JPH10228172A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the surface roughness of an image carrier at an allowable level and to restrain the lowering of image density and the irregularity of the image density by making the surface of a contact member shaving the surface of the image carrier the most, which comes in contact with the surface of the image carrier, the smoothest surface as compared with the surfaces of other contact members, which come in contact with the surface of the photoreceptor. SOLUTION: The surface of the photoreceptor 1 is often shaved by various members coming in contact therewith. It is shaved in a direction following the surface roughness of the smooth surface of the contact member shaving the surface of the photoreceptor 1 the most of the contact members, that is, the blade part 211 of the eletrifying member 21 of a holding and electrifying device 2. In such a case, the surface of the contact member shaving the surface of the photoreceptor 1 the most is made the smoothest surface as compared with the contact surfaces of other contact members. As a result, the surface of the photoreceptor 1 is uniformly shaved to such an extent that an adhesive discharge product or filmed toner on the surface thereof is removed, while the surface roughness of the photoreceptor 1 is restrained to such an extent that the deterioration of the image occuring because the degree of the irregular reflection of light gets large in the case of image exposure is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer, and more particularly to a method for transferring a visible toner image formed on an image carrier having a moving surface onto a transfer object. The present invention relates to a cleanerless electrophotographic image forming apparatus that removes toner remaining on an image carrier by another cleaning unit without using a dedicated cleaner for removing transfer residual toner.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus such as a copying machine or a printer, the surface of an image carrier is generally uniformly charged, and the charged area is subjected to image exposure in accordance with a document image or image data. Then, an electrostatic latent image is formed, and the latent image is developed to be a visible toner image. The visible toner image is immediately transferred to a transfer material such as transfer paper and fixed, or, as in a color image forming apparatus, transferred to an intermediate transfer member and transferred from the intermediate transfer member onto a transfer material. , May be established.

After transfer, the toner remaining on the image carrier is
Usually, it is removed by a dedicated cleaner, but today, instead of mounting the dedicated cleaner, other cleaning means, for example, a developing device also serves as a toner removing and collecting cleaner means, so-called cleanerless image forming. Devices have also been proposed. In such a cleanerless type image forming apparatus, a brush type charging member is often employed as a device for charging the image carrier prior to image exposure.
This is because the transfer residual toner is scattered by the brush-type charging member so that the toner does not cause inconvenience such as so-called exposure kick at the next image exposure for forming an electrostatic latent image.

[0004] Such a brush-type charging member is also used for shaving the surface of an image carrier. When the image carrier is an organic photoreceptor, when the image carrier is an organic photoreceptor, discharge products such as ozone resulting from discharge from a charging device adhere to the photoreceptor, absorb moisture by the deposit, and further absorb moisture. In order to avoid the disadvantage that the surface of the photoreceptor is made conductive by the above-mentioned process and the image exposure is not successfully performed due to the conductive process, it is required to remove such a discharge product. Also, regardless of whether the image carrier is an organic photoreceptor, since it is a cleanerless type, toner adheres to the surface of the image carrier and filming easily occurs, and when such a toner film is formed, Since image exposure cannot be performed well, it is required to appropriately cut the surface of the image carrier to avoid such a situation.

[0005]

However, in the conventional cleaner-less type image forming apparatus for shaving the surface of the image carrier, the shaved surface of the image carrier tends to have a large roughness. This tendency is large when shaving with a brush type charging member. If the surface roughness of the image carrier is too large, the image carrier surface irregularly reflects light during image exposure, and good image exposure is hindered. For example, in the case of an image forming apparatus that performs reversal development, the potential of a portion where toner is to be adhered is not sufficiently attenuated by exposure, and as a result, toner is insufficiently adhered to that portion, resulting in insufficient density of a final image. There is.

[0006] When the surface of the image carrier is shaved so as to be too large, the surface roughness of each part of the surface of the image carrier often becomes uneven, and when the surface roughness becomes uneven on the image carrier. This causes density unevenness in the final image.
In addition, it is easy to cause a situation where a part is cut deeply or not so much, and this may appear as streak noise in a final image.

