JP6233118B2 - Charging device, image forming unit, and image forming apparatus - Google Patents

Description

  The present invention relates to a charging device, an image forming unit, and an image forming apparatus.

  Patent Document 1 discloses a charging device that reverses a DC bias applied to a charging roller during a cleaning sequence to an image forming operation (image formation) in order to remove contaminants attached to the outer peripheral surface of the charging roller. Is described.

Japanese Patent Laid-Open No. 11-174784

  An object of the present invention is to effectively remove foreign matters attached to the outer peripheral surface of a charging member in a configuration using a cleaning member in which an elastic member protrudes from the entire side surface of a shaft.

  The charging device according to claim 1 is in contact with an image carrier that rotates or circulates at a determined peripheral speed, and the rotational force of the image carrier is transmitted, and a load that suppresses the rotation is applied to rotate and stop. And charging the outer peripheral surface of the image holding member, and a charging member satisfying the formula (1) when the average peripheral velocity is Vb and the peripheral velocity of the image holding member is Vp, is rotatably supported. And an elastically deformable elasticity that protrudes from the entire side surface of the shaft when viewed from the axial direction of the shaft and that is inclined with respect to the shaft and arranged at a plurality of distances in the axial direction when viewed from the radial direction of the shaft A cleaning member that contacts the outer peripheral surface of the charging member and rotates while following the charging member to clean the outer peripheral surface of the charging member. .

0.3 ≦ (Vb / Vp) ≦ 0.8 Expression (1)
An image forming unit according to a second aspect is formed on the outer peripheral surface of the image holding member and the charging device according to claim 1 for charging the outer peripheral surface of the image holding member with a charging member. And a developing device for developing the electrostatic latent image as an image.

  An image forming apparatus according to a third aspect is formed on the outer peripheral surface of the image holding member and the charging device according to claim 1, wherein the outer peripheral surface of the image holding member is charged by a charging member. A developing device that develops the electrostatic latent image as an image; and a transfer member that transfers the image developed on the outer peripheral surface of the image carrier to a recording medium.

  According to the charging device of the first aspect, the elastic member adheres to the outer peripheral surface of the charging member in the configuration using the cleaning member that protrudes from the entire side surface of the shaft as compared with the case where the charging member does not repeat rotation and stop. The removed foreign matter can be effectively removed.

  According to the image forming unit of the second aspect, as compared with the case where the charging device according to the first aspect is not provided, charging failure of the image carrier caused by the foreign matter attached to the outer peripheral surface of the charging member is suppressed. be able to.

  According to the image forming apparatus of the third aspect, as compared with the case where the charging device according to the first aspect is not provided, it is possible to suppress the quality defect of the output image caused by the foreign matter attached to the outer peripheral surface of the charging member. Can do.

1 is a side view showing a charging device and an image carrier according to an embodiment of the present invention. (A) (B) (C) (D) It is process drawing used in explaining the cleaning process of a charging member in the charging device which concerns on embodiment of this invention. It is drawing which showed the evaluation result of the Example of the charging device which concerns on embodiment of this invention, and a comparative example with the table | surface. It is the perspective view which showed the charging member and supporting member of the charging device which concern on embodiment of this invention. 1 is a front view showing a charging device and an image carrier according to an embodiment of the present invention. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention.

  An example of a charging device, an image forming unit, and an image forming apparatus according to an embodiment of the present invention will be described with reference to FIGS. In addition, arrow UP shown in a figure shows the vertical direction upper direction.

(overall structure)
As shown in FIG. 6, an image processing unit 12 that performs image processing on input image data is provided inside the main body 10 </ b> A of the image forming apparatus 10.

  The image processing unit 12 processes input image data into gradation data of four colors of yellow (Y), magenta (M), cyan (C), and black (K). An exposure device 14 that receives the processed gradation data and performs image exposure with the laser beam LB is provided on the center side in the main body 10A.

  Above the exposure device 14, four image forming units 16Y, 16M, 16C, and 16K of yellow (Y), magenta (M), cyan (C), and black (K) are arranged in the horizontal direction (left and right in the figure). (Direction). When there is no need to distinguish between Y, M, C, and K, Y, M, C, and K may be omitted.

