Charging device, image forming unit, and image forming apparatus

Abstract

The invention provides a charging device, an image forming unit, and an image forming apparatus. The charging device includes: a discharge electrode; and a control electrode disposed between the discharge electrode and a charged body charged by the discharge electrode, the control electrode having: a plurality of linear conductors disposed so as to intersect the direction of rotation of the charged body at an arbitrary angle; and a plurality of connecting parts that connect the linear conductor in the direction of rotation of the charged body and that are disposed in a central region more than regions at both ends of the charged body in a direction intersecting the direction of rotation.

Description

Technical Field

[0001] The present invention relates to a charging device, an image forming unit, and an image forming device. Background Art

[0002] Conventionally, as technologies related to charging devices, technologies disclosed in Patent Documents 1 and 2, for example, have been proposed.

[0003] Patent Document 1 discloses a technology in which a grid electrode has a plurality of regions having different opening pitches in the rotation axis direction, and the opening pitch of a region facing a discharge electrode is smaller than the opening pitch of a non-facing region.

[0004] Patent document 2 is a technology constructed as follows: the potential control plate includes: more than 3 structural wires, which are arranged along the circumferential direction of the charged body and extend linearly along the axial direction of the charged body; and multiple connecting parts, which are arranged along the axial direction of the charged body and connect a part of the more than 3 structural wires that is continuous in the circumferential direction of the charged body, and the structural wires connected by one connecting part among the multiple connecting parts are different from those connected by another connecting part in at least a part.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-045060

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2012-203364 Summary of the Invention

[0007] An object of the present invention is to suppress the occurrence of uneven charging due to vibration of a control electrode, compared to a case where a plurality of connecting portions constituting the control electrode are uniformly arranged in the axial direction.

[0008] The invention according to claim 1 is a charging device comprising:

[0009] discharge electrodes; and

[0010] The control electrode is arranged between the discharge electrode and the charged object charged by the discharge electrode.

[0011] The control electrode has:

[0012] a plurality of linear conductors arranged to intersect the rotation direction of the charged body at arbitrary angles; and

[0013] The plurality of connection portions connect the linear conductors along the rotation direction of the charged body and are arranged more in the central region than in regions at both ends of the charged body in a direction intersecting the rotation direction.

[0014] The invention according to claim 2 is a charging device comprising:

[0015] discharge electrodes; and

[0016] The control electrode is arranged between the discharge electrode and the charged object charged by the discharge electrode.

[0017] The control electrode has:

[0018] a plurality of linear conductors arranged to intersect the rotation direction of the charged body at arbitrary angles; and

[0019] The plurality of connecting portions connect the linear conductors along the rotation direction of the charged body and are more frequently arranged in the facing region where the discharge electrode and the control electrode face each other than in the non-facing region where the discharge electrode and the control electrode do not face each other in the rotation direction of the charged body.

[0020] The invention described in claim 3 is the charging device according to claim 1, wherein the plurality of connecting portions connect adjacent ones of the plurality of linear conductors to each other.

[0021] The invention described in Option 4 is a charged device according to Option 3, wherein the multiple connecting parts are arranged in the following manner: the density of the connecting parts is the highest in the area of ​​the central part of the control electrode in a direction intersecting with the rotation direction of the charged body, and the density of the connecting parts gradually decreases toward the two end parts of the control electrode.

[0022] The invention described in claim 5 is the charging device described in claim 1, wherein the plurality of connection portions are arranged so as to include a non-opposing region where the discharge electrode and the control electrode do not face each other.

[0023] The invention described in Scheme 6 is a charged device according to Scheme 5, wherein the multiple connecting parts are arranged in the following manner: the density of the connecting parts in the opposing area where the discharge electrode and the control electrode are opposed to each other is increased compared to the density of the connecting parts in the non-opposing area where the discharge electrode and the control electrode are not opposed to each other in a direction intersecting the rotation direction of the charged body.

[0024] The invention described in claim 7 is the charging device according to claim 1, wherein the opening ratio of the control electrode in a direction intersecting with the rotation direction of the charged body is uniform.

[0025] The invention described in Scheme 8 is a charged device according to Scheme 7, wherein, among the multiple connecting parts, the line width of the connecting part in the central part is narrower than the line width of the connecting part in the area of ​​the two ends of the control electrode in the direction intersecting with the rotation direction of the charged body.

[0026] The invention described in claim 9 is the charging device according to claim 1, wherein a plurality of the discharge electrodes are arranged along the rotation direction of the charged body.

[0027] The invention described in claim 10 is the charging device according to claim 9, wherein the applied voltage at the most upstream side of the discharge electrode in the rotation direction of the charged body is higher than that at other locations.

[0028] The invention according to claim 11 is an image forming unit including the charging device according to any one of claims 1 to 10, wherein the image forming unit is attachable to and detachable from the image forming apparatus.

[0029] The invention according to claim 12 is an image forming apparatus comprising:

[0030] Image holding member;

[0031] a charging member for charging the surface of the image holding member; and

[0032] an electrostatic latent image forming member for forming an electrostatic latent image on the surface of the image holding member charged by the charging member,

[0033] The image forming apparatus uses the charging device according to any one of aspects 1 to 10 as the charging member.

[0034] Effects of the Invention

[0035] According to the first aspect of the present invention, compared to the case where a plurality of connection portions constituting the control electrode are uniformly arranged in the axial direction, the occurrence of uneven charging due to vibration of the control electrode can be suppressed.

[0036] According to the second aspect of the present invention, compared to the case where the plurality of connecting portions constituting the control electrode are equally arranged in the non-opposing region where the discharge electrode and the control electrode do not face each other and in the facing region where the discharge electrode and the control electrode face each other, the occurrence of uneven charging due to vibration of the control electrode can be suppressed.

[0037] According to the third aspect of the present invention, vibration of the linear conductors can be suppressed compared to a case where adjacent linear conductors are not connected to each other.

[0038] According to the fourth scheme of the present invention, compared with the case where multiple connecting parts are arranged with equal density in the central area of ​​the control electrode and the areas at both ends of the control electrode in a direction intersecting with the rotation direction of the charged body, the generation of vibration of the linear conductor can be effectively suppressed.

[0039] According to the fifth aspect of the present invention, compared to the case where a plurality of connection portions are arranged only in the facing region where the discharge electrode and the control electrode face each other, vibration of the linear conductor can be effectively suppressed.

[0040] According to the sixth embodiment of the present invention, compared to the case where a plurality of connecting portions are arranged so that the density of connecting portions in the non-opposing area where the discharge electrode and the control electrode are not opposed in a direction intersecting the rotation direction of the charged body is equal to the density of connecting portions in the opposing area where the discharge electrode and the control electrode are opposed, the vibration of the linear conductor can be effectively suppressed.

[0041] According to the seventh aspect of the present invention, compared to a case where the aperture ratio of the control electrode along the axial direction of the charged body is different, occurrence of unevenness in the charge potential along the axial direction of the charged body can be suppressed.

[0042] According to the eighth embodiment of the present invention, the aperture ratio can be easily set compared to the case where the line width of the connection portion in the area of ​​both ends of the control electrode in a direction intersecting the rotation direction of the charged body among multiple connection portions is equal to the line width of the connection portion in the central portion.

[0043] According to the ninth aspect of the present invention, the charging capability can be improved compared to the case where a single discharge electrode is provided.

[0044] According to the tenth aspect of the present invention, the charging characteristics of the charged body can be improved compared to the case where the applied voltage is set higher than that at the discharge electrode other than the most upstream side in the rotation direction of the charged body.

[0045] According to the eleventh aspect of the present invention, compared to a case where the charging device according to any one of the first to tenth aspects is not provided, occurrence of uneven charging due to vibration of the control electrode can be suppressed.

[0046] According to the twelfth aspect of the present invention, compared with the case where the charging device described in any one of aspects 1 to 10 is not used as the charging member, the occurrence of uneven charging due to vibration of the control electrode can be suppressed, and image quality can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Embodiments of the present invention will be described in detail with reference to the following drawings.

