JP2658424C - - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a charging device. More specifically, the present invention relates to a charging device that performs a charging process (including a static elimination process) on a surface of a charged body by bringing a rotating body for charging such as a rotating roller or a rotating belt for direct charging or frictional charging into contact with the charged body. . (Prior Art) For example, in an image forming apparatus such as an electrophotographic copying machine, a laser beam printer, an electrostatic recording apparatus, etc., an image carrier such as a photoconductor and a dielectric, and a charged body such as a transfer material are charged. A corona discharge device has been widely used as a processing device. The corona discharge device is effective as a means for uniformly charging a surface of a charged body such as an image carrier to a predetermined potential. However, there are problems that a high voltage power supply (5 to 8 KV DC) is required, a relatively large amount of ozone is generated when corona is generated, and power efficiency is low. In view of this, attention has been paid to the contact-type charging device as described above. In particular, a direct charging method or apparatus for directly transferring (injecting) charges to a surface of a charged object and charging the charged members to a predetermined potential by bringing a charging member to which a bias voltage is applied into contact with the charged object and relatively moving the charged member is known. The applied voltage required to obtain the desired potential on the charged surface is reduced, and the amount of ozone generated during the charging process is extremely small, eliminating the need for an ozone removal filter. It has advantages such as simplification of the structure of the exhaust system, maintenance-free operation, and simplicity of the structure, and many research and development proposals for its practical use have been made. 57-178267 ・ 56-104351 ・ 58-405
No. 66 / 58-139156 / 58-150975). The present applicant also applies a superimposed voltage of a DC voltage and a pulsating voltage having a peak-to-peak voltage of twice or more the charging start voltage to the charging member for the purpose of uniform charging processing without charging unevenness or the like. Various proposals have been made such as forming a charging member into a multi-layer structure in order to eliminate abnormal discharge and dielectric breakdown from the charging member to the member to be charged (Japanese Patent Application No. 61-29841).
9, 62-230334). FIG. 3 is a schematic configuration diagram of an example of a transfer type electrophotographic image forming apparatus using a direct charging device as a charging unit of the image carrier. Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as an image carrier, which is rotationally driven at a predetermined peripheral speed (process speed) in a counterclockwise direction indicated by an arrow m. Reference numeral 5 denotes a charging roller as a direct charging member, which is in contact with the surface of the photosensitive drum 1 with a predetermined pressing force. Reference numeral 5a denotes a power supply for applying a predetermined bias voltage to the charging roller 5. Thus, the surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential by the charging roller 5. Next, the uniformly charged surface of the photosensitive drum 1 is subjected to light image exposure L by image information exposure means (laser beam scanning exposure, light image projection slit exposure, etc.) in an exposure section 7 to obtain target image information. Is formed. The latent image is then developed with toner in a developing device 8, and the developed image is transferred to a transfer material P introduced from a paper supply unit (not shown) to a transfer unit between the photosensitive drum 1 and the transfer roller 11 at an appropriate timing. Is transcribed. The transfer material P that has passed through the transfer unit is separated from the surface of the photosensitive drum 1 and transported to an image fixing unit (not shown). After the transfer of the image, the surface of the photosensitive drum 1 is cleaned by the cleaning device 2 to remove adhered contaminants such as untransferred toner, and is repeatedly used for image formation. The cleaning device 2 of this embodiment is of a blade cleaning type, in which the leading edge of the cleaning blade 4 is brought into contact with the surface moving direction of the photosensitive drum 1 with a predetermined pressing force in the direction of the counter. Photosensitive drum 1 at contact edge
The transfer residual toner and the like on the surface are wiped and removed, and the surface of the photosensitive drum 1 is cleaned. The cleaning blade 4 has a solid lubricant polyvinylidene fluoride (PV) at the time of manufacture.
DF) is applied to prevent so-called blade turning during initial use of the apparatus. The above-mentioned charging roller 5 is rotatably supported and accommodated in a recess provided at the bottom of the container 3 of the cleaning device 2, and is provided on the container wall 3a in the vicinity thereof.
