JP2007017954A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability of a charging roller while suppressing an optical record device from being contaminated by an extraneous material such as toner which floats or toner which is attached to the charging roller when charging the image carrier by the charging roller. <P>SOLUTION: The charging roller 3a faces a photosensitive body 2 at a predetermined charging gap G and charges the photosensitive body 2 in a non-contact state. The rotation center 3a<SB>1</SB>of the charging roller 3a is lower than a horizontal line α passing through the rotation center 2a of the photosensitive body 2 and located at a downstream side in the rotation direction of the photosensitive body 102 than the horizontal line α. In this case, the rotation center 3a<SB>1</SB>of the charging roller 3a is located at an upstream side in the rotation direction of the photosensitive body 2 just below the rotation center 2a of the photosensitive body 102. A cleaning member 3b for cleaning the charging roller 3a in close contact with the charging roller 3a is disposed so as to be rotatable. The rotation center 3b<SB>1</SB>of the cleaning member 3b is located below a horizontal line β passing through the rotation center 3a<SB>1</SB>of the charging roller 3a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technical field of an image forming apparatus configured to perform non-contact charging on an image carrier with a charging roller in an image forming apparatus such as an electrophotographic, electrostatic copying machine, printer, or facsimile. A charging roller, an optical writing device, and a developing roller device are sequentially arranged around the rotating image carrier, toward the downstream side in the rotation direction of the image carrier, and a cleaning member pressed against the charging roller. The present invention relates to a technical field of an image forming apparatus configured to clean the charging roller.

Conventionally, as an image forming apparatus such as an electrophotography, an electrostatic copying machine, a printer, and a facsimile, a charging roller, an optical writing device, and a developing roller device are disposed on the downstream side in the rotation direction of the image carrier around the rotating image carrier. There is known an image forming apparatus sequentially arranged toward the front (see, for example, Patent Document 1). The image forming apparatus disclosed in Patent Document 1 rotates the contact-type charging brush in the same direction as the photoreceptor while contacting the photoreceptor (the circumferential speed direction of the photoreceptor and the circumferential speed direction of the contact-type charging brush). (Reverse direction) Charge the photoconductor uniformly, write an electrostatic latent image on the photoconductor with an optical writing device, and develop the electrostatic latent image on the photoconductor with toner conveyed by the developing roller. Is supposed to form.
JP 2004-66758 A.

  By the way, in the image forming apparatus disclosed in Patent Document 1, the optical writing device is located below the contact position of the contact-type charging brush with the photoconductor (charge position of the photoconductor by the contact-type charging brush). Foreign matter such as toner remaining after transfer is separated from the photosensitive member by contact with the contact charging brush and floats in the apparatus or adheres to the contact charging brush. Then, although the optical writing device is soiled by the foreign matter that floats, it can be put to practical use, but there is a possibility that a high-quality image cannot be obtained over a long period of time. Further, since the circumferential speed direction of the photoconductor and the circumferential speed direction of the contact-type charging brush are opposite to each other, it is conceivable that the floating of the foreign matter becomes more remarkable. In addition, it is considered that it is difficult to perform good charging over a long period of time due to foreign matters adhering to the contact-type charging brush, and the durability of the contact-type charging brush is impaired.

  The present invention has been made in view of such circumstances, and an object of the present invention is to detect light by foreign matters such as toner floating when the image carrier is charged by the charging roller and foreign matters such as toner adhering to the charging roller. An object of the present invention is to provide an image forming apparatus capable of improving the durability of a charging roller while suppressing contamination of a writing device as much as possible.

  In order to solve the above-described problems, an image forming apparatus according to a first aspect of the present invention includes a charging device including a charging roller, an optical writing device, and a developing device including a developing roller around a rotating image carrier. In the image forming apparatus arranged in this order toward the downstream side in the rotation direction of the image carrier, the charging roller performs non-contact charging with a predetermined charging gap with respect to the image carrier. And the rotation center of the charging roller is located below the horizontal line passing through the rotation center of the image carrier and downstream of the horizontal line in the rotation direction of the image carrier, and further the rotation center of the image carrier. A cleaning member is provided on the upstream side in the rotational direction of the image carrier from directly below. The cleaning member is pressed against the charging roller and cleans the charging roller. It is characterized in that the rotational center of the training member is provided below the horizontal line passing through the center of rotation of the charging roller.