[0048] Figure 1 is a diagram showing the overall configuration of an image forming apparatus to which a charging device according to Embodiment 1 of the present invention is applied;

[0049] Figure 2 1 is a structural diagram showing an image forming apparatus according to an image forming apparatus of a first embodiment of the present invention;

[0050] Figure 3 is a perspective structural diagram showing an image forming unit according to Embodiment 1 of the present invention;

[0051] Figure 4is a perspective structural diagram showing a unit main body of an image forming unit according to Embodiment 1 of the present invention;

[0052] Figure 5 1 is a perspective view showing the structure of a grid electrode of a charging device according to a first embodiment of the present invention;

[0053] Figure 6 is a structural diagram showing a control unit of a grid electrode;

[0054] Figure 7 It is a structural diagram showing the principle of the live device;

[0055] Figure 8 1 is a perspective view showing the structure of a grid electrode of a charging device according to a first embodiment of the present invention;

[0056] Figure 9 1 is a perspective structural diagram showing a charging device according to a first embodiment of the present invention;

[0057] Figure 10 1 is a perspective structural diagram showing an insulating block at the rear end of the charging device according to the first embodiment of the present invention;

[0058] Figure 11 1 is a perspective structural diagram showing an insulating block at the front end of the charging device according to the first embodiment of the present invention;

[0059] Figure 12 It is a structural diagram showing the tensioning components;

[0060] Figure 13 It is a cross-sectional structural diagram showing the main parts of the front end insulating block;

[0061] Figure 14 1 is a plan view showing the structure of a grid electrode of a charging device according to a first embodiment of the present invention;

[0062] Figure 15 1 is a schematic diagram showing an opposing region of a charging device according to Embodiment 1 of the present invention;

[0063] Figure 16 1 is a plan view showing the structure of a grid electrode of a charging device according to a second embodiment of the present invention;

[0064] Figure 17 1 is a plan view showing the structure of a grid electrode of a charging device according to a third embodiment of the present invention;

[0065] Figure 18 It is a planar structural diagram showing a grid electrode of a charging device according to a fourth embodiment of the present invention.

[0066] Explanation of symbols

[0067] 1- image forming device, 12- charging device, 120- shielding case, 121- discharge line, 122- grid electrode, 122a- control unit, 122b, c- connecting unit, 122f- linear conductor, 122g- connecting unit. DETAILED DESCRIPTION

[0068] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0069] [Implementation Method 1]

[0070] Figure 1 This is a diagram showing the overall outline of an image forming apparatus to which a charging device and an image forming unit according to Embodiment 1 of the present invention are applied.

[0071] <Overall Structure of Image Forming Apparatus>

[0072] The image forming apparatus 1 according to the first embodiment is configured as, for example, a color printer. Figure 1 As shown, the image forming apparatus 1 includes a plurality of imaging devices 10, an intermediate transfer device 20, a paper feeding device 50, and a fixing device 40. The plurality of imaging devices 10 form toner images developed with toner constituting a developer. The intermediate transfer device 20 holds the toner images formed by each imaging device 10 and finally transports them to a secondary transfer position where they are secondary transferred onto a recording paper 5, which is an example of a recording medium. The paper feeding device 50 accommodates and transports the recording paper 5 required to be supplied to the secondary transfer position of the intermediate transfer device 20. The fixing device 40 fixes the toner image on the recording paper 5 that has been secondary transferred in the intermediate transfer device 20. In addition, the double-dashed line in the figure indicates the main transport path for transporting the recording paper 5 within the image forming apparatus 1.

[0073] The image forming apparatus 10 is composed of four image forming devices 10Y, 10M, 10C, and 10K, each specialized for forming toner images of four colors: yellow (Y), magenta (M), cyan (C), and black (K). These four image forming devices 10 (Y, M, C, K) are arranged in a horizontal row within the interior space of the image forming apparatus 1.

[0074] like Figure 2As shown, each imaging device 10 (Y, M, C, K) has a rotating photosensitive drum 11 as an example of a charged body and an image holding member. Around the photosensitive drum 11, there are a charging device 12 as an example of a charging member involved in this embodiment 1, an exposure device 13 as an example of an electrostatic latent image forming member, a developing device 14, a primary transfer device 15 and a drum cleaning device 16. The charging device 12 charges the peripheral surface (image holding surface) of the photosensitive drum 11 that can form an image to a desired potential. The exposure device 13 irradiates the charged peripheral surface of the photosensitive drum 11 with light based on the information (signal) of the image to form an electrostatic latent image (for each color) with a potential difference. The developing device 14 develops the electrostatic latent image with a toner of a developer of the corresponding color (Y, M, C, K) to form a toner image. The primary transfer device 15 transfers each toner image to the intermediate transfer device 20.

[0075] The drum cleaning device 16 removes and cleans attached matter such as toner remaining on the image holding surface of the photosensitive drum 11 after the primary transfer.

[0076] The photosensitive drum 11 is formed by forming an image holding surface having a photoconductive layer (photosensitive layer) made of a photosensitive material on the circumference of a cylindrical or columnar substrate subjected to grounding treatment. The photosensitive drum 11 is supported so as to rotate in the direction indicated by arrow A, which is an example of a moving direction, by transmitting a driving force from a driving member (not shown). Figure 2 As shown, the surface of the photosensitive drum 11 is curved into a circular shape having a desired curvature radius around the rotation axis.

[0077] The charging device 12 is composed of a so-called scorotron-type charger arranged in a state separated from the photosensitive drum 11. The scorotron-type charging device 12 has a higher charging capacity for the photosensitive drum 11 than a roller-shaped charging roller. Therefore, the scorotron-type charging device 12 is particularly effective in a high-productivity image forming device 1 that increases the rotation speed of the photosensitive drum 11 that determines the processing speed. A charging voltage and a control voltage are supplied to the charging device 12. As the charging voltage, when the developing device 14 performs reverse development, a voltage or current having the same polarity as the charging polarity of the toner supplied from the developing device 14 is supplied. In addition, the structure of the charging device 12 will be described in detail later.

[0078] The exposure device 13 is comprised of an LED printhead. The LED printhead utilizes a plurality of LEDs (light emitting diodes) arranged axially along the photosensitive drum 11 to illuminate the photosensitive drum 11 with light corresponding to image information, thereby forming an electrostatic latent image. Alternatively, the exposure device 13 may employ an exposure device that deflects and scans a laser beam formed in accordance with image information along the axial direction of the photosensitive drum 11.

[0079] like Figure 2 As shown, the developing device 14 is composed of a developing roller 141, a stirring and supplying member 142, a developer supply roller 143, a stirring and transporting member 144, and a layer thickness limiting member 145 arranged inside a frame 140. The frame 140 is formed with an opening at a position opposite to the photosensitive drum 11 and a developer storage chamber. The developing roller 141 holds the developer and transports it to the developing area facing the photosensitive drum 11. The stirring and supplying member 142 is composed of an auger or the like, which stirs the developer while supplying it through the developing roller 141. The developer supply roller 143 supplies the developer supplied from the stirring and supplying member 142 to the developing roller 141. The stirring and transporting member 144 is composed of an auger or the like, which stirs the developer while transporting it to the stirring and supplying member 142. The layer thickness limiting member 145 limits the amount (layer thickness) of the developer held on the developing roller 141. In the developing device 14, a developing voltage is supplied from a power supply (not shown) between the developing roller 141 and the photosensitive drum 11. As the developer of the four colors, for example, a two-component developer containing non-magnetic toner and magnetic carrier is used.

[0080] The primary transfer device 15 is a contact-type transfer device including a primary transfer roller. The primary transfer roller rotates while in contact with the periphery of the photoreceptor drum 11 via the intermediate transfer belt 21, and is supplied with a primary transfer voltage. A DC voltage having a polarity opposite to the charged polarity of the toner is supplied from a power supply (not shown) as the primary transfer voltage.

[0081] The drum cleaning device 16 is composed of a main body 160, a cleaning brush 161, a cleaning plate 162 and a delivery component 163. A portion of the main body 160 is formed in the shape of an open container. The cleaning brush 161 is configured to contact the peripheral surface of the photosensitive drum 11 after the primary transfer with a required pressure to scrape off residual toner and other attachments and clean them. The cleaning plate 162 is configured to contact the peripheral surface of the photosensitive drum 11 with a required pressure to remove residual toner and other attachments and clean them. The delivery component 163 is composed of a spiral conveyor and the like, which recovers the toner and other attachments removed by the cleaning brush 161 and the cleaning plate 162 and delivers them to a recovery system not shown in the figure. As the cleaning plate 162, a plate-shaped component (such as a scraper) made of a material such as rubber is used.

[0082] An antistatic lamp 17 is disposed between the drum cleaning device 16 and the charging device 12. The antistatic lamp 17 evenly exposes the surface of the photosensitive drum 11 from which residual toner and other attached substances have been removed by the drum cleaning device 16, thereby eliminating static electricity.

[0083] like Figure 1As shown, the intermediate transfer device 20 is positioned vertically below each imaging device 10. The intermediate transfer device 20 primarily comprises an intermediate transfer belt 21, a plurality of belt support rollers 22 to 24, a secondary transfer device 30, and a belt cleaning device 25. The intermediate transfer belt 21 rotates in the direction indicated by arrow B while passing through the primary transfer position between the photosensitive drum 11 and the primary transfer device 15 (primary transfer rollers). The plurality of belt support rollers 22 to 24 rotatably support the intermediate transfer belt 21 while maintaining the desired state from its inner surface. The secondary transfer device 30 is positioned on the outer peripheral surface (image holding surface) of the intermediate transfer belt 21 supported by the belt support rollers 24 to secondary transfer the toner image on the intermediate transfer belt 21 onto the recording paper 5. The belt cleaning device 25 removes and cleans any residual toner, paper dust, and other adhering matter that remains on the outer peripheral surface of the intermediate transfer belt 21 after passing through the secondary transfer device 30.

