JP2658424B2 - Charging device - 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, it has problems such as requiring a high voltage power supply (5 to 8 KV DC), generating a relatively large amount of ozone when corona is generated, and inefficient power.

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 ・ 58−40566 ・ 58−139156 ・ 58-1
No. 50975).

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, Various proposals have been made, for example, to make the charging member 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 Nos. 61-298419 and 62-2303).
No. 34).

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.
In this embodiment, the photosensitive drum 1 is driven to rotate with the rotation of the photosensitive drum 1. 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 adhering 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. At the contact edge portion, transfer residual toner and the like on the surface of the photosensitive drum 1 are wiped and removed, and the surface of the photosensitive drum 1 is cleaned. The cleaning blade 4 is coated with polyvinylidene fluoride (PVDF), which is a solid lubricant at the time of manufacturing, so as to prevent the so-called blade turning during the initial use of the apparatus.

The above-mentioned charging roller 5 is rotatably supported and accommodated in a concave portion provided at the bottom of the container 3 of the cleaning device 2, and the cleaning member 6 of the charging roller 5 is adhered to a container wall 3 a in the vicinity thereof. It is arranged.

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.

Although the direct charging originally generates only a small amount of charge products (ozone, NOx, etc.), even if the device is used repeatedly, the charge products and foreign matter such as paper dust adhering to the charging roller 5 as a charging member are reduced. Since the toner is directly rubbed from the charging roller 5 to the surface of the photosensitive drum 1, a low-resistance substance is accumulated on the surface of the photosensitive drum 1 over time, and an image defect such as image deletion or image blurring 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 the photosensitive drum with the rotation of the charging roller 5, poor charging occurs only in that portion, and at the same interval as the cycle of the charging roller 5. Image defects and image defects such as black spots or white spots occur.
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 of 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, as shown in FIG. 4 (A), a sponge material serving as the cleaning member 6 is pressed against the sponge material tip surface against the charging roller 5 surface, and the opposite surface is attached to the mounting support member surface 3a (in this example). In this case, the charging roller 5 is adhered to the cleaning device container 3 containing the charging roller 5).
The sponge material 6 is compressed against the elasticity by a maximum C by pressing contact with the charging roller 5. As a result, the cleaning member 6 reliably rubs against the unevenness and eccentricity of the charging roller 5 so that the adhered foreign matter can be effectively removed.

(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 cleaning member 6 and the charging roller 5
Due to the frictional force, the sponge material as the cleaning member 6 is deformed as shown in FIG. 4 (B). In other words, the charging roller 5 gradually inclines to 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. 4 (C), 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 as small as C ′, the mutual frictional force between the cleaning member 6 and the charging roller 5 is increased. Decreases, so
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, the sponge material is deformed according to the shape of the charging roller due to elastic force, and thus the deformation amount is too large, that is, the pressing force against the charging roller is too strong. When the deformation amount is too small, that is, when the pressing force is too weak, a portion where the charging roller does not come into contact with the sponge material is generated, and there is a problem that the cleaning property 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.

(Means for Solving the Problems) The present invention relates to a sponge material which is in contact with a surface of a charging rotating body which contacts a member to be charged and charges the surface of the member to be charged and which is rubbed and cleaned. A charging device characterized in that the sponge material mounting support member surface is arranged such that the perpendicular line when the perpendicular line is drawn from the center of the sponge material coincides with the end face of the sponge material or has a gap.

(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 has the end surface 61 whose charging roller 5
The gap b is perpendicular to the wall d of the cleaning container 3 to which the cleaning member is attached and supported.
The wall surface 3a is brought into contact with the charging roller 5 in a
It is attached and arranged. 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 the charging roller 5 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. Even if b> 0.2r, the thickness of the cleaning member 6 may be increased accordingly.

FIG. 2 shows a state 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. The wall 3a is formed so as to have a gap b from the perpendicular d to the mounting support surface.
FIG. Also in this case, the amount of compression 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. And charging roller 5
Cleaning is performed efficiently, 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 a photosensitive drum 1, a charging roller 5, and a developing device 8.
The four process devices of the cleaning device 2 are collectively configured as a process cartridge K that is detachable from the image forming apparatus main body. 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 driven to rotate at a predetermined peripheral speed in a clockwise direction n shown by an arrow.

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 attached 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 a perpendicular d to the support frame 9 from the center of the charging roller 5. Are arranged in a relationship. Cleaning member 6 by charging roller 5
The compression amount C is the same as that shown in FIGS. 4 (A), 1 and 2.

In this embodiment, the cleaning member 6 has two perpendicular lines d and e from the center of the charging roller 5 to the support frame 9.
5 is not limited to the position shown in FIG. 5, but the end face 61 of the cleaning member 6 is in a relationship with the perpendicular d or e or has a gap b, and the amount of compression C of the cleaning member is Any position that satisfies is acceptable. However, in this embodiment, since the charging roller 5 is located 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.
This is the position shown in FIG. 6 and FIG.

In the image forming apparatus shown in FIGS. 3 and 5, the transfer roller 11 is a charging roller to which a bias voltage is applied from the power supply 11a and which 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.

(Effect of the Invention) As described above, the sponge material is used for the cleaning member of the charging rotator such as the charging roller, so that the foreign matter adhering to the charging rotator can be reliably and inexpensively removed. When a perpendicular is drawn from the center of the charging rotating body to the mounting support member surface of the cleaning member,
By arranging the perpendicular line and the surface where the charging rotator and the cleaning member are in contact with each other or having an appropriate gap b, even if the cleaning member is pressed against the charging rotator for a long time and used repeatedly. The cleaning member can be prevented from being detached or torn from the surface of the mounting support member, and the compression amount of the cleaning member can be sufficiently rubbed against the charging rotator sufficiently to secure the compression amount C of the cleaning member. Foreign matter can be reliably removed.

[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 another arrangement 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. 6 and 7 are views each 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, and 6 is a sponge material as a cleaning member.

Claims (1)

(57) [Claims] 1. A sponge material which contacts a surface of an object to be charged and charges a surface of the object to be charged and which is in contact with a surface of a rotating body for charging and rubs and is cleaned. A charging device, wherein a perpendicular line when a perpendicular line is drawn to a member surface and an end face of a sponge material are arranged so as to match or have a gap.