JP3573404B2 - Developer carrier in developing device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developer carrier used in a developing device of an electrophotographic image forming apparatus.
[0002]
[Prior art]
FIG. 2 shows a cross section of a conventional developing device used in an electrophotographic image forming apparatus, and FIG. 3 shows a cross section of a developing sleeve which is a developer carrier used in the developing device.
[0003]
In the developing device shown in FIG. 2, reference numeral 11 denotes a developing container, and the developing container 11 and the lid 12 are hermetically sealed with sealing means or the like so that toner as a developer does not leak outside. Reference numeral 13 denotes a screw, which functions to transport toner supplied from a hopper (not shown) disposed in front of the developing device to the back side, and to uniformly drop the toner into the developing container 11 in the longitudinal direction. Fulfill.
[0004]
Reference numerals 14 and 15 denote stirring rods which rotate in the direction of the arrow shown in the figure. These stirring rods have functions of stirring the toner in the developing container 11 and conveying the toner in the direction of the developing sleeve S. On the photosensitive drum D side of the developing container 11, a developing sleeve S, which is a developer carrier, is rotatably supported by the developing container 11, and the toner in the developing container 11 is adsorbed on the developing sleeve S. The thickness of the coating layer is controlled by a doctor blade 16 having a predetermined gap with the developing sleeve S, and is supplied to the photosensitive drum D on which an electrostatic latent image is formed by being rotationally conveyed to a portion close to the photosensitive drum D and the developing sleeve S. Is done.
[0005]
Here, the details of the developing sleeve S will be described below with reference to FIG.
[0006]
The developing sleeve S is configured such that the magnet 1 magnetized such that the magnetic poles face a predetermined position is fixed in the sleeve 6 which is a rotatable raw tube so as not to rotate. For example, S1 is a transport pole for sucking and transporting the toner in the developing container 11, a cut pole N1 at a position facing the doctor blade 16, a developing pole N2 at a position facing the photosensitive drum D, and these poles S1, Transport poles S2, S3, and N3 for restraining the toner on the sleeve 6 are provided between the rollers N1 so that the toner is not scattered by rotation.
[0007]
Incidentally, the magnet 1 is molded around the fixed shaft 2 while maintaining coaxiality. The fixed shaft 2 has both ends of the drive input flange 4 and the fixed shaft through flange 5 via the bearings 3-1 and 3-2. It is supported rotatably. Particularly, a hole is formed in the fixed shaft through flange 5 so that the fixed shaft 2 of the magnet 1 can be fixed from the outside. The sleeve 6, the drive input flange 4 and the fixed shaft through flange 5 are press-fitted to ensure strength and coaxiality between the magnet 1 and the sleeve 6.
[0008]
The developing sleeve S is rotatably supported on the developing container 11 by the bearing 7, and is rotated by the gear 8 provided on the drive input flange 4, while being provided on the fixed shaft through flange 5 side. The magnet 1 inside is rotated and fixed at a predetermined position by the pole determining plate 9.
[0009]
[Problems to be solved by the invention]
However, in the above-described conventional example, in order to maintain the required strength of the magnet 1 and the sleeve 6 while maintaining the coaxiality thereof, it is necessary to increase the press-fitting allowance of the sleeve 1 and the flanges 4 and 5 at both ends. There has been no method that satisfies the two contradictory propositions of the need for downsizing of the developing device and securing of the developing area, which are required by the downsizing of the photographic image forming apparatus.
[0010]
Accordingly, a first object of the present invention is to provide a developer carrier in a developing device capable of securing a wide effective magnetic force area without increasing the length in the longitudinal direction.
[0011]
Also, a second object of the present invention is to provide a developer in a developing device which can make the surface magnetic force uniform after assembly by increasing the surface magnetic force of the small diameter portion at both ends of the magnet to be higher than the surface magnetic force of other portions. It is to provide a carrier.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes a rotating cylindrical element tube, a magnet having a plurality of magnetic poles in a circumferential direction and fixed on the same axis as the element tube, In a developer carrying member in a developing device comprising a shaft supporting both ends of a magnet and press-fitted into both ends of the base tube, a magnet facing surface of the shaft has a countersink shape, and a diameter of both ends of the magnet Is made smaller in diameter than the other portions, and both ends are supported by the counterbored portion of the shaft.
[0013]
According to a second aspect of the present invention, in the first aspect of the invention, the surface magnetic force of the small-diameter portions at both ends of the magnet is magnetized higher than the surface magnetic forces of the other portions, so that the surface magnetic force of the base tube is increased in the axial direction. It is characterized by being made uniform.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0015]