[0084] The intermediate transfer belt 21 is, for example, an endless conveyor belt made of a material obtained by dispersing a resistance modifier such as carbon black in a synthetic resin such as a polyimide resin or a polyamide resin. The belt support roller 22 is a drive roller that is rotationally driven by a drive device (not shown). The belt support roller 23 is a surface smoothing roller that maintains the image forming surface of the intermediate transfer belt 21. The belt support roller 24 is an opposing roller that faces the secondary transfer device 30. The belt support roller 22 also serves as a support roller for the back surface of the belt cleaning device 25.

[0085] like Figure 1 As shown, the secondary transfer device 30 is a contact-type transfer device equipped with a secondary transfer roller 31. The secondary transfer roller 31 rotates while in contact with the circumference of the intermediate transfer belt 21 at the secondary transfer position, which is the outer circumference of the intermediate transfer belt 21 supported by the belt support roller 24 in the intermediate transfer device 20. A DC voltage having a polarity opposite to or the same as the charged polarity of the toner is supplied as the secondary transfer voltage from a power supply (not shown) to the secondary transfer roller 31 or the belt support roller 24 of the intermediate transfer device 20.

[0086] The fixing device 40 is constructed by arranging a heating rotating body 42 and a pressurizing rotating body 43 inside a frame 41. An inlet and an outlet for the recording paper 5 are formed on the frame 41. The heating rotating body 42 is formed in a belt form or a roller form that rotates in the direction indicated by the arrow and is heated by a heating member so that the surface temperature is maintained at a predetermined temperature. The pressurizing rotating body 43 is formed in a roller form or a belt form that contacts and rotates driven by the heating rotating body 42 at a predetermined pressure in a state roughly along the axial direction. In the fixing device 40, the contact portion between the heating rotating body 42 and the pressurizing rotating body 43 becomes a fixing nip portion N that performs the required fixing process (heating and pressurization).

[0087] The paper feed device 50 is located below the intermediate transfer device 20. The paper feed device 50 is primarily composed of a single (or multiple) paper container 51 and feed devices 52 and 53. The paper container 51 holds recording paper 5 of a desired size and type. The feed devices 52 and 53 feed recording paper 5 one by one from the paper container 51. The paper container 51 is configured to be drawn out, for example, toward the front of the device main body (not shown) (the side facing the user during operation).

[0088] Examples of recording paper 5 include plain paper used in electrophotographic copiers and printers, thin paper such as tracing paper, and OHP sheets. To further improve the smoothness of the image surface after fixing, the surface of the recording paper 5 is preferably as smooth as possible. Examples of recording paper 5 that can be preferably used include coated paper (plain paper coated with a resin or the like), and thick paper with a relatively high basis weight, such as coated printing paper.

[0089] A plurality of or a single paper transport roller pairs 54, 55 and a paper transport path 56 are provided between the paper feed device 50 and the secondary transfer device 30. The paper transport roller pairs 54, 55 transport the recording paper 5 fed from the paper feed device 50 to the secondary transfer position. The paper transport path 56 is composed of a transport guide device (not shown). The paper transport roller pair 55, which is arranged immediately before the secondary transfer position on the paper transport path 56, is configured as, for example, a roller (registration roller) for adjusting the transport timing of the recording paper 5. Furthermore, a plurality of or a single paper transport roller pairs 57, 58 or a paper transport path 59 are provided between the secondary transfer device 30 and the fixing device 40 for transporting the recording paper 5 fed from the secondary transfer device 30 to the fixing device 40 after the secondary transfer. In addition, a paper discharge portion (not shown) for discharging the fixed recording paper 5 fed from the fixing device 40 is provided on the side of the image forming device 1.

[0090] Furthermore, the image forming apparatus 1 may include a double-sided paper conveying path (not shown) for forming images on both sides of the recording paper 5 .

[0091] exist Figure 1 In the figure, reference numeral 100 denotes a control device that centrally controls the operation of the image forming apparatus 1. The control device 100 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), a bus connecting the CPU and ROM, and a communication interface, etc. (not shown).

[0092] <Structure of the Image Forming Unit>

[0093] like Figure 2 As shown, the image forming apparatus 1 according to the first embodiment includes multiple image forming units 200 corresponding to the respective imaging devices 10 (Y, M, C, and K) to improve maintainability. Each image forming unit 200 is constructed by integrating multiple components constituting each imaging device 10, including at least the photosensitive drum 11. Each image forming unit 200 is individually attachable to and detachable from the image forming apparatus 1.

[0094] In this embodiment 1, as Figure 2 As shown, the photosensitive drum 11, the charging device 12, and the drum cleaning device 16 are integrally formed into an image forming unit 200. Alternatively, the charging device 12 can be configured to be independently attachable and detachable from the photosensitive drum 11 and the drum cleaning device 16. The image forming unit 200 is replaced when components such as the photosensitive drum 11 reach the end of their service life. Furthermore, if the charging device 12 or the drum cleaning device 16 malfunctions, the image forming unit 200 is also replaced with a new component. When the image forming unit 200 does not include the developing device 14, a common image forming unit 200 can be used for all imaging devices 10.

[0095] like Figure 3 As shown, the image forming unit 200 includes a unit main body 201. The unit main body 201 includes front and rear support portions 202 and 203 and a connecting portion 204.

[0096] The front and rear support parts 202 and 203 rotatably support both ends of the photosensitive drum 11 in the axial direction. The connecting part 204 connects the front and rear support parts 202 and 203 on one side of the photosensitive drum 11. Figure 4 As shown, the front and rear support parts 202 and 203 are provided with front and rear positioning parts 205 and 206 for positioning the two ends along the longitudinal direction of the charging device 12. The front and rear positioning parts 205 and 206 are respectively opened with positioning holes 205a, 205b and 206a, 206b for positioning the charging device 12.

[0097] Curved portions 207 and 208 are provided on the front and rear support portions 202 and 203 of the unit body 201. When the charging device 12 is mounted, the curved portions 207 and 208 support the grid electrode 122 of the charging device 12 in a curved shape that follows the surface shape of the photosensitive drum 11. The curved portions 207 and 208 are formed into arc-shaped shapes that protrude a desired distance from the surface of the photosensitive drum 11, which is rotatably mounted on the image forming unit 200. The height of the curved portions 207 and 208 determines the gap (DGS) between the surface of the photosensitive drum 11 and the grid electrode 122 of the charging device 12.

[0098] And, as Figure 3As shown, the connecting portion 204 of the unit body 201 also serves as the main body 160 of the drum cleaning device 16. Furthermore, a drive shaft 209 having a spiral protrusion 209a on its outer circumference is rotatably mounted on the upper portion of the charging device 12. The drive shaft 209 drives a cleaning device (not shown) that cleans the charging device 12 in the axial direction of the photosensitive drum 11. An adapter portion 209b is provided at the inner end of the drive shaft 209 in the axial direction. This adapter portion 209b transmits driving force from the image forming device 1 when the image forming unit 200 is mounted on the image forming device 1.

[0099] The image forming unit 200 is configured to be insertable and removable from an opening provided on the front of the image forming apparatus 1 along a depth direction intersecting the width direction of the image forming apparatus 1. At this time, the image forming apparatus 1 has its front cover (not shown) opened.

[0100] <Operation of Image Forming Apparatus>

[0101] Hereinafter, a basic image forming operation by the image forming apparatus 1 will be described.

[0102] Here, an operation in a full-color mode in which a full-color image composed of a combination of toner images of four colors (Y, M, C, and K) is formed using the four image forming devices 10 will be described.

[0103] Image forming apparatus 1 receives image information and a command message requesting full-color image formation (printing) from a personal computer (not shown) or image reader, etc. Then, control device 100 activates four image forming units 10, intermediate transfer unit 20, secondary transfer unit 30, fixing unit 40, etc.

[0104] Moreover, if Figure 1 As shown, in each imaging device 10, each photosensitive drum 11 first rotates in the direction indicated by arrow A. Each charging device 12 charges the surface of each photosensitive drum 11 to a desired polarity (negative polarity in the first embodiment) and potential. Next, the exposure device 13 irradiates the charged surface of the photosensitive drum 11 with light based on the image signal converted into each color component (Y, M, C, K). As a result, an electrostatic latent image of each color component, with a desired potential difference, is formed on the surface of the photosensitive drum 11.

[0105] Next, each developing device 14 supplies a toner of the corresponding color (Y, M, C, K) charged to a desired polarity (negative polarity) from the developing roller 141 to the electrostatic latent image of each color component formed on the photosensitive drum 11, causing it to electrostatically adhere and develop. Through this development, the electrostatic latent image of each color component formed on each photosensitive drum 11 is visualized as a toner image of four colors (Y, M, C, K) developed by the toner of the corresponding color.

[0106] Next, the toner images of each color formed on the photosensitive drum 11 of each imaging device 10 are transported to the primary transfer position. Then, the primary transfer device 15 performs primary transfer by sequentially superimposing the toner images of each color on the intermediate transfer belt 21 rotating in the direction indicated by arrow B of the intermediate transfer device 20.