According to a second aspect of the present invention, the rotation direction of the charging roller is set to be opposite to the rotation direction of the image carrier, and the rotation direction of the cleaning member is opposite to the rotation direction of the charging roller. It is characterized by being set.
Further, the invention according to claim 3 is characterized in that the peripheral speed of the charging roller and the peripheral speed of the image carrier are set to be the same or substantially the same (peripheral speed ratio is 1 or substantially 1).

    Furthermore, in the invention of claim 4, a straight line connecting the rotation center of the charging roller and the rotation center of the image carrier and a straight line connecting the rotation center of the charging roller and the rotation center of the cleaning member intersect each other. It is characterized by being set to.

  According to the image forming apparatus of the present invention configured as described above, the cleaning member is positioned below the horizontal line passing through the rotation center of the charging roller, that is, the cleaning member is disposed below the charging roller in the direction of gravity. Therefore, when the cleaning member scrapes off the foreign matter such as toner on the charging roller, the scraped foreign matter can be naturally dropped downward. As a result, the foreign matter such as the scraped toner does not travel toward the optical writing device, and it is difficult for such foreign matter to adhere to the optical writing device, and stable image formation can be realized in the long term. it can. In particular, since the charging roller performs non-contact charging with respect to the image carrier, the floating of foreign matter from the image carrier during non-contact charging is suppressed, so that contamination of the optical writing device can be more effectively suppressed.

  In particular, according to the second aspect of the present invention, the image carrier and the charging roller are rotated in the opposite directions, the cleaning member and the charging roller are rotated in the opposite directions, and the optical writing device is moved from the charging roller. Since it is disposed downstream of the image carrier in the rotation direction, foreign matters such as toner scraped off from the cleaning member by the charging roller can be advanced to the side opposite to the optical writing device side. Therefore, it is possible to prevent foreign matters such as toner floating on the optical writing device side from being moved by the cleaning member as a wall. This makes it difficult for such foreign matter to adhere to the optical writing device more effectively, and it is possible to realize stable image formation over a long period of time.

  According to the third aspect of the present invention, the peripheral speed of the charging roller and the peripheral speed of the image carrier are set to be the same or substantially the same (peripheral speed ratio is 1 or approximately 1). Can be made difficult to occur, and adhesion of foreign matter to the optical writing device can be further suppressed. Furthermore, since the peripheral speed of the cleaning member and the peripheral speed of the charging roller are set to be the same or substantially the same (peripheral speed ratio is 1 or approximately 1), it is possible to make it difficult for foreign matters such as toner to float. Adherence of foreign matter to the optical writing device can be further effectively suppressed.

  Further, according to the invention of claim 4, the straight line connecting the rotation center of the charging roller and the rotation center of the image carrier and the straight line connecting the rotation center of the charging roller and the rotation center of the cleaning member intersect each other. Therefore, the influence of the pressing force of the cleaning member on the charging roller on the proximity distance between the charging roller and the image carrier can be suppressed. Thereby, even when the cleaning member is brought into pressure contact with the charging roller, the charging gap can be stably set over the entire charging region over a long period of time.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram schematically illustrating an example of an embodiment of an image forming apparatus according to the present invention.

  As shown in FIG. 1, the image forming apparatus 1 of this example includes a photoconductor 2 that is an image carrier on which an electrostatic latent image and a toner image are formed, and the photoconductor 2 is provided around the photoconductor 2. The non-contact charging device 3, the optical writing device 4, the developing device 5, the transfer device 6, and the cleaning device 7 are arranged in order from the upstream side to the downstream side in the rotation direction (clockwise in FIG. 1). I have.

