JP3260971B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic apparatus based on the so-called Carlson process, for example, a copying machine, a printer,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device incorporated in a facsimile or a charging device incorporated in a process cartridge of such a device. In particular, a charging brush, a charging roller, and an electrophotographic device for charging a belt-shaped or drum-shaped photosensitive member by particle charging. The present invention relates to the invention applied as:

[0002]

2. Description of the Related Art Conventionally, respective process means of exposure, development, transfer, cleaning (removal of residual toner), charge elimination and charging are arranged on the outer peripheral surface of a photosensitive drum, and an image is formed by a predetermined electrophotographic process. Electrophotographic apparatuses based on the so-called Carlson process are well known.

The charging means used in this type of apparatus is generally a corotron type in which a high voltage is applied to a thin tungsten wire to perform corona discharge, or a charging means in which a voltage of several hundred volts is applied to a conductive roller to contact and charge a photosensitive drum. (Japanese Unexamined Patent Publication (Kokai) No. 5-297690, etc.), a device in which a voltage is applied to a conductive brush to charge while making contact with a photoreceptor drum, and a brush is formed by attaching magnetic particles to a conductive sleeve in which a magnet is inserted. A so-called particle charging method has also been proposed in which a magnetic bias is applied to a group of magnetic particles by applying a charging bias to a group of magnetic particles via a sleeve by rubbing a magnetic magnetic brush on a photosensitive drum (JP-A-59-133569 and others).

However, since the corotron method uses a high voltage and has many safety and environmental problems such as generation of ozone, the charging roller, the charging brush, and the charged particles are brought into contact with the photosensitive drum. Therefore, a so-called contact charging method, in which charging is performed while applying a charging bias to the photosensitive drum via these contact charging members, has been attracting attention. In order to perform charging while always in contact with the photoconductor drum, residual toner adhering to the photoconductor drum after transfer and paper powder adhering at the time of transfer adhere to the charged body, causing uneven charging and smooth charging. May not be possible.

For this reason, a cleaning blade is generally arranged upstream of the charging position in the rotation direction of the photosensitive drum.
Although the residual toner is removed by the cleaning blade, the blade merely presses the elastic body having a wedge-shaped cross section against the surface of the photosensitive drum. The pressing force is reduced, so that it is impossible to scrape the residual toner or the like sufficiently at both ends of the blade, and the toner or paper powder adhered to the image carrier by slipping through the blade adheres to the charged body, resulting in uneven charging. May occur. In addition, the residual toner and paper dust protruding from both ends of the blade may also protrude from the side of the blade, which may cause contamination of the charging roller.

In order to solve such a drawback, side seals 2 are attached to both ends of the blade 3 as shown in FIG. 5, but the side seals 2 are for preventing toner and the like from escaping from the end of the blade. The drum touches the surface,
It is necessary to use a soft elastic material as compared with the blade 3. For example, when a polyurethane elastomer is used for the blade, artificial leather is used for the side seal 2.

On the other hand, in recent years, the photosensitive drum 1 uses an OPC drum in terms of stability, manufacturing cost, and environmental resistance. However, the image forming is performed by combining the blade 3 and the side seal 2 of the material with the OPC drum. When the apparatus is configured, the following problems occur.

[0008]

The OPC drum is formed by depositing an OPC photoconductive layer made of a relatively soft organic resin layer on an aluminum tube and has a thickness of 30 to several tens μm.
Since the thin film is about m in thickness, as shown in FIG.
When the side seal 2 is pressed against the rotating OPC drum 1 together with the blade 3 for a long time,
As shown in FIG. 2B, the side seal 2 gradually scrapes off the surface of the photoconductive layer 1a of the OPC drum 1 to form a gap 1d between the charging roller 4 and the surface of the photoconductor drum 1, and the image is formed for a long period of time. In this process, the photoconductive layer 1a becomes thinner than the leak-resistant film thickness, and the leakage of the charging roller 4 gradually starts between the photoconductive layer 1a and the aluminum tube on the raw tube 1b side. , Various obstacles such as "light printing (light printing)", "density unevenness" or "carrier pulling" occur depending on the usage condition and environmental conditions, and finally the interval 1d exceeds the limit and the pipes When the surface of the OPC drum 1 is reached, the leakage of the charging roller 4 is maximized as shown in FIG. Then do Beam exchange is needed in a few million copies unit,
For this reason, it has been difficult to construct a device having a long life of 100,000 sheets or more without replacing the drum.