[0107] After the primary transfer is complete, the drum cleaning device 16 in each imaging device 10 scrapes away any deposits and cleans the surface of the photosensitive drum 11. The static elimination lamp 17 then evenly exposes the surface of the photosensitive drum 11 to eliminate static electricity. This allows each imaging device 10 to be ready for the following imaging operation.

[0108] Next, the intermediate transfer device 20 holds the toner image, which has been primarily transferred by the rotation of the intermediate transfer belt 21, and transports it to the secondary transfer position. Meanwhile, the paper feed device 50 delivers the required recording paper 5 to the paper feed path 56 in conjunction with the image formation operation. On the paper feed path 56, a paper feed roller pair 55, serving as registration rollers, delivers the recording paper 5 to the secondary transfer position in conjunction with the transfer timing.

[0109] At the secondary transfer position, the secondary transfer device 30 secondary transfers the toner image on the intermediate transfer belt 21 onto the recording paper 5. After the secondary transfer is completed, the belt cleaning device 25 in the intermediate transfer device 20 removes and cleans toner and other attached materials remaining on the surface of the intermediate transfer belt 21 after the secondary transfer.

[0110] Next, the recording paper 5, to which the toner image has been secondary transferred, is peeled from the intermediate transfer belt 21 and conveyed to the fixing device 40 via the paper conveying path 59. In the fixing device 40, the recording paper 5, after secondary transfer, is guided into the contact portion between the rotating heating rotator 42 and the pressing rotator 43 and passed through. Thus, the necessary fixing process (heating and pressing) is performed to fix the unfixed toner image onto the recording paper 5. Finally, the recording paper 5, after fixing, is discharged, for example, to a paper discharge portion provided on the side of the device main body (not shown).

[0111] Through the above-described operation, the recording paper 5 on which a full-color image formed by combining the toner images of four colors is output.

[0112] <Structure of the live device>

[0113] like Figure 2 and Figure 3 As shown, the charging device 12 according to the first embodiment is arranged along the axial direction of the photosensitive drum 11, which is an example of a direction intersecting the rotational direction A of the photosensitive drum 11. Here, the axial direction of the photosensitive drum 11 is the longitudinal direction of the charging device 12. Figure 3 In FIG. 1 , symbol L indicates the longitudinal direction of the charging device 12 , symbol W indicates the width direction of the charging device 12 , and symbol H indicates the height direction of the charging device 12 .

[0114] In addition, Figure 3 , the charging device 12 is shown as being positioned directly above the photosensitive drum 11. In this case, the height direction H of the charging device 12 coincides with the vertical direction. However, the charging device 12 is not limited to being positioned directly above the photosensitive drum 11. The charging device 12 may be positioned at an angle along the circumference of the photosensitive drum 11. In this case, the height direction H of the charging device 12 differs from the vertical direction.

[0115] like Figure 2 As shown, the charging device 12 generally includes a shielding case 120 as an example of a frame, a single or multiple (three in the example shown) discharge wires 121a, 121b, 121c as an example of a discharge electrode, and a grid electrode 122 as an example of a control electrode.

[0116] The shielding shell 120 is made of a metal such as stainless steel or aluminum. The shielding shell 120 acts as a counter electrode when a corona discharge is generated by applying a high voltage to the discharge wires 121a, 121b, and 121c. The shielding shell 120 is formed into a rectangular parallelepiped shape that is slender along the axial direction of the photosensitive drum 11 and has an opening portion 123 that is open to the entire surface of the surface facing the photosensitive drum 11 (the lower surface in the figure). The shielding shell 120 includes a top wall 120a, left and right side walls 120b and 120c, and two partition walls 120d and 120d. The top wall 120a is located at the upper end portion on the side opposite to the photosensitive drum 11. The left and right side walls 120b and 120c are provided in a state of being bent from both ends in the width direction W along the top wall 120a toward the bottom facing the photosensitive drum 11. Partition wall 120d partitions the space within shield case 120 along the rotational direction A, or width direction W, of photoconductor drum 11, depending on the number of discharge wires 121a, 121b, and 121c. If there is only one discharge wire 121, partition wall 120d is not provided. Shield case 120 is either applied with the same high voltage as grid electrode 122 or grounded. As described above, the cylindrical or columnar conductive substrate of photoconductor drum 11 is grounded.

[0117] The top wall 120a of the shield case 120 has an opening 120e for supplying air into the shield case 120. The opening 120e extends along the entire length of the top wall 120a, located at the center of the top wall 120a in the width direction W. Air is supplied from the opening 120e to the surface of the photosensitive drum 11. This allows discharge products such as ozone generated by corona discharge to be removed.

[0118] Discharge wires 121a, 121b, and 121c are made of tungsten, tungsten carbide, gold-plated tungsten, or the like. A negative high voltage of several kilovolts to approximately 8 kilovolts is applied to discharge wires 121a, 121b, and 121c, for example, by a high-voltage power supply (not shown). For example, the same high voltage is applied to all discharge wires 121a, 121b, and 121c. However, different high voltages may be applied to discharge wires 121a, 121b, and 121c. For example, the highest high voltage is applied to discharge wire 121a, located furthest upstream in the rotational direction A of the photosensitive drum 11. The other discharge wires 121b and 121c may be applied with the same lower voltage, or with successively lower high voltages applied to the discharge wires 121b and 121c, as they are positioned in the order of rotation. The reason why the applied voltage of the discharge wire 121 a located on the most upstream side in the rotation direction A of the photoconductor drum 11 is set to the highest value is that the charge potential of the photoconductor drum 11 is substantially determined by the discharge wire 121 a .

[0119] The grid electrode 122 is arranged in an arc-shaped configuration that follows the surface of the photosensitive drum 11, within an opening 123 of the shield case 120 that faces the photosensitive drum 11. To achieve a desired charge potential on the photosensitive drum 11, a high voltage substantially equal to the desired potential is applied to the grid electrode 122, for example, from a high-voltage power supply (not shown). The grid electrode 122 does not necessarily need to be arranged in a curved configuration that follows the surface of the photosensitive drum 11; it may be bent to follow the surface of the photosensitive drum 11, or may be flat.

[0120] like Figure 5 As shown, the grid electrode 122 is formed into a thin, rectangular, flat plate shape corresponding to the opening 123 of the shield case 120 by etching or stamping a thin plate-like member made of metal such as tungsten, tungsten carbide, or gold-plated tungsten. The grid electrode 122 integrally includes a control portion 122a and connecting portions 122b and 122c. The control portion 122a is provided over the entire area of ​​the grid electrode 122 along the longitudinal direction L, excluding the two end portions. Figure 3As shown, the control portion 122a of the grid electrode 122 has a length along the axial direction of the photosensitive drum 11 that is equal to the image forming area of ​​the photosensitive drum 11. The connecting portions 122b and 122c are respectively provided at both ends of the control portion 122a along the longitudinal direction. A boundary portion 122d formed in a short strip shape along the longitudinal direction L is provided between the control portion 122a and the connecting portions 122b and 122c. Figure 6 As shown, slightly wider band-shaped edge portions 122 e may be provided at both ends of the grid electrode 122 in the width direction W.

[0121] As the control unit 122a of the grid electrode 122, Figure 6 As shown in (a), a plurality of linear conductors 122f, 122f, ... having narrow widths along the longitudinal direction L are arranged in parallel with each other at a desired density along the width direction W. As the control portion 122a of the grid electrode 122, as shown in FIG. Figure 6 As shown in (b), a plurality of narrow linear conductors 122f, 122f, ..., inclined in a direction intersecting the longitudinal direction L, are arranged in parallel with each other at a desired density. The control portion 122a has small gaps G formed uniformly between the plurality of linear conductors 122f, 122f, ..., along the width direction W and the longitudinal direction L.

[0122] like Figure 7 As shown, the control unit 122a of the grid electrode 122 causes charged particles such as ions generated by corona discharge caused by applying a high voltage to the discharge wires 121a, 121b, and 121c to pass through the gaps formed between the narrow linear conductors 122f, 122f, ... and adhere to the surface of the photosensitive drum 11, thereby charging the photosensitive drum 11. The control unit 122a of the grid electrode 122 controls the charge potential of the photosensitive drum 11 by the action of the electric field formed by the voltage applied to the control unit 122a. Figure 7 In FIG. 1 , for convenience, the surface of the photosensitive drum 11 and the grid electrode 122 are shown as planes.

[0123] like Figure 5 As shown, the connection parts 122b and 122c of the grid electrode 122 are formed by protruding trapezoidal frames at both ends along the longitudinal direction L. The connection parts 122b and 122c are locked to locking parts provided on an insulating block described later and are fixed in a tensioned state.

[0124] In addition, if Figure 8 As shown, as the connecting portions 122b and 122c of the grid electrode 122, a plurality of groups of annular connecting pieces 122b', 122c', 122b", and 122c" arranged in the width direction W may be used.