The charging device 3 includes a charging roller 3a that is not in contact with the photoreceptor 2 and a cleaning member 3b that is in pressure contact with the charging roller 3a. The rotation center 3a ₁ of the charging roller 3a is located below the horizontal line α passing through the rotation center 2a of the photosensitive member 2 and downstream of the horizontal line α in the rotation direction of the photosensitive member 2. In that case, the rotation center 3a ₁ of the charging roller 3a is provided upstream of the rotation center 2a of the photosensitive member 2 in the rotation direction of the photosensitive member 2.

That is, the rotation center 3a ₁ of the charging roller 3a is set at a position of an angle P (°) in the rotation direction of the photosensitive member 2 from the horizontal line portion α _{1 of the} horizontal line α where the rotation direction of the photosensitive member 2 is downward. Yes. The rotation center 3a ₁ of the charging roller 3a is not set at a position where the angle P is 90 ° or more. This is because if the rotation center 3a ₁ of the charging roller 3a is set at a position where the angle P is 90 ° or more, the space between the developing device 5 and the charging roller 3a becomes narrow, and it becomes difficult to install the optical writing device 4. This is because the installed optical writing device 4 is positioned directly below or substantially below the developing roller 5a, so that foreign matter such as toner dropped from the developing roller 5a may contaminate the optical writing device 4. Therefore, in the present invention, the charging roller 3a is set in a range of 0 ° <angle P <90 °.

Further, the rotational center 3b ₁ of the cleaning member 3b is located upstream in the rotational direction of the charging roller than β downwards a and the horizontal line from the horizontal line β passing through the rotation center 3a ₁ of the charge roller 3a. That is, the rotation center 3b ₁ of the cleaning member 3b is opposite to the rotation direction of the charging roller 3a from the horizontal line portion β _{1 in} which the rotation direction of the charging roller 3a is upward in the horizontal line β passing through the rotation center 3a ₁ of the charging roller 3a. It is set at a position of an angle C (°) in the direction. The rotation center 3b ₁ of the cleaning member 3b needs to be provided so as not to interfere with the photoreceptor 2 and the optical writing device 4.

  In this way, the charging roller 3a and the cleaning member 3b are both disposed below the photoconductor 2 in the direction of gravity, and the cleaning member 3b is further disposed below the charging roller 3a in the direction of gravity. .

The position angle P (°) of the rotation center 3a ₁ of the charging roller 3a and the position angle C (°) of the rotation center 3b ₁ of the cleaning member 3b are set to be different from each other. In other words, such that the straight line connecting the charging roller 3a rotation center 3a ₁ of the straight line connecting the rotation center 2a of the photoconductor 2 and the charging roller 3a rotational center 3b ₁ of the rotation center 3a ₁ and the cleaning member 3b of the cross each other Is set to

  In this example, the charging roller 3 a rotates in a direction that rotates with the rotation of the photosensitive member 2 in a state where insulating layers 3 j and 3 k for setting a charging gap G described later are in contact with the photosensitive member 2. Therefore, the rotation direction of the charging roller 3a is opposite to the rotation direction of the photosensitive member 2 (counterclockwise in FIG. 1). Further, the cleaning member 3b is configured to rotate in a direction that rotates with the rotation of the charging roller 3a by being in pressure contact with the charging roller 3a. Therefore, the rotation direction of the cleaning member 3b is opposite to the rotation direction of the charging roller 3a (clockwise in FIG. 1; the same direction as the photoconductor 2).

  In this case, in this specification, the rotation direction of the cleaning member 7 in the rotation direction is defined as the forward direction. In this example, the forward direction of the charging roller 3a is counterclockwise, and the forward direction of the cleaning member 3b is clockwise. Around. Further, due to the rotation, the peripheral speed of the charging roller 3a and the peripheral speed of the photosensitive member 2 are set to be the same or substantially the same (that is, the peripheral speed ratio is 1 or approximately 1), and the peripheral speed of the cleaning member 3b is set. The circumferential speed of the charging roller 3a is set to be the same or substantially the same (that is, the circumferential speed ratio is 1 or substantially 1).

  The charging roller 3a uniformly charges the photoreceptor 2 in a non-contact manner, and the cleaning member 3b cleans the charging roller 3a to remove foreign matters such as toner and dust attached to the charging roller 3a.

