JPH0441348B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device in an image forming apparatus, and more particularly to a developing device in which a method for supporting a developing sleeve and a magnetic roller is improved.

2. Description of the Related Art Conventionally, there has been known a developing device that uses a developing sleeve made of a non-magnetic hollow cylinder and a magnetic roller provided inside the developing sleeve, and transports developer to a developing position based on a relative speed difference between the two. Normally, this kind of developing sleeve has a magnetic roller pushed into the sleeve, fixed to the sleeve with a flange, and the axis of the sleeve and magnetic roller as a reference in order to improve the accuracy of the outer circumferential surface of the sleeve. The outer circumferential surface of the sleeve was ground to ensure accuracy. This machining process has the drawback that because the sleeve contains a magnetic roller, it is impossible to bring a grinding tool made of a magnetic substance carelessly close to the sleeve surface, resulting in poor workability and high costs. .

Conventionally, the shaft at one end of the magnetic roller is supported by a flange provided at one end of the developing sleeve, and the shaft protruding from this flange is supported by a developer storage housing, while the other end of the developing sleeve is supported by a developer storage housing. A developing device in which the shaft at the other end of the magnetic roller protrudes from a hole in a flange provided in the flange and is supported by the housing is often used. Since the degree of eccentricity of members other than the developing sleeve overlaps when the developing sleeve is assembled into the developing sleeve, it has been difficult to make the developing sleeve rotatable without eccentricity.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a developing device having a developing sleeve that eliminates the above-mentioned conventional drawbacks, simplifies the processing process, and increases productivity, and to provide a developing device that has a developing sleeve that can be rotated with as little eccentricity as possible. It is an object of the present invention to provide a developing device capable of obtaining a good developed image.

An embodiment of the present invention will be described below in comparison with a conventional device.

FIG. 1 shows an example of a developing device using a one-component developer. Reference numeral 1 denotes a cylindrical developing sleeve made of a non-magnetic material such as stainless steel, which is rotated counterclockwise as shown by the arrow in the figure. A magnetic roller 2 is inserted into the hollow interior. The magnetic toner 3 is attracted onto the sleeve 1 by the magnet roller 2. The thickness of the toner on the sleeve 1 is adjusted to be thinner than the gap between them by the cooperation of the magnetic blade 4, which is a thickness regulating member, and the opposing magnetic pole N provided on the magnet roller 2. Next, the toner applied to the surface of the sleeve 1 is transferred to the photosensitive drum 5.
Development is performed by adhering to the electrostatic latent image on the photosensitive drum 5 at a position facing the photosensitive drum 5. In the figure, 6 is a housing that also serves as a hopper section of the developing device, and 7 is a lid.

By the way, the content of magnetic powder in the developer used above is determined by the amount of magnetic powder contained in the developer used because the toner is bonded to the transfer paper using means such as heat or pressure in order to fix the toner image on the transfer paper. , it naturally becomes limited. In practice, magnetic powder accounts for 10% to 60% by weight of toner particles, but due to the difference in specific gravity between resin and magnetic powder, the volume occupancy of magnetic powder in toner particles is less than 20%. Since the volume occupancy of the magnetic powder in the toner is very small, the behavior of the toner in the magnetic field is different from that of magnetic powder alone, and it is difficult to form long brushes with sparse density at the magnetic pole position. Become. Therefore, when the thickness of the toner layer on the sleeve 1 is restricted to several mm or less, the toner layer on the sleeve 1 tends to become uneven and non-uniform.

This non-uniformity of the toner layer on the support member is likely to be directly reproduced in the developed image, and since the toner layer is dense, variations in layer thickness may cause the surface of the photoconductor, which is the electrostatic image holding member 5, to There is a risk of toner agglomeration or damage to the photoconductor. Therefore, in this sense, it is necessary to form a uniform thin layer of toner on the sleeve 1 in a developing method using a one-component magnetic toner.

Under these circumstances, in order to regulate the layer thickness of toner on the surface of the sleeve 1, the magnetic blade 4, which is a thickness regulating member, must be brought very close to the sleeve surface. Incidentally, in this example, the interval between the two is
At 250μ, the toner layer thickness is about 80 to 100μ. Also,
The toner coated on the surface of sleeve 1 is
The toner adheres to the latent image on the photosensitive drum 1 and is subjected to development. However, since the coating on the sleeve is a thin layer and the toner is spatially transferred from the sleeve to the drum by electric force, the developing process is necessary. Place the sleeve 1 close to the surface of the drum 5 (300μ in this example)
It is necessary to keep it constant. Also,
It is preferable to apply an alternating bias voltage between the sleeve and the drum as described in JP-A-55-18656-9. In order to ensure such precision, the external dimensions of the sleeve 1 are required to have mechanical precision on the order of several tens of microns.

FIG. 2 shows a sectional view of a conventional sleeve. The magnet roller 2 shown in the figure is connected to flanges 10 and 11 of the sleeve 1 through bearings 8 and 9, and the shaft end 10a of one of the flanges 10 of the sleeve 1 is connected to the developing device through a bearing 12. It is pivotally supported by the housing 6 of. Magnet roller 4
is fixed to the developing device housing 6 so that one end 4a thereof is prevented from rotating by a fixing plate 13 and the magnetic pole position is constant.

The sleeve 1 receives a drive from a drive source via a gear 14 and rotates. 15 and 16 are spacer rollers that come into contact with the photosensitive drum surface for spacing, and 17 and 18 are seal members that prevent toner from entering into the bearings 9 and 12.

