Charger

Abstract

This prevents the accumulation of discharge-generated products and dust within the space surrounded by the counter electrodes of the charger. [Solution] A group of counter electrodes, each consisting of multiple counter electrodes 50 corresponding to multiple wire electrodes 48, surrounds the wire electrodes 48 from three sides other than the photoreceptor 46 side. The group of counter electrodes has an introduction opening 54 on the side opposite to the photoreceptor 46 for introducing airflow F into the space surrounded by the group of counter electrodes. Multiple diffusion members 60 are arranged along the direction of movement M on the upstream side of the airflow F of the group of counter electrodes. The diffusion members 60 diffuse the airflow F, suppressing the occurrence of unevenness in the airflow within the space surrounded by the group of counter electrodes, and preventing the accumulation of discharge products and dust.

Description

Technical Field

[0001] The present invention relates to a charger.

Background Art

[0002] An electrophotographic image forming apparatus includes a charger that charges the surface of a photoreceptor on which an electrostatic latent image is formed. The charger has a wire electrode disposed adjacent to the photoreceptor and a counter electrode disposed so as to surround three sides of the wire electrode except for the photoreceptor side. While moving the surface of the photoreceptor, a corona discharge is generated between the wire electrode and the counter electrode. Thereby, the surface of the photoreceptor is charged. In some cases, a grid electrode in a lattice shape is disposed between the wire electrode and the photoreceptor.

[0003] Products generated by discharge and paper dust generated from paper may adhere to the wire electrode, the grid electrode, etc. In order to suppress this, a device for sending an air current into the space surrounded by the counter electrode may be provided. Patent Documents 1 to 3 below show image forming apparatuses provided with a device for sending an air current into the space surrounded by the counter electrode.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] If there is a bias in the air current in the space surrounded by the counter electrode in the moving direction of the photoreceptor, the ability to discharge dust such as products generated by discharge and paper dust in a region where the air current is relatively weak decreases, and products generated by discharge and dust remain.

[0006] The present invention aims to suppress uneven airflow within the space surrounded by the counter electrodes, thereby inhibiting the accumulation of discharge-induced products and dust. [Means for solving the problem]

[0007] The invention according to claim 1 is a group of counter electrodes comprising a plurality of wire electrodes, each extending along an intersecting direction that intersects the direction of movement of a photoreceptor and arranged along the direction of movement, and a plurality of counter electrodes facing each of the plurality of wire electrodes, wherein the group of counter electrodes is arranged to surround the plurality of wire electrodes, with an open bottom surface facing the photoreceptor, and an introduction opening formed on the ceiling surface opposite to the bottom surface for introducing airflow into the space surrounded by the group of counter electrodes, and a plurality of diffusion members, each extending along the intersecting direction and arranged along the direction of movement, wherein the diffusion members are arranged in a range in the direction of movement from the end counter electrodes, which are counter electrodes facing the wire electrodes at both ends of the arrangement, and upstream of the airflow from the ceiling surface, and diffuse the airflow that hits the diffusion members in the direction of movement, It is a charger that includes a diffusion member.

[0008] The invention according to claim 2 is the charger according to claim 1, wherein the side surface of the diffusion member with respect to the airflow is curved in a direction along the airflow.

[0009] The invention according to claim 3 is a charger according to claim 2, wherein intermediate opposing electrodes facing intermediate wire electrodes other than the wire electrodes at both ends in the arrangement direction are arranged on the ceiling surface, the introduction opening is formed between the intermediate opposing electrodes and the end opposing electrodes and between the intermediate opposing electrodes themselves, and at least one of the diffusion members is located on the airflow upstream side of the introduction opening.

[0010] The invention according to claim 4 is the charger according to claim 3, wherein one of the diffusion members is located upstream of the airflow of the intermediate counter electrode.

[0011] The invention according to claim 5 is the charger according to claim 2, comprising a plurality of additional diffusion members arranged along the direction of movement upstream of the plurality of diffusion members, wherein the additional diffusion members are located between the diffusion members located downstream of the airflow in the direction of movement.

[0012] The invention according to claim 6 is the charger according to claim 1, wherein the diffusion member directs a portion of the airflow to the region behind the diffusion member itself relative to the airflow. [Effects of the Invention]

[0013] According to the invention of claim 1, the airflow is diffused in the direction of movement by the multiple diffusion members, suppressing bias, and compared to the absence of diffusion members, the accumulation of discharge products and dust in the space surrounded by the counter electrodes is suppressed.