Cleaning member 6 is bonded and disposed. The image forming apparatus according to the present embodiment is configured such that the four process devices of the photosensitive drum 1, the charging roller 5, the developing device 8, and the cleaning device 2 are collectively and detachably attached to the image forming device main body as a process cartridge K. Is simplified, but this is outside the gist of the present invention, and the description is omitted. Direct charging originally generates little charge products (such as ozone and NOx), but if the device is used repeatedly, the charge products and foreign matters such as paper dust adhering to the charging roller 5 as a charging member may be reduced. As a result, the low-resistance substance is accumulated on the surface of the photosensitive drum 1 over time,
Image defects such as image deletion and image blur may occur. Also, dust and dirt in the air and on the transfer material, in particular, polyvinylidene fluoride, which is a solid lubricant applied to the cleaning blade 4 at the time of manufacture, is subjected to vibration and impact during transportation of the apparatus, vibration due to rotation of the photosensitive drum 1, and the like. As a result, the photosensitive drum 1 is separated from the cleaning blade 4 and adheres to the surface of the charging roller 5 as the photosensitive drum 1 rotates. Since polyvinylidene fluoride is an insulator, when polyvinylidene fluoride enters between the photosensitive drum and the charging roller 5, poor charging occurs only in that portion.
Image defects and image defects such as black spots or white spots occur at the same interval as the period of. Further, the foreign matter adhering to the surface of the charging roller 5 damages the surface of the photosensitive drum 1 with time, causing a streak-like image defect. Therefore, a configuration is adopted in which a cleaning member is brought into contact with the surface of the charging roller 5 to perform cleaning. When a film-shaped scraper is used as a cleaning member for the charging roller 5, the scraper does not easily follow minute irregularities on the surface of the charging roller 5, and a minute gap is easily generated between the charging roller and the scraper. However, there is a disadvantage that it is likely to remain partially. If the contact pressure of the scraper is increased to eliminate this drawback, the charging roller is easily damaged. In order for a flexible scraper to accurately abut against the charging roller, the scraper must be bonded to a sturdy support such as a sheet metal to form a unit, and the unit must be attached to the device with high accuracy. Increase. Therefore, a configuration has been adopted in which a sponge material is used as the cleaning member 6, and the sponge material is brought into contact with the charging roller 5 to rub the roller surface for cleaning. Since the sponge material 6 is porous, polyvinylidene fluoride and a charged product on the charging roller 5 can be trapped in the holes of the sponge material. In addition, since the sponge material has elasticity and is easily deformed in accordance with the shape of the surface of the member to be cleaned, it is possible to reliably remove the attached matter without particularly requiring the mounting accuracy. As the sponge material, for example, foamed polyurethane or foamed polyethylene is used. Conventionally, the sponge material as the cleaning member 6 is pressed against the sponge material tip surface against the charging roller 5 surface as shown in FIG. 4A, and the opposite surface is attached to the mounting support member surface 3a (in this example). In the case, the cleaning device container 3 containing the charging roller 5
(Recess wall surface). The sponge material 6 is compressed against the elasticity by a maximum C by pressing contact with the charging roller 5. Thereby, the cleaning member 6
Can reliably rub against the unevenness and eccentricity of the charging roller 5 to effectively remove the adhered foreign matter. (Problems to be Solved by the Invention) However, when the charging roller 5 rotates in the direction indicated by the arrow in the figure and is used repeatedly, the sponge material as the cleaning member 6 is caused to be in the second position by the frictional force between the cleaning member 6 and the charging roller 5. 4 Deforms as shown in FIG. In other words, the charging roller 5 gradually inclines toward the downstream side in the rotation direction, and a large tensile stress is applied to the vicinity 6a of the lower adhesive surface of the cleaning member 6 so that the adhesive surface is peeled off or the cleaning member 6 is partially removed. Sometimes it was torn. Therefore, as shown in FIG. 4C, when the pressure of the sponge material as the cleaning member 6 against the charging roller 5 is lightened and the compression amount of the sponge material is set to a small value C ', the mutual frictional force between the cleaning member 6 and the charging roller 5 is increased. Is reduced, so that the cleaning member 6 does not deform in the rotation direction of the charging roller 5. However, since the amount of compression of the cleaning member 6 is as small as C ', it is not possible to sufficiently cope with the unevenness and eccentricity of the surface of the charging roller 5, and it is impossible to reliably remove the adhered foreign matter (deterioration in cleaning performance). That is, when the pressing force of the sponge material as the cleaning member 6 against the charging roller 5 is reduced, the charging roller and the sponge material may be partially changed due to variations in component dimensions, particularly, variations in the thickness of the sponge material, deflection of the charging roller, and poor straightness. Some non-contact parts cannot be cleaned and the charging roller at the non-contact part cannot be cleaned. When a sponge material is used as the cleaning member 6 of the charging roller 5 as described above,
Since the sponge material is deformed by the elastic force in accordance with the shape of the charging roller, if the amount of deformation is too large, that is, if the pressing force against the charging roller is too strong, a problem of tearing or peeling of the sponge material occurs, and the amount of deformation is small. If the pressing force is too low, the charging roller and the sponge material may partially not contact with each other, resulting in a problem that cleaning performance is poor. The above-mentioned problem is a common problem when the charging member for direct charging or frictional charging is not limited to the roller type but is a rotating body (rotating body) such as a belt type. The present invention also uses a sponge material as a cleaning member of the charging rotating body, but solves the above-mentioned problem. The present invention (means for solving the problem), a charging rotary member for charging the charged member surface in contact with the member to be charged, said band
In a charging device having a sponge material for rubbing and cleaning an electric rotating body and a supporting member for supporting the sponge material, the sponge material has a corner, and the corner has a corner.
