photoreceptor, 6...Magnetic brush developing device, 9
...Developing roller, 12...Sleeve, 13...Magnetic roller, 15...Magnetic brush, 15a...
... Convex portion of magnetic brush 15, 15b... Concave portion of magnetic brush 15, 17... Rotating shaft, 18... One-way clutch, 21... Iron piece.

Claims (1)

[Claims] 1. A developer is supplied to the circumferential surface of a developing roller comprising a rotatably supported magnet roller disposed within a sleeve provided close to the surface of an electrostatic image holding member. A magnetic brush developing device that forms a magnetic brush with a magnetic brush includes a drive means for rotating a magnet roller disposed in the sleeve about its axis, and a drive means for transmitting rotational force from the drive means to the magnet roller. , and a one-way clutch for interrupting the rotational force from the magnet roller to the driving means, and made of a high magnetic permeability material that is disposed close to one axial end of the magnet roller and fixed at a predetermined fixed position. and a suction piece, the suction piece is configured to cause the spikes of the magnetic brush on the sleeve to be attached to the electrostatic image holding member by the magnetic attraction force between the magnetic poles of the magnet roller and the suction piece when the magnet roller stops. The rotation of the magnet roller is stopped so that the concave portion is positioned with respect to the surface of the developing area of the electrostatic image holding member, and the magnetic brush is positioned so that the surface of the developing area of the electrostatic image holding member is separated from the bristles of the magnetic brush. Magnetic brush developing device.