[0014] According to the invention of claim 2, a portion of the airflow wraps around to the area behind the diffusion member along the curvature of the side surface of the diffusion member, and the occurrence of unevenness in the airflow in the direction of movement is suppressed compared to the case where the side surface of the diffusion member is not curved.

[0015] According to the invention of claim 3, the vortex generated by the diffusion member is sent to the space surrounded by the counter electrodes.

[0016] According to the invention of claim 4, an airflow is directed toward the introduction openings on both sides of the intermediate electrode.

[0017] According to the invention of claim 5, the airflow is diffused more effectively than when there is no additional diffusion member.

[0018] According to the invention of claim 6, the occurrence of unevenness in the airflow in the direction of movement is suppressed. [Brief explanation of the drawing]

[0019] [Figure 1] This is a diagram showing the schematic configuration of an image forming apparatus. [Figure 2] This is a schematic diagram showing the configuration of a charger. [Figure 3] It is a diagram showing an example of the cross-sectional shape of the diffusion member. [Figure 4] It is a diagram showing an example of the cross-sectional shape of the diffusion member. [Figure 5] It is a diagram showing an example of the cross-sectional shape of the diffusion member. [Figure 6] It is a diagram schematically showing another configuration example of the charger.

Embodiments for Carrying Out the Invention

[0020] FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus 10. The image forming apparatus 10 includes an image reading unit 12, an image forming unit 14, and a document conveyance unit 16. The image reading unit 12 is a means for optically reading an image of a document. The document is placed on a platen glass 18, and the image on the document is optically read by an image reading element 20 composed of a CCD or the like. By moving the image reading element 20 along the platen glass 18, an image of the entire document is read. Also, the document may be conveyed by the document conveyance unit 16, and the image on the document may be read by the image reading element 20 during the conveyance process. The document is conveyed one by one from a document feed tray 22 of the document conveyance unit 16 to a document discharge tray 24, and is read during that process. In this case, the image reading element 20 remains stationary and an image of the entire document is read.

[0021] The image forming unit 14 forms an image on the paper P based on image information read by the image reading unit 12 or image information sent from an external device such as a personal computer. The image forming unit 14 is an electrophotographic device that forms a color image on the paper P using four colors of developer. The image forming unit 14 includes image forming units 26Y, 26M, 26C, and 26K, which each form developer images of yellow (Y), magenta (M), cyan (C), and black (K). The image forming units 26Y, 26M, 26C, and 26K are identical except for the color they form, and when there is no need to distinguish between colors, Y, M, C, and K will be omitted and they will be described simply as image forming unit 26. The image forming unit 14 includes an intermediate transfer belt 28 to which the developer images formed by each color image forming unit 26 are transferred, a transfer unit 30 that transfers the developer images on the intermediate transfer belt 28 onto the paper P, and a fixing unit 32 that fixes the transferred developer images onto the paper P. Furthermore, the image forming unit 14 includes a paper holder 34 for storing the paper P, and a paper transport device 36 for transporting the paper P one sheet at a time from the paper holder 34, passing it sequentially through the transfer unit 30 and the fixing unit 32.

[0022] The developer images of each color formed in the image forming unit 26 are transferred onto the intermediate transfer belt 28 and stacked. The developer images on the intermediate transfer belt 28 are sent to the transfer unit 30 as the intermediate transfer belt 28 rotates, where they are transferred to the paper P that has been transported by the paper transport device 36. The paper P is then transported by the paper transport device 36 to the fixing unit 32, where it is heated and pressurized to fix the developer image to the paper P. The paper P with the formed image is then sent onto the output tray 38 by the paper transport device 36.

[0023] As exemplified by the yellow image forming unit 26Y, the image forming unit 26 includes a developing unit 40, a charger 42, and an exposure unit 44. The developing unit 40 supplies developer to the photoreceptor 46. The charger 42 charges the surface of the photoreceptor 46. The exposure unit 44 irradiates the charged surface of the photoreceptor 46 with light such as laser light to form an electrostatic latent image on the surface of the photoreceptor 46. The exposure unit 44 controls the light to be irradiated based on image information acquired from the image reading unit 12 or an external device to form the electrostatic latent image. Developer is supplied from the developing unit 40 onto the photoreceptor 46 on which the electrostatic latent image has been formed, and the latent image is developed.