Accordingly, the present invention relates to a cleanerless electrophotographic image forming apparatus which can maintain the roughness of the surface of an image carrier at an acceptable level, thereby suppressing image density reduction and image density unevenness. It is an object to provide a forming apparatus.

[0008]

An image forming apparatus according to the present invention for solving the above-mentioned problems is a cleanerless electrophotographic image forming apparatus, and includes a contact member arranged in contact with the surface of the image carrier. The surface of the contact member that best scrapes the surface of the image carrier, which is in contact with the surface of the image carrier, is the smoothest surface as compared with the surface of the other contact member that contacts the surface of the image carrier. And

Here, the cleanerless electrophotographic image forming apparatus refers to a toner image remaining on the image carrier after transferring a visible toner image formed on the image carrier to a transfer material. This is an image forming apparatus of a type that removes toner by using other cleaning means, for example, a development cleaning device that collects transfer residual toner simultaneously with the development of the electrostatic latent image, without using a dedicated cleaner for removing the toner.

According to the image forming apparatus of the present invention, the image carrier is uniformly charged prior to image exposure, and the image is exposed to the charged area to form an electrostatic latent image. The image is developed into a visible toner image, and the visible toner image is transferred to a transfer target such as a transfer material or an intermediate transfer member. In any case, finally, the visible toner image is transferred to a transfer material and fixed.

The transfer residual toner remaining on the image carrier after the visible toner image has been transferred to the transfer receiving body is cleaned by a cleaning means, for example, a development cleaning capable of collecting and removing the transfer residual toner simultaneously with the development of the electrostatic latent image. It is removed and collected by the device. Also, the surface of the image carrier is shaved by a member in contact with the image carrier,
When viewed as a whole, of the contact members, the contact member that best scrapes the surface of the image carrier is scraped in a direction according to the surface roughness of the smooth surface that comes into contact with the surface of the image carrier.

As a result, the surface of the image carrier is uniformly ground to the extent that the adhered discharge products, filmed toner and the like on the image carrier are removed, while the surface roughness of the image carrier is reduced. The surface roughness can be suppressed to such a level that the degree of irregular reflection of light upon exposure is not increased and the image density is not reduced. Thus, the shaving amount of each part of the surface of the image carrier can be made uniform to suppress the occurrence of image density unevenness, and the surface roughness of the image carrier can be maintained at a level at which the image density does not decrease due to irregular reflection on the surface of the image carrier. .

The contact member for shaving the surface of the image carrier best includes a contact member dedicated for shaving the surface of the image carrier, and a contact member for transferring a visible toner image to a transfer object in the moving direction of the surface of the image carrier. A transfer residual toner or the like, which is arranged between the transfer portion and the main charging device for charging the surface of the image carrier and has a polarity opposite to the polarity of the voltage applied to the main charging device, is applied to the main charging device. And an auxiliary charging member for charging to the same polarity as the voltage to be applied.

The image bearing member is not limited thereto, but a typical example is an organic photosensitive member. The surface roughness of the surface of the contact member that contacts the image carrier surface of the contact member that cuts the image carrier surface best is not limited thereto, but the surface roughness of the image carrier is suppressed to a level that does not cause a decrease in image density. For this reason, Rz can be set to about 5 μm or less, and the lower limit is not limited thereto, but the shaving amount is such that the adhered discharge products on the image carrier, the filmed toner, and the like are removed. In order to obtain, approximately 1 in Rz
It can be set to μm or more.

When the surface of the image carrier is scraped by the use of the image forming apparatus, the difference in the minute surface roughness of each part of the surface of the image carrier in the range of 30 μm in the image carrier surface direction is determined by the image exposure. In order to suppress diffuse reflection as much as possible, the smaller the better, the better, but not limited thereto.
・ It is good to keep it to 6 μm or less. Further, the surface roughness of the image carrier may be suppressed to 200 μm or more in Sm and 3 μm or less in Rz.

