JP3349596B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a laser printer.

[0002]

2. Description of the Related Art FIG. 1 is an overall schematic configuration diagram of an internal mechanism of an image forming apparatus which is also applied to the present invention and whose basic configuration is widely known.

Around a photosensitive drum 1 (for example, an organic photosensitive member, an OPC or a belt) which is a latent image carrier located substantially at the center of the apparatus main body, a charging device 15, an optical writing unit, a developing device 16, A transfer charger, a cleaning device 23, and a discharge lamp are arranged. Further, a paper feed unit 17 for feeding paper to the photoreceptor 1, a fixing device having a fixing heater, and an exhaust fan are provided outside the electrophotographic process means.

When a print switch (not shown) is pressed, a scanning optical system 5 including a light source 3 for illuminating the original and a mirror 4 is operated.
Then, the scanning optical system 8 including the mirrors 6 and 7 moves, and the scanning of the original placed on the contact glass 2 is performed. The scanned image information is read as an image signal by an image reading element 10 provided behind the lens 9. The read image signal is digitized and subjected to image processing. A laser diode (LD) (not shown) is driven based on the image-processed signal, and a laser beam from the LD is reflected by a polygon mirror 13 and then reflected by a mirror 14.
Irradiates the photosensitive drum 1 that is driven to rotate clockwise as viewed in the figure.

Prior to this, the surface of the photosensitive drum 1 is uniformly charged by the charging device 15, and an electrostatic latent image is formed on the photosensitive drum 1 by light writing by laser light irradiation as described above. You. This latent image is visualized by toner when passing through the developing device 16. This visible image is transferred by the transfer device 18 onto the recording paper conveyed to the photosensitive drum 1 at the same time from the paper supply unit 17. The recording paper on which the visible image has been transferred is the photosensitive drum 1
The visible image is fixed by being separated from the front surface and guided by the conveyor belt 21 through the nip portion of the fixing roller pair 22. Then, the recording paper is further discharged to a paper discharge unit.

On the other hand, the photosensitive drum 1 after the transfer of the visible image
The cleaning device 23 removes residual toner and paper dust.

[0007]

The developing device 16, the charging device 15, the transfer device 18, the cleaning device 23 and the like arranged around the photoreceptor are fixed to the photoreceptor in order to carry out the respective processes without fail. It needs to be positioned with a gap. Therefore, conventionally, in order to form such a gap, a gap management member such as a spacer is attached to each image forming unit side, such as both ends of a developing roller of a developing device and a transfer device, and the gap management member is attached to a photosensitive member for image formation. Contact is made outside the area.

These gap management members are attached so that they cannot be easily removed from each image forming unit, and exist until the life of each unit.
Some units are used without being replaced almost until the end of the mechanical life, and as a result, the time during which the gap management member and the photoconductor are in contact is increased. Therefore, the amount of wear of the gap management member also increases, and the gap between each unit and the photoconductor decreases with time.

The gap management member is used to maintain a development gap or the like. For example, when the number of components from the developing roller to the photosensitive member contact surface increases, the tolerance increases and the error increases. . Although it is possible to manufacture the parts with high accuracy so as to reduce the error, in that case, the cost of each individual part increases, and the cost increases by the number of parts.

More specifically, in the case of a developing roller or the like, a gap from the surface of the developing roller to the surface of the photoreceptor, that is, a gap of about 0.5 to 1 mm is often provided as a developing gap. Is 0.5 mm, the tolerance at such a development gap is approximately ±
It is required to be within 0.1 mm. On the contrary,
When the developing roller is arranged with a gap on the photoconductor, as shown in FIG. 2C, abutting rollers 31 are arranged coaxially at both ends of the developing roller 30, and this is brought into contact with the photoconductor 1. By doing so, a predetermined developing gap is obtained. At this time, for example, the outer peripheral tolerance of the developing roller having a diameter of 16 mm is about ± 0.05 mm (FIG. 2A).
The shaft tolerance of the roller shaft 32 having a diameter of 6 mm of the developing roller 30 is about 0 mm to -0.03 mm. The tolerance of the inner hole of the abutting roller 31 fitted into the shaft 32 of the developing roller is +
It is about 0.03mm ~ 0mm, and the tolerance of the roller circumference is ±
It is about 0.05 mm (FIG. 2B). Therefore, in calculation, the maximum play is 0.16 mm, and the desired ±
It will not be within the tolerance of 0.1 mm.

