JP2006259036A - Image forming apparatus and cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a charging device in which the condition of contact between a charging roller and a photoreceptor is improved and image noise is prevented. <P>SOLUTION: The image forming apparatus has the charging roller, a cleaning blade, a primary transfer body and a developing unit, which are disposed around a photoreceptor. The charging roller is disposed vertically below the photoreceptor in close contact with the photoreceptor. A nip is formed between the charging roller and the photoreceptor by pressing both ends of the charging roller against the photoreceptor. In the image forming apparatus, a push-up member is disposed vertically below the charging roller almost along the entire length of the shaft of the charging roller in close contact with the charging roller. The pressing force applied to the charging roller by the middle part of the push-up member is greater than that by either end of the push-up member. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic image forming apparatus and a cartridge such as a copying machine, a printer, and a facsimile, and more particularly to an image forming apparatus and a cartridge in which the configuration of a charging roller of a charging device and a member that supports the charging roller is improved.

  Conventionally, as a configuration of a charging device in an image forming apparatus, there is an image forming apparatus described in Patent Document 1. In order to suppress charging unevenness caused by the vibration of the charging roller, a vibration preventing member is provided in contact with the charging roller, and the vibration preventing member extends over the entire image forming width. It is characterized by contacting.

  Further, as an image forming apparatus having another configuration, there is an image forming apparatus described in Patent Document 2. This is because an image forming apparatus having a contact / separation mechanism for contacting / separating the charging roller to / from a cleaning pad for cleaning the surface of the photosensitive member and the charging roller has a charging roller case for holding the cleaning pad in the contact / separation mechanism. A first pressurizing arm and a second pressurizing arm that pressurize both ends in the longitudinal direction, and a static elimination lamp holder having a pressurizing unit that pressurizes the central part are provided. The pressurization by the three points prevents the central portion of the charging roller case from being bent in a mountain shape, and the cleaning pad is brought into substantially uniform contact with the surface of the charging roller over the entire area in the longitudinal direction. It removes dirt on the surface.

  Further, as an image forming apparatus having another configuration, there is an image forming apparatus described in Patent Document 3. This is because the charging roller that presses against the photosensitive drum and performs a charging action is provided with a sponge member as a pressing member behind the central portion, and provided in a compressed state with the support member. Thus, the central portion of the charging roller can be pressed. The charging roller is provided with pressing springs at both ends of the shaft member so that the charging roller contacts the photosensitive drum with a predetermined pressing force. By disposing the pressing member with respect to the charging roller, it is possible to suppress an increase in charging noise due to the central portion of the charging roller being separated from the surface of the photosensitive drum.

  Further, as an image forming apparatus having another configuration, there is an image forming apparatus described in Patent Document 4. This is because a charging roller is arranged opposite to the photosensitive drum, and a black developing device is arranged in contact with the downstream side of the charging roller in the rotation direction of the photosensitive drum to form a black visible image and remain. The toner is removed. The charging roller is disposed vertically below the photoreceptor.

Further, as an image forming apparatus having another configuration, there is an image forming apparatus described in Patent Document 5. This is provided with a charging roller for charging the photosensitive member while being driven to rotate while being pressed against the photosensitive member, and a cleaning member for cleaning the charging roller by being pressed against the charging roller, and the cleaning member contacts the charging roller. And a charging roller case for holding the charging roller and the cleaning member, and a direction in which the charging roller is separated from the cleaning member. A biasing means for biasing; and a pressing means for pressing the cleaning member against the charging roller, pressing the charging roller in a direction pressing against the photosensitive member, and changing the pressing force. In the charging mode for charging the photosensitive member, the pressing means is applied by the urging force of the urging means. The charging roller is pressed with a pressing force that presses against the photoconductor, and in the cleaning mode, the pressing means resists the urging force of the urging means, the cleaning member is applied to the charging roller, and the charging roller is applied to the photoconductor. It is characterized by being pressed with a pressing force that presses together.
JP 2002-91139 A JP-A-9-90841 JP-A-7-199595 JP-A-5-249796 Japanese Patent Laid-Open No. 10-3200