In any case, the contact member for best shaving the surface of the image carrier is a paper powder, a powder of a special coating material applied to the surface of the transfer paper, or a paste at or near the contact start position with the image carrier. If such a state continues to be caught by a foreign substance, such as this, the surface of the image carrier is cut in a streak shape, and as a result, streak-like image noise is likely to appear. Therefore, in order to quickly pass such foreign matter from between the contact member and the image carrier, the contact member that cuts the surface of the image carrier best is moved along the image carrier surface (for example, reciprocating motion). ) May be provided.
Due to the movement of the contact member by the member driving device, the foreign matter is embraced between the contact member and the image carrier and quickly passes.

In this case, in order to allow the foreign matter to pass through quickly and more reliably, the member driving device includes a contact member that cuts the surface of the image carrier best, and a contact member that contacts the image carrier with the contact member. It is preferable to reciprocate over a distance equal to or greater than the nip width. The form of the contact member for best shaving the surface of the image carrier is not particularly limited, but a representative example is a blade-like member.

Here, the blade-like member supports a blade portion directly contributing to the shaving of the surface of the image carrier with a support portion, and is generally blade-shaped, literally blade-shaped, sheet-shaped or sheet-shaped. Film-like materials are included. When a blade-like member is employed as a contact member for cutting the surface of the image carrier most, the blade-like member can be a flexible blade-like member having elastic restoring force. By applying and releasing the pressing force to the blade-like member,
A cam device having a cam capable of reciprocating the blade member along the surface of the image carrier by utilizing the elastic restoring force of the blade member; Provided with an electrostatic attraction force applying device capable of reciprocating the blade-like member along the surface of the image carrier by utilizing the elastic restoring force of the blade-like member by performing application and release of And a solenoid-type driving device capable of acting on the blade-shaped member to reciprocate the blade-shaped member along the surface of the image carrier.

In any case, the member driving device reciprocates a contact member that repeatedly cuts the surface of the image carrier best while the surface of the image carrier moves.
Timing outside of image formation, for example, timing of pre-operation of the image carrier before image formation, timing between images when forming several images, timing of post-operation of image carrier after image formation, etc. The image carrier is reciprocated by a contact member that cuts the surface of the image carrier best, the timing of a predetermined operation on the image forming apparatus, for example, the timing of opening and closing the outer cover of the printer body, the timing of replacing parts, and the like. A member that reciprocates a contact member that cuts the body surface best can be exemplified.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a schematic configuration of a laser beam printer that performs reversal development, which is an example of an image forming apparatus according to the present invention. In the laser beam printer, an image carrier having a thin film layer made of an organic photoconductive material (OPC) formed on the outer peripheral surface of a cylindrical body, that is, a drum-shaped organic photoconductor 1 is provided at a substantially central portion. The photoconductor 1 is negatively charged, and is rotationally driven in a direction indicated by an arrow a in the figure by a driving device (not shown).

An auxiliary charging device 2, a main charging device 3, a developing cleaning device 4, and a transfer roller 5 are sequentially arranged around the photoreceptor 1 along the rotation direction thereof, and a laser is provided behind the developing cleaning device 4. An image exposure device 6 using a beam is provided. Further, a paper feed cassette 7 is provided below the developing / cleaning device 4, and the transfer paper SH stored in the paper feed cassette 7 is provided.
Is pulled out by the paper feed roller 8 at a predetermined timing.

Transfer paper S pulled out of paper feed cassette 7
H is guided by a guide and conveyed to the timing roller pair 9. Further, a fixing roller pair 10 is disposed above the transfer roller 5, and a sheet discharging roller pair 11 and a sheet discharging tray 12 are provided following the fixing roller pair 10. In addition, a power supply 13 is provided at one corner at the bottom of the device.