  As shown in FIG. 2A, the non-contact charging roller 3a includes a cored bar 3c, and the cored bar 3c is configured as a conductive shaft having conductivity, such as a metal shaft. As this conductive shaft, for example, a SUM 22 surface with Ni plating can be used.

  On the outer peripheral surface of both ends of the cored bar 3c, annular recesses 3d and 3e are formed, respectively. A conductive layer 3g is formed on the outer peripheral surface of the center portion 3f of the cored bar 3c inside these depressions 3d and 3e by applying a conductive coating material by, for example, spray coating. In that case, the conductive coating material also penetrates into both the depressions 3d and 3e and partially covers the portions where the depressions 3d and 3e of the cored bar 3c are formed. The conductive layer 3g constitutes a charging unit that performs non-contact charging with respect to the photoreceptor 2 with a predetermined charging gap G.

  Insulating layers 3j and 3k are formed on the outer peripheral surfaces of both end portions 3h and 3i of the cored bar 3c outside the recesses 3d and 3e by spray coating an insulating coating material, for example. In that case, the insulative coating material also penetrates into both depressions 3d and 3e to partially cover the formation portions of both depressions 3d and 3e of the cored bar 3c and also cover both end surfaces of the cored bar 3c. . The outer diameters of these insulating layers 3j and 3k are set to be equal to each other. The thicknesses of both insulating layers 3j and 3k are set larger than the thickness of the conductive layer 3g. Therefore, these insulating layers 3j and 3k constitute a gap portion that is in contact with the photoreceptor 2 and sets a predetermined charging gap G based on the difference in film thickness between the conductive layer 3g and the photoreceptor 2. is doing. Thus, the insulating layers 3j and 3k as gap members are formed on the outer peripheral surface (surface) of the cored bar 3c.

Then, the depth t ₁ of the 3d recess as shown in FIG. 2 (b), is set larger than the sum of the thickness t ₂ of the conductive layer 3g with a thickness t ₃ of the insulating layer 3j [t ₁ > (T ₂ + t ₃ )]. Accordingly, the depth t ₁ of the recess 3d is set to be larger than both the film thickness t ₂ of the conductive layer 3g and the film thickness t ₃ of the insulating layer 3j (t ₁ > t ₂ , t ₁ > t ₃ , t ₃ > T ₂ ).
In addition, the edges forming the recess 3d of the cored bar 3C are all chamfered (C cut) c. Further, the edge of the end 3h of the cored bar 3c is also chamfered (C cut) c. These chamfers c are usually referred to as R portions, and the edge portions are cut and rounded with curved surfaces. Of course, the chamfer c can also be formed by cutting the edge with a flat inclined surface.

2B shows the depression 3d and the insulating layer 3j on the one end 3h side, the depression 3e and the insulating layer 3k on the other end 3i side are also shown on the end 3h side. It is formed in the same manner as the recess 3d and the insulating layer 3j.
Regardless of the order of forming the conductive layer 3g and the two insulating layers 3j, 3k on the cored bar 3c, the two insulating layers 3j, 3k may be formed after the conductive layer 3g is formed first, or vice versa. Good.

  As the cleaning member 3b, a known member can be used. For example, the cleaning member 3b can be constituted by a cleaning roller such as an insulating sponge, a conductive sponge, an insulating brush, or a conductive brush. In this case, the biting depth d between the cleaning member 3b and the charging roller 3a by pressure contact is set to a predetermined value (for example, 0.5 mm) corresponding to the image forming apparatus 1.

The optical writing device 4 is provided below the horizontal line α and writes an electrostatic latent image on the photosensitive member 2 by, for example, laser light. The developing device 5 includes a developing roller 5a, a toner supply roller 5b, and a toner layer thickness regulating member 5c. The rotation center 5a ₁ of the developing roller 5a is located below the horizontal line α in the image forming apparatus ₁ of this example. The setting position of the rotation center 5a ₁ of the developing roller 5a is not limited to this.

