JP3694500B2 - Scorotron charger - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a scorotron charger provided to face a photoreceptor of an image forming apparatus and used for main charging or transfer charging. More specifically, the present invention relates to a grid of a scorotron charger, a surface of the photoreceptor, and The present invention relates to a scorotron charger capable of easily adjusting the distance between the two.
[0002]
[Prior art]
In electrophotographic image forming apparatuses such as copying machines, facsimiles, and printers, a main charger uniformly charges the photosensitive member positively or negatively, and images are irradiated by light irradiation based on predetermined image information. An electrostatic latent image is formed by exposure, and the electrostatic latent image is developed by a developing method such as a magnetic brush developing method, whereby a toner image is formed on the surface of the photoreceptor. The toner image formed on the surface of the photoreceptor in this manner is transferred to transfer paper using an electrostatic force using a transfer device, and the transfer paper onto which the toner image has been transferred is introduced into a fixing device, and is subjected to heat and pressure. Thus, image formation is performed by fixing the toner image on the surface of the transfer paper. On the other hand, after the transfer is completed, the toner remaining on the surface of the photosensitive member is cleaned by a cleaning device, and further, static elimination is performed as necessary. Thus, one cycle of the image forming process is completed and the next image forming is performed. .
[0003]
As the main charging device as described above, a scorotron charger is widely used. In this scorotron charger, a grid is provided on the discharge opening surface of the shield case on which the corona wire is stretched. Corona discharge from the corona wire to the surface of the photoconductor via the grid is caused by the potential difference between the corona wire and the grid. And the surface of the photoreceptor is charged to a predetermined potential having a predetermined polarity.
In such a scorotron charger, in order to perform uniform charging, it is necessary to keep a constant distance between the surface of the photoreceptor and the grid. For this reason, it is known that a charging unit equipped with a scorotron charger is provided with a roller that contacts the surface of the photoconductor, thereby maintaining a constant distance between the grid of the scorotron charger and the surface of the photoconductor ( Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-132042
[Problems to be solved by the invention]
However, although the conventionally known scorotron charger can keep the distance between the grid and the surface of the photosensitive member constant, it is difficult to adjust the distance appropriately.
Further, when the photosensitive member is used for a long period of time, the deterioration of the photosensitive member proceeds non-uniformly, and as a result, variation in charging may occur along the axial direction of the photosensitive member. In the above scorotron charger, it is also difficult to adjust such a variation in charging.
[0006]
Accordingly, an object of the present invention is to easily adjust the gap between the grid and the surface of the photosensitive member, and further, to adjust the dispersion of charging in the photosensitive member axial direction. Is to provide.
[0007]
[Means for Solving the Problems]
According to the present invention, in a scorotron charger comprising a corona wire stretched in a conductive shield case and a grid provided on a discharge opening surface of the shield case, the scorotron charger disposed facing the photoconductor ,
At the end of the shield case, a plurality of positioning rollers having different outer diameters are accommodated in parallel along the longitudinal direction of the shield case, and both ends of the center axis of the positioning rollers are bearing members. Is held by
The bearing member has a recess for retraction fitting and a recess for positioning fitting that communicate with each other. When the central shaft of the positioning roller is fitted in the positioning fitting recess, the positioning roller is a photosensitive member. A scorotron charger is provided in which the positioning roller is held apart from the photosensitive drum when the central axis of the positioning roller is fitted in the recess for retraction fitting in contact with the surface. The
[0008]
In the present invention, it is preferable that the plurality of positioning rollers are accommodated in both end portions of the shield case and held by the bearing member.
[0009]
In the scorotron charger of the present invention, a plurality of positioning rollers having different outer diameters are accommodated at the end of the shield case, and each of these positioning rollers has two fitting fixing positions (recessed fitting recesses and recesses). Since the center axis is held by the bearing member having the positioning fitting recess), the distance between the grid and the surface of the photoreceptor can be easily adjusted. That is, the positioning roller whose center shaft fitting and fixing position is a recess for retraction fitting does not contact the surface of the photosensitive member, and the center shaft fitting and fixing position is a positioning fitting recess. The roller for use contacts the surface of the photoreceptor. Therefore, if the center axis of the positioning roller having the smaller outer diameter is held by the positioning fitting recess, the distance between the grid and the photosensitive member surface can be reduced, and the center of the positioning roller having the larger outer diameter can be reduced. If the shaft is held by the positioning fitting recess, the distance between the grid and the surface of the photoreceptor can be increased.