[0125] If the structure of the charging device 12 is further described, Figure 9 As shown, the charging device 12 includes a guide member 124, front and rear insulating blocks 125 and 126, and a mounting member 127. The guide member 124 is provided on the side of the shield case 120 opposite the photosensitive drum 11 (the lower surface in the figure) along the longitudinal direction. The front and rear insulating blocks 125 and 126 are respectively arranged at both ends of the shield case 120 along the longitudinal direction L. The mounting member 127 is provided at the end near the front of the front insulating block 125, which is arranged on the front side of the image forming apparatus 1.

[0126] The guide member 124 is formed of a synthetic resin or the like into a slender, flat plate. Two guide protrusions 124a and 124b are provided on the outer side of the guide member 124 at either end along its longitudinal direction to guide the charging device 12 when it is mounted on the image forming apparatus 1. The two guide protrusions 124a and 124b are formed so that the guide protrusion 124b located on the back side of the image forming apparatus 1 is longer than the guide protrusion 124a located on the front side of the image forming apparatus 1.

[0127] The front and rear insulating blocks 125 and 126 are composed of a single or multiple insulating components made of synthetic resin. The insulating blocks 125 and 126 are fixed to the two ends of the shielding case 120 along the longitudinal direction L by means of snap fastening or other methods. Three discharge wires 121a, 121b, and 121c and the grid electrode 122 are tensioned across the front and rear insulating blocks 125 and 126. One end of each discharge wire 121a, 121b, and 121c is fixed to one of the front and rear insulating blocks 125 and 126, while the other end is fixed to the other insulating block 125 by applying the desired tension via an elastic member such as a coil spring.

[0128] like Figure 10 As shown, a curved retaining portion 126a and a plurality of latching claws 126b, 126b, ... are provided on the insulating block 126 at the rear end. The retaining portion 126a deforms the rear end portion of the grid electrode 122 into a curved shape along the surface shape of the photosensitive drum 11 and retains it. The plurality of latching claws 126b, 126b, ... are fixed in a state of latching the connecting portion 122c of the grid electrode 122. In addition, a semi-cylindrical and square-cylindrical shaped conducting portion 126c is provided at the front end of the insulating block 126 at the rear end. The conducting portion 126c has a plurality of conducting electrodes (not shown) built in for respectively conducting electricity to the shielding shell 120, the discharge wires 121a, 121b, 121c and the grid electrode 122. When the charging device 12 is mounted on the image forming device 1, the conducting portion 126c of the insulating block 126 at the rear end is connected to the electrodes on the image forming device 1 side. Thus, the shield case 120 , the discharge wires 121 a , 121 b , and 121 c , and the grid electrode 122 can be energized.

[0129] Positioning pins 126d, 126d are provided in the insulating block 126 at the rear end so as to protrude toward the inner side in the longitudinal direction. Figure 4 As shown, the positioning pins 126 d and 126 d are fitted into the positioning holes 206 a and 206 b of the positioning portion 206 provided on the support portion 203 at the rear end of the image forming unit 200 , thereby positioning the charging device 12 .

[0130] like Figure 11 As shown, the front-end insulating block 125 is provided with a curved retaining portion 125a and a tensioning member 60. The retaining portion 125a deforms the front end of the grid electrode 122 into a curved shape that conforms to the surface of the photosensitive drum 11 and holds it there. The tensioning member 60 applies tension to the grid electrode 122 by displacing the connecting portion 122b of the grid electrode 122 outward relative to the charged area of ​​the grid electrode 122. The tensioning member 60 is mounted on the front-end insulating block 125 so as to be rotatable about a rotation axis extending in the width direction W of the charging device 12.

[0131] like Figure 13 As shown, the retaining portions 125a and 126a of the insulating blocks 125 and 126 and the curved portions 207 and 208 of the image forming unit 200 are arranged so as to slightly protrude toward the other component relative to the tensioned position of the grid electrode 122. As a result, the shape and position of the grid electrode 122 are determined by the curved portions 207 and 208 of the image forming unit 200.

[0132] like Figure 11 As shown, the insulating block 125 at the front end is provided with a rising wall 125d, and the rising wall 125d is opened with an insertion hole 125c for the connection portion 122b of the grid electrode 122 to pass through. In addition, positioning pins 125e, 125e (refer to Figure 9 ) is provided in a manner protruding toward the charged area of ​​the photosensitive drum 11 along the longitudinal direction L. Figure 9 As shown, when the charging device 12 is mounted on the image forming apparatus 1 , the positioning pins 125 e and 125 e position the front end portion of the charging device 12 along the width direction of the upper portion of the insertion hole 125 c.

[0133] like Figure 12As shown, the tensioning member 60 of the insulating block 125 provided at the front end is formed by stamping or bending a metal plate made of a metal such as stainless steel or by integral molding of a synthetic resin. The tensioning member 60 includes a main body 601, a plurality of latching claws 602, 602..., pivot supports 603, 603 and a connecting portion 604. The front shape of the main body 601 is formed into a horizontally long rectangular shape along the width direction W of the charging device 12. A plurality of latching claws 602, 602... are provided at the upper end of the main body 601 in a manner protruding upward at required intervals. The pivot supports 603, 603 are bent orthogonally from both ends along the width direction of the main body 601. The connecting portion 604 is bent in the same direction as the pivot supports 603, 603 at the lower end of the main body 601 and connects one end of a coil spring 605 as an example of a force-applying member.

[0134] The locking claws 602, 602, ... of the tension member 60 are positioned near the grid electrode 122 at both ends along the width direction W. As a result, the locking claws 602, 602, ... are positioned approximately equidistant from the respective connecting pieces 122b', 122b" of the connecting portion 122b of the curved grid electrode 122.

[0135] The pivot support portions 603, 603 of the tension member 60 are provided with rotation shafts 603a, 603a so as to protrude toward both ends in the width direction. Figure 13 As shown, the rotation shafts 603a, 603a of the tension member 60 are rotatably supported by a pivot support portion 125f provided inside the insulation block 125 at the front end.

[0136] like Figure 13 As shown, one end of a coil spring 605 is connected to the connecting portion 604 of the tensioning member 60. The other end of the coil spring 605 is fixed inside the insulating block 125. As a result, the tensioning member 60 is biased counterclockwise in the figure. Tension is applied to the grid electrode 122, which is engaged by the engaging claws 602, 602, etc. of the tensioning member 60, by the coil spring 605.

[0137] The mounting member 127 of the charging device 12 is a member for mounting the charging device 12 in a fixed state when the charging device 12 is mounted on the image forming apparatus 1. Figure 13 As shown, a fixed arm 127a, which is biased counterclockwise by a spring 127b, is rotatably mounted on the mounting member 127. The charging device 12 is released from the image forming apparatus 1 by manually grasping a release lever (not shown) provided on the mounting member 127 to rotate the fixed arm 127a clockwise.

[0138] However, if Figure 7 As shown, the charging device 12 configured as described above generates corona discharge by applying a high voltage to the discharge wires 121a, 121b, and 121c. The charging device 12 then charges the photoconductive drum 11 by causing charged particles such as ions generated by the corona discharge to pass through the grid electrode 122 and adhere to the surface. Furthermore, the control unit 122a of the grid electrode 122 controls the charge potential of the photoconductive drum 11 through the electric field generated by the voltage applied to the control unit 122a.

[0139] At this time, an ion wind 300 is generated in the charging device 12, flowing from the discharge wires 121a, 121b, and 121c toward the surface of the photosensitive drum 11 located directly below. Furthermore, the charging device 12 is configured to remove discharge products by sending air (air 301) from the air outlet 120e of the shield case 120 toward the surface of the photosensitive drum 11. Therefore, the control portion 122a of the grid electrode 122, which is tensioned on the opening 123 of the shield case 120, is susceptible to vibration due to the influence of the ion wind 300 and air 301.

[0140] Furthermore, the charging device 12 is configured such that a plurality of linear conductors 122f, 122f, ... are stretched in the longitudinal direction L by the control unit 122a of the grid electrode 122. Therefore, the linear conductors 122f, 122f, ... of the grid electrode 122 are likely to resonate and vibrate with a drive motor that rotationally drives the photosensitive drum 11, the developing device 14, the intermediate transfer belt 21, and other components of the image forming apparatus 1, and with drive gears that transmit the driving force.

[0141] The charging device 12 has the following technical problem: when the linear conductors 122 f, 122 f, . . . of the control portion 122 a vibrate, charged particles such as ions passing through the control portion 122 a are affected by the vibration, causing unevenness in the charged potential on the surface of the photosensitive drum 11 .

[0142] Therefore, the charging device according to the first embodiment is configured as follows: the control electrode has:

[0143] A plurality of linear conductors are arranged to intersect the rotation direction of the charged body at an arbitrary angle; and

[0144] The plurality of connection portions connect the linear conductors along the rotation direction of the charged body and are arranged more in the central region than in the regions at both ends in a direction intersecting the rotation direction of the charged body.