  The toner T, which is a developer, is supplied onto the developing roller 5a by the toner supply roller 5b, and the toner T on the developing roller 5a is regulated in thickness by the toner layer thickness regulating member 5c. The electrostatic latent image on the photoconductor 2 is developed with the conveyed toner T, and a toner image is formed on the photoconductor 2.

Further, the closest portion 3m of the charging roller 3a to the photosensitive member 2 connects the closest portion 5a ₂ of the developing roller 5a to the photosensitive member ₂ (the rotational center 5a ₁ of the developing roller 5a and the rotational center 2a of the photosensitive member 2). It is arranged below in the direction of gravity from the outer peripheral portion of the developing roller 5a where the straight lines intersect.

  In the image forming apparatus 1 of this example, the image carrier 2, the charging device 3, and the optical writing device 4 are integrated and configured as an image carrier cartridge in the same manner as the image forming apparatus disclosed in Patent Document 1 described above. Has been. Further, including the developing device 5, the image carrier 2, the charging device 3, the optical writing device 4, and the developing device 5 can be integrated to form an image forming cartridge.

  The transfer device 6 has a transfer roller 6a, and a toner image is transferred onto the photosensitive member 2 by the transfer roller 6a onto a transfer medium 8 such as transfer paper or an intermediate transfer medium. When the toner image is transferred to the transfer paper that is the transfer medium 8, the toner image on the transfer paper is fixed by a fixing device (not shown), an image is formed on the transfer paper, and the toner image is transferred to the transfer medium 8. When the toner image is transferred to the intermediate transfer medium, the toner image on the intermediate transfer medium is further transferred to the transfer paper, and then the toner image on the transfer paper is fixed by a fixing device (not shown) to form an image on the transfer paper. Is done.

  The cleaning device 7 includes a cleaning member 7a such as a cleaning blade. The photosensitive member 2 is cleaned by the cleaning member 7a, and the transfer residual toner on the photosensitive member 2 is removed and collected.

According to the image forming apparatus 1 of this embodiment configured as described above, is positioned below a horizontal line cleaning member 3b passing through the rotation center 3a ₁ of the charging roller 3a, i.e., a cleaning member 3b to the charging roller 3a Since the cleaning member 3b scrapes off foreign matter such as toner on the charging roller 3a, the scraped foreign matter can be naturally dropped downward. As a result, the foreign matter such as toner scraped off does not travel toward the optical writing device 4, and it is difficult for such foreign matter to adhere to the optical writing device 4, thereby realizing stable image formation over the long term. be able to. In particular, since the charging roller 3a performs non-contact charging with respect to the photoconductor 2, floating of foreign matters such as toner from the photoconductor 2 at the time of non-contact charging is suppressed, so that contamination of the optical writing device 4 is more effective. Can be suppressed.

  Further, the photosensitive member 2 and the charging roller 3a are rotated in opposite directions, the cleaning member 3b and the charging roller 3a are rotated in opposite directions, and the optical writing device 4 is moved from the charging roller 3a to the photosensitive member 2. Since it is arranged on the downstream side in the rotation direction, foreign matters such as toner scraped off from the cleaning member 3b by the charging roller 3a can be advanced to the side opposite to the optical writing device 4 side, and furthermore, scraped off. It is possible to prevent foreign substances such as floating toner from proceeding to the optical writing device 4 side with the cleaning member 3b serving as a wall. As a result, it becomes difficult for such foreign matter to adhere to the optical writing device 4 more effectively, and stable image formation can be realized over a long period of time.

  Further, since the peripheral speed of the charging roller 3a and the peripheral speed of the photosensitive member are set to be the same or substantially the same (peripheral speed ratio is 1 or approximately 1), it is possible to make it difficult for foreign matters such as toner to float. Adhesion to foreign matter on the optical writing device 4 can be further effectively suppressed. Furthermore, since the peripheral speed of the cleaning member 3b and the peripheral speed of the charging roller 3a are set to be the same or substantially the same (peripheral speed ratio is 1 or approximately 1), it is difficult to cause foreign matters such as toner to float. It is possible to suppress the adhesion of foreign matter to the optical writing device 4 more effectively.