On the other hand, fibrous paper powder cannot be cleaned by the blade, and it is inevitable that the powder adheres to the charged body 4. For this reason, in an apparatus using the charging roller 4 as the charging member 4, a cleaning roller 5 made of a sponge material or a fibrous brush roller is brought into contact with the back side of the charging roller 4, and the rotation of the cleaning roller 5 Removal of toner and the like adhering to the surface of the charging roller 4 is attempted.

However, even in such an apparatus, if the paper dust or the like adhering to the cleaning roller 5 is not efficiently removed, it reattaches to the charging roller 4 side or damages the surface of the charging roller 4, resulting in a long period of time. A stable charging function cannot be maintained.

[0011] In view of the disadvantages of the prior art, the present invention provides
Even in a device in which a side seal of a cleaning blade is brought into contact with a photoreceptor drum 1 using an OPC drum and other image carriers, the drum is stably charged for a long period without replacing the drum in units of tens of thousands of sheets. It is another object of the present invention to provide an image forming apparatus capable of forming an image. Another object of the present invention is an apparatus in which a cleaning roller is disposed on a charging roller, and maintains a stable charging property for a long period of time without causing deterioration of the cleaning roller or reduction in cleaning ability even after long-term use. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

[0012]

A cleaning blade for providing powdery developer on a drum by providing side seals at both ends in a longitudinal direction of the blade along a moving direction of an image carrier using an OPC drum, and an image carrier. In an image forming apparatus in which a charging roller that performs uniform charging on a body is sequentially disposed in contact with a charging roller, a rotatable cleaning roller is disposed in contact with the charging roller, and the rotation of the cleaning roller captures the charging roller from the charging roller side. The surface shape of the cleaning roller is formed by winding the surface of the cleaning roller with a fibrous material or a brush-like cord so that the attached matter can move from the center side toward the shaft platform, and a direction perpendicular to the moving direction of the image carrier. An image forming apparatus characterized in that the respective process means and the width of the recording medium in (1) are defined as in the following formula (1). A>B>C>D> E 1) A: width of the image carrier B: contact width of the cleaning blade with the image carrier C: width between the inner ends of the side seals D: contact width of the charging roller with the image carrier E: Maximum image forming area width

A charging roller is used as the charging member 4,
In the image forming apparatus having the cleaning roller 5 rotatably arranged in contact with the charging roller, both ends of the cleaning roller 5 protrude from the ends of the charging roller.
It is better to set to the following length. F> D 2) F: axial length of the cleaning roller 5 and, in particular, by the rotation of the cleaning roller 5, the surface shape of the cleaning roller 5 so that the deposits captured from the charging roller side can move from the center side to the axial end side. Should be formed.

In this case, preferably, the peripheral speeds of the cleaning roller 5 and the charging roller are made different, and the peripheral speed ratio is set to 1.1.
It is better to set it in the range of 1.5 . The specific surface shape of the cleaning roller 5 for allowing the attached matter to move toward the shaft end side from the center side is formed by distributing in a spiral shape with different circumferential directions left and right from the center side. Is good. In addition, as long as the charging member 4 comes into contact with the image carrier, a charging brush or particle charging can be used in addition to the charging roller.

[0015]

According to this technical means, the width C between the inner ends of the side seals 2 is made wider than the contact width of the charging member 4, so that the contacting side seals 2 are abraded due to long-term running of the image carrier. Then, that part is thinned, and
Even when b is exposed, since the charging roller 4 does not face the worn portion, no charge leakage occurs, and the above described image defects such as light printing, density unevenness, carrier pulling and the like do not occur, and Even when the surface of the base tube 1b is exposed, uniform charging can be performed for a long period regardless of the exposure.

Also, since the maximum width of the image forming area, in other words, the width of the recording medium is also located within the contact width of the charging member 4,
An image in a stable area is guaranteed. Further, by making the width of the cleaning blade 3 wider than the contact width of the charging member 4, even if an axis shift or the like occurs between the cleaning blade 3 and the charging roller 4, the contact area range of the charging member 4 can be smoothly cleaned. .