The main charging device 3 includes a charging brush roller 31
The charging brush roller 31 includes a photosensitive member 1
In order to charge the surface of the photoreceptor prior to image exposure for forming an electrostatic latent image to be described later, the photoreceptor is rotationally driven by a driving device (not shown), and a predetermined voltage is supplied from the power supply 13. Applied. The voltage applied to the charging brush roller 31 may be a DC voltage having a constant value, or a voltage obtained by superimposing an AC component on the DC voltage. Although not limited thereto, here, -1350 [V] and-
A DC voltage of 300 [V] is alternately applied by switching operation of switching elements in the power supply. The application of such an alternating voltage makes it possible to uniformly charge the surface of the photoreceptor and significantly reduce charging unevenness as compared with the case where only a DC voltage is applied.

As shown in FIG. 2, the auxiliary charging device 2 includes a flexible blade-shaped charging member 21 and a charging member driving device 22 having elastic restoring force as a whole.
The blade-shaped charging member 21 includes a band-shaped blade portion 211 that is arranged in contact with the surface of the photoconductor 1 and a support portion 212 that supports the blade portion. The support portion 212 is a flexible leaf spring member having a high elastic restoring force. The downstream end in the photosensitive member surface moving direction a is cantilevered at a fixed position, and the blade portion 211 is attached to the upstream end. I support it. The blade portion 211 has a smooth surface 21 facing the photoconductor 1.
1a (see FIG. 3), a part of which is placed in contact with the surface of the photoconductor 1.

The blade section 211 has a resistance value of 10 here.
It is formed from a material in which carbon particles are dispersed in a styrene elastomer having a particle size of ⁴ to 10 ⁹ Ωcm. The surface roughness (Rz) of each part of the surface 211a of the blade part 211 facing the photoconductor 1
Is set to 5 μm or less and 1 μm or more.

As shown in FIGS. 1 and 2, the charging member driving device 22 includes a rotating cam 221 which contacts the support portion 212 of the charging member 21 from above and a mechanism 222 for interlocking the cam with the rotation of the photosensitive member. In. The cam 221 is formed by cutting off a part of the outer peripheral surface of a member having a circular cross section in parallel with the rotation center line of the cam to form a flat surface fs. The cam 221 is driven to rotate in conjunction with the rotation of the photosensitive member 1. Outer curved surface cs and flat surface fs
Can alternately contact the support portion 212.

The support portion 212 is pressed downward by contact of the outer peripheral curved surface cs of the cam 221 with the support portion 212.
And the position shown in FIG. In the state shown in FIG. 3A, the blade portion 211 contacts the photoconductor at a downstream portion P1 in the surface movement direction a of the photoconductor 1, and a protruding portion 211x upstream of the blade portion 211 moves from the surface of the photoconductor 1 Separated. Further, when the cam 221 rotates and its flat surface fs comes into contact with the support portion 212, the support portion 212 is elastically restored and assumes the position shown in FIGS. 2B and 3B. FIG.
In the state shown in FIG. 4B, the blade 211 is
In the surface movement direction a of FIG. 3A, the portion P2 on the downstream side of the portion P1 comes into contact with the photoreceptor, and the protruding portion 211y further upstream thereof is the protruding portion 211 as shown in FIG.
The protrusion amount is larger than x.

That is, as the cam 221 rotates,
The blade-shaped charging member 21, or more specifically, the blade portion 211, reciprocates along the surface of the photoconductor, and the amount of protrusion from the contact portion with the photoconductor 1 changes. Further, the pressing force of the blade portion 211 against the photoconductor 1 also changes. In the state shown in FIG. 3B, the pressing force is weaker. Here, the one-way moving distance of the blade portion 211 is the blade portion 21 at the time of pressing the blade portion (in the state shown in FIG. 3A).
1 and the photoconductor 1 have a mutual nip width W or more.

A DC voltage of -1350 [V] is applied from the power source 13 to the charging member 21, more precisely, from the power source 13 to the blade portion 211. The role of the auxiliary charging device 2 will be described later. The developing / cleaning device 4 includes a hopper 41 that contains a negatively charged non-magnetic one-component toner T. The hopper 41 opens toward the photoreceptor 1, and has an arrow b in the drawing.
Sleeve 4 which is driven to rotate in the direction of
2, a rotating member 43 for supplying the toner T to the developing sleeve 42, and a stirring blade 44 for supplying the toner and preventing aggregation are provided in the hopper.