[0024] The image forming apparatus 10 is equipped with four image forming units 26, corresponding to the four colors of developer. The number of image forming units corresponds to the number of developer colors. If there is only one developer color, there is one image forming unit. In the image forming apparatus 10, the developer image formed by the image forming unit 26 is indirectly transferred to the paper P via an intermediate transfer belt 28. Alternatively, the apparatus may be configured so that the developer image is transferred directly from the image forming unit to the paper.

[0025] Figure 2 is a cross-sectional view showing the schematic configuration of the charger 42. The charger 42 is positioned adjacent to the cylindrical photoreceptor and extends in a direction along the centerline of the cylinder of the photoreceptor 46. The photoreceptor 46 rotates clockwise in Figure 2 around its centerline as an axis. The direction of rotation is indicated by the symbol R in the figure. The direction along the movement of the portion of the photoreceptor 46 facing the charger 42 is described as the "movement direction M," and the direction intersecting this movement direction M, particularly the direction in which the centerline of the photoreceptor 46 extends, is described as the "intersection direction C." In Figure 2, the left-right direction is the movement direction M, and the direction that penetrates the plane of the paper is the intersection direction C.

[0026] The charger 42 has a length corresponding to the photoreceptor 46 in the intersecting direction C, and has the cross-sectional shape shown in Figure 2 along its entire length. The charger 42 has a wire electrode 48 extending along the intersecting direction C and a counter electrode 50 positioned opposite the wire electrode 48. A housing 52 is provided to surround the charger 42 from all four sides in a plane defined by the direction of movement M and the intersecting direction C. An airflow F, sent from a fan (not shown), flows through the housing 52 toward the photoreceptor 46. At least a portion of this airflow F passes through the inside of the charger 42.

[0027] Multiple wire electrodes 48 are arranged along the direction of movement M. This charger 42 has three wire electrodes 48. The number of wire electrodes 48 may be other than three. If necessary, the two wire electrodes 48 located at both ends of the arrangement are described as end wire electrodes 48E, and the remaining wire electrodes 48 are described as intermediate wire electrodes 48B.

[0028] The counter electrode 50 facing the end wire electrode 48E is referred to as the end counter electrode 50E, and the electrode facing the intermediate wire electrode 48B is referred to as the intermediate counter electrode 50B. The counter electrode group, composed of the end counter electrode 50E and the intermediate counter electrode 50B, surrounds the three wire electrodes 48 from three sides other than the side facing the photoreceptor 46. The bottom surface of the counter electrode group is open on the side facing the photoreceptor 46, and an introduction opening 54 is formed on the top surface, which is the surface opposite the bottom surface, to introduce the airflow F flowing inside the housing 52. The airflow F flows into the space surrounded by the counter electrode group through the introduction opening 54. The surface of the counter electrode group that is positioned to sandwich the three wire electrodes 48 in the direction of movement M is referred to as the lateral surface.

[0029] The end counter electrode 50E includes a side member 56 that forms the lateral surface of the counter electrode group and a ceiling member 58 that forms part of the ceiling surface. The intermediate counter electrode 50B forms part of the ceiling surface of the counter electrode group. The intermediate counter electrode 50B is also positioned so as to sandwich the corresponding intermediate wire electrode 48B between the surface of the photoreceptor 46 and the photoreceptor 46 in the radial direction of the photoreceptor 46. A gap is formed between the end counter electrode 50E and the intermediate counter electrode 50B on the ceiling surface of the counter electrode group, and this gap constitutes an introduction opening 54. Furthermore, if multiple intermediate counter electrodes 50B are provided, introduction openings 54 are also formed between the intermediate counter electrodes 50B.

[0030] The charger 42 has a plurality of diffusion members 60 positioned upstream of the airflow F from the ceiling surface of the counter electrode group. The diffusion members 60 are rod-shaped members. This charger 42 has three diffusion members 60. Each diffusion member 60 extends in a crossing direction C, and its length corresponds to the length of the counter electrode group. The three diffusion members 60 are arranged along the direction of movement M. The three diffusion members 60 are arranged in the range between the two end counter electrodes 50E in the direction of movement M. At least one diffusion member 60 may be positioned upstream of the inlet opening 54, corresponding to it. A diffusion member 60 may be positioned for each of the inlet openings 54, or a diffusion member 60 may be provided for some of the inlet openings 54.

