Patent Application
20080008499
A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner.
Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, preferred embodiments of the present invention are described.
Referring to
In
The conductive supporting member 201 is formed in a cylindrical shape extending in a longitudinal direction thereof. At one end of the conductive supporting member 201, a power pack 105 that serves as a voltage applying power source may be connected so as to apply a predetermined voltage to the charging roller 102.
The electrical resistance control layer 202 is arranged around an outer circumferential surface of the conductive supporting member 201 and is formed in a hollow circular cylindrical shape, extending in a longitudinal direction thereof.
The gap retaining member 203 is formed in a cylindrical shape having a hole at the center thereof. The respective gap retaining members 203 may be mounted on the outer circumferential surfaces at both ends of the electrical resistance control layer 202.
The charging roller 102 serves as a conductive charging member according to an exemplary embodiment of the present invention. However, it should be understood that the shape of the charging member is not limited as such and can be of any shape which can be used to achieve the charging functions. Specifically, the charging member according to the present invention can be of any shape if the gap retaining member 203 includes a material having a high sliding ability or if the gap retaining member 203 merely can be rotated with a photoconductor drum 101 (see also
The charging roller 102 is disposed opposite to the photoconductor drum 101 while being pressed toward the photoconductor drum 101. A gap retaining member 203 is mounted at both ends of the charging roller 102 and held in contact with the photoconductive drum 101. The charging roller 102 employs a non-contact charging method to charge the photoconductive drum 101 without contacting the photoconductor drum 101.
Specifically, an outer diameter of the electrical resistance control layer 202 is made slightly smaller than an outer diameter of the gap retaining member 203. With such structure, a gap may be formed between an outer surface of the electrical resistance control layer 202 and an outer surface of the photoconductor drum 101.
Further, the charging roller 102 is disposed so that the gap retaining member 203 can be held in contact with an outside of an image formation region or charging region of the photoconductor drum 101, which is a non-image formation region thereof. With the above-described structure, the charging roller 102 may be applied with a predetermined voltage to charge the image formation region of the photoconductor drum 101.
The charging roller 102 and the photoconductor drum 101 rotate while facing each other. By rotating as such, stress caused by the operating current on the same surface of the charging roller 102 or the photoconductor drum 101 may be sequentially diffused, and the life of the charging roller 102 and the photoconductor drum 101 can be extended.
Further, the photoconductor drum 101 and the charging roller 102 are not limited to be formed in a cylindrical shape. Alternatively, the photoconductor drum 101 and the charging roller 102 can be formed in an elliptical cylinder shape. Specifically, the preferable shape is based on the assumption that a gap between an outer circumferential surface of the photoconductor drum 101 and the electrical resistance control layer 202 of the charging roller 102 is constantly the same. Under such a condition, the shape is formed, for example, so that an amount of projection of the gap retaining member 203 projecting from the electrical resistance control layer 202 of the charging roller 102 is substantially constant.
The charging roller 102 that employs a non-contact charging method may need to maintain the distance of the gap at a predetermined interval and to be uniformly provided.
When the gap becomes greater, a condition of applying a voltage to the charging roller 102 needs to be higher. This can easily cause an electrical degradation and/or abnormal electrical discharge with respect to the photoconductor drum 101. Therefore, it is preferable that the gap is equal to or smaller than 100 μm.
Referring to
As shown in
In the above-described structure, the reinforcement part 203a and the contact part 203b do not need to have an identical width size. Specifically, even if the width or distance of the circumferential surface of the reinforcement part 203a in the longitudinal or axial direction of the charging roller 102 is smaller than the width or distance of the circumferential surface of the contact part 203b in the longitudinal or axial direction of the charging roller 102, the functional purpose of the reinforcement part 203a can be achieved. That is, the gap retaining member 203 can enhance the rigidity or strength of the charging roller 102. Further, when the electrical resistance control layer 202 expands with time due to aging, the gap retaining member 203 may not be easily affected.
The gap retaining member 203 may have a structure with an outer diameter gradually decreasing its size or becoming smaller in a direction from the end of the charging roller 102 toward a center of the image formation region or charging region.