The developing sleeve 42 is provided with a toner T having a charge having the same polarity as the charged polarity of the photosensitive member 1 so that the toner T can be conveyed to the photosensitive member 1 in order to develop an electrostatic latent image described later. -100 [V] to -500 [V] (here -300 [V] from the power supply 13) such that an electric field in which the toner T travels from the developing sleeve 42 to the laser beam irradiation section (exposure section) on the photoconductor 1 is generated. ) Is applied. The rotating member of the developing cleaning device 4 is driven to rotate by a driving device (not shown).

The transfer voltage from the power source 13 to the transfer roller 5 is not limited to +1 [kV] to +5 [kV]. And, under the transfer voltage application,
The visible toner image on the photoconductor is electrostatically attracted to the transfer paper SH conveyed between the transfer roller 5 and the photoconductor 1, and can be transferred.

The laser device 6 irradiates the surface of the photosensitive member 1 located between the charging brush 31 and the developing / cleaning device 4 with a laser beam BM according to image information.
Thus, an electrostatic latent image is formed by generating a potential attenuating portion on the surface of the photoreceptor uniformly charged in advance. According to the laser beam printer described above, the photoreceptor 1 is driven to rotate during image formation, and the surface thereof is uniformly charged by the charging brush roller 31 under the influence of the charging by the auxiliary charging device 2. , Here -800
[V]. The charged area is exposed from the laser device 6 based on the image information to form an electrostatic latent image, and the electrostatic latent image is developed by the developing / cleaning device 4 to be a visible toner image. On the other hand, the transfer paper SH is pulled out of the paper supply cassette 7 by the paper supply roller 8 and conveyed to the timing roller pair 9 where the transfer paper SH is synchronized with the toner image on the photoconductor 1 and is transferred to the transfer roller 5 and the photoconductor 1. Is transferred to the transfer section. Thus, the visible toner image is transferred onto the transfer sheet SH by the transfer roller 5, and thereafter, the transfer sheet SH passes through the fixing roller pair 10 to fix the toner image thereon, and is discharged by the discharge roller pair 11. It is discharged onto the tray 12.

After the transfer, the untransferred toner remaining on the photoreceptor 1 includes a positively charged toner having a polarity opposite to the normal charge polarity due to the influence of the application of a positive voltage from the transfer roller 5 during the transfer. It is included. When this arrives at the charging brush roller 31 as it is, it adheres to the roller 31 to which the negative voltage is applied, hinders the charging of the photoconductor 1, and causes image problems such as black streaks and roughness in a halftone image. .

However, in this case, the transfer residual toner first reaches the auxiliary charging device 2 as the photosensitive member 1 rotates.
Here, a DC voltage of -1350 [V] is applied to the charging member 21 of the auxiliary charging device 2 as described above, and both the transfer residual toner passing therethrough while charging the photosensitive member surface are removed. In this example, the charge is performed to about -900 [V]. Thus, the transfer residual toner charged to the opposite polarity is charged to the regular negative polarity, and is prevented from adhering to the charging brush roller 31 arriving after that, so that the photosensitive member can be charged by the brush roller 31 without any trouble.

The transfer residual toner is charged by the charging brush roller 3.
1 so that the so-called exposure kick or the like at the time of exposure by the laser device 6 is suppressed. When image formation is not continued, the transfer residual toner goes to the developing / cleaning device 4 as it is, but when image formation is continued, the laser device 6 applies the next image information to the surface of the photoconductor 1 in which the residual toner is dispersed. The corresponding laser beam BM is irradiated. The potential of a portion irradiated with the laser (hereinafter, referred to as an image portion) is attenuated with respect to a portion not irradiated with the laser (hereinafter, referred to as a non-image portion), whereby a new electrostatic latent image is formed.

