Image forming apparatus

Abstract

An image forming apparatus includes: a first charging unit configured to apply a voltage to a first image holding body to charge the first image holding body, the voltage having a frequency of an alternating current component at a first frequency; a first developing section that develops a latent image formed on the first image holding body with a toner of a reference color; a second charging unit that charges a second image holding body by applying a voltage to the second image holding body, the voltage being different from the first frequency and the frequency of the AC component being a second frequency; and a second developing section that develops a latent image formed on the second image holding body with a toner of a special color.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus. Background Art

[0002] Patent document 1 below discloses an AC bias applying device for applying an AC bias to a plurality of image generating units constituting an electronic photographic device. The AC bias applying device is characterized in that, when the AC frequency applied to the plurality of units becomes an integer multiple of an odd number, the peaks and peaks or peaks and valleys of the phases are merged and then applied.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-184573 Summary of the Invention

[0004] The object of the present invention is to improve the quality of the output image compared to a case where the frequency of the AC component of the voltage applied to the charging portion for charging each image holder is the same in a structure in which latent images formed on multiple image holders are developed separately using a colorant of a base color and a colorant of a special color.

[0005] The image forming device involved in the first embodiment comprises: a first charging unit, which applies a voltage with an AC component having a first frequency to a first image holder to charge the first image holder; a first developing unit, which develops a latent image formed on the first image holder with a colorant of a reference color; a second charging unit, which applies a voltage with an AC component having a second frequency different from the first frequency to a second image holder to charge the second image holder; and a second developing unit, which develops the latent image formed on the second image holder with a colorant of a special color.

[0006] An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect, wherein the second charging section applies a voltage having a second frequency higher than the first frequency to the second image holding member.

[0007] The image forming device involved in the third embodiment is the image forming device involved in the first embodiment or the second embodiment, wherein the first developing unit develops the latent image by applying a voltage having an AC component with a frequency of a third frequency, and the second developing unit develops the latent image by applying a voltage having an AC component with a frequency of a fourth frequency that is different from the third frequency.

[0008] An image forming apparatus according to a fourth aspect is the image forming apparatus according to the third aspect, wherein the second developing section develops the latent image by applying a voltage having a fourth frequency lower than the third frequency.

[0009] The image forming device involved in the 5th mode is an image forming device involved in any one of the 1st to 4th modes, and further comprises: a first wiring connecting a power supply that outputs a voltage of the second frequency and the second charging unit; a second wiring connecting a power supply that outputs a voltage of a fourth frequency different from the second frequency and the second developing unit; and a separation structure that separates the first wiring and the second wiring by more than a specified distance.

[0010] An image forming apparatus according to a sixth aspect is the image forming apparatus according to the fifth aspect, wherein the separation structure includes a spacer disposed between the first wiring and the second wiring.

[0011] Effects of the Invention

[0012] According to the image forming device involved in the first embodiment, the quality of the output image is improved compared to a case where the frequency of the AC component of the voltage applied to the charging part for charging each image holding body is the same in a structure in which latent images formed on multiple image holding bodies are separately developed using a colorant of a base color and a colorant of a special color.

[0013] According to the image forming apparatus of the second aspect, compared to a case where the first frequency is higher than the second frequency, wear of the first image holding member is suppressed and the quality of the output image is improved.

[0014] According to the image forming apparatus of the third aspect, compared with a configuration in which the third frequency and the fourth frequency are the same, wear of the first image holding member or the second image holding member is suppressed.

[0015] According to the image forming apparatus of the fourth aspect, compared with a case where the third frequency is lower than the fourth frequency, wear of the first image holding member is suppressed and the degree of freedom in selecting a power source for applying a voltage to the second developing unit is improved.

[0016] According to the image forming apparatus of the fifth aspect, degradation of image quality of special colors can be suppressed compared to a configuration in which the first wiring and the second wiring are close to each other within a predetermined distance.

[0017] According to the image forming apparatus according to the sixth aspect, it is possible to maintain the first wiring and the second wiring separated from each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Embodiments of the present invention will be described in detail with reference to the following drawings.

[0019] Figure 1 This is a schematic diagram showing the structure of the image forming apparatus according to the first embodiment as viewed from the front side;

[0020] Figure 2This is a schematic diagram showing the connection relationship between the developing device, the charging device, and the power supply according to the first embodiment as viewed from the back side;

[0021] Figure 3 This is a graph comparing the frequency of applied voltage at each productivity for the developing device and the charging device according to the first embodiment;

[0022] Figure 4 is a schematic diagram showing the structure of an image forming apparatus according to a second embodiment as viewed from the front side;

[0023] Figure 5 This is a schematic diagram showing the connection relationship between the developing device, the charging device, and the power supply according to the second embodiment as viewed from the back side;

[0024] Figure 6 middle, Figure 6 (A) is a cross-sectional view taken along line S6-S6. Figure 6 (B) is a modified example of (A).

[0025] Explanation of symbols

[0026] 10-Image forming device, 12-Image forming unit, 20-Toner image forming unit, 21-Photosensitive drum, 21V-Photosensitive drum (an example of a second image holding member), 21Y-Photosensitive drum (an example of a first image holding member), 22-Charging device, 22V-Charging device (an example of a second charging unit), 22Y-Charging device (an example of a first charging unit), 23-Exposure device, 24-Developing device, 24V-Developing device (an example of a second developing unit), 24Y-Developing device (an example of a first developing unit), 30-Transfer device , 40-fixing device, 50-transmitting device, 68-power supply, 70-shielding member (an example of a spacer, a separation structure), 72-wiring, 72V-wiring (an example of a first wiring, a separation structure), 74-wiring, 74V-wiring (an example of a second wiring, a separation structure), 80-control unit, 110-image forming device, 112-image forming unit, f1-frequency (an example of a first frequency), f2-frequency (an example of a second frequency), f3-frequency (an example of a third frequency), f4-frequency (an example of a fourth frequency). DETAILED DESCRIPTION

[0027] The following describes a method for implementing the present invention. In the following description, the direction indicated by the arrow UP in the accompanying