The positioning position of the central axis of the positioning roller can be easily changed by pushing or pulling the central axis by hand because the recess for retraction fitting and the recess for positioning fitting communicate with each other. It is possible.
[0010]
In addition, by providing a plurality of positioning rollers respectively held by the bearing members as described above at both ends of the shield case, it is possible to easily adjust the charging variation in the photosensitive member axial direction. it can. That is, since the distance between the grid and the photoconductor can be adjusted independently at both ends of the shield case, the grid interval and the surface of the photoconductor can be adjusted at the end on one side, for example, depending on the state of charge variation. This is because the gap between the grid and the photosensitive member surface can be set small at the other end.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1 showing a perspective view of a main part (one end portion on the bottom side) of the scorotron charger of the present invention and in FIG. 2 showing a bottom view of the main part, this scorotron charger (hereinafter simply referred to as a scorotron) A corona wire 3 is stretched in a conductive shield case 1, and a grid 5 is provided over substantially the entire discharge opening surface 1a of the shield case 1 (in FIGS. 1 and 2, one of the grids 5 is provided). Part is omitted).
That is, the scorotron is disposed so that the discharge opening surface 1a faces the surface of the photoreceptor of the image forming apparatus, and a high voltage is applied between the corona wire 3 and the grid 5 to 5, corona discharge is performed on the surface of the photoconductor, thereby charging the surface of the photoconductor to positive or negative. The scorotron is urged toward the surface of the photosensitive member by an elastic material such as a spring in a state where the scorotron is incorporated in the image forming apparatus for positioning setting by a positioning roller described later.
[0012]
A holder 7 made of a frame-like electrically insulating member is fitted into one end of the shield case 1 of the scorotron.
A handle 9 is integrally formed on the outer surface of the holder 7, and a cleaning protrusion 11 is detachably locked. The handle 9 is used when the scorotron is attached to or detached from the image forming apparatus. Although not shown in the drawings, a cleaning member such as a felt for cleaning the corona wire 3 is attached to the projecting piece 11 via an appropriate rod. The projecting piece 11 is removed from the outer surface of the holder 7. By pulling out, the corona wire 3 is rubbed and cleaned by the cleaning member.
Further, a part of the holder 7 is covered with an openable / closable cover 13, and a fixing tool for the corona wire 3 is provided therein.
In addition, a holder made of a frame-like electrically insulating member is fitted into the other end portion of the shield case 1 of the scorotron. This holder is not provided with a handle 9 or a cleaning protrusion 11, and the corona wire 3 is connected to an electrode protruding outward in the longitudinal direction.
[0013]
In the present invention, two positioning rollers 20 and 21 are arranged in parallel along the longitudinal direction of the shield case 1 in the open portion of the holder 7 that is not covered with the cover 13. These positioning rollers 20 and 21 have different outer diameters. In the example shown in the drawing, the positioning roller 20 has a large outer diameter, and the positioning roller 21 has a small outer diameter.
[0014]
In the positioning rollers 20 and 21, both ends of the central shafts 20a and 21a are supported by bearing members 22 and 24, respectively.
[0015]
The bearing members 22 and 24 have a pair of bearing plates 30 and 30 that face each other. In FIG. 3 showing a front view of the bearing plate 30, the bearing plate 30 has a concave portion 32 for bearing.
The bearing recess 32 opens downward in FIG. 3, and includes an upper retraction fitting recess 32a and a lower positioning fitting recess 32b. That is, both ends of the central shafts 20a and 21a of the positioning rollers 20 and 21 are fitted and supported in either the retracting fitting recess 32a or the positioning fitting recess 32b. Further, as is clear from FIG. 3, the retracting fitting recess 32a and the positioning fitting recess 32b communicate with each other, and therefore, the fitting portions of the central shafts 20a and 21a can be easily switched.