When the newly formed electrostatic latent image reaches the position of the developing sleeve 42 of the developing and cleaning device 4 as the photosensitive member 1 rotates, it is developed under a developing bias. At the same time as the development, the transfer residual toner T located in the non-image portion is electrostatically attracted to the developing sleeve 42 by the difference between the potential of the non-image portion and the developing bias potential, and is collected.

Further, as described above, the charging member driving device 22 of the auxiliary charging device 2 removes dirt on the blade portion 211 due to toner or the like attracted to the surface of the blade portion 211 by the Coulomb force because of the opposite polarity. As shown in (2), the blade portion 211 is reciprocated in the direction of movement of the photoconductor surface in conjunction with the rotation of the photoconductor, so that the surface of the photoconductor is rubbed and removed. That can be suppressed.

The surface of the photoreceptor 1 is shaved by various members that come into contact with it, but as a whole, of the contact members, the contact member that cuts the surface of the photoreceptor best, ie, in this case,
The auxiliary charging device 2 is ground in a direction according to the surface roughness of the smooth surface 211a of the blade portion 211 of the charging member 21 of the auxiliary charging device 2. As a result, the surface of the photoconductor 1 is uniformly ground to the extent that the adhered discharge products, filmed toner, and the like are removed, while the surface roughness of the photoconductor 1 is reduced during image exposure. The surface roughness can be suppressed to such an extent that the degree of irregular reflection of light does not increase and the image density does not decrease. Thus, the shaving amount of each part of the surface of the photoreceptor 1 can be made uniform to suppress the occurrence of image density unevenness, and the level of the photoreceptor 1 does not decrease due to irregular reflection on the surface of the photoreceptor 1.
Surface roughness can be maintained.

Also, foreign matter 100 such as paper powder, powder of a special coating material applied to the surface of the transfer paper, glue or the like at or near the position where the blade portion 211 of the charging member 21 comes into contact with the photosensitive member 1 (see FIG. 3). ) Continues to bite,
Due to this, the surface of the photoreceptor 1 is cut in a streak shape, and as a result, streak-like image noise tends to appear. Here, the blade portion 211 is reciprocated by the charging member driving device 22 as shown in FIG. Therefore, the foreign matter 100 is embraced between the blade portion 211 and the photoconductor 1 as the blade portion 211 reciprocates, and quickly passes therethrough. Also, the blade unit 211
The reciprocating drive is performed over a distance equal to or more than the contact nip width W with the photoreceptor 1 so that the foreign matter 100 can be passed quickly and more reliably.

FIG. 6 shows the relationship between the difference in surface roughness at each part of the surface of the photosensitive member 1 and the difference in image density based on the difference.
It is a graph showing an example, and it can be seen that by suppressing the difference in surface roughness described above on the surface of the photoconductor 1 to approximately 0.6 μm or less, the occurrence of image density unevenness can be suppressed to a level that does not hinder practical use. . Therefore, as described above, the charging member 21
The surface roughness of the surface 211a of the blade portion 211 contacting the photoreceptor 1 is 5 μm or less, but the difference in surface roughness due to the photoreceptor surface shaving accompanying use of the printer is approximately 0.6 μm.
m so that the surface 211a of the blade portion 211
Preferably, the surface roughness is determined.

In the above description, the charging member 21 is reciprocated relative to the photosensitive member in association with the rotation of the photosensitive member. However, the charging member 21 is driven at a timing other than the time of image formation, for example,
This may be performed at the timing of pre-rotation of the photoconductor before image formation, the timing between images when forming several images, the timing of post-rotation of the photoconductor after image formation, or a predetermined timing for the printer. Operation may be performed, for example, at the timing of opening and closing the outer cover of the printer main body, or at the timing of replacing parts.

Also, the photosensitive member 1 may be moved irregularly at a cycle in which the roughness of the surface can be suppressed to an acceptable level. The movement of the charging member 21 at such a timing can be performed, for example, by operating the charging member driving device 22 under the control of the control unit CONT that controls the operation of the entire printer.