Further, since the contact width of the charging member 4 is wider than the paper width of the recording medium, in other words, the paper width is smaller than the uniform charging width, even if the charging roller 4 is misaligned or the recording medium is skewed. Smooth image formation can be guaranteed.

In the relationship between the charging roller 4 and the cleaning roller 5, the length of the cleaning roller 5 is set so that both shaft ends of the cleaning roller 5 protrude from the shaft end of the charging roller 4. 5, even if the shaft deviation due to the rotation of the charging roller 4 or the attached matter at the end of the charging roller 4 or the attached matter leaked from the side seal 2 outside the image area adheres to the axial end of the charging roller 4. Capture and recovery can prevent the effect on the development side. In particular, by the rotation of the cleaning roller 5, the surface of the cleaning roller 5 is formed so that the deposits captured from the charging roller 4 side can move from the center side toward the shaft end side.
It is possible to prevent the deposits captured by the cleaning roller 5 from repeatedly contacting the charging roller 4 for a long period of time and damaging the surface of the charging roller 4. Further, since the attached matter moved to the shaft end side by the rotation of the cleaning roller 5 is set such that both shaft ends of the cleaning roller 5 are set to protrude from the shaft end of the charging roller 4, the attached matter is removed. If it is collected at the shaft end side, the charging roller 4 of the attached matter can be more efficiently and in a short time.
Can be eliminated and the charging roller 4 can be more efficiently used for a long period of time.

In this case, if the rotation of the cleaning roller 5 is synchronized with the charging roller 4, the contact position becomes the same in the circumferential direction, and the above-mentioned effect cannot be achieved. On the other hand, if the rotation is too fast, the cleaning roller 5 is generally formed in a fibrous material or a brush shape, so that the cleaning roller 5 may lose its hair or the like, and the roller is worn and cannot be used for a long time. Therefore, in the present invention, the peripheral speed between the cleaning roller 5 and the charging roller 4 is made different, and the relative peripheral speed difference is set in the range of 1.1 to 3 . The material of the charging roller 4 is different from that of the two-layer structure type. By forming the charging roller 4 into a single-layer conductive rotating body having a molecular weight distribution and a degree of cross-linking increased in the radial direction from the conductive support at the center toward the surface layer, Improves the durability of itself.

With respect to the relationship between the cleaning roller 5 and the charging roller 4, by adopting the above-mentioned configuration, a stable charging mechanism having a long life without any change in the surface of both rollers can be obtained. By setting the width of the recording medium and the width of the recording medium as in the expression (1), it is possible to provide a long-life apparatus without replacing parts for a long period of time.

[0021]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. Not just. FIG.
FIG. 2 shows a main configuration of an image forming apparatus to which the present invention is applied, in particular, a process unit around a photosensitive drum 1 of a printer.
Shows the basic configuration of the LED unit 8, the developing unit 60, and the developing unit 60 along the drum rotation direction (clockwise).
Transfer roller 7, cleaning blade 3, charging roller 4
The exposure latent image is written by the LED unit 8 on the photosensitive drum 1 uniformly charged by the charging roller 4 as is well known, and the exposure latent image is reversal-developed to form a toner image by the developing unit 60. The toner image is transferred to the transfer roller 7.
After the transfer to the recording medium 10, the residual toner is removed by the cleaning blade 3. The residual toner removed by the cleaning blade 3 is
Is stored in a waste toner bottle (not shown).

Next, the respective process means will be described. The photoconductor drum 1 uses an OPC drum 1 (organic photoconductor) having a diameter of 30φ and a negative polarity and is configured to be rotatable around an axis 1c in a direction of an arrow at a predetermined peripheral speed.
Then, the thickness (GG) of the photoconductive layer 1a of the photosensitive drum 1 is set.
(The total thickness of L, CTL, etc.) is set to 30 μm.

As is well known, the LED units 8 are
It consists of an LED head with D elements arranged and a focusing lens,
An exposure latent image corresponding to image information can be written on the photosensitive drum 1.