The sponge material comes into contact with the surface of the charging rotating body so as to be crushed.
Hanging from the center of the rotating body to the mounting support surface of the sponge material on the support member
A line and an end face of the sponge material forming the corner on the downstream side in the rotation direction of the charging rotating body.
In the rotation direction of the charging rotator so that
A charging device, wherein the charging device is disposed in a region where the space between the surface of the charging rotator and the support member is narrowed . (Operation) That is, by arranging the sponge material as a cleaning member so as to come into contact with the charging rotator, the contact area is reduced while securing the compression amount of the sponge material with respect to the charging rotator. As a result, foreign substances adhering to the charging rotator can be surely removed, that is, the charging rotator can be effectively cleaned, and the sponge material is prevented from peeling and tearing to improve durability. Is what I was able to do. (Embodiment) FIG. 1 is a view of a main portion showing a state in which a sponge material as a cleaning member 6 for a charging roller 5 is arranged according to the present invention in the image forming apparatus of FIG. That is, the cleaning member 6 comes into contact with the charging roller 5 such that the end surface 61 has a gap b from a perpendicular d that is lowered from the center of the charging roller 5 to the wall surface 3a of the cleaning container 3 to which the cleaning member is attached and supported. Then, it is stuck and arranged on the wall surface 3a. The amount of compression of the cleaning member due to contact with the charging roller 5 is C, which is the same as in the case of FIG. 4A, but the length of contact between the charging roller 5 and the cleaning member 6 is as shown in FIG. , And the frictional force between the charging roller 5 and the cleaning member 6 is correspondingly small. Therefore, as shown in FIG. 4 (B), the cleaning member 6 is durable without being greatly deformed in the rotation direction of the charging roller 5, and the cleaning member 6 is surely protected against unevenness and eccentricity of the charging roller 5. By rubbing in contact, the attached matter is efficiently removed. When the thickness of the cleaning member 6 is the same, the compression amount C of the cleaning member 6 by the charging roller 5 is slightly different between the case of FIG. 4A and the case of FIG. 1, but in the case of FIG. If the distance b from is sufficiently smaller than the radius r of the charging roller 5,
The compression amount C of the cleaning member 6 by the charging roller 5 hardly changes. Specifically, when b ≦ 0.2r, C decreases by 2% or less. B> 0.2r
Even so, the thickness of the cleaning member 6 may be increased accordingly. FIG. 2 is a reference example, in which the cleaning member 6 is moved to the downstream side in the rotation direction of the charging roller 5 in the same manner as in FIG. FIG. 6 is a diagram when the film is attached to the wall surface 3a such that a gap b exists from a perpendicular d to the wall surface 3a, that is, a cleaning member mounting support surface. Also in this case, the compression amount C of the cleaning member 6 has the same amount as in FIG. 4A, and the length of contact between the charging roller 5 and the cleaning member 6 is the same as in FIG. Similarly, efficient cleaning of the charging roller 5 is performed and durable use is possible. FIG. 5 shows a schematic configuration of an image forming apparatus having a configuration different from that of the image forming apparatus shown in FIG. This apparatus is also a transfer type electrophotographic image forming apparatus like the apparatus shown in FIG. 3, and includes four process devices including a photosensitive drum 1, a charging roller 5, a developing device 8, and a cleaning device 2 collectively. Is configured as a process cartridge K that can be detached from the cartridge. The same reference numerals are given to the same constituent members and portions as those of the apparatus in FIG. 3 and the description will not be repeated. The photosensitive drum 1 is clockwise n as indicated by the arrow.