In the charging device 2 described above, the charging member 21 is driven by a cam mechanism. However, as shown in FIG. 4, the charging member 21 may be reciprocated by a driving device 220 using a solenoid SOL. As shown, an AC voltage is applied to the charging member 21 from the AC power supply PW in the charging device 2, thereby changing the electrostatic attraction force to the photoreceptor 1 in accordance with the voltage application cycle, thereby causing the charging member 21 to vibrate. This may also remove dirt and allow foreign matter to pass through. However, in this case, the charging unit 211 is, for example, 10 ⁴ to 10 ⁹ Ω so that an electrostatic attraction force is generated.
cm of semiconductive material (carbon particles dispersed in styrene elastomer). Also, in this case,
The cam mechanism can be omitted.

Next, the relationship between the roughness of the surface of each contact member that comes into contact with the surface of the photoconductor 1 and the roughness (Sm and Rz) of the surface of the photoconductor 1 after shaving the photoconductor 1 and the surface roughness of the photoconductor 1 An experiment will be described in which a difference between the density of an image formed in the initial state without shaving and the density of the same image formed on the photoreceptor 1 after shaving is examined. Note that Rz is a 10-point average roughness. Sm is the distance between the peaks.

The experimental conditions are as follows. Charging brush roller 31: The pile forming the brush is 5 mm in length. The surface roughness of the developing sleeve 42 of the developing cleaning device 4 is Rz5.
μm Surface roughness of the surface 211 a of the blade portion 211 of the auxiliary charging device 2: Rz 1 μm Surface roughness of the transfer roller 5: Rz about 1 μm Order in which member cuts the photoconductor 1 most: Blade portion = transfer roller> Charging brush roller> developing sleeve These members were brought into contact with the surface of the photoconductor 1 alone or in combination of two or more, and the photoconductor 1 was rotated at a predetermined speed. The results are shown in Tables 1, 2 and 3 below.

In Tables 1 and 2, the “initial” column shows the initial state of the photoconductor 1, and the “durability” column shows the photoconductor 1 in Table 1 after rotating the photoconductor 1 by an amount corresponding to 20,000 sheets of image formation. , Table 2
Also indicates the roughness of the photoconductor surface after rotating the photoconductor 1 by an amount equivalent to 20,000 sheets of image formation, and the “density difference” indicates the density of the image formed when the photoconductor was in the initial state, and the density after endurance. The difference from the density of the same image formed by the photoreceptor is indicated by “濃度” when the image density difference is acceptable, and “X” when the image density difference is not acceptable.

From Tables 1 and 2, it is found that Sm is 200 μm or more, Rz is 3 μm or less, or Sm is 200 μm or less so that the unevenness at an acceptable level, ie, the Macbeth density as shown in FIG. , Rz is 0.6 in a measurement range of 30 μm in the circumferential direction of the photosensitive drum.
It can be said that the condition of μm or less should be satisfied. Table 3 shows the experimental results when the photoconductor (P / C) 1 already having a surface roughness was shaved with only the developing sleeve. The endurance is the rotation of the photoconductor equivalent to 20,000 sheets of image formation.

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

[Table 3]

[0051]

As described above, according to the present invention,
It is possible to provide an image forming apparatus of a cleanerless electrophotographic type, which can maintain the surface roughness of an image carrier at an allowable level, thereby suppressing a decrease in image density and uneven image density. .

[Brief description of the drawings]

FIG. 1 shows an example of an image forming apparatus according to the present invention (printer).
It is a figure which shows schematic structure of.

FIG. 2A is an enlarged side view of an auxiliary charging device in the printer of FIG. 1, showing a state where the charging member is located at one position, and FIG. The state where it is in another position is shown.

3A is a partially enlarged view of FIG. 2A, and FIG. 3B is a partially enlarged view of FIG. 2B.

FIG. 4 is a diagram showing another example of the auxiliary charging device.

FIG. 5 is a diagram showing still another example of the auxiliary charging device.