[0145] Furthermore, the charging device involved in this embodiment 1 is constructed as follows: the control electrode has: a plurality of straight conductors, which are arranged to intersect with the rotation direction of the charged body at an arbitrary angle; and a plurality of connecting parts, which connect the straight conductors along the rotation direction of the charged body, and are more arranged in the opposing area where the discharge electrode and the control electrode are opposed to each other than the non-opposing area where the discharge electrode and the control electrode are not opposed to each other in the rotation direction of the charged body.

[0146] That is, Figure 14 As shown, in the charging device 12 involved in this embodiment 1, the following grid electrode is used as the grid electrode 122: the straight conductors 122f, 122f,... arranged along the axial direction of the photosensitive drum 11, that is, the long side direction L of the charging device 12 are arranged parallel to each other with a small gap G separated along the rotation direction of the photosensitive drum 11, that is, the width direction W of the charging device 12.

[0147] Furthermore, the grid electrode 122 of the charging device 12 includes a plurality of connecting portions 122g, 122g, ... that connect the linear conductors 122f, 122f, ... to one another along the rotational direction of the photosensitive drum 11, i.e., the width direction W of the charging device 12. Furthermore, the plurality of connecting portions 122g, 122g, ... may connect the linear conductors 122f, 122f, ... to one another along the width direction W of the charging device 12. That is, the plurality of connecting portions 122g, 122g, ... are not limited to being arranged along the width direction W of the charging device 12 and may also be arranged obliquely with respect to the width direction W of the charging device 12.

[0148] The plurality of connecting portions 122g, 122g, ... are configured as follows: when the grid electrode 122 is divided into three equal parts along the longitudinal direction L of the charging device 12, namely, the central portion 400 and the two end portions 401 and 402, more are arranged in the central portion than in the two end portions of the grid electrode 122. In addition, for the sake of convenience, in Figure 14 In the figure, the central portion 400 is shown to be slightly wider than the two end portions 401 and 402.

[0149] To further explain the multiple connecting portions 122g, 122g, ..., focus on the uppermost linear conductor 122f1 and the second linear conductor 122f2 adjacent to the linear conductor 122f1 along the width direction W of the charging device 12. Thus, only one of the multiple connecting portions 122g, 122g, ... is provided in the regions of the two end portions 401, 402 of the grid electrode 122, whereas three are provided in the central portion 400.

[0150] Similarly, focusing on the second linear conductor 122f2 and the adjacent third linear conductor 122f3 from the uppermost linear conductor 122f1 along the width direction of the charging device 12, the plurality of connecting portions 122g, 122g, ... are provided only one in the regions of the two end portions 401, 402 of the grid electrode 122, whereas four are provided in the central portion 400.

[0151] Similarly, regarding the other linear conductors 122 f , the plurality of connecting portions 122 g , 122 g , . . . are provided more in the region of the central portion 400 than in the regions of the both end portions 401 , 402 of the grid electrode 122 .

[0152] In other words, the plurality of connecting portions 122g, 122g, ... are arranged so that the density in the central portion 400 of the grid electrode 122 is higher than in the regions at the end portions 401, 402. Here, the density of the plurality of connecting portions 122g, 122g, ... refers to the number of connecting portions 122g, 122g, ... arranged per unit length along the longitudinal direction L of the linear conductor 122f.

[0153] And, as Figure 14 As shown, the charging device 12 involved in this embodiment 1 is constructed as follows: compared with the non-opposing area 411 where the discharge wires 121a, 121b, 121c and the grid electrode 122 are not opposite, the connecting parts 122g, 122g, ... of the grid electrode 122 are mostly arranged in the opposing area 410 where the discharge wires 121a, 121b, 121c and the grid electrode 122 are opposite.

[0154] Here, if Figure 7 As shown, the opposing region 410 where the discharge wires 121a, 121b, 121c and the grid electrode 122 are opposed to each other is not only the position directly below the discharge wires 121a, 121b, 121c, but also the region directly affected by the ion wind 300 generated when a high voltage is applied to the discharge wires 121a, 121b, 121c. The region directly affected by the ion wind may also change depending on the applied voltage of the discharge wires 121a, 121b, 121c or the distance between the discharge wires 121a, 121b, 121c and the grid electrode 122. Here, as shown in FIG. Figure 15As shown, facing region 410 is a region where, when a perpendicular line 420 perpendicular to the surface of grid electrode 122 is drawn from discharge lines 121a, 121b, and 121c, n linear conductors 122f are located on both sides of a position 421 where the perpendicular line 420 intersects the surface of grid electrode 122. The value of n depends on the arrangement density of the linear conductors 122f, 122f, ..., and is, for example, 10 or less, preferably 5 or less. Furthermore, when grid electrode 122 is curved, a perpendicular line passing through discharge lines 121a, 121b, and 121c is drawn relative to a tangent to the surface of grid electrode 122.

[0155] like Figure 15 As shown, in the illustrated embodiment, when a perpendicular line 420 is drawn from the discharge lines 121a, 121b, and 121c to the surface of the grid electrode 122, the area where two linear conductors 122f exist on both sides of the position where the perpendicular line 420 intersects the surface of the grid electrode 122 is the opposing area 410.

[0156] To further illustrate, in the illustrated embodiment, Figure 14 As indicated by the dotted line in FIG, the linear conductor 122f located at the uppermost portion and located in the region 410 facing the discharge wire 121a is a region where four linear conductors 122f, namely the third to sixth linear conductors 122f from the uppermost portion, are present.

[0157] Likewise, in the illustrated embodiment, Figure 14 As shown, the linear conductors 122f located in the center and in the region facing the discharge line 121b are located in a region where four linear conductors 122f, from the tenth to the thirteenth linear conductor 122f from the uppermost linear conductor 122f, are present.

[0158] Furthermore, in the illustrated embodiment, Figure 14 As shown, the linear conductor 122f located at the bottom and located in the region facing the discharge line 121c is a region where four linear conductors 122f, namely the third to sixth linear conductors from the bottom linear conductor 122f, are present.

[0159] Focusing on the linear conductors 122f located in the opposing regions, for example, the number of connecting portions 122g, 122g, ... connecting the third and fourth linear conductors 122f from the top linear conductor 122f is nine. Furthermore, the number of connecting portions 122g, 122g, ... connecting the fourth and fifth linear conductors 122f from the top linear conductor 122f is ten. Furthermore, the number of connecting portions 122g, 122g, ... connecting the fifth and sixth linear conductors 122f from the top linear conductor 122f is nine.

[0160] In contrast, if we focus on the linear conductors 122f located in the non-opposing area outside the opposing area, for example, the multiple connecting portions 122g, 122g, ... connecting the first and second linear conductors 122f from the top linear conductor 122f are 5, and the multiple connecting portions 122g, 122g, ... connecting the second and third linear conductors 122f from the top linear conductor 122f are 6.

[0161] Thus, in the charging device 12 according to the first embodiment, Figure 14 As shown, the number of connecting portions 122g, 122g, ... of the grid electrode 122 is 5 or 6 in the non-opposing region where the discharge electrode and the control electrode are not opposed to each other, whereas in the opposing region where the discharge electrode and the control electrode are opposed to each other, there are more connecting portions 122g, 122g, ..., which is about twice as many.

[0162] The same applies to the opposing regions facing the other discharge wires 121b and 121c.

[0163] Furthermore, in the charging device 12 according to this embodiment, the fourth and fifth linear conductors 122f from the top linear conductor 122f are located in the region facing the discharge line. Thus, the plurality of connecting portions 122g, 122g, ..., which connect these linear conductors 122f to each other, are provided in the regions of the two end portions 401, 402 of the grid electrode 122, while a greater number, six, are provided in the region of the central portion 400.

[0164] <Function of the live device>

[0165] In the charging device according to the first embodiment, as described below, the occurrence of uneven charging due to vibration of the control electrode can be suppressed compared to the case where a plurality of connection portions constituting the control electrode are arranged without considering the vibration characteristics of the control electrode.

[0166] In the image forming apparatus 1, as Figure 1 As shown, when each image forming device 10 of yellow (Y), magenta (M), cyan (C) and black (K) forms an image, the surface of each photosensitive drum 11 is uniformly charged to a desired potential by the charging device 12.

[0167] At this time, in the charging device 12, as shown in FIG. Figure 2 As shown, a high voltage is applied to the discharge lines 121 a , 121 b , 121 c , and a desired high voltage is applied to the grid electrode 122 .

[0168] In the charging device 12, as Figure 7As shown, the linear conductors 122f, 122f, ..., constituting the grid electrode 122 are prone to vibration. As described above, this is due to the influence of ion wind 300 generated by applying a high voltage to the discharge wires 121a, 121b, and 121c, and the air 301 introduced from the air outlet 120e of the shield case 120. This, in turn, causes the vibration of the drive motors and drive force transmission components that drive the photosensitive drum 11, the developing device 14, and the intermediate transfer device 20 disposed around the charging device 12 to be transmitted via the frame and the like.