Now, in the developing sleeve configured as shown in Fig. 2, in order to achieve precision such as coaxiality of the outer peripheral surface of the sleeve with respect to the shaft end, a magnet roller is pushed into the sleeve, and both flanges 10 and 11 are attached to the sleeve. After fitting and fixing, the outer peripheral surface of the sleeve is ground with reference to the flange shaft end 10a and one end 4a of the magnetic roller to improve accuracy. In this machining process, since a magnet is contained within the sleeve, a grinding tool made of a magnetic material cannot be brought close to the sleeve, resulting in poor workability and high costs.

In the conventional example shown in FIG. 2, the eccentricity of the left side of the sleeve 1 includes the eccentricity of the magnetic roller shaft support hole of the flange 10,
On the other hand, the degree of eccentricity of the right side of the sleeve 1 is related to the degree of eccentricity of the through hole of the magnetic roller shaft 4a of the flange 11, and the degree of eccentricity of the magnetic roller shaft 4a. For these reasons, it is difficult to rotate the sleeve 1 without eccentricity, and the spacer roller 15 in contact with the photosensitive drum 5,
Uneven wear occurs on the drum 16, causing the distance between the drum 5 and the sleeve 1 to fluctuate, and the developing device to vibrate slightly, causing abnormal noise.

FIG. 3 shows a cross-sectional view of the developing sleeve of the present invention, in which the magnet roller 19 has two
It has two protruding shafts 19a and 19b. Magnetic roller 19 and the shafts 19a, 19b
, hollow developing sleeve 20 to this sleeve 20
The ends of the shafts 19a, 19b are attached to the magnetic roller shaft support portions 6a, 6 provided in the housing 6 without contacting or engaging with any member integrally fixed to the shafts 19a, 19b.
By being fixedly supported at b, it is supported by the housing 6 independently of the sleeve 20.

On the other hand, the sleeve 20 is connected to the magnetic roller 19.
It is rotatably supported by the developing device housing 6 via bearings 21 and 22 separately from the developing device casing 6 . That is, the outer circumferential surfaces of both ends of the hollow developing sleeve 20 are connected to the bearings 2, respectively.
1 and 22, and these two bearings 2
1 and 22 are supported by bearing support parts 6c and 6d of the housing 6.

Note that 23 and 24 are spacer rollers for interfacing with the photosensitive drum, 25 is a flange, and 26 is a drive gear. 23 and 24 are spacer rollers for interfacing with the photosensitive drum, 25 is a flange, and 26 is a drive gear.

As in the above configuration, since the magnetic roller 19 and the sleeve 20 are supported separately from the housing, the accuracy of the sleeve 20 can be ensured by itself. Furthermore, since there is no step of assembling the magnet inside, the processing step is simplified and workability is improved. Furthermore, bearings 8 and 9 shown in FIG. 2 for holding the magnetic roller and sealing material 1 are provided.
7 and 18 are also unnecessary. As described above, according to the present invention, costs can be reduced in terms of processing steps and number of parts, and productivity can be improved.

Further, the developing sleeve can be rotated without being affected by the eccentricity of the magnetic roller shaft or the flange at the end of the sleeve.

As shown in FIG. 4 as a modification of the present invention, rings 27 and 28 having a thickness equal to the distance between the photosensitive drum and the sleeve are used as spacer rollers on the outer circumferential surface of the sleeve 20, respectively, on the bearings 21 and 22. If the sleeve is coated at a position closer to the inside, the structure of the sleeve can be simpler and the cost can be lowered. Further, the present invention can be applied to a developing device using a two-component developer as well as one using a one-component developer as shown in FIG.

The present invention includes a housing that stores a developer, a rotating hollow developing sleeve that carries out the developer in the housing and supplies it to an electrostatic latent image carrier, and a rotary hollow developing sleeve that is fixedly disposed within the hollow developing sleeve and that extends from both ends. In a developing device having a magnetic roller each having a protruding shaft, the hollow developing sleeve has two bearings fitted to outer circumferential surfaces of both ends thereof, and the housing includes:
A developing device comprising: a bearing support section that supports the two bearings; and a magnet roller shaft support section that supports the two protruding shafts of the magnet roller independently of the hollow developing sleeve. be. That is, according to the present invention, since the hollow developing sleeve and the magnetic roller are supported by the housing separately and independently from each other, it is easy to reduce the eccentricity of the rotating hollow sleeve as much as possible.
Contributes to the formation of good developed images.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a developing device, FIG. 2 is a sectional view of a conventional developing sleeve, FIG. 3 is a sectional view of a developing sleeve according to the present invention, and FIG. 4 is a sectional view of another embodiment of the present invention. be. In the figure, 6...Developing device housing, 19...Magnetic roller, 20...Sleeve, 23,2
4...represents a spacer roller, 26...represents a gear.

Claims (1)

[Scope of Claims] 1. A housing for storing a developer, a rotary hollow phenomenon sleeve that carries out the developer in the housing and supplies it to an electrostatic latent image carrier, and a rotating hollow phenomenon sleeve that is fixedly disposed within the hollow developing sleeve. , a developing device having a magnetic roller with a shaft protruding from both ends thereof, the hollow developing sleeve has two bearings fitted on the outer circumferential surfaces of both ends thereof, and the housing 1. A developing device comprising: a bearing support portion that supports two bearings; and a magnet roller shaft support portion that supports two protruding shafts of the magnetic roller independently of the hollow developing sleeve. 2. On the inner peripheral surfaces of the bearings at both ends of the hollow developing sleeve, there is a space between the electrostatic latent image carrier and the hollow developing sleeve that comes into contact with the electrostatic latent image carrier.
2. The developing device according to claim 1, further comprising a spacer ring for holding the spacer ring.