FIG. 6 is a graph showing an example of a relationship between a difference in surface roughness at each part of the photoconductor surface and an image density difference based on the difference.

[Explanation of symbols]

 Reference Signs List 1 photoconductor (image carrier) 2 auxiliary charging device 21 charging member (blade charging member) 211 blade portion 211a smooth surface 212 support portion 22 charging member driving device 221 rotating cam fs flat surface of cam 221 cs outer periphery of cam 221 Curved surface 222 Interlocking mechanism 100 Foreign object 3 Main charging device 31 Charging brush roller 4 Developing device 5 Transfer roller 6 Laser device 7 Paper cassette SH Transfer paper 8 Paper feed roller 9 Timing roller pair 10 Fixing roller pair 11 Paper discharging roller pair 12 Paper discharging Tray 13 Power supply CONT Control unit 20 Charging device 23 Cleaning blade 220 Charging member drive SOL Solenoid drive PW Alternating current (AC) power supply

Claims (14)

[Claims] An image forming apparatus of a cleanerless electrophotographic type, wherein a contact member, which is arranged in contact with the surface of an image carrier and which best scrapes the surface of the image carrier, is provided on the surface of the image carrier. An image forming apparatus characterized in that the contact surface is the smoothest surface as compared with the contact surface of another contact member on the surface of the image carrier. 2. The image bearing member according to claim 1, wherein said image bearing member is an organic photosensitive member.
The image forming apparatus as described in the above. 3. The surface roughness of the surface of the contact member for best shaving the surface of the image bearing member which is in contact with the surface of the image bearing member is 5 in Rz.
The image forming apparatus according to claim 1, wherein the thickness is set to μm or less. 4. The image bearing member has a surface roughness of 200 in Sm.
3. The structure according to claim 1, wherein Rm is not more than 3 μm.
Or the image forming apparatus according to 3. 5. An image carrier surface direction 3 of each part of the image carrier.
5. The image forming apparatus according to claim 1, wherein a difference in minute surface roughness in a range of 0 [mu] m is suppressed to 0.6 [mu] m or less. 6. An image according to claim 1, further comprising a member driving device capable of reciprocating a contact member for shaving the surface of the image carrier best along the surface of the image carrier. Forming equipment. 7. The image forming apparatus according to claim 6, wherein said member driving device reciprocates a contact member for shaving the surface of the image carrier best over a distance equal to or greater than a contact nip width between the contact member and the image carrier. apparatus. 8. The image forming apparatus according to claim 6, wherein the contact member for shaving the surface of the image carrier best is a blade-shaped member. 9. The blade-shaped member is a flexible blade-shaped member having an elastic restoring force, and the member driving device applies and releases a pressing force to the blade-shaped member, whereby the blade-shaped member is released. 9. The image forming apparatus according to claim 8, further comprising a cam device having a cam capable of reciprocating the blade-shaped member along the surface of the image carrier by using an elastic restoring force of the member. 10. The blade-like member is a flexible blade-like member having an elastic restoring force, and the member driving device comprises:
By applying and releasing the electrostatic attraction force to the blade-like member, the blade-like member can reciprocate along the surface of the image carrier using the elastic restoring force of the blade-like member. 9. The image forming apparatus according to claim 8, further comprising an electroadhesive force applying device. 11. The blade-like member is a flexible blade-like member having an elastic restoring force, and the member driving device comprises:
9. The image forming apparatus according to claim 8, further comprising a solenoid-type driving device that acts on the blade-shaped member to reciprocate the blade-shaped member along the surface of the image carrier. 12. The image forming apparatus according to claim 6, wherein the member driving device reciprocates a contact member that cuts the surface of the image carrier best while the surface of the image carrier is moving. Image forming apparatus. 13. An image forming apparatus according to claim 6, wherein said member driving device reciprocates a contact member which cuts the surface of said image carrier best at a time other than during image formation. . 14. The image forming apparatus according to claim 6, wherein said member driving device reciprocates a contact member which cuts the surface of the image carrier best at a predetermined operation timing of the image forming apparatus. Image forming device.