The developing unit 60 includes a DC bias power supply 65
(Approximately 250 V) is applied to the developing gap between the photosensitive drum 1 and the photosensitive drum 1 via the developing sleeve 6 to generate a toner image by low electric field reversal development.

The transfer roller 7 has a resistivity of 10 ⁵ Ω · cm.
Using the following elastic roller, specifically, a urethane rubber roller, the transfer bias 10 is set to +250 V which is opposite to the surface potential of the photoconductor and the polarity of the toner image charge.

On the other hand, the cleaning blade 3 has a plate-like polyurethane elastomer material attached to the lower side of a support 31 forming a part of the unit housing with screws 32, and the corners of the cleaning blade 3 contact the photosensitive drum 1 almost in line. At the same time, side seals 2 made of artificial leather are screwed to the support 31 and attached to the photosensitive drum 1 by surface contact at both ends in the axial direction of the blade.

The charging roller 4 is formed by molding a polyurethane rubber 42 to which a conductive component is added around a core metal 41 made of a 6φ stainless steel solid shaft, polishing the surface and shaping the surface into a 12φ roller shape. In this embodiment, a single-layer conductive rubber layer 62 is formed by increasing the molecular weight distribution and the degree of cross-linking in the radial direction of the polyurethane rubber 42 from the metal core 41 to the rubber surface layer, and forming a fluororesin on the surface if necessary. It is formed by performing coating. Preferably, the surface layer of the rubber layer 42 is hardened. A DC voltage is applied to the metal core 41 as a charging bias 43 so that the photoconductor layer 1a is charged with a potential of -400 V while being rotated in synchronization with the photosensitive drum 1. .

A cleaning roller 5 is disposed in contact with the back side of the charging roller 4. The cleaning roller 5 may be a known fur brush roller. However, as shown in FIG. 6, preferably, a surface of a metal core is covered with a rubber layer 51, and then a sponge body, a fiber material,
Alternatively, a string 50 made of soft rubber or the like, preferably a thick filamentous chemical fiber or a string 50 with long fibers planted on its surface, is spirally wound in different circumferential directions from the center to the left and right. It is preferable that the rotation of the cleaning roller 5 causes the adhered matter adhered to the roller 5 to move from the center side toward the shaft end.

The winding pitch is not particularly limited. However, if the winding pitch is set too far in the direction perpendicular to the axis, efficient movement becomes impossible. Preferably, it is set to about 10 to 45 °. The diameter of the cleaning roller 5 is preferably set to be slightly smaller than the diameter of the charging roller 4, that is, the radius from the axis to the contact with the charging roller 4 is slightly smaller than the radius of the charging roller 4. The axial length of the cleaning roller 5 is set longer than the axial length of the charging roller 4 so that both axial ends of the cleaning roller 5 protrude from the axial end of the charging roller 4.

The direction of rotation of the cleaning roller 5 may be either forward rotation or opposite rotation with respect to the charging roller 4 at the contact position with the charging roller 4. of at different circumferential speed ratio, the peripheral speed ratio 1.1-1.
5, preferably in the range of 1.1 to 1.2 . Thus the peripheral speed ratio is set in the range of 1.1 to 1.2, the rotation preferably forward direction to the charging roller 4, thus charging roller 4 as in FIG. 2 is anti to clockwise rotation Clockwise rotation is set.

The periphery of the cleaning roller 5 and the back side of the charging roller 4 is surrounded by a collection container 40. The adhered matter caught from the charging roller 4 by the rotation of the cleaning roller 5 is removed by the spiral wound fiber. After moving from the center side to the shaft end side by the string-shaped body 50, further moving from the shaft end of the charging roller 4 to both shaft ends of the cleaning roller 5, the collection container 40
It is configured to be collected inside. In this embodiment, A: the width of the photoconductive layer formed on the photosensitive drum B: the contact width of the cleaning blade drum C: the width between the inner edges of the side seal D: the drum contact width of the charging roller 4 E: the maximum image forming area width G: transfer roller H: developing roller The width of the body is defined as in the following formula 1). A>B>C> (D, G) ≧ H> E (1) In this case, the transfer roller 7 and the developing sleeve 6 may have the same length, but the transfer roller 7 has a side bias because the transfer bias 71 is applied. It is necessary that the width be smaller than the width C between the inner ends of the side seals in order to prevent a leak from the wear portion 20 of the seal 2. Further, the relationship between the drum contact width D of the charging roller 4 and the axial length F of the cleaning roller 5 is defined by the following formula 2) as described above. F> D 2)