  These four image forming units 16Y, 16M, 16C, and 16K are all configured similarly. Each image forming unit 16 includes a cylindrical image holder 18 that is rotationally driven at a predetermined speed, and a charging member 20 for primary charging that charges the outer peripheral surface of the image holder 18. ing. Further, each image forming unit 16 develops the electrostatic latent image formed on the outer peripheral surface of the image carrier 18 charged by the image exposure of the exposure device 14 described above with toner of a predetermined color, and generates a toner image. As shown in FIG. Each image forming unit 16 includes a cleaning blade 24 that cleans the outer peripheral surface of the image carrier 18. Further, a cleaning member 64 that cleans the outer peripheral surface of the charging member 20 by contacting and rotating with the rotating charging member 20 to clean the outer peripheral surface of the charging member 20 is provided below the charging member 20. .

  The charging member 20 and the cleaning member 64 constitute a charging device 70, and details of the charging device 70 will be described later.

  The exposure device 14 is provided with four semiconductor lasers (not shown) that are configured in common to the four image forming units 16Y, 16M, 16C, and 16K. The laser beams LB-Y, LB-M, LB-C, and LB-K are emitted from these semiconductor lasers according to the gradation data.

  The laser beams LB-Y, LB-M, LB-C, and LB-K emitted from the semiconductor laser are irradiated to a polygon mirror 26, which is a rotating polygon mirror, through an f-θ lens (not shown). The mirror 26 is deflected and scanned. The laser beams LB-Y, LB-M, LB-C, and LB-K deflected and scanned by the polygon mirror 26 pass through the imaging lens (not shown) and a plurality of mirrors on the image carrier 18. The exposure point is scanned and exposed from obliquely below.

  Further, since this exposure device 14 scans and exposes an image on the image carrier 18 from below, this exposure device 14 includes four image forming units 16Y, 16M, 16C, and 16K positioned above. There is a risk that toner or the like may fall from the developing device 22 or the like. Therefore, the periphery of the exposure device 14 is sealed by a rectangular parallelepiped frame 28. In addition, on the upper portion of the frame 28, four laser beams LB-Y, LB-M, LB-C, and LB-K are directed onto the image carriers 18 of the image forming units 16Y, 16M, 16C, and 16K. And transparent glass windows 30Y, 30M, 30C, and 30K are provided.

  On the other hand, a primary transfer unit 21 is provided above the image forming units 16Y, 16M, 16C, and 16K. The primary transfer unit 21 has an endless intermediate transfer belt 32, an intermediate transfer belt 32 wound around, a driving roll 40 that rotates and rotates the intermediate transfer belt 32 in the direction of the arrow, and an intermediate transfer belt 32 is wound. The image bearing members 18Y, 18M, 18C, and 18K are sandwiched between the tension applying roll 36 that applies tension to the intermediate transfer belt 32, the cleaning blade 38 that cleans the outer peripheral surface of the intermediate transfer belt 32, and the intermediate transfer belt 32. Primary transfer rolls 34Y, 34M, 34C, and 34K disposed on the opposite side.

  The four primary transfer rolls 34Y, 34M, 34C, and 34K cause the toner images of the respective colors that are sequentially formed on the image carrier 18 of the image forming units 16Y, 16M, 16C, and 16K on the intermediate transfer belt 32. In this configuration, multiple transfer is performed.

  A secondary transfer roll 42 (an example of a transfer member) is provided on the opposite side of the drive roll 40 across the intermediate transfer belt 32. The toner images of each color transferred onto the intermediate transfer belt 32 in a multiple manner are conveyed by the intermediate transfer belt 32, sandwiched between the drive roll 40 and the secondary transfer roll 42, and conveyed along the paper conveyance path 56. Secondary transfer is performed on a sheet member P as a medium.

  Further, on the downstream side in the conveyance direction of the sheet member P with respect to the secondary transfer roll 42 (hereinafter simply referred to as “the downstream side in the conveyance direction”), the toner image transferred to the sheet member P is heated and pressed by the sheet member. A fixing device 44 for fixing to P is provided.

  Further, on the downstream side of the fixing device 44 in the conveyance direction, a discharge roll 46 that discharges the sheet member P on which the toner image is fixed to a discharge portion 48 provided on the upper portion of the main body 10A of the image forming apparatus 10 is provided.

