JPH08240992A - Developing device - Google Patents

Abstract

PURPOSE: To keep the distance between a developing sleeve and a magnet roller with high accuracy and to prevent an image from being faulty by fixing a bearing on the inner periphery of the developing sleeve and supporting the magnet roller with the bearing. CONSTITUTION: The magnet roller 19 included in the developing sleeve 12 is thick in the central part 19c with plural magnetic poles and thin in both end parts 19a and 19b. Both end parts 19a and 19b are held by the bearing 22 and a holder 21b respectively. Thus, the roller 19 is directly force-fitted or stuck/ fixed into the sleeve 21 and held in a state where the roller 19 is floated by the bearing 22 and the holder 21b, plastic having slidability such as polyacetal is used for the bearing 22 and working tolerance and part piling up tolerance to the holding part of the roller 19 against the sleeve 12 are suppressed as little as possible. Thus, the roller 19 is held with high accuracy and slidability, change in a positional relation with a photoreceptor drum is reduced to suppress the occurrence of a fault in the image such as density unevenness, and the sleeve 12 can be obtained at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine or a printer for developing an electrostatic image on an image carrier.

[0002]

2. Description of the Related Art FIG. 4 is a partial sectional view of a developing device which is a background of the present invention.

It has a non-magnetic hollow cylindrical developing sleeve, a bearing for supporting the developing sleeve, and a magnet provided inside the developing sleeve. In FIG. 5, 19
Is a magnet roller, 12 is a developing sleeve, 17 is a sleeve flange that is adhered to the developing sleeve and is press-fitted, 22 is a bearing that is press-fitted and fixed to the sleeve flange, 18 is a bearing that rotatably receives the sleeve flange, and 12a is A sleeve gear for receiving rotational drive from a photosensitive drum (not shown) and transmitting it to the developing sleeve is a holder for holding the developing sleeve in a frame (not shown) via bearings 18 and 25.

Here, both the developing sleeve 12 and the free flange 17 are made of non-magnetic aluminum and are made by cutting, and they are very highly accurate parts. The bearings 18, 22, 25 are made of expensive ball bearings or slidable plastic such as polyacetal in order to rotate the developing sleeve with high precision.

As described above, in the conventional developing device, the magnet roller 19 is contained in the developing sleeve 12, and the gear side is supported by the sleeve flange 17 via the bearing 22.
The opposite side is fixedly supported by the holder 21b so as not to rotate. The developing sleeve 12 has a sleeve flange 17, and the bearing 18 and the bearing 25 form a holder 2
It is rotatably held by 1a and a holder 21b.
Further, in the developing sleeve 12, from the image forming apparatus main body,
A developing bias is applied via the electrodes 23 and 24.

FIG. 5 shows a partial sectional view of another example.

The developing sleeve comprises a cylindrical developing sleeve 100 rotating in a fixed direction and a magnet roller 101 disposed in the developing sleeve 100 and having a plurality of magnetic poles N1, N2, S1 and S2. . The other end 101b of the cored bar portion of the magnet roller 101 is formed by cutting a part of the cored bar cylindrical portion as shown in FIG. A plurality of magnetic poles are set at predetermined positions in the developing device 110 by using the cut flat surface portion. Then, the core bar 101b is fixed to a holder 111b fixed to the developing device main body 110. The other end 101a of the magnet roller is pivotally supported by a bearing 103 that is press-fitted or adhesively fixed in the sleeve flange. Development sleeve 1
00 is a magnet portion 101c of the magnet roller 101
Is arranged so as to cover the magnet roller 101 with a slight gap, and both ends thereof are bearing members 102a, 102a.
It is pivotally supported by the developing device main body 110 via b. In this configuration, the magnet roller 101 is received in the thrust direction by the magnet roller core metal parts 101a and 101b.
Is received by the end face of the abutting bearing 103 or holder 111b.

In the example shown in FIGS. 4 and 5, the sleeve flange is engaged with the developing sleeve by high-frequency thermal caulking, and the bearing is supported by the sleeve flange to prevent the bearing from being deteriorated by heat during caulking. ing.

[0009]

In the above-mentioned example, the bearing is fixed to the sleeve flange, so in order to obtain a stable image, -1) the outer peripheral portion of the sleeve flange which is press-fitted or adhesively fixed to the hollow cylindrical member. Accuracy of the sleeve flange outer circumference of the sleeve flange insertion portion, -2) Inner circumference of the sleeve flange that press-fits and fixes the bearing, and run-out accuracy of the sleeve flange outer circumference that is press-fitted or adhesively fixed to the hollow cylindrical member, -3) It was necessary to secure accuracy in many parts such as the inner peripheral part of the sleeve flange that is press-fitted and fixed and the outer peripheral part runout accuracy of the sleeve gear insertion part. In addition, each part had to be finished with high precision, resulting in a significant increase in processing cost.