[0169] However, if Figure 14 As shown, the charging device 12 involved in this embodiment 1 has a plurality of connecting parts 122g, 122g,..., among the plurality of connecting parts 122g, 122g,..., for the straight conductors 122f, 122f,... that constitute the grid electrode 122, the adjacent straight conductors 122f, 122f,... are connected to each other along the rotation direction of the photosensitive drum 11, that is, the width direction W of the charging device 12.

[0170] Furthermore, the plurality of connecting portions 122g, 122g, ... are arranged more frequently in the region of the central portion 400 than in the regions of the two end portions 401, 402 of the grid electrode 122. In other words, the plurality of connecting portions 122g, 122g, ... are arranged at a higher density in the region of the central portion 400, where vibration is more likely to occur, than in the regions of the two end portions 401, 402 of the grid electrode 122.

[0171] Furthermore, the plurality of connecting portions 122g, 122g, ... are arranged more frequently in the facing region 410 where the discharge wires 121a, 121b, 121c and the grid electrode 122 face each other and are more likely to vibrate due to the ion wind 300 from the discharge wires 121a, 121b, 121c, relative to the non-facing region 411 where the discharge wires 121a, 121b, 121c and the grid electrode 122 do not face each other. In other words, the plurality of connecting portions 122g, 122g, ... are arranged at a higher density in the facing region 410 where the discharge wires 121a, 121b, 121c and the grid electrode 122 face each other, compared to the non-facing region 411 where the discharge wires 121a, 121b, 121c and the grid electrode 122 do not face each other.

[0172] Therefore, in the charging device 12 according to the first embodiment, adjacent linear conductors 122f, 122f, ... of the grid electrode 122 are connected by a large number of connecting portions 122g, 122g, ... in areas where vibration is likely to occur. This prevents or even suppresses the occurrence of vibration in the linear conductors 122f, 122f, .... Furthermore, the occurrence of uneven charging caused by the vibration of the linear conductors 122f, 122f, ... of the grid electrode 122 can be prevented or even suppressed.

[0173] Implementation Method 2

[0174] Figure 16 1 is a diagram showing a configuration of a charging device according to Embodiment 2 of the present invention. The charging device according to Embodiment 2 is configured such that the aperture ratio of the control electrodes in a direction intersecting the rotation direction of the charged body is uniform.

[0175] That is, Figure 16 As shown, the charging device 12 according to the second embodiment is configured such that the line widths of the plurality of connecting portions 122g, 122g, ... are different depending on the arrangement density of the connecting portions 122g, 122g, ... .

[0176] like Figure 7 As shown, the control unit 122a of the grid electrode 122 causes charged particles such as ions generated by corona discharge caused by applying a high voltage to the discharge wires 121a, 121b, and 121c to pass through the gaps formed between the narrow linear conductors 122f, 122f, ... and adhere to the surface of the photoconductive drum 11, thereby charging the drum. Furthermore, the control unit 122a of the grid electrode 122 controls the charge potential of the photoconductive drum 11 through the action of the electric field formed by the voltage applied to the control unit 122a.

[0177] Therefore, if the arrangement density of the multiple connecting parts 122g, 122g, ... that connect the linear conductors 122f, 122f, ... that constitute the grid electrode 122 is different along the direction intersecting the rotation direction of the photosensitive drum 11, that is, the long side direction L of the charging device 12, the opening ratio of the grid electrode 122 will be different along the long side direction L of the charging device 12.

[0178] Here, the aperture ratio (%) of the grid electrode 122 is (area of ​​the gap G per unit area / unit area)*100.

[0179] By arranging multiple connecting parts 122g, 122g,... at a high density, if the opening ratio of the grid electrode 122 is small, the number of charged particles such as ions generated on the discharge wires 121a, 121b, and 121c that pass through the gap G and head toward the surface of the photosensitive drum 11 will decrease, and the proportion flowing to the grid electrode 122 will increase.

[0180] On the other hand, if the aperture ratio of the grid electrode 122 is too large, the potential compensation capability of the photosensitive drum 11 by the grid electrode 122 is reduced, and the state becomes close to that of a corotron, which is not preferable. Therefore, the aperture ratio of the grid electrode 122 is preferably uniform, that is, 86% to 95%.

[0181] like Figure 16As shown, the charging device 12 involved in this embodiment 2 is constructed as follows: according to the arrangement density of multiple connecting parts 122g, 122g,..., narrow connecting parts 122g, 122g,... are set with line widths in areas with high arrangement density, and wide connecting parts 122g, 122g,... are set with line widths in areas with low arrangement density, thereby making the opening ratio along the long side direction L of the grid electrode 122 the same.

[0182] In addition, the aperture ratio of the grid electrode 122 does not need to be strictly constant along the longitudinal direction L. For example, the aperture ratio of the grid electrode 122 is preferably uniform, that is, in the range of 86% to 95%.

[0183] The charging device 12 involved in this embodiment 2 is constructed so that the opening ratio of the grid electrode 122 along the long side direction L is the same. Therefore, by providing multiple connecting parts 122g, 122g,... on the grid electrode 122, the opening ratio of the grid electrode 122 can be suppressed and the charging performance can be changed along the long side direction L.

[0184] The other structures and functions are the same as those in the first embodiment, so their description is omitted.

[0185] Implementation 3

[0186] Figure 17 1 is a structural diagram showing a charging device according to Embodiment 3 of the present invention. The charging device according to Embodiment 3 is configured as follows: the number of divisions of the control electrode in a direction intersecting the rotation direction of the charged body is increased, and the line widths of the plurality of connecting portions in each division area are made different.

[0187] That is, Figure 17 As shown, the charging device 12 according to the third embodiment is configured such that the grid electrode 122 is divided into five equal parts along the longitudinal direction and divided into five regions.

[0188] The grid electrode 122 includes a central portion 400 located in the center along the longitudinal direction, regions at both end portions 401 and 402 located at both ends along the longitudinal direction, and intermediate portions 403 and 404 located between the central portion and the end portions.

[0189] In addition, for the sake of convenience, here, the case where the grid electrode 122 is divided into 5 equal parts along the longitudinal direction is described. However, in an actual charging device, for example, it is preferable to divide it into 30 equal parts along the longitudinal direction while keeping the aperture ratio the same.

[0190] like Figure 17As shown, in the charging device 12 according to the third embodiment, the grid electrode 122 has a plurality of connecting portions 122g, 122g, ... arranged such that there are 50 connecting portions 122g, 122g, ... with a line width of 0.8 mm in the center portion 400, 30 connecting portions 122g, 122g, ... with a line width of 1.3 mm in the middle portions 403 and 404, and 15 connecting portions 122g, 122g, ... with a line width of 2.7 mm in the end portions 401 and 402. As a result, the area (aperture ratio) occupied by the connecting portions 122g, 122g, ... due to the provision of the plurality of connecting portions 122g, 122g, ... on the grid electrode 122 can be maintained approximately constant at 50 × 0.8 = 40, 30 × 1.3 = 39, and 15 × 2.7 = 40.5, according to simple calculation, because the lengths of the connecting portions 122g, 122g, ... are constant.

[0191] Since the arrangement density has a greater impact on the vibration suppression effect of the grid electrode 122 than the line width of the multiple connecting parts 122g, 122g,..., even if the line width of the multiple connecting parts 122g, 122g,... is changed, the impact on the vibration suppression effect can be small enough to be negligible.

[0192] The other structures and functions are the same as those in the first embodiment, so their description is omitted.

[0193] Implementation 4

[0194] Figure 18 1 is a structural diagram showing a charging device according to a fourth embodiment of the present invention. The charging device according to the fourth embodiment is configured such that the plurality of connection portions of the control electrode are not arranged along the rotation direction of the charged body but are arranged obliquely relative to the rotation direction of the charged body.

[0195] That is, Figure 18 As shown, the charging device 12 involved in this embodiment 4 is constructed as follows: a plurality of connecting portions 122g, 122g, ... that connect the linear conductors 122f, 122f, ... that constitute the grid electrode 122 are arranged at an inclination relative to the rotation direction of the photosensitive drum 11, that is, the width direction W of the charging device 12.

[0196] If further explanation is given, Figure 18 As shown, the charging device 12 according to the fourth embodiment is arranged so that the start points and end points of the plurality of connection portions 122g, 122g, ... do not overlap.

[0197] If the plurality of connecting portions 122g, 122g, ... connecting the linear conductors 122f, 122f, ... constituting the grid electrode 122 are arranged so that the starting and ending points overlap, the overlapping positions may become "nodes" of vibration, thereby generating new vibrations.

[0198] Therefore, in the charged device 12 involved in this embodiment 4, by configuring the starting points and end points of the multiple connecting parts 122g, 122g, ... not to overlap, it is possible to prevent or even suppress the multiple connecting parts 122g, 122g, ... from becoming "nodes" of vibration and generating new vibrations.

[0199] The other structures and functions are the same as those in the first embodiment, so their description is omitted.

[0200] (Note) (1)

[0202] A charging device comprising:

[0203] discharge electrodes; and

[0204] The control electrode is arranged between the discharge electrode and the charged object charged by the discharge electrode.