However, in the charging device in the image forming apparatus described above, when the charging roller is below the photoconductor, the nip force with which the charging roller presses the photoconductor is pressure-contacted using the influence of the self-weight of the charging roller and the end of the charging roller. By applying force, the charging roller bends and the pressure for pushing up the photosensitive member does not become uniform in the axial direction, and the pressure tends to decrease in the central portion compared to the end portion. Depending on this pressure difference, the charging property that the charging roller gives to the photoconductor is different. Thus, there is a problem in that background stains occur in a portion having low chargeability, resulting in an image having a darker density than usual.
SUMMARY An advantage of some aspects of the invention is to provide an image forming apparatus and a cartridge including a charging device that improves the contact state between a charging roller and a photosensitive member and does not generate image noise.

  In order to solve the above-mentioned problems, the invention of claim 1 is arranged such that a charging roller, a cleaning blade, a primary transfer member, and a developing device are arranged around the photosensitive member, and the charging roller is closely attached to the lower side in the vertical direction of the photosensitive member. In the image forming apparatus in which both ends of the charging roller are pressed toward the photoconductor to form a nip with the photoconductor, the charging roller is vertically below the charging roller. A push-up member is arranged in close contact with the charging roller over substantially the entire area in the axial direction, and the central portion of the push-up member has a higher pressing force to the charging roller than the end portion.

  According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a charging roller, a cleaning blade, a primary transfer member, and two developing devices are disposed around the photosensitive member.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the push-up member also serves as a charging roller cleaning unit.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the push-up member is fixed to a holder.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the portion of the push-up member fixed to the holder that contacts the charging roller is any one of a nonwoven fabric, a film, and a malt plane. .

  According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the push-up member is constituted by a rotating member, and is rotated by being driven by the charging roller.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the portion of the push-up member that contacts the charging roller is any one of a nonwoven fabric, rubber, and metal.

  According to an eighth aspect of the present invention, a charging roller, a cleaning blade, a primary transfer member, and a developing device are disposed around the photosensitive member, the charging roller is disposed in close contact with the photosensitive member in the vertical direction, and the charging member is disposed. In an image forming apparatus that forms a nip with the photosensitive member by pressing both end portions of the roller toward the photosensitive member, the roller is pushed up only in the axially central portion below the charging roller in the vertical direction. The member is arranged in close contact with the charging roller.

  According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, a charging roller, a cleaning blade, a primary transfer member, and two developing devices are disposed around the photosensitive member.

  According to a tenth aspect of the present invention, in the image forming apparatus according to the eighth or ninth aspect, the push-up member also serves as a cleaning unit for the charging roller.

  According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the eighth to tenth aspects, the push-up member is fixed to a holder.

  According to a twelfth aspect of the present invention, in the image forming apparatus according to the eleventh aspect, the portion of the push-up member fixed to the holder that contacts the charging roller is any one of a nonwoven fabric, a film, and a malt plane. .

  According to a thirteenth aspect of the present invention, in the image forming apparatus according to any one of the eighth to twelfth aspects, the push-up member is constituted by a rotating member, and is rotated by being driven by the charging roller.

  According to a fourteenth aspect of the present invention, in the image forming apparatus according to the thirteenth aspect, the portion of the push-up member that contacts the charging roller is any one of a nonwoven fabric, rubber, and metal.

  A fifteenth aspect of the present invention is a cartridge mounted on the image forming apparatus according to any one of the first to fourteenth aspects, and includes the photosensitive member, a charging roller, a push-up member, a cleaning blade, and one or two developing devices. It is characterized by that.

  As described above, according to the image forming apparatus of the present invention, since the push-up member pushes the center portion stronger than the end portion, there is no background stain image, and there is no density difference in the axial direction even in the halftone image. A good image is obtained.

  Further, according to the image forming apparatus of the present invention, since the push-up member pushes up only the central portion, there is no background stain image, and a good image with no density difference in the axial direction can be obtained even in a halftone image.