At a predetermined peripheral speed. In this example, the charging roller 5 is disposed above the photosensitive drum 1 and is surrounded by a support frame 9. The cleaning member (sponge material) 6 is adhered to the corner of the support frame 9 as shown in the figure, and the end face 61 of the cleaning member 6 has a gap b from the perpendicular d to the support frame 9 from the center of the charging roller 5. Are arranged in a relationship. The amount of compression C of the cleaning member 6 by the charging roller 5 is the same as that in the example of FIGS. 4 (A), 1 and 2. In this embodiment, the perpendiculars from the center of the charging roller 5 to the support frame 9 are indicated by d, e and 2 in FIG.
The position of the cleaning member 6 attached to the support frame 9 is not limited to the position shown in FIG. 5, and the end surface 61 of the cleaning member 6 is aligned with the perpendicular d or e or has a gap b, and Any position that satisfies the compression amount C of the member may be used. However, in this embodiment, since the charging roller 5 is above the photosensitive drum 1, the cleaning member 6 is positioned so that dust and polyvinylidene fluoride scraped off from the charging roller 5 by the cleaning member 6 do not fall onto the photosensitive drum 1. It is good to decide. That is, in addition to the position shown in FIG. 5, the position shown in FIG.
FIG. 6 is a reference example. In the image forming apparatus shown in FIGS. 3 and 5, the transfer roller 11 is connected to a power supply 11a.
Since the charging roller is a charging roller to which a bias voltage is applied and is directly charged in contact with the back surface of the transfer material P, the present invention can also be applied as a cleaning unit configuration of the transfer roller 11. As has been described (Effect of the Invention), remove deposited foreign matter on inexpensively and reliably charging rotary member by using a sponge material to the cleaning member of the charging rotary member such as a charging roller, further said sponge material Is provided with a corner, and the charging rotation is performed so that the corner is crushed.
The sponge material contacts the surface of the body, and the support member
A perpendicular drawn to the mounting support surface of the sponge material and a spong forming the corner
The end of the charging material coincides with the end face on the downstream side in the rotation direction of the charging rotating body, or has a gap.
As described above, in the rotation direction of the charging rotator, the surface of the charging rotator and the
Since the cleaning member is disposed in a region where the space between the cleaning member and the support member is narrow , even if the cleaning member is pressed against the charging rotating body for a long time and is repeatedly used, the cleaning member is prevented from being detached from the mounting member surface or torn off. It is possible to secure the amount of compression C of the cleaning member that can sufficiently and sufficiently rub the charging rotator, thereby reliably removing the foreign matter adhering to the charging rotator.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an example in which a sponge material as a cleaning member is arranged in contact with a charging roller according to the present invention. FIG. 2 is a diagram of a reference example . FIG. 3 is a schematic configuration diagram of an example of an image forming apparatus using a charging roller. FIGS. 4 (A), (B) and (C) are views showing a conventional cleaning member arrangement example and its disadvantages. FIG. 5 is a schematic configuration diagram of another example of the image forming apparatus. FIG. 6 is a diagram of a reference example. FIG. 7 is a view showing another example of the arrangement of the cleaning member. 1 is a photosensitive drum as an image carrier, 5 is a charging roller as a direct charging member, 6
Is a sponge material as the cleaning member.

Claims (1)

Claims (1) and the charging rotary member for charging the charged member surface in contact with the member to be charged, the charging times
A sponge material for rubbing and cleaning the rolling element, and a support portion for supporting the sponge material
The sponge material has a corner, and the sponge material is provided on the surface of the charging rotating body so that the corner is crushed.
The sponge material abuts on the support member from the center of the charging rotating body.
A vertical line drawn to the mounting support surface of the sponge material, and the front of the sponge material forming the corner;
The end face on the downstream side in the rotation direction of the charging rotator is aligned with or has a gap.
A surface of the charging rotator and the support member in a rotation direction of the charging rotator;
A charging device, wherein the charging device is arranged in a region where the space between the charging device and the device is narrowed .