[0205] The control electrode has:

[0206] a plurality of linear conductors arranged to intersect the rotation direction of the charged body at arbitrary angles; and

[0207] The plurality of connection portions connect the linear conductors along the rotation direction of the charged body and are arranged more in the central region than in regions at both ends of the charged body in a direction intersecting the rotation direction. (2)

[0209] A charging device comprising:

[0210] discharge electrodes; and

[0211] The control electrode is arranged between the discharge electrode and the charged object charged by the discharge electrode.

[0212] The control electrode has:

[0213] a plurality of linear conductors arranged to intersect the rotation direction of the charged body at arbitrary angles; and

[0214] The plurality of connecting portions connect the linear conductors along the rotation direction of the charged body and are more frequently arranged in the facing region where the discharge electrode and the control electrode face each other than in the non-facing region where the discharge electrode and the control electrode do not face each other in the rotation direction of the charged body. (3)

[0216] The charging device according to (1), wherein the plurality of connecting portions connect adjacent ones of the plurality of linear conductors to each other. (4)

[0218] The charging device according to (3), wherein the plurality of connecting portions are arranged in the following manner: the density of the connecting portions is highest in the central region of the control electrode in a direction intersecting the rotation direction of the charged body, and the density of the connecting portions gradually decreases toward the two end portions of the control electrode. (5)

[0220] The charging device according to (1), wherein the plurality of connection portions are arranged so as to include a non-opposing region where the discharge electrode and the control electrode do not face each other. (6)

[0222] The charging device according to (5), wherein the plurality of connecting portions are arranged in such a manner that the density of the connecting portions in the opposing region where the discharge electrode and the control electrode are opposed to each other is higher than the density of the connecting portions in the non-opposing region where the discharge electrode and the control electrode are not opposed to each other in a direction intersecting the rotation direction of the charged body. (7)

[0224] The charging device according to (1), wherein the opening ratio of the control electrode in a direction intersecting with the rotation direction of the charged body is uniform. (8)

[0226] The charging device according to (7), wherein, among the plurality of connecting portions, the line width of the connecting portion in the central portion is narrower than the line width of the connecting portion in the regions of both ends of the control electrode in a direction intersecting the rotation direction of the charged body. (9)

[0228] The charging device according to (1), wherein a plurality of the discharge electrodes are arranged along the rotation direction of the charged body. (10)

[0230] The charging device according to (9), wherein

[0231] The voltage applied to the discharge electrode at the most upstream side in the rotation direction of the charged body is higher than that applied to other parts. (11)

[0233] An image forming unit includes the charging device described in any one of (1) to (10), wherein the image forming unit is attachable to and detachable from an image forming apparatus. (12)

[0235] An image forming apparatus comprising:

[0236] Image holding member;

[0237] a charging member for charging the surface of the image holding member; and

[0238] an electrostatic latent image forming member for forming an electrostatic latent image on the surface of the image holding member charged by the charging member,

[0239] The image forming apparatus uses the charging device described in any one of (1) to (10) as the charging member.

[0240] According to the charging device according to (1), compared with a case where a plurality of connection portions constituting the control electrode are uniformly arranged in the axial direction, occurrence of uneven charging due to vibration of the control electrode can be suppressed.

[0241] According to the charging device involved in (2), compared with the case where multiple connecting parts constituting the control electrode are equally arranged in the non-opposing area where the discharge electrode and the control electrode are not opposite to each other and the opposing area where the discharge electrode and the control electrode are opposite to each other, the occurrence of charging unevenness caused by vibration of the control electrode can be suppressed.

[0242] According to the charging device according to (3), vibration of the linear conductors can be suppressed compared to a case where adjacent linear conductors are not connected to each other.

[0243] According to the charging device involved in (4), compared with the case where multiple connecting parts are arranged with equal density in the area of ​​the central part of the control electrode and the areas of the two end parts of the control electrode in the direction intersecting the rotation direction of the charged body, the generation of vibration of the linear conductor can be effectively suppressed.

[0244] According to the charging device according to (5), the vibration of the linear conductor can be effectively suppressed compared to the case where a plurality of connecting portions are arranged only in the facing region where the discharge electrode and the control electrode face each other.

[0245] According to the charging device involved in (6), compared with the case where a plurality of connecting parts are arranged so that the density of the connecting parts in the non-opposing area where the discharge electrode and the control electrode are not opposite in the direction intersecting the rotation direction of the charged body and the density of the connecting parts in the opposing area where the discharge electrode and the control electrode are opposite are equal, the vibration of the linear conductor can be effectively suppressed.

[0246] According to the charging device according to (7), it is possible to suppress the occurrence of unevenness in the charging potential along the axial direction of the charged body, compared to a case where the aperture ratio of the control electrode along the axial direction of the charged body is different.

[0247] According to the charging device involved in (8), the aperture ratio can be easily set compared to the case where the line width of the connection portion in the area of ​​the two end portions of the control electrode in the direction intersecting the rotation direction of the charged body among multiple connection portions is equal to the line width of the connection portion in the central portion.

[0248] According to the charging device according to (9), the charging capability can be improved compared to a case where a single discharge electrode is used.

[0249] According to the charging device according to (10), the charging characteristics of the charged body can be improved compared to the case where the applied voltage is set higher than that at the discharge electrode other than the most upstream side in the rotation direction of the charged body.

[0250] According to the image forming unit of (11), the occurrence of uneven charging due to vibration of the control electrode can be suppressed compared to a case where the charging device according to any one of (1) to (10) is not provided.

[0251] According to the image forming apparatus involved in (12), compared with the case where the charging device described in any one of (1) to (10) is not used as the charging member, the occurrence of uneven charging due to vibration of the control electrode can be suppressed, and the image quality can be improved.

[0252] The above-described embodiments of the present invention are provided for the purpose of illustration and explanation. In addition, the embodiments of the present invention do not fully and exhaustively include the present invention, and do not limit the present invention to the disclosed embodiments. It is obvious that various modifications and variations are self-evident to those skilled in the art to which the present invention belongs. The present embodiment is selected and described in order to most easily explain the principles of the present invention and its application. Thus, other technical personnel in this field can understand the present invention through various modifications optimized for specific uses of the assumed various embodiments. The scope of the present invention is defined by the above claims and their equivalents.

Claims

1. A charging device comprising: discharge electrodes; and The control electrode is arranged between the discharge electrode and the charged object charged by the discharge electrode. The control electrode has: a plurality of linear conductors arranged to intersect the rotation direction of the charged body at arbitrary angles; and The plurality of connection portions connect the linear conductors along the rotation direction of the charged body and are arranged more in the central region than in regions at both ends of the charged body in a direction intersecting the rotation direction.

2. A charging device comprising: discharge electrodes; and The control electrode is arranged between the discharge electrode and the charged object charged by the discharge electrode. The control electrode has: a plurality of linear conductors arranged to intersect the rotation direction of the charged body at arbitrary angles; and The plurality of connecting portions connect the linear conductors along the rotation direction of the charged body and are more frequently arranged in the facing region where the discharge electrode and the control electrode face each other than in the non-facing region where the discharge electrode and the control electrode do not face each other in the rotation direction of the charged body.

3. The charging device according to claim 1, wherein: The plurality of connecting portions connect adjacent ones of the plurality of linear conductors to each other.

4. The charging device according to claim 3, wherein: The plurality of connecting portions are arranged such that a density of the connecting portions is highest in a central region of the control electrode in a direction intersecting the rotation direction of the charged body and gradually decreases toward both ends of the control electrode.

5. The charging device according to claim 1, wherein The plurality of connection portions are arranged so as to include a non-opposing region where the discharge electrode and the control electrode do not face each other.

6. The charging device according to claim 5, wherein: The plurality of connection portions are arranged so that a density of the connection portions in the facing region where the discharge electrode and the control electrode face each other is higher than a density of the connection portions in the non-facing region where the discharge electrode and the control electrode do not face each other in a direction intersecting the rotation direction of the charged body.

7. The charging device according to claim 1, wherein: The control electrode has a uniform aperture ratio in a direction intersecting the rotation direction of the charged body.

8. The charging device according to claim 7, wherein: Among the plurality of connecting portions, the connecting portion in the center has a narrower line width than the connecting portions in regions at both ends of the control electrode in a direction intersecting the rotation direction of the charged body.

9. The charging device according to claim 1, wherein: A plurality of the discharge electrodes are arranged along the rotation direction of the charged body.

10. The charging device according to claim 9, wherein: The voltage applied to the discharge electrode at the most upstream side in the rotation direction of the charged body is higher than that applied to other parts. 11 . An image forming unit comprising the charging device according to claim 1 , wherein the image forming unit is detachable from an image forming apparatus.

12. An image forming apparatus comprising: Image holding member; a charging member for charging the surface of the image holding member; and An electrostatic latent image forming member forms an electrostatic latent image on a surface of the image holding member charged by the charging member, and the image forming apparatus uses the charging device according to any one of claims 1 to 10 as the charging member.

Images