To gradually decrease the outer diameter of the gap retaining member 203, the shape of the gap retaining member 203 may be formed in various shapes. For example, the present invention can be applied to the gap retaining member 203 of a tapered shape as shown in
The start position to change the size of the outer diameter is arbitrarily decidable. It is, however, preferable that the size of the outer diameter is changed within an effective region of the electrical resistance control layer 202. By so doing, it is greatly effective to stably retain a gap from a large expansion with age of the electrical resistance control layer 202.
For example, when the electrical resistance control layer 202 expands to increase the size of the outer diameter thereof, the portion of a gap retaining member 233 overlapping with the electrical resistance control layer 202 may be pushed up, as shown in
Referring to
In
The photoconductor drum 101 serves as an image carrying member and forms an electrostatic latent image on a surface thereof.
The charging roller 102 is disposed facing the photoconductor drum 101 in a contact or non-contact manner and charges the surface of the photoconductor drum 101.
The light beam 103 corresponds to a laser light beam emitted by a writing unit (not shown) or a light reflected from an original document.
The developing roller 104 supplies toner onto the electrostatic latent image formed on the surface of the photoconductor drum 101 to develop the electrostatic latent image to a visible toner image.
The voltage applying power source 105 applies a predetermined voltage to the charging member 102.
The transfer roller 106 transfers the visible toner image formed on the surface of the photoconductor drum 101 onto a recording medium 107 that is fed from a sheet feeding part (not shown).
The cleaning unit 108 removes residual toner remaining on the photoconductor drum 101 after the transfer operation.
The surface potential electrometer 109 measures the surface potential of the photoconductor drum 101.
Referring to
The configuration and functions of the image forming apparatus 110 of
However, the image forming apparatuses 100 and 110 can achieve the image forming operations and functions in a same manner.
Such operations performed by each of the image forming apparatuses 100 and 110 are described below.
The charging roller 102 uniformly charges the surface of the photoconductor drum 101 to a desired potential level.
The writing unit emits a light beam 103 to irradiate the surface of the photoconductor drum 101 so as to form an electrostatic latent image corresponding to a desired image on the surface of the photoconductor drum 101.
The developing roller 104 develops the electrostatic latent image formed on the surface of the photoconductor drum 101 to a visible toner image.
The transfer roller 106 transfers the visible toner image on the photoconductor drum 101 onto the recording medium 107.
The cleaning unit 108 removes residual toner remaining on the surface of the photoconductor drum 101.
The recording medium 107 having the toner image on a surface thereof is conveyed to a fixing unit (not shown) so that the fixing unit can apply heat and pressure to fix the toner image onto the recording medium 107.
By repeating the above-described image forming operations, a desired image may be formed on each recording medium 107.
As described above, the charging roller 102, according to an exemplary embodiment of the present invention, includes the gap retaining member 203 that is disposed around the outer circumferential surface of the conductive supporting member 201 and in the vicinity of both ends of the conductive supporting member 201. The gap retaining member 203 is arranged to decrease its amount of projection from the electrical resistance control layer 202 in a direction toward the center of the image formation region or charging region. Thereby, even after the charging roller 102 changes in size with age, a constant distance of the gap can be retained.
In addition, the gap retaining member 203 is controlled such that the amount of projection of the gap retaining member 203 decreases in the effective region of the electrical resistance control layer 202. It is in the effective region of the electrical resistance control layer 202 that the size of the charging roller 102 mostly changes with age. Thus, without the gap retaining member 203 described herein, it may be difficult to counteract an adverse affect due to the change of the charging roller 102 in size with age to the charging roller 102.
Further, the maximum projecting part of, or the greatest outer diameter of, the gap retaining member 203 is located outside the electrical resistance control layer 202 where the least change in size of the charging roller 102 is caused. Thereby, the gap between the charging roller 102 and the photoconductor drum 101 can be retained with a constant distance, from the initial time period and after a given time has elapsed.
Further, if the charging roller 102 is incorporated into the process cartridge 111, an easily replaceable process cartridge 111 can be provided. By providing such a process cartridge 111 to an electrophotographic image forming apparatus, a high quality image can be produced and stably maintained for a long period of time.
The above-described example embodiments are illustrative, and numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative and exemplary embodiments herein may be combined with each other and/or substituted for each other within the scope of this disclosure. It is therefore to be understood that, the disclosure of this patent specification may be practiced otherwise than as specifically described herein.
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, the invention may be practiced otherwise than as specifically described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-186764 | Jul 2006 | JP | national |