  On the other hand, a sheet feeding member 50 on which the sheet members P are stacked is provided on the lower side in the main body 10 </ b> A of the image forming apparatus 10. Further, a sheet feeding roll 52 for feeding the sheet members P stacked on the sheet feeding member 50 to the sheet conveying path 56 is provided, and the sheet members P are separated one by one on the downstream side in the conveying direction of the sheet feeding roll 52. Separating roll 54 is provided. Further, an alignment roll 58 for adjusting the conveyance timing is provided on the downstream side of the separation roll 54 in the conveyance direction. Thus, the sheet member P supplied from the sheet feeding member 50 is moved to a position (secondary transfer position) where the intermediate transfer belt 32 and the secondary transfer roll 42 are in contact with each other by the alignment roll 58 that rotates at a predetermined timing. It is configured to be sent out.

  Further, next to the discharge roll 46, the sheet member P on which the image is fixed on the surface by the fixing device 44 is transported to the double-side transport path 62 without being discharged directly onto the discharge portion 48 by the discharge roll 46. A roll 60 is provided. As a result, the sheet member P conveyed along the double-sided conveyance path 62 is conveyed again to the alignment roll 58 with the front and back sides reversed, and this time, the toner image is transferred to the back surface of the sheet member P. It is fixed and discharged onto the discharge unit 48.

(Operation of the overall configuration)
With this configuration, an image is formed on the sheet member P as follows.

  First, the gradation data of each color is sequentially output from the image processing unit 12 to the exposure device 14, and the laser light of each color emitted from the exposure device 14 according to the gradation data is charged by the charging member 20. 18 is exposed to scanning on the outer peripheral surface. Then, an electrostatic latent image is formed on the outer peripheral surface of the image carrier 18. The electrostatic latent images formed on the image holding member 18 are yellow (Y), magenta (M), cyan (C), and black (K) toners by developing devices 22Y, 22M, 22C, and 22K, respectively. Visualized as an image.

  Further, the toner images of the respective colors formed on the image holding member 18 are circulated on the rotating intermediate transfer belt 32 by the primary transfer roll 34 of the primary transfer unit 21 disposed over the image forming units 16 of the respective colors. Multiple transcriptions are made.

  In addition, the toner images of the respective colors transferred in multiple on the intermediate transfer belt 32 are secondly transferred to the sheet member P conveyed by the secondary transfer roll 42 to the sheet conveyance path 56 by the alignment roll 58 at a predetermined timing. Next transferred.

  Further, the sheet member P to which the toner image has been transferred is conveyed to the fixing device 44. The toner image transferred to the sheet member P is fixed to the sheet member P by the fixing device 44 and fixed, and then discharged to the discharge portion 48 provided at the upper portion of the main body 10A of the image forming apparatus 10 by the discharge roll 46. The

  On the other hand, when images are formed on both surfaces of the sheet member P, the sheet member P on which the image is fixed on the surface by the fixing device 44 is not discharged as it is onto the discharge unit 48 by the discharge roll 46, but the conveyance direction is switched. The sheet is conveyed to the duplex conveyance path 62 via the conveyance roll 60. Then, by conveying the sheet member P along the duplex conveyance path 62, the front and back of the sheet member P are reversed, and the sheet member P is conveyed again to the alignment roll 58. This time, the toner image is transferred / fixed on the back surface of the sheet member P, transferred and fixed, and then discharged onto the discharge portion 48 by the discharge roll 46.

(Main part configuration)
Next, the configuration of the charging device 70 will be described.

  As shown in FIG. 6, the charging device 70 is in contact with the image holding body 18, and is in contact with the charging member 20, and a charging member 20 that charges the image holding body 18 while rotating by following the rotating image holding body 18. A cleaning member 64 that cleans the outer peripheral surface of the charging member 20 while rotating following the rotating charging member 20. Further, the charging device 70 includes a support member 72 (bearing) that rotatably supports the charging member 20 and the cleaning member 64.

(Support member)
As shown in FIG. 5, the support member 72 is disposed on both ends of the charging member 20 extending in the left-right direction in the drawing and the cleaning member 64 extending in the left-right direction in the drawing.