[0010]

SUMMARY OF THE INVENTION The present invention for solving the above-mentioned problems is provided with a developer container for containing a developer, a developing sleeve for carrying the development in the container, and a developing sleeve provided in the developing sleeve. In a developing device having a magnet roller, a bearing is fixed to the inner peripheral surface of the developing sleeve, and the magnet roller is supported by the bearing.

According to the present invention, a high accuracy can be obtained between the developing sleeve and the magnet roller to prevent image defects, and it is also suitable for reuse of the magnet roller.

[0012]

【Example】

Example 1 An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a process cartridge 6 having a developing device according to an embodiment of the present invention and a photosensitive drum, which is an image carrier for carrying an electrostatic image, as at least an integrated unit.

In FIG. 1, reference numeral 1 denotes a photosensitive drum which is an image bearing member which rotates in the direction of the arrow, and around the photosensitive drum 1, process devices such as a charging device 2, a developing device 3 and a cleaning device 4 are arranged. Then, these devices are integrally incorporated in the cartridge container 6a and are detachably disposed as the process cartridge 6 in the main body of the image forming apparatus, so that, for example, the photosensitive drum 1 reaches the end of its life or is developed. When the toner (developer) in the apparatus 3 is used up, the entire process cartridge 6 is replaced to facilitate maintenance.

The developing device 3 has a developing section 10 having a developing sleeve 12 which is a developer bearing member facing the photosensitive drum 1 side, and a toner which holds toner T therein and supplies the toner T to the developing section 10. Although it is composed of a storage section 11, a lid member 13 having an opening 13 a is sandwiched and held between the developing section 10 and the developer storage section 11. Then, a sealing device 20 described later is attached to the opening 13a of the lid member 13, and the toner T in the developer accommodating portion 11 moves to the developing portion 10 when not in use, and the toner T is discharged to the outside of the process cartridge 6. In addition to preventing T from flowing out, when the process cartridge 6 is mounted in the main body of the image forming apparatus for use, the sealing device 20 is used.
The toner in the developer accommodating portion 11 can be supplied to the developing portion 10 by operating the to open the opening 13a.

The cleaning device 4 rubs the photosensitive drum 1 to remove the residual toner on the photosensitive drum 1, a cleaning blade 4a, and a waste toner storage portion 4b for storing the waste toner removed by the cleaning blade 4a. The residual toner on the photosensitive drum 1 is cleaned to prepare the photosensitive drum 1 for the next image forming apparatus.

Reference numeral 5 is a shutter for protecting the photosensitive drum 1. When the process cartridge 6 is mounted in the main body of the image forming apparatus, the shutter 5 is located on one side of the photosensitive drum 1 (of the cleaning device 4). It is designed to evacuate to the lower side.

In the apparatus of this embodiment as described above, when the photosensitive drum 1 uniformly charged by the charger 2 is exposed to the image light L from the scanning optical system (not shown), the photosensitive drum 1 is exposed. Forms an electrostatic latent image. The electrostatic latent image is directed toward the developing device 3 as the photosensitive drum 1 rotates, and the developing sleeve 12 of the developing device 3 supplies the toner T to visualize the electrostatic latent image. Then, this toner image is transferred onto a transfer material via transfer means (not shown),
After the transfer, the photosensitive drum 1 is cleaned of residual toner by the cleaning device 4, and is prepared for the next image formation.

The transfer material is a paper feed cassette (not shown).
The toner image is transferred from the inside to the photosensitive drum 1, the toner image is transferred from the photosensitive drum 1, and then the toner image is transferred to a fixing device (not shown), and the toner image is fixed by the fixing device. It

FIG. 2 shows a partially enlarged sectional view of the developing device of the embodiment of the present invention.

Reference numeral 17 denotes a sleeve flange, which has a boss portion which is fixed to an end portion of the developing sleeve and projects outward in the longitudinal direction from the developing sleeve, and the boss portion is rotatably supported by a bearing 18.

The sleeve flange 17 is press-fitted into the developing sleeve in a non-heated state to grind the bulge of the developing sleeve due to the press-fitting.