[0031] The airflow F that strikes the diffusion member 60 diffuses in the direction of movement M and spreads out within the space surrounded by the counter electrodes 50, that is, within the inner space of the counter electrode group, thereby suppressing the stagnation of air within this space. In addition, when the airflow F strikes the diffusion member 60, a vortex T is generated downstream of the diffusion member 60, and this vortex T helps to suppress stagnation in the inner space of the counter electrode group.

[0032] The sides of the diffusion member 60 with respect to the airflow F, i.e., the left and right sides in Figure 2, are curved in the direction of the airflow F. This curvature is a curve that bulges in the center. The cross-section of the diffusion member 60 shown in Figure 2 is circular, and the cross-section of the side is an arc. A portion of the airflow F flows along the curved side due to the Coanda effect and is directed towards the area behind the diffusion member 60, i.e., the area that is in the shadow of the diffusion member 60 when viewed from the upstream side. As a result, even with the diffusion member 60 in place, the airflow F is directed to the area behind it.

[0033] The spacing between adjacent diffusion members 60 may be greater than or equal to the dimension of the diffusion member 60 in the direction of movement M. In the case of a diffusion member 60 with a circular cross-sectional shape, the spacing between adjacent diffusion members 60 may be greater than or equal to its diameter.

[0034] Figure 3-5 shows examples of diffusers that can be used as substitutes for the aforementioned diffuser 60. The diffusers shown in Figure 3-5 have different cross-sectional shapes from the aforementioned diffuser 60. The cross-sectional shape of the diffuser 62 shown in Figure 3 is elliptical. The major axis of the ellipse extends in the direction along the airflow F. The cross-sectional shapes of the diffusers 64 and 66 shown in Figure 4 are teardrop or drop-shaped. Figure 4(a) shows an example where the pointed side of the teardrop shape faces the upstream side of the airflow F, and (b) shows an example where the pointed side faces the downstream side. The cross-sectional shapes of the diffusers 68 and 70 shown in Figure 5 are shapes in which one or two arcs have been cut out from a circle. Figure 5(a) shows an example where the downstream side of the airflow F has been cut out from a circle, and (b) shows examples where both the upstream and downstream sides of the airflow F have been cut out.

[0035] Figure 6 shows another example of the configuration of the charger. The charger 72 differs from the charger 42 described above in the configuration of the diffusion members. The charger 72 includes several additional diffusion members 74 in addition to the diffusion member 60 similar to that of the charger 42. The other components of the charger 72 are the same as those of the charger 42 and are given the same reference numerals, and their descriptions are omitted. The additional diffusion members 74 are arranged upstream of the airflow F from the diffusion member 60, along the direction of movement M. The sides of the additional diffusion members 74 with respect to the airflow F, i.e., the left and right sides in Figure 6, are curved in the direction along the airflow F. This curvature is a curve with a bulge in the center. The cross-sectional shape of the additional diffusion members 74 may be circular or the shape shown in Figure 3-5. Similar to the diffusion member 60, the additional diffusion members 74 are arranged in the range between the two end opposing electrodes 50E in the direction of movement M. Each additional diffusion member 74 may be positioned between adjacent diffusion members 60 in the direction of movement M. In the direction of movement M, the dimensions of the additional diffusion members 74 may be smaller than the spacing between the diffusion members 60. Also, the number of additional diffusion members 74 may be less than the number of diffusion members 60.

[0036] The chargers 42 and 72 are Corotron-type chargers, but they may also be Scorotron-type chargers in which a grid-like grid electrode is provided between the wire electrode 48 and the photoreceptor 46. The grid electrode may be arranged to cover the entire opening on the photoreceptor 46 side of the counter electrode group, which is composed of multiple counter electrodes 50.