Furthermore, cross a straight line connecting the charging roller 3a rotation center 3a ₁ of the rotation center 2a of the photosensitive member 2, and a straight line connecting the rotational center 3b ₁ of the rotation center 3a ₁ and the cleaning member 3b of the charging roller 3a to each other Therefore, the influence of the pressing force of the cleaning member 3b on the charging roller 3a on the proximity distance between the charging roller 3a and the photoreceptor 2 can be suppressed. Thus, even when the cleaning member 3b is brought into pressure contact with the charging roller 3a, the charging gap G can be stably set over the entire charging region over a long period of time.

Next, examples and comparative examples of the non-contact charging roller of the present invention will be described. The image forming apparatuses of the examples belonging to the present invention and the comparative examples not belonging to the present invention were produced, and using these image forming apparatuses, it was demonstrated that the image forming apparatus of the present invention can obtain the above-described effects. An experiment conducted for this purpose will be described.
Table 1 shows the charging roller and the cleaning member of the image forming apparatus and the experimental results in the examples and comparative examples used in the experiment.

  In Table 1, Nos. 1-4, 6-9, 11, 12, 14, and 19 are examples of the present invention, and Nos. 5, 10, 13, 15-18, and 20-23. These are comparative examples of the present invention. The charging roller is as shown in FIGS. 2A and 2B, and the unit of the shaft diameter of the cored bar 3c (the diameter φ of the portion of the cored bar 3c where the conductive layer 3g is formed) is mm. The film thickness of the conductive layer 3g is 15 μm, and the film thickness of the insulating layers 3j and 3k, that is, the charging gap G is 20 μm. In Table 1, P45 ° means that the angle P is 45 °, and C90 ° means that the angle C is 90 °.

The shaft diameter of the cored bar (the diameter of the portion where the conductive layer 3g of the cored bar 3c is formed) of each example charging roller is φ8 mm. As the core 3c, a SUM 22 surface with Ni plating was used. All the depressions formed in the cored bar were set to 100 μm.
The conductive coating material and the insulating coating material shown in Table 2 were used.

As shown in Table 2, the conductive coating material is a coating liquid in which conductive SnO ₂ is mixed with 19 wt% (wt%), polyurethane (PU) resin is 18 wt%, ionic conductive material is 3 wt%, and water is 60 wt%. It is. Conductive SnO ₂ is available from Gemco Co., Ltd. shown in Table 3. Details of those are available on the Gemco website (http://www.jemco-mmc.co.jp/corporate/index.html). It is posted.

The conductive SnO ₂ used in this example and this comparative example is trade name “T-1” of Gemco Co., Ltd., and “T-1” is a tin-antimony oxide. Of course, other conductive SnO ₂ can be used in the present invention.
In addition, the ion conductive material is for imparting conductivity to the conductive coating material, and the ion conductive material used in this example and this comparative example is “YP-12” (manufactured by Maruhishi Oil Chemical Co., Ltd.). ).
Moreover, the insulating coating material painted on the gap portion is 100 wt% of polyurethane (PU) resin.

  In the charging roller manufacturing method of each example, for the charging rollers of Nos. 1 to 3, 10 to 13, and 16, an insulating coating material is first applied to both ends of the core metal by spray coating. After forming the conductive layer, the conductive coating material was then applied to the central portion of the core metal by spray coating to form a conductive layer.

  The cleaning member was formed as a cleaning roller made of any of an insulating sponge, a conductive sponge, an insulating brush, and a conductive brush. Each of these cleaning rollers has a diameter of φ12 ± 0.2 mm. The insulating sponge is made of polyurethane, the conductive sponge is made of conductive polyurethane, the insulating brush is made of polyester, and the conductive brush is made of conductive polyester.

  The photosensitive material is the same material as LP-9000C manufactured by Seiko Epson Corporation, and the thickness of each photosensitive layer is set to 23 μm. The unit of diameter φ of the photosensitive member in Table 1 is mm. The peripheral speed of the body was set to 250 mm / sec.