  The support member 72 is formed of a resin material (in this embodiment, as an example, polyacetal (POM)). Each of the support members 72 has a recess 74 that supports the charging member 20 (shaft member 78) so as to be rotatable while sliding, and a recess 84 that supports the cleaning member 64 (shaft member 80) so as to be rotatable while sliding. Is formed. Moreover, the recessed part 74 and the recessed part 84 are made into the column shape. Thus, the support member 72 is a sliding bearing. The inner diameter of the recess 74 will be described together with the outer diameter of the shaft member 78 of the charging member 20 described later.

(Charging member)
The charging member 20 includes a columnar shaft member 78 extending along the rotation axis direction of the image carrier 18 and a cylindrical elastic member 76 through which the shaft member 78 passes.

  The elastic member 76 is a member in which a surface layer in which an electron conductive substance is dispersed is laminated on an ion conductive elastic layer. In the present embodiment, the elastic member 76 is, for example, a cylindrical shape having an outer diameter of 12 [mm], an inner diameter of 8 [mm], and a total length of 320 [mm], and ternary epichlorohydrin rubber is used as the elastic layer. ing.

  On the other hand, the shaft member 78 is a conductive member. In the present embodiment, the shaft member 78 is, for example, a cylindrical shape having an outer diameter of 8 [mm] and a total length of 355 [mm], and sulfur composite free-cutting steel (SUM) is used as the conductive member. . Then, both end sides of the shaft member 78 are inserted into the above-described recess 74 (see FIGS. 4 and 5).

  Here, the inner diameter of the recess 74 of the support member 72 is smaller than the outer diameter of the shaft member 78 (for example, 7.0 to 7.7 [mm]). As a result, when the charging member 20 rotates, a so-called stick-slip phenomenon occurs between the outer peripheral surface 78A of the shaft member 78 and the inner peripheral surface 74A of the recess 74 shown in FIG. Due to this stick slip phenomenon, the charging member 20 that rotates following the image carrier 18 rotating at a predetermined peripheral speed repeats rotation and stoppage. Thus, the charging member 20 rotates intermittently.

  The stick slip phenomenon means that the inner peripheral surface 74A and the outer peripheral surface 78A are caused by the frictional force generated between the inner peripheral surface 74A of the recess 74 and the outer peripheral surface 78A of the shaft member 78 and the rotational force transmitted to the shaft member 78. Is a phenomenon in which adhesion and sliding repeat.

  In this configuration, when the peripheral speed of the image carrier 18 is Vp and the average peripheral speed of the charging member 20 is Vb, the following formula (1) is established for the peripheral speed ratio (Vb / Vp).

0.3 ≦ (Vb / Vp) ≦ 0.8 Expression (1)
Here, the average peripheral speed of the charging member 20 is the charge that rotates intermittently when the image carrier 18 having an outer diameter of 30 [mm] is rotated 200,000 times at a peripheral speed of 250 [mm / sec]. This is the peripheral speed of the charging member 20 when the member 20 is considered to have rotated at a constant peripheral speed. The number of rotations of the charging member 20 can be determined by, for example, adding a marking that reflects light to a part of the charging member 20 and counting the number of times that the marking has passed the position facing the sensor. Derived. The average peripheral speed of the charging member is derived from the number of times the charging member 20 has rotated and the time required for the rotation.

[Cleaning member]
As shown in FIG. 5, the cleaning member 64 includes a cylindrical shaft member 80 (an example of a shaft) that extends along the rotation axis direction of the charging member 20, and a rectangular cross-section that is spirally wound around the shaft member 80. Foam body 82 (an example of an elastic member).

  In the present embodiment, the foam 82 is made of, for example, an elastically deformable urethane resin foam, and is fixed to the outer peripheral surface of the shaft member 80 using a double-sided tape (not shown). In addition, in the cross section orthogonal to the longitudinal direction of the foam 82, as shown in FIG. 2 (A), the both ends 82A of the foam 82 are formed from the center portion while being wound around the shaft member 80. Also protrudes in the radial direction of the shaft member 80 (hereinafter simply referred to as the radial direction). In other words, when viewed from the axial direction of the shaft member 80, the foam material 82 protrudes from the entire side surface of the shaft member 80, and when viewed from the radial direction of the shaft member 80, the foam material 82 is inclined with respect to the shaft member 80. They are lined up in the direction.