FIG. 1 is a sectional view of a developing sleeve which is a developer carrying member according to the present invention. In FIG. 1, the same elements as those shown in FIG. 3 are denoted by the same reference numerals.
[0016]
In the developing sleeve S according to the present invention, reference numeral 1 denotes a magnet formed so as to ensure coaxiality around the fixed shaft 2. A required magnetic force is magnetized at a predetermined position in the circumferential direction of the magnet 1. ing.
[0017]
Further, small diameter portions 1-1 whose diameters are smaller than those of other portions are formed at both ends of the magnet 1. One end of the fixed shaft 2 is rotatably supported by the drive input flange 4 via the bearing 3-1 and the other end is rotatably supported by the fixed shaft through flange 5 via the bearing 3-2.
[0018]
Counterbore portions 4-1 and 5-1 having a diameter larger than the small diameter portion 1-1 of the magnet 1 are formed on a surface of the drive input flange 4 and the fixed shaft through flange 5 facing the end surface of the magnet 1, respectively. After the assembly, the end of the magnet 1 and the flanges 4 and 5 can be overlapped.
[0019]
Reference numeral 6 denotes a sleeve made of a non-magnetic SUS pipe material (base tube) whose surface is blasted. The sleeve 6 has both ends in the axial direction pressed into the outer circumferences of the flanges 4 and 5. The necessary press-fitting margin is secured to guarantee later strength and coaxiality between the magnet 1 and the sleeve 6.
[0020]
The developing sleeve S is supported at both ends in the axial direction by the developing container 11 by the bearings 7, and is rotated by the gear 8 provided on the drive input flange 4, whereby the sleeve 6 is rotated, while the fixed shaft is rotated. The internal magnet 1 is rotated and fixed at a predetermined position by a pole determining plate 9 provided on the through flange 5 side.
[0021]
Next, a method of magnetizing the magnet 1 in the longitudinal direction will be described.
[0022]
FIG. 1A shows the magnetic force on the surface of the magnet 1 and FIG. 1B shows the magnetic force on the surface of the sleeve 6. The magnetic force tends to decrease as the distance from the surface of the magnet 1 increases. Therefore, by magnetizing the small-diameter portions 1-1 formed at both ends of the magnet 1 so that the surface magnetic force increases, the magnetic force on the surface of the sleeve 6 can be made uniform in the axial direction.
[0023]
By adopting the above configuration, it is possible to secure a wide effective range of the magnetic force without extending the entire length of the developing sleeve S.
[0024]
Needless to say, the shapes of both ends of the magnet 1, the shapes of the spot facing portions 4-1 and 5-1 of the flanges 4 and 5, and the surface magnetic force of the magnet 1 are not limited to the present embodiment.
[0025]
【The invention's effect】
As apparent from the above description, according to the first aspect of the present invention, the magnet facing surface of the shaft has a counterbore shape, the diameter of both ends of the magnet is made smaller than that of the other portions, and the two ends are made the same. Since the shaft is supported by the counterbored portion of the shaft, an effect that a wide effective area of the magnetic force can be secured without increasing the longitudinal length of the developer carrying member is obtained.
[0026]
According to the second aspect of the present invention, the surface magnetic force of the small-diameter portions at both ends of the magnet is magnetized to be higher than the surface magnetic forces of the other portions so that the surface magnetic force of the base tube becomes uniform in the axial direction. Therefore, an effect is obtained that the surface magnetic force of the developer carrier after assembly can be made uniform.
[Brief description of the drawings]
FIG. 1 is a sectional view of a developing sleeve which is a developer carrying member according to the present invention.
FIG. 2 is a sectional view of a conventional developing device.
FIG. 3 is a sectional view of a developing sleeve which is a conventional developer carrier.
[Explanation of symbols]
1 magnet 1-1 small diameter section 4 drive input flange (shaft)
4-1 Counterbore part 5 Fixed shaft through flange (shaft)
5-1 Counterbore part 6 Sleeve (base tube)
S developing sleeve (developer carrier)

Claims (2)

A rotating cylindrical element tube, a magnet having a plurality of magnetic poles in the circumferential direction and fixed on the same axis as the element pipe, and both ends of the magnet are supported and pressed into both ends of the element tube. And a developer carrying member in a developing device composed of
A magnet facing surface of the shaft having a counterbore shape, wherein both ends of the magnet are made smaller in diameter than other portions, and the both ends are supported by the counterbored portion of the shaft. Developer carrier. 2. The magnet according to claim 1, wherein the surface magnetic force of the small-diameter portion at both ends of the magnet is magnetized higher than the surface magnetic force of the other portion so that the surface magnetic force of the base tube becomes uniform in the axial direction. Developer carrying member in the developing device.

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