The experimental apparatus of the image forming apparatus was configured by modifying the LP-9000C so as to have the same configuration as the LP-9000C described above. The applied voltage V _C (V) of the charging roller 3a is obtained by superimposing the _AC voltage AC component V _AC (V) on the DC voltage DC component V _DC (V),
V _C = V _DC + V _AC = −650 + (1/2) V _PP · sin2πft
(Here, V _PP = 1800 V, f = 1.5 kHz, and V _AC is a sin wave.)
Set to. In the experiment, in a room environment at a temperature of 23 ° C. and a humidity of 50%, a solid printing of 25% halftone on A4 plain paper was performed, and a monochrome durability test of 10k (10000) sheets was performed.
In the comparative examples of Nos. 17, 20, and 21, the rotation direction of the cleaning member is set to the rotation direction (counter-forward direction) opposite to the rotation direction of the charging roller. The charging roller is set in the following direction (forward direction).

  An image with a good image quality obtained by visual inspection and a determination that the optical writing device 4 is not contaminated is indicated by a circle, and an optical writing device 4 that is contaminated is determined to be defective. Expressed in

In each of Examples Nos. 1-4, 6-9, 11, 12, 14, and 19, the experimental results are all good, and the optical writing device is not smudged even when printing 10k sheets. An image of good quality was obtained. On the other hand, each of the comparative examples of Nos. 5, 10, 13, 15-18, and 20-23 has an experimental result of “x”, and the optical writing device becomes dirty within less than 1000 prints. The image quality was poor.
From this experiment, it was proved that the above-described effect of the present invention can be obtained by the image forming apparatus 1 of the present invention that performs non-contact charging of the photoreceptor 2 by the charging roller 3.

The image forming apparatus of the present invention includes:
The present invention relates to an image forming apparatus configured to perform non-contact charging with respect to an image carrier with a charging roller in an image forming apparatus such as an electrophotography, an electrostatic copying machine, a printer, and a facsimile machine. Around the image carrier, a charging roller, an optical writing device, and a developing roller device are sequentially disposed toward the downstream side in the rotation direction of the image carrier, and the charging roller is provided by a cleaning member that is pressed against the charging roller. Can be suitably used for an image forming apparatus that is designed to be cleaned.

1 is a diagram schematically illustrating an example of an embodiment of an image forming apparatus according to the present invention. FIG. 2 shows an example of a charging roller used in the image forming apparatus of the present invention, where (a) is a sectional view along the axial direction, and (b) is a partially enlarged sectional view in (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Photoconductor, 3 ... Non-contact charging device, 3a ... Charging roller, 3b ... Cleaning member, 4 ... Optical writing device, 5 ... Developing device, 5a ... Developing roller, (alpha), (beta) ... Horizontal line

Claims (4)

An image in which a charging device including a charging roller, an optical writing device, and a developing device including a developing roller are arranged in this order around the rotating image carrier toward the downstream side in the rotation direction of the image carrier. In the forming device,
The charging roller is a charging roller that performs non-contact charging with a predetermined charging gap with respect to the image carrier,
The rotation center of the charging roller is located below a horizontal line passing through the rotation center of the image carrier and downstream of the horizontal line in the rotation direction of the image carrier, and further from the position directly below the rotation center of the image carrier. It is provided upstream of the rotation direction of the carrier,
A cleaning member that is pressed against the charging roller to clean the charging roller is rotatably provided, and the rotation center of the cleaning member is provided below a horizontal line passing through the rotation center of the charging roller. An image forming apparatus.   The rotation direction of the charging roller is set to be opposite to the rotation direction of the image carrier, and the rotation direction of the cleaning member is set to be opposite to the rotation direction of the charging roller. The image forming apparatus according to claim 1.   3. The image forming apparatus according to claim 2, wherein a peripheral speed of the charging roller and a peripheral speed of the image carrier are set to be the same or substantially the same (peripheral speed ratio is 1 or approximately 1).   The straight line connecting the rotation center of the charging roller and the rotation center of the image carrier and the straight line connecting the rotation center of the charging roller and the rotation center of the cleaning member are set to intersect each other. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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