[0016]
In FIG. 4 for explaining the fitting position of the central shafts 20a, 21a of the positioning rollers 20, 21, when the central shaft 20a or 21a is fitted in the retracting fitting recess 32a (FIG. 4 ( A)) The positioning roller 20 or 21 is not in contact with the surface of the photoreceptor. On the other hand, when the central shaft 20a or 21a is fitted in the positioning fitting recess 32b (FIG. 4B), the positioning roller 20 or 21 is in contact with the surface of the photoreceptor.
[0017]
As can be understood from the above description, the positioning roller in which the central axis is fitted in the retracting fitting recess 32a is in the retracting position, and depending on the roller, the scorotron is not positioned, and the positioning fitting recess. The scorotron is positioned by the positioning roller fitted to 32b, and the distance between the photoreceptor surface and the grid 5 is set.
[0018]
For example, when the central shaft 20a of the positioning roller 20 having a large outer diameter is fitted into the positioning fitting recess 32b, the distance between the photosensitive member surface and the grid 5 is increased. On the other hand, when the center shaft 21a of the positioning roller 21 having a small outer diameter is fitted into the positioning fitting recess 32b, the distance between the photosensitive member surface and the grid 5 is reduced. As described above, according to the present invention, the distance between the photosensitive member surface and the grid 5 can be easily adjusted by appropriately switching the positioning rollers 20 and 21 to be fitted in the positioning and fitting recesses 32b.
[0019]
Of course, the positioning rollers 20 and 21 described above can also be provided at the other end of the shield case 1 not shown in FIGS. 1 and 2, thereby adjusting the distance between the photosensitive member surface and the grid 5. The width expands. That is, since the distance can be adjusted independently at both ends of the shield case 1, for example, the distance between the photosensitive member surface and the grid 5 is increased at one end of the shield case 1, and at the other end. , The interval can be reduced. Therefore, it is possible to easily adjust the charging variation in the photosensitive member axial direction.
[0020]
In the present invention described above, only two types of positioning rollers are provided. However, if there is a margin in the size (length) of the shield case, a larger number of positioning rollers can be provided. The range for adjusting the distance between the grid and the photoreceptor surface can be increased.
[0021]
【The invention's effect】
According to the scorotron charger of the present invention, by providing a plurality of positioning rollers having different outer diameters so as to be able to switch between contact and retraction, the distance between the grid and the photosensitive member surface can be easily adjusted. Therefore, it is possible to easily adjust the variation in charging in the direction of the photosensitive member axis.
[Brief description of the drawings]
FIG. 1 is a perspective view of a main part of a scorotron charger according to the present invention.
2 is a bottom view of the main part of the scorotron charger of FIG. 1; FIG.
3 is a front view of a bearing plate provided in the scorotron charger of FIG. 1. FIG.
FIG. 4 is a diagram for explaining an outer diameter position of a positioning roller according to a fitting position of a central axis.
[Explanation of symbols]
1: Shield case 3: Corona wire 5: Grid 20: Large diameter positioning roller 21: Small diameter positioning roller 22, 24: Bearing member 30: Bearing plate 32: Bearing recess 32a: Retraction fitting recess 32b: Positioning Recess 32b for fitting

Claims (2)

In a scorotron charger, which is composed of a corona wire stretched in a conductive shield case and a grid provided on the discharge opening surface of the shield case, and is arranged facing the photoconductor.
At the end of the shield case, a plurality of positioning rollers having different outer diameters are accommodated in parallel along the longitudinal direction of the shield case, and both ends of the center axis of the positioning rollers are bearing members. Is held by
The bearing member has a recess for retraction fitting and a recess for positioning fitting that communicate with each other. When the central shaft of the positioning roller is fitted in the positioning fitting recess, the positioning roller is a photosensitive member. A scorotron charger, wherein the positioning roller is held away from the photosensitive drum when the central axis of the positioning roller is fitted in the recess for retraction fitting while abutting the surface. 2. The scorotron charger according to claim 1, wherein the plurality of positioning rollers are accommodated in both end portions of the shield case and held by the bearing member.

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