  Further, both end sides of the shaft member 80 are inserted into the above-described recess 84 as shown in FIG.

  In addition, the foam 82 is compressed on the outer peripheral surface of the charging member 20 by a predetermined amount with the shaft member 80 supported by the support member 72. With this configuration, the cleaning member 64 is rotated following the rotating charging member 20 by the frictional force generated between the foam 82 and the charging member 20.

[Others]
The image carrier 18 described above has, for example, an outer diameter of 30 [mm], and the charging member 20 is pressed against the image carrier 18 at 4.75 [N]. Further, as an example, the image carrier 18 rotates at a peripheral speed of 250 [mm / sec].

(Effects of main components)
Next, the operation of the charging device 70 will be described.

  The image carrier 18 to which the rotational force of the motor (not shown) is transmitted rotates in the direction of arrow A as shown in FIG. Further, the charging member 20 rotates in the arrow B direction following the image carrier 18 rotating in the arrow A direction. In this state, a charging voltage is applied to the charging member 20, whereby the outer peripheral surface of the image carrier 18 is charged.

  Here, the circumferential speed ratio (Vb / Vp) between the image carrier 18 and the charging member 20 satisfies the above-described formula (1). As a result, the image carrier 18 rotates at a predetermined peripheral speed, whereas the charging member 20 intermittently rotates in the direction of arrow B as described above.

  Further, the cleaning member 64 rotates in the arrow C direction following the charging member 20 rotating in the arrow B direction. Thereby, foreign substances such as external additives attached to the outer peripheral surface of the elastic member 76 of the charging member 20 are removed (cleaned) from the charging member 20 by the cleaning member 64.

  Hereinafter, a process of removing foreign matters attached to the outer peripheral surface of the elastic member 76 of the charging member 20 will be described.

  As shown in FIGS. 2A, 2B, and 2C, the foreign matter adhering to the outer peripheral surface of the elastic member 76 of the charging member 20 rotating in the arrow B direction is driven and rotated in the arrow C direction. It is pushed and aggregated by the end portion 82A of the 64 foams 82. Then, as shown in FIG. 2 (D), the end portion 82A of the foam 82 is released from contact with the charging member 20, so that the elastic deformation of the foam 82 is restored. The foreign matter is repelled from the outer peripheral surface of the charging member 20.

  Here, as described above, the charging member 20 rotates intermittently. For this reason, the cleaning member 64 that rotates following the charging member 20 also rotates intermittently.

  Since the cleaning member 64 rotates intermittently, the cleaning member 64 starts rotating and ends a plurality of times. When the rotation of the cleaning member 64 starts and ends, rubbing occurs between the foam 82 of the cleaning member 64 and the outer peripheral surface of the elastic member 76, and the adhesion force of the foreign matter attached to the outer peripheral surface of the elastic member 76 is weakened. It is done. For this reason, compared with the case where the cleaning member 64 does not rotate intermittently, many foreign substances are repelled from the outer peripheral surface of the charging member 20. In other words, the foreign matter adhering to the outer peripheral surface of the charging member 20 is effectively removed.

(Evaluation)
Here, the result of evaluating the example of the charging device 70 according to the present embodiment and the comparative example will be described with reference to FIG.

1. Evaluation Specifications / Example 1 The peripheral speed ratio was set to 0.3 by setting the outer diameter of the shaft member 78 to 8.0 [mm] and the inner diameter of the recess 74 to 7.0 [mm].
Example 2: The peripheral speed ratio was set to 0.6 by setting the outer diameter of the shaft member 78 to 8.0 [mm] and the inner diameter of the recess 74 to 7.4 [mm].
Example 3: The peripheral speed ratio was set to 0.8 by setting the outer diameter of the shaft member 78 to 8.0 [mm] and the inner diameter of the recess 74 to 7.7 [mm].
Comparative Example 1: The peripheral speed ratio was set to 0.1 by setting the outer diameter of the shaft member 78 to 8.0 [mm] and the inner diameter of the recess to 6.7 [mm].
Comparative Example 2: The peripheral speed ratio was set to 1.0 by setting the outer diameter of the shaft member 78 to 8.0 [mm] and the inner diameter of the recess to 8.0 [mm]. In other words, the charging member does not rotate intermittently.