Then, printing was performed on 100,000 sheets under the above-mentioned conditions, but no deterioration in image quality occurred. When disassembled, the thickness of the photoconductive layer 1a in the side seal 2 was lost, and the aluminum tube 1b was exposed. Next, the thickness of the photoconductive layer 1a of the photosensitive drum 1 is reduced from 30 μm to 20 μm.
After performing the same experiment as described above, the thickness of the photoconductive layer 1a at the side seal 2 was lost and the aluminum tube 1b was exposed after about 60,000 sheets. After printing the sheets, no deterioration in image quality occurred.

Next, an experiment similar to the above was carried out using the photosensitive drum 1 in which the width C between the inner ends of the side seal 2 was made smaller than the contact width of the drum of the charging roller 4 and the photoconductive layer 1a had a thickness of 30 μm. As a result, when about 50,000 sheets were in the light printing state, after 70,000 sheets, the leakage from the charging roller 4 became excessive, and a desired image could not be obtained.

[0034]

As described above, according to the present invention, even in an apparatus in which the side seal 2 of the cleaning blade is brought into contact with the photosensitive drum or other image bearing member using the OPC drum, the drum replacement can be performed in units of tens of thousands. And stable charging and image formation can be performed for a long period of time. According to the present invention, in the apparatus in which the cleaning roller is disposed on the charging roller 4, stable charging performance can be maintained for a long period of time without causing deterioration of the cleaning roller or deterioration of the cleaning ability even after long-term use. Thus, image formation can be performed stably. As a result, according to the present invention, it is possible to provide an apparatus capable of performing image formation in free maintenance for a long time without replacing a process unit. And so on.

[Brief description of the drawings]

FIG. 1 is a schematic diagram that defines the width of a photosensitive drum, a process unit, and a recording medium of the apparatus shown in FIG. 2;

FIG. 2 is a basic configuration diagram of an image forming apparatus used in the present invention.

FIG. 3 is a detailed view around the process of FIG. 2;

FIG. 4 is a front view showing a configuration of a charging roller and a cleaning roller used in FIG. 2, and an enlarged view thereof.

5 is an enlarged perspective view of an essential part of a cleaning blade and a side seal portion of FIG. 3;

FIG. 6 is a diagram illustrating a surface shape (A) of a cleaning roller and an enlarged view thereof.

[Explanation of symbols]

 1: image carrier (photosensitive drum) 2: side seal 3: cleaning blade 4: charged body (charging roller) 5: cleaning roller 6: developing means (developing roller or developing sleeve) 7: transfer roller 8: LED unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 21/10-21/12 G03G 15/00 550 G03G 21/16-21/18 G03G 15/02 103

Claims (2)

(57) [Claims] 1. A cleaning blade for removing powder developer on a drum by providing side seals at both ends in a blade longitudinal direction along a moving direction of an image carrier using an OPC drum, and a uniform cleaning blade on the image carrier. And a charging roller for charging.
In the image forming apparatus having the contact arrangement in order, a rotatable cleaning roller is arranged in contact with the charging roller, and the rotation of the cleaning roller causes deposits made of paper powder or powder toner captured from the charging roller side. the surface shape of the movable cleaning roller toward the Jikudan side from the center side, thereby forming by winding a fiber material or brush-like string-like body, the process of each in the direction perpendicular to the moving direction of the image carrier An image forming apparatus characterized in that the width of the recording medium and the recording medium are defined as in the following expression 1). A>B>C>D> E 1) A: width of the image carrier B: contact width of the cleaning blade with the image carrier C: width between the inner ends of the side seals D: contact width of the charging roller with the image carrier E: Maximum image forming area width 2. The image forming apparatus according to claim 1, wherein peripheral speeds of said cleaning roller and said charging roller are made different, and a peripheral speed ratio is set in a range of 1.1 to 1.5 .