As the development gap becomes narrower, the tolerance also needs to be kept within a narrower range. On the other hand, the play in assembling the parts is the accumulation of the tolerances of the parts, so if the development gap is to be kept within a predetermined range, the precision of the parts must be increased. Increasing the accuracy raises the problem of increased costs. Then, the abutting rollers for holding the developing gap are firmly attached to the both end surfaces of the developing roller and used for a long time, so that they are worn out with time, the gap gradually narrows, and therefore excessive bias is applied. This will affect image quality.

When a predetermined gap is formed between the image forming units and the photosensitive member, if a gap management member such as an abutting roller is attached to the image forming unit as described above, the tolerances of the respective components are stacked. As a result, play may occur, which may cause image density unevenness in the running direction of the recording paper.

In order to solve such a problem, Japanese Patent Application Laid-Open No. 63-195675 discloses a photosensitive drum having a substantially cylindrical outer peripheral surface provided with a photosensitive layer. In order to prevent a situation in which the spacer member is displaced in the axial direction of the photosensitive drum as use is repeated, the outer diameter of the spacer member mounting portion of the photosensitive drum is set to at least the outside diameter thereof. There has been proposed a configuration in which the outer diameter of the developing roller is smaller than the outer diameter of the portion, and the edge of the developing roller contacts the middle of the outer peripheral surface of the spacer member in the width direction.

However, this technique only solves the problem with respect to the developing gap between the photosensitive member and the developing device, and the other gaps or bites relating to the charging roller and the transfer roller remain unchanged.

Accordingly, the present invention provides an image forming apparatus capable of reducing the number of parts, suppressing an increase in cost, increasing the gap or biting accuracy, and simultaneously maintaining a plurality of gaps or biting into the image carrier with high accuracy. The task is to provide

[0016]

According to the present invention, in order to solve the above-mentioned problems, according to the present invention, at both ends of a cylindrical image carrier, a plurality of image forming apparatuses are arranged so as to extend outward in the axial direction of the image carrier. The image forming apparatus is provided with a positioning multi-stage flange having a large diameter, and a gap or a bite required for each image forming apparatus is formed by each step of the flange.

It is preferable that at least the surface of the contact step of the flange with the peripheral image forming device is made of a material having a small coefficient of friction.

It is also preferable that at least the surface of the contact step of the flange with the peripheral image forming device is made of an insulating material.

[0019]

In the case where the image bearing member is a photosensitive member, it is more preferable that the developing gap is formed at the innermost step of the flange.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on an embodiment shown in the drawings.

The mechanism of the entire image forming apparatus is basically the same as that of the related art, and predetermined devices necessary for forming an image around the photoreceptor, for example, a charging device, an exposing device, a developing device, etc. However, for the sake of simplicity, the same parts as those in the related art will be described in the section of the related art, and the parts particularly related to the present invention will be described here.

As shown in FIG. 3, the photosensitive member 1 according to the present invention comprises a drum main body 51 and positioning members 52 fitted on both ends of the main body 51. The positioning member 52 has a plurality of steps, and the distance between these steps and the surface of the drum main body defines a predetermined gap in each image forming unit or regulates the amount of bite.

Although the developing roller is made of resin or metal, it is effective to bring the roller 30 into direct contact with the positioning member 52 when the surface is hard. Further, the transfer roller 35 and the charging roller 36
In the case of a roller made of a flexible material such as resin, urethane sponge, and rubber, the respective shafts and the positioning member 52 are brought into contact as shown in FIGS.

If the diameter of the photoreceptor is supposed to be φ30 mm and the gap amount is, for example, 0.5 mm in the developing device, the diameter of the developing gap step portion of the positioning member is adjusted to 31 mm. As described above, the tolerance for the gap of 0.5 mm is required to be within ± 0.1 mm, but realizing this at the 31 mm step portion of the positioning member is particularly difficult with the current component manufacturing technology. It is easy without increasing the accuracy. ± 31 mm
A tolerance of 0.05 mm is also possible. Therefore, the developing gap can be managed only by the tolerance of the positioning member.

Further, if the charging roller is assumed to have a biting amount of 0.5 mm, a charging roller diameter of φ14 mm, and a shaft diameter of φ4 mm, the charging step of the positioning member has a diameter of φ39 mm ± 0.1 mm. I just need. Further, the adjustment may be performed in the same manner for the transfer roller.

In the above embodiment, the roller type has been described. However, the present invention is also applicable to a charging or proximity minute gap type apparatus. Since a bias must be applied to each of the developing roller, the charging roller, and the transfer roller, it is desirable that the surface or the entirety of the positioning member be formed of an insulating material such as polyester. By doing so, it is possible to prevent a mechanical failure or an abnormal screen from occurring due to a leak or the like.