2. Evaluation Method The charging devices of Examples 1 to 3 and Comparative Examples 1 and 2 were attached to DocuCenter IVC5570 manufactured by Fuji Xerox Co., Ltd., and a black halftone 50% image was formed on 50,000 A4 size sheet members P. It was. The outer diameter of the image carrier 18 is 30 [mm], and the peripheral speed of the image carrier 18 is 250 [mm / sec].

  And the image of the sheet | seat member P output at the end was evaluated visually (sensory evaluation). When no streaks or the like were generated in the output image and the quality of the output image was hardly deteriorated, “◯” was given. In addition, when a streak or the like is generated but the level is acceptable to the user, “Δ” is given. In other words, “◯” and “Δ” are in the order of few foreign matters adhering to the outer peripheral surface of the charging member.

3. Evaluation Results As shown in the table of FIG. 3, as a result of evaluating the output image, “◯” was obtained for Examples 1 to 3 and “Δ” was given for Comparative Examples 1 and 2.

(Summary of main components)
As can be seen from the above evaluation results, the charging member 20 and the cleaning member 64 are set so that the peripheral speed ratio (Vb / Vp) between the image carrier 18 and the charging member 20 satisfies the above-described formula (1). Rotate intermittently. Thereby, in the configuration using the cleaning member 64 in which the foam 82 is wound around the core material, the outer peripheral surface of the elastic member 76 (the outer peripheral surface of the charging member 20) is compared with the case where the above-described formula (1) is not satisfied. Adhering foreign matter is effectively removed.

  Further, in the image forming unit 16, the foreign matter adhering to the outer peripheral surface of the elastic member 76 is effectively removed, so that charging failure of the image carrier 18 is suppressed.

  Further, in the image forming apparatus 10, the foreign matter adhering to the outer peripheral surface of the elastic member 76 is effectively removed, so that deterioration in the quality of the toner image formed on the sheet member P is suppressed.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments can be taken within the scope of the present invention. This will be apparent to those skilled in the art. For example, in the above-described embodiment, the cleaning member 64 includes the foam 82 that is spirally wound around the shaft member 80, but a plurality of ring-cut members formed by obliquely cutting the cylindrical foam into round-cut members. May be attached to the shaft member 80 at intervals.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 16 Image forming unit 18 Image holding body 20 Charging member 22 Developing apparatus 42 Secondary transfer roll (an example of transfer member)
64 Cleaning member 70 Charging device 80 Shaft member (an example of a shaft)
82 Foam (an example of an elastic member)

Claims (3)

The outer periphery of the image carrier is repeatedly rotated and stopped by contacting the image carrier that rotates or circulates at a determined peripheral speed, the rotational force of the image carrier is transmitted, and a load that suppresses rotation is applied. A charging member that satisfies the formula (1) when the surface is charged, the average peripheral speed is Vb, and the peripheral speed of the image carrier is Vp;
A shaft that is rotatably supported, and projects from the entire side surface of the shaft when viewed from the axial direction of the shaft, and is inclined with respect to the shaft when viewed from the radial direction of the shaft, and is arranged at a plurality in the axial direction An elastic member that can be elastically deformed, and the elastic member is in contact with the outer peripheral surface of the charging member, rotates while being driven by the charging member, and cleans the outer peripheral surface of the charging member;
A charging device comprising:
0.3 ≦ (Vb / Vp) ≦ 0.8 Expression (1) An image carrier,
The charging device according to claim 1, wherein an outer peripheral surface of the image carrier is charged with a charging member;
A developing device that develops an electrostatic latent image formed on the outer peripheral surface of the charged image carrier as an image;
An image forming unit comprising: An image carrier,
The charging device according to claim 1, wherein an outer peripheral surface of the image carrier is charged with a charging member;
A developing device that develops an electrostatic latent image formed on the outer peripheral surface of the charged image carrier as an image;
A transfer member for transferring an image developed on the outer peripheral surface of the image carrier to a recording medium;
An image forming apparatus comprising:

Images