  Further, according to the cartridge of the present invention, since the cartridge is constituted by the photosensitive member, the charging roller, the push-up member, the cleaning blade, and one or two developing devices, the parts are inspected, repaired, handled and replaced. Operation becomes easy.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an outline of a color image forming apparatus in which two image forming units in which two developing devices are arranged on the periphery of an image bearing member, and the developing device and the image bearing member are mounted on the main body of the image forming device. Shows the unit installed. The main part of this color image forming apparatus will be described with reference to FIG. Four developing units 31 (31a, 31b, 31c, 31d) each containing toner of a different color as a developer, and an image carrier drum 22 arranged in combination with two of these developing units 31. (22a, 22b).

  Around this image carrier drum 22, there are cleaning blades 23 (23a, 23b) for scraping the residual toner after the primary transfer, and a toner transport screw 24 (24a) for transporting the scraped toner to a waste toner bottle (not shown). 24b) are provided with charging rollers 21 (21a, 21b) that come into contact with the drum 22, and constitute an image carrier unit 20 (20a, 20b) in which these are integrated. As will be described later, the housing of this image carrier unit is configured to be able to incorporate a developing device.

  In addition, there is an intermediate transfer unit including an intermediate transfer belt 28 that circulates around a driving roller 26, a driven roller 27, and primary transfer rollers 29 (29a, 29b) that are in contact with each other. Reference numeral 36 (36a, 36b) denotes a laser beam for exposing the photosensitive member. A negative bias voltage in which alternating current and direct current are superimposed is applied to a cored bar of the developing roller 32 of each developing device 31 from a bias power source (not shown). Also, a DC negative potential bias voltage is applied to each charging roller 21 from another bias power source.

  One image carrier drum 22a combined with the two developing devices 31a and 31b, the cleaning blade 23a in contact with the image carrier drum 22a, and the charging roller 21a form a first image forming unit. Similarly, one image carrier drum 22b combined with the two developing devices 31c and 31d, the cleaning blade 23b contacting the image carrier drum 22b, and the charging roller 21b form a second image forming unit. Yes.

  Next, the operation will be described. The cleaning blade 23a cleans toner stains remaining on the peripheral surface of the image carrier drum 22a. The charging roller 21a is initialized by charging the peripheral surface of the cleaned image carrier drum 22a to a uniform high potential. Then, the laser beam 36a is applied to the image carrier drum 22a of the first image forming unit. The image carrier drum 22b of the second image forming unit is irradiated with a laser beam 36b. As a result, the peripheral surface of the image carrier drum 22a charged to the uniform high potential is selectively exposed based on the image data, and the low potential portion where the potential is attenuated by this exposure and the high potential due to the initialization. An electrostatic latent image consisting of a portion is formed.

  The developing device 31a forms (develops) a toner image by transferring toner to the low potential portion (or high potential portion) of the electrostatic latent image. The image carrier drum 22 a rotates and conveys the toner image and transfers it to the intermediate transfer belt 28. The second image forming unit operates in the same manner as described above in accordance with the timing at which the toner image on the intermediate transfer belt 28 comes into contact with the image carrier drum 22b. The electrostatic latent image on 22b is converted into a toner image (development), and the image carrier drum 22b rotates and conveys the toner image and superimposes and transfers the toner image on the intermediate transfer belt 28.

  Subsequently, the intermediate transfer belt 28 circulates and the first image forming unit operates again in accordance with the timing at which the above-transferred toner image comes into contact with the image carrier drum 22a. The apparatus 31b converts the electrostatic latent image on the image carrier drum 22a into a toner image, and the image carrier drum 22a rotates and conveys the toner image to further superimpose the toner image on the intermediate transfer belt 28. Transcript. Finally, the second image forming unit operates again in accordance with the timing at which the triple transferred toner image on the intermediate transfer belt 28 comes into contact with the image carrier drum 22b. 31d converts the electrostatic latent image on the image carrier drum 22b into a toner image, and the image carrier drum 22b rotates and conveys the toner image to further superimpose and transfer the toner image onto the triple toner image on the intermediate transfer belt 28. The intermediate transfer belt 28 onto which the four color toner images have been transferred is continuously circulated to convey the quadruple toner image, and the toner image is transferred onto the paper P by the secondary transfer roller 39.