A sleeve gear 12 is further provided on the developing sleeve.
The a is assembled in a state in which the rotation is stopped by means such as a key and a set screw. Therefore, the developing sleeve 12 is driven by the drum gear 1a assembled to the photosensitive drum 1 to the sleeve gear 12a, and is rotated in a predetermined rotational speed direction.

On the other hand, a bearing 25 is engaged with the developing sleeve 12 on the opposite side (right side in the drawing) of the developing sleeve 12.

Further, as shown in FIG. 2, a bias electrode 24 is incorporated inside the developing sleeve 12 via an electrode base 25. The bias electrode is made of a stainless plate for spring, a phosphor bronze plate, or the like.
Has a spring property and contacts the electrode plate 23 with a predetermined force to establish electrical connection with the inner circumference of the developing sleeve 12.

That is, when the cartridge is mounted in the main body of the image forming apparatus, the developing bias is transmitted from the developing bias power feeding portion (not shown) to the electrode plate 14 through the contact (not shown), and the bias electrode 16 is further provided. The developing bias of the developing sleeve 12 is supplied via the.

On the other hand, in the magnet roller 19 contained in the developing sleeve 12, the central portion 19C is thick and has a plurality of magnetism, and both end portions 19a and 19b are thin.
The both ends 19a and 19b are held by the bearing 22 and the holder 21b, respectively. In addition, the shaft portion 19b of the magnet roller 19 has a square cross-section, which prevents the shaft portion 19b from rotating with respect to the holder 21b and positions the plurality of magnetic poles with respect to the photosensitive drum 11 at predetermined positions. It is fixed. And the holders 21a, 2
1b is positioned in the developing container 20 and fixed by a screw stopper or the like.

As a result, the magnet roller 19 is held in a floating state by the bearing 22 and the holder 21b, which are directly press-fitted or adhesively fixed to the developing sleeve 12, and the bearing 22 is slidable by polyacetal or the like. By using plastic to suppress the processing up to the magnet roller 19 holding portion for the developing sleeve 12 and the component stacking tolerance as much as possible, the magnet roller is held with high precision and high slidability, and the positional relationship (distance) with the photosensitive drum is maintained. By reducing the change, the occurrence of image defects such as density unevenness can be suppressed, and a low-cost developing sleeve can be realized.

<Embodiment 2> FIG. 3 shows a partially enlarged sectional view of a developing device according to another embodiment of the present invention.

In this embodiment, the magnet roller 19 is fixed to both the developing sleeve 12 and the sleeve flange 17 by press fitting.

According to this embodiment, the step of fixing the sleeve flange to the developing sleeve becomes unnecessary.

[0032]

As described above, according to the present invention, the processing up to the magnet roller holding portion and the component stacking tolerance can be suppressed as much as possible, the magnet roller can be held with high precision and high slidability, and it can be connected to the photosensitive drum. It is possible to reduce changes in the positional relationship (distance), suppress image defects such as density unevenness, and realize a low-cost developing sleeve.

[Brief description of drawings]

FIG. 1 is a sectional view of a process cartridge to which an embodiment of the present invention is applied.

FIG. 2 is a partially enlarged sectional view of the developing device according to the embodiment of the present invention.

FIG. 3 is a partially enlarged view of a developing device according to another embodiment of the present invention.

FIG. 4 is a partially enlarged cross-sectional view of a developing device which is the background of the present invention.

FIG. 5 is a partially enlarged cross-sectional view of a developing device that is the background of the present invention.

FIG. 6 is a partial perspective view showing a shaft portion of a magnet roller.

[Explanation of symbols]

 12 developing sleeve 17 sleeve flange 18, 22, 25 bearing 21 holder 23 electrode plate 24 bias plate

Claims (6)

[Claims] 1. A developing device having a developer container for containing a developer, a developing sleeve for carrying the developer in the container, and a magnet roller provided in the developing sleeve, wherein: A developing device characterized in that a bearing is fixed to the peripheral surface and a magnet roller is supported by the bearing. 2. The developing device according to claim 1, wherein the bearing is a sliding bearing made of slidable plastic and is press-fitted into a developing sleeve. 3. The developing device according to claim 1, wherein the bearing is adhesively fixed to the inner peripheral surface of the developing sleeve. 4. The developing device according to claim 1, further comprising a flange rotatably supported by being press-fitted into an end portion of the developing sleeve. 5. The apparatus according to claim 1, further comprising a flange rotatably supported at an end portion of the developing sleeve, and the bearing is also fixed to an inner peripheral surface of the flange. Developing device. 6. An end portion of the magnet roller opposite to the bearing is rotatably supported, and a developing sleeve rotates with respect to the magnet roller.
To 5 developing devices.