Further, since the positioning member is constantly in contact with the roller and the shaft, it is preferable that the positioning member is formed of a material that reduces the frictional resistance of the contact surface. The above polyester is advantageous because it has excellent abrasion resistance. By doing so, the wear of the contact surface can be suppressed.

Further, in the positioning member, the diameter of each step portion gradually increases from the photosensitive member side to the outside. Thereby, the displacement of the imaging unit in the axial direction can be prevented. Further, the developing gap between the developing roller and the developing roller is formed by contact between the innermost step of the positioning member and the developing roller. By doing so, it is possible to prevent toner stains and the like from the developing roller from being transferred to another image forming unit via another step.

By providing the photosensitive member with the positioning member, the positioning member can be replaced with a new one along with the replacement of the life of the photosensitive member. Therefore, it is possible to reduce the variation of the gap or the bite amount due to the wear over time. Is fulfilled. Normally, the machine life differs depending on the model, so it cannot be said unconditionally. However, it is about 600k sheets, and in the method in which the positioning member is provided on the image forming unit side, a material that does not wear even when using 600k sheets of the positioning member Although limited, in the present method, the photoconductor is replaced with a new one with a much shorter life, and therefore, there is little material limitation in maintaining the specified values of the gap and the bite.

In the above embodiment, the developing roller, the charging roller, and the transfer roller have been described. However, a cleaning device, a writing device, an erasing device, a pre-transfer device, in which gaps and bites should be controlled by a positioning member around the photosensitive member. Naturally, the static eliminator, the static eliminator before cleaning, the static eliminator before charging, and the like are also effective.

In the above embodiment, the photosensitive member is described as an example of the image bearing member. However, the present invention relates to a cylindrical visible image bearing member such as a transfer drum for color superposition in a multicolor image forming apparatus. Is also applicable.

[0033]

According to the image forming apparatus of the present invention, both ends of the cylindrical image carrier have a larger diameter toward the outside in the axial direction of the image carrier for a plurality of image forming apparatuses. Because it has a multi-stage positioning flange, for gaps and bites that should be defined between the peripheral imaging device,
Accumulation of tolerances can be avoided, gaps and bites can be easily adjusted, multiple gaps / bites can be adjusted at the same time, the number of parts can be reduced, and the number of parts can be reliably prevented from shifting in the axial direction. Possible without increasing

According to the image forming apparatus of the second aspect,
Since at least the surface of the contact step of the flange with the peripheral image forming device is made of a material having a small coefficient of friction, in addition to the effect of claim 1, wear is reduced, and fluctuation of gap / bite amount is suppressed. Becomes possible.

According to the image forming apparatus of the third aspect,
Since at least the surface of the contact step portion of the flange with the peripheral image forming device is made of an insulating material, the applied bias or the like does not leak, and is appropriately applied to the image carrier.

[0036]

According to the image forming apparatus of the fourth aspect,
When the image carrier is a photoreceptor, since the developing gap is formed at the innermost step of the flange, toner scattering from the developing device is prevented, and contamination of other image forming devices is prevented. it can.

[Brief description of the drawings]

FIG. 1 is an overall schematic configuration diagram of an internal mechanism of an image forming apparatus.

FIGS. 2A and 2B are diagrams for explaining a gap shift between a photosensitive member and a developing roller, wherein FIG. 2A shows a developing roller tolerance, FIG. 2B shows a contact roller tolerance, and FIG. Is shown.

FIG. 3 is a schematic view showing a state where the positioning member according to the present invention is fitted to a photoconductor.

FIG. 4 is a diagram showing a state in which the positioning member restricts the development gap, the transfer roller, and the charging roller from biting around the photoconductor;

FIG. 5 is a diagram omitting a developing roller from a direction different from FIG. 5;

[Explanation of symbols]

 1 Photoconductor 51 Drum main body 52 Positioning member

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiko Ishii 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Nobuto Yokokawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Masako Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (56) References JP-U 4-81173 (JP, U) JP-A 61- 81673 (JP, U) Japanese Utility Model 1-173765 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 21/00 G03G 15/08

Claims (4)

(57) [Claims] 1. A multi-stage positioning flange having a larger diameter toward the outside in the axial direction of an image carrier for a plurality of image forming apparatuses at both ends of a cylindrical image carrier. A gap or a bite necessary for each image forming apparatus. 2. The image forming apparatus according to claim 1, wherein at least a surface of the step portion of the flange that makes contact with the peripheral image forming device is made of a material having a small coefficient of friction. 3. The image forming apparatus according to claim 1, wherein at least a surface of a step portion of the flange and a peripheral image forming device is made of an insulating material. 4. The image forming apparatus according to claim 1, wherein when the image bearing member is a photosensitive member, a developing gap is formed at an innermost step of the flange.