  Next, the characteristics and various settings of the roller charging and push-up member used in this embodiment will be described. In the embodiment, the charging roller has an elastic portion and is subjected to surface layer processing. The core metal diameter has a lower limit of φ3 and the upper limit is not particularly limited. However, considering the charging roller, it is about φ20, this time it is φ6, and the rubber part is about 10 mm at most from 0.5 mm thickness to 0.5-3 mm, and this time it is 2 mm thickness. The outer diameter of the roller is about φ5 to φ20, and this time is φ10. Rubber hardness is 50-75 ° (JIS-A), surface treatment is covered with coating, tubes, etc. The surface treatment is performed for the purpose of surface treatment because silicon contained in the rubber is not exposed or volatilized. And

  In addition, as a feature of the charging roller used this time, it is conductive, and its resistance value (when DC 100 V is applied) is about 10 4 to 10 7, and this time, 10 6 is used. The roller was crown-shaped and its amount was about 200 μm at the maximum, and this time it was 50 μm. In the embodiment, after the setup, the charging roller is always urged to contact the photoconductor. If the charging roller and the photosensitive member are kept in contact until setup, the portion in contact with the photosensitive member is deformed, and the charging roller has a non-uniform cycle. For this reason, it is desirable to evacuate until setup. Similarly, when the main body power is turned off for a long period of time, it is desirable that the charging roller and the photosensitive member be separated from each other. A spring is used for contact with the photosensitive member, and the force is about 1.5 to 8N (both sides), and this time is 3N.

  In the embodiment, the charging roller is driven to rotate by pressure contact with the photosensitive member. This is driven rotation for cost reduction. It is also possible to provide a gear on the charging roller so that the drive source is separate from the photoreceptor. In the embodiment, a DC bias is applied to the charging roller during image formation. This time, it is set with a bias of only DC (−1100 ± 200V). The applied bias is (electrically) connected to the charging roller via a conductive bearing. Note that there is no problem even if DC + AC is used. Rather, the charging property itself suppresses uneven charging due to local resistance villages of the conductive rubber and improves uniformity.

  In this embodiment, when the charging roller is below the photoconductor, an image is printed by pressing the end of the charging roller toward the photoconductor axis, and the background portion is shifted from the end in the axial direction to the center. Towards, the dirt on the background worsened. The background stain was measured using a color difference meter (CR-241 manufactured by MINOLTA) and L * was measured. The background stain was determined as noise on the image when L * was 86 or less. In the halftone portion of the printed pattern, the density increased from the end in the axial direction toward the center. The reflection density (manufactured by X-Rite) was used for the measurement. As the measurement conditions, a print pattern or each bias setting of the engine was set so that the average density in the axial direction was 0.3, and when the density at the center was 10% or more higher than the edge, it was determined that the image was defective.

  In this embodiment, the following four patterns were implemented. When 1 is a charging roller only, when 2 is a push-up member is pushed up uniformly in the axial direction below the charge roller, and when 3 is a push-up member is under the charge roller, the push-up pressure is at the center in the axial direction from the end. 4 is a case where there is a push-up member at the lower part of the charging roller as 4 and the push-up member is 100 mm at the center and the push-up pressure is higher at the center in the axial direction than at the end.