[0037] (Note) (((1))) Each extends along an intersecting direction that intersects the direction of movement of the photoreceptor, and a plurality of wire electrodes are arranged along the direction of movement, A group of opposing electrodes comprising a plurality of opposing electrodes facing each of the plurality of wire electrodes, wherein the group of opposing electrodes is arranged to surround the plurality of wire electrodes, the bottom surface facing the photoreceptor is open, and an introduction opening is formed on the ceiling surface opposite to the bottom surface to introduce airflow into the space surrounded by the group of opposing electrodes, A plurality of diffusion members, each extending in the aforementioned intersecting direction and arranged along the aforementioned direction of movement, wherein the diffusion members are positioned in a range in the direction of movement from the end opposing electrodes, which are opposing electrodes facing the wire electrodes at both ends of the arrangement, and on the upstream side of the airflow from the ceiling surface, and the airflow that strikes the diffusion members is diffused in the direction of movement. A charger that includes a charger. (((2))) The charging device according to (((1))), wherein the side surface of the diffusion member with respect to the airflow is curved in the direction along the airflow. (((3))) The charger according to (((1))) or (((2))), wherein intermediate opposing electrodes are arranged on the ceiling surface in the arrangement direction, facing the intermediate wire electrodes other than the wire electrodes at both ends, the introduction opening is formed between the intermediate opposing electrodes and the end opposing electrodes and between the intermediate opposing electrodes themselves, and at least one of the diffusion members is located on the airflow upstream side of the introduction opening. (((4))) The charger according to (((3))), wherein one of the diffusion members is located upstream of the airflow of the intermediate counter electrode. (((5))) A charger according to any one of (((1))) to (((4))), comprising a plurality of additional diffusers arranged along the direction of movement upstream of the plurality of diffusers, wherein the additional diffusers are located between the diffusers located downstream of the airflow in the direction of movement. (((6))) The charger according to (((1))), wherein the diffusion member directs a portion of the airflow to the region behind the diffusion member itself relative to the airflow.

[0038] According to the configuration described in (((1))), the airflow is diffused in the direction of movement by multiple diffusion members, suppressing bias, and compared to the case without diffusion members, the accumulation of discharge products and dust in the space surrounded by the counter electrodes is suppressed. According to the configuration of (((2))), a portion of the airflow wraps around to the area behind the diffusion member along the curvature of the side surface of the diffusion member, and the occurrence of unevenness in the airflow in the direction of movement is suppressed compared to the case where the side surface of the diffusion member is not curved. According to the configuration of (((3))), the vortex generated by the diffusion member is sent to the space surrounded by the counter electrodes. According to the configuration of (((4))), airflow is directed toward the inlet openings on both sides of the intermediate electrode. According to the configuration of (((5))), the airflow is diffused more effectively than when there is no additional diffusion member. According to the configuration of (((6))), the occurrence of unevenness in the airflow in the direction of movement is suppressed. [Explanation of Symbols]

[0039] 10 Image forming apparatus, 40 Developing apparatus, 42, 72 Charger, 44 Exposure apparatus, 46 Photoreceptor, 48 Wire electrode, 48E End wire electrode, 48B Intermediate wire electrode, 50 Counter electrode, 50E End counter electrode, 50B Intermediate counter electrode, 54 Inlet aperture, 60, 62, 64, 66, 68, 70 Diffusing members, 74 Additional diffusion member, M Direction of movement, C Direction of intersection.

Claims

1. Each extends along an intersecting direction that intersects the direction of movement of the photoreceptor, and a plurality of wire electrodes are arranged along the direction of movement, A group of opposing electrodes comprising a plurality of opposing electrodes facing each of the plurality of wire electrodes, wherein the group of opposing electrodes is arranged to surround the plurality of wire electrodes, the bottom surface facing the photoreceptor is open, and an introduction opening is formed on the ceiling surface opposite to the bottom surface to introduce airflow into the space surrounded by the group of opposing electrodes, A plurality of diffusion members, each extending in the aforementioned intersecting direction and arranged along the aforementioned direction of movement, wherein the diffusion members are positioned in a range in the direction of movement from the end opposing electrodes, which are opposing electrodes facing the wire electrodes at both ends of the arrangement, and on the upstream side of the airflow from the ceiling surface, and the airflow that strikes the diffusion members is diffused in the direction of movement. A charger that includes a charger.

2. The charger according to claim 1, wherein the side surface of the diffusion member with respect to the airflow is curved in the direction along the airflow.

3. The charger according to claim 2, wherein intermediate opposing electrodes are arranged on the ceiling surface opposite to the intermediate wire electrodes other than the wire electrodes at both ends in the arrangement direction, the introduction opening is formed between the intermediate opposing electrodes and the end opposing electrodes and between the intermediate opposing electrodes themselves, and at least one of the diffusion members is located on the airflow upstream side of the introduction opening.

4. The charger according to claim 3, wherein one of the diffusion members is located upstream of the airflow of the intermediate counter electrode.

5. The charger according to claim 2, further comprising a plurality of additional diffusion members arranged along the direction of movement upstream of the plurality of diffusion members, wherein the additional diffusion members are located between the diffusion members located downstream of the airflow in the direction of movement.

6. The charger according to claim 1, wherein the diffusion member directs a portion of the airflow to the region behind the diffusion member itself relative to the airflow.

Images