  As a result, as shown in FIG. 4, with respect to the background stain, as shown in FIG. Moreover, although the conventional example of the pattern 2 did not have 86 or less, background stain | pollution | contamination worsened in the center part compared with the edge part. On the other hand, the first embodiment of the pattern 3 achieves 90 to 91 in the entire axial direction, and the second embodiment of the pattern 4 also has the same range of 90 to 91, which can be sufficiently improved as compared with the conventional example. It was. Regarding the halftone density, as shown in FIG. 5, a density difference of 20% or more occurred in the conventional examples of patterns 1 and 2 with respect to the reflection density value of 0.3. On the other hand, in Examples 1 and 2 of Patterns 3 and 4, the density difference was within 5%, and sufficient improvement was achieved compared to the conventional example.

  Hereinafter, Examples 1 and 2 will be described. In the first embodiment, as shown in FIG. 2, the holder is positioned below the charging roller (there is a gap with the roller), and the nonwoven fabric, film, and malt plane are attached to the holder. Here, the holder has substantially the same length as the charging roller in the axial direction, and the gap between the holder and the roller is narrow at the center in the axial direction and wide at the end. When a non-woven fabric is attached to the holder (the non-woven fabric and the holder are attached with a double-sided tape or the like), the non-woven fabric comes into contact with the charging roller, and the non-woven fabric is slightly crushed by contact to form a nip with the charging roller.

  The nip width can be up to 7 mm, but is preferably around 3 mm. The gap between the holder and the charging roller is adjusted in advance so that the nip width is substantially constant in the axial direction. The charging roller used this time was 80 g, and the total nip pressure between the nonwoven fabric and the charging roller was 100 gf. Uniformity could be secured from the total pressure of 40 gf, and the upper limit was 400 gf. The direction of 40 to 400 gf is the same as the direction in which the charging roller presses the photoreceptor. If the charging roller is within ± 10 ° with the direction in which the photosensitive member is pressed, uniformity can be ensured without any problem. In addition, the nonwoven fabric used this time is Clarino (7600-10-0000 and 0279L45-7000, manufactured by Kuraray), and other alternatives are Exeine (manufactured by Toray), GLORE (manufactured by Mitsubishi Rayon), QE (manufactured by Asahi Kasei). Etc.

  When the member that pushes up the charging roller is a film, one end of the film is attached to the holder, and the vicinity of the other end is brought into contact with the charging roller while being bent. By using this contact pressure, the same effect as the nonwoven fabric is obtained. Specifically, the film was a pet film, a polyimide film, and the thickness was 75 μm to 500 μm. In this case as well, the holder shape needs to be determined so that the length from the end of the holder to the contact portion is shorter in order for the central portion to increase the contact pressure than the end portion. The total pressure to be pushed up is equivalent to the above.

  When the member that pushes up the charging roller is malt plain, as in the case of non-woven fabric, when the malt plane is attached to the holder (the malt plane and the holder are attached with double-sided tape, etc.) The plane is crushed by contact and forms a nip with the charging roller. The nip width can be up to 7 mm, but is preferably around 3 mm. The gap between the holder and the charging roller is adjusted in advance so that the nip width is substantially constant in the axial direction. The charging roller used this time was 80 g, and the total nip pressure between the nonwoven fabric and the charging roller was 100 gf. Uniformity could be secured from the total pressure of 40 gf, and the upper limit was 400 gf. In addition, the non-woven fabric, film, and malt plain can contact the charging roller to wipe off toner or toner external additives attached to the charging roller, and also serves as a mechanical charging roller cleaning means. .

  Next, a case where a rotating body is disposed under the charging roller and uniformity is ensured by utilizing contact with the rotating body will be described. The axis of the rotating body is substantially on the extension line (within ± 10 °) between the photosensitive member and the charging roller axis. In addition, the rotating body does not have any driving means and contacts the charging roller to rotate following the charging roller. In addition, the rotating body has a crown shape in the axial direction. The crown shape is used to contact the charging roller, and the pressure contact at the center portion is higher than the pressure contact at the end portion. 40-400 gf. Moreover, the surface layer of a rotary body is a nonwoven fabric, rubber | gum, or a metal, and in the case of a nonwoven fabric and rubber | gum, it serves as a cleaning means similarly to the above. Since the cleaning means is also used in this way, it is possible to remove the toner and the toner external additive from the charging roller. The nonwoven fabric is the same as described above.

  In Example 2, as shown in FIG. 3, the holder is located at the lower part of the charging roller (there is a gap with the roller), and the same effect can be obtained even in the axial direction about 100 mm (50 mm to 150 mm) at the center of the charging roller. In contact with the charging roller. A nonwoven fabric, a film, and a malt plane can be attached to the holder. When a non-woven fabric is attached to the holder (the non-woven fabric and the holder are attached with a double-sided tape or the like), the non-woven fabric comes into contact with the charging roller, and the non-woven fabric is slightly crushed by contact to form a nip with the charging roller.

  The nip width can be up to 7 mm, but is preferably around 3 mm. The gap between the holder and the charging roller is adjusted in advance so that the nip width is substantially constant in the axial direction. The charging roller used this time had a weight of 80 g, and the total nip pressure between the nonwoven fabric and the charging roller was 50 gf. Uniformity could be ensured from the total pressure of 30 gf, and the upper limit was 150 gf. The direction of 30 to 150 gf is the same as the direction in which the charging roller presses the photoreceptor. In addition, if the charging roller is within a range of ± 10 ° from the direction in which the photosensitive member is pressed, uniformity can be ensured without any problem. In addition, the nonwoven fabric used this time is Clarino (7600-10-0000 and 0279L45-7000, manufactured by Kuraray). Etc.

  When the member that pushes up the charging roller is a film, one end of the film is attached to the holder, and the vicinity of the other end is brought into contact with the charging roller while being bent. By using this contact pressure, the same effect as the nonwoven fabric is obtained. Specifically, the film is a pet film, a polyimide film, and the thickness is 75 μm to 500 μm. The total pressure to be pushed up is equivalent to the above. When the member that pushes up the charging roller is malt plain, when the malt plane is attached to the holder as in the case of non-woven fabric (the malt plane and the holder are attached with double-sided tape, etc.), the malt plane comes into contact with the charging roller, Is crushed by contact and forms a nip with the charging roller. The nip width can be up to 7 mm, but is preferably around 3 mm.

  The gap between the holder and the charging roller is adjusted in advance so that the nip width is substantially constant in the axial direction. The charging roller used this time had a weight of 80 g, and the total nip pressure between the nonwoven fabric and the charging roller was 50 gf. Uniformity could be ensured from the total pressure of 30 gf, and the upper limit was 150 gf. In addition, the above non-woven fabric, film, and malt plain contact with the charging roller can wipe off the toner or toner external additives attached to the charging roller only at the center, but the mechanical charging roller Also serves as a cleaning means. Since the cleaning means is also used in this way, it is possible to remove the toner and the toner external additive from the charging roller. Table 1 shows the results of comparison of the cleaning effect depending on the presence or absence of these push-up members and the type of push-up member.

  Next, a case where a rotating body is disposed under the charging roller and uniformity is ensured by utilizing contact with the rotating body will be described. The axis of the rotating body is substantially on the extension line (within ± 10 °) between the photosensitive member and the charging roller axis. The rotating body is in contact with the charging roller at a central portion of 100 mm (the same effect can be obtained from 50 mm to 150 mm), and is driven to rotate by being driven by the charging roller in contact with the charging roller. Further, the rotating body has a straight shape in the axial direction, and the uniformity is ensured by press-contacting only at the central portion. The total pressure at this time is 30 to 150 gf. The surface layer of the rotator is a nonwoven fabric, rubber, or metal. In the case of a nonwoven fabric or rubber, it also serves as a cleaning means although it is only the central portion as described above. The nonwoven fabric is the same as described above.

  Further, when referring to the cartridge form, the cartridge form is not particularly defined in the embodiment, but there are no side effects and no problem when each component is made into the cartridge form. It seems that it is preferable to use a cartridge in an actual machine. As for the bias, although the application bias of the charging roller has been described as DC in the present embodiment, it may be AC (+ DC). The settings for AC (+ DC) are AC: 1 to 2.5 kV and DC: −100 to −600 V.

  The present invention can be used for an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile machine including a photosensitive member and a charging roller.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to the present invention. FIG. 3 is an explanatory diagram of a photoconductor and a charging roller portion showing Embodiment 1. FIG. 6 is an explanatory diagram of a photoconductor and a charging roller portion showing Embodiment 2. It is the graph which compared the background dirt. It is the graph which compared the halftone.

Explanation of symbols

20, 20a, 20b Image carrier units 21, 21a, 21b Charging rollers 22, 22a, 22b Image carrier drums 23, 23a, 23b Cleaning blades 24, 24a, 24b Toner conveying screw 26 Drive roller 27 Drive roller 28 Intermediate transfer belt 29, 29a, 29b Primary transfer rollers 31, 31a, 31b, 31c, 31d Developing device 32 Developing rollers 36, 36a, 36b Laser beam 39 Secondary transfer roller P Paper

Claims (15)

A charging roller, a cleaning blade, a primary transfer member, and a developing device are disposed around the photosensitive member, the charging roller is disposed in close contact with the photosensitive member in the vertical direction, and both ends of the charging roller are disposed on the photosensitive member. In an image forming apparatus that forms a nip with the photoreceptor by pressing toward the body side,
A push-up member is arranged in close contact with the charging roller in the vertical direction below the charging roller and substantially in the entire axial direction of the charging roller, and the central portion of the pushing member has a pressing force on the charging roller as compared with the end portion. An image forming apparatus characterized by being expensive. The image forming apparatus according to claim 1.
An image forming apparatus, wherein a charging roller, a cleaning blade, a primary transfer member, and two developing devices are disposed around the photosensitive member. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the push-up member also serves as a cleaning unit for the charging roller. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus, wherein the push-up member is fixed to a holder. The image forming apparatus according to claim 4.
The image forming apparatus according to claim 1, wherein a portion of the push-up member fixed to the holder that contacts the charging roller is one of a nonwoven fabric, a film, and a malt plane. The image forming apparatus according to claim 1,
2. The image forming apparatus according to claim 1, wherein the push-up member is constituted by a rotating member and is rotated by following the charging roller. The image forming apparatus according to claim 6.
The image forming apparatus according to claim 1, wherein a portion of the push-up member that contacts the charging roller is one of a nonwoven fabric, rubber, and metal. A charging roller, a cleaning blade, a primary transfer member, and a developing device are disposed around the photosensitive member, the charging roller is disposed in close contact with the photosensitive member in the vertical direction, and both ends of the charging roller are disposed on the photosensitive member. In an image forming apparatus that forms a nip with the photoreceptor by pressing toward the body side,
An image forming apparatus, wherein a push-up member is disposed in close contact with the charging roller only in a central portion in an axial direction of the charging roller, which is vertically below the charging roller. The image forming apparatus according to claim 8.
An image forming apparatus, wherein a charging roller, a cleaning blade, a primary transfer member, and two developing devices are disposed around the photosensitive member. The image forming apparatus according to claim 8 or 9, wherein
The image forming apparatus, wherein the push-up member also serves as a cleaning unit for the charging roller. The image forming apparatus according to claim 8,
The image forming apparatus, wherein the push-up member is fixed to a holder. The image forming apparatus according to claim 11.
The image forming apparatus according to claim 1, wherein the portion of the push-up member fixed to the holder that contacts the charging roller is one of a nonwoven fabric, a film, and a malt plane. The image forming apparatus according to claim 8,
2. The image forming apparatus according to claim 1, wherein the push-up member is constituted by a rotating member and is rotated by following the charging roller. The image forming apparatus according to claim 13.
The image forming apparatus according to claim 1, wherein a portion of the push-up member that contacts the charging roller is one of a nonwoven fabric, rubber, and metal. A cartridge mounted on the image forming apparatus according to claim 1,
A cartridge comprising the photosensitive member, a charging roller, a push-up member, a cleaning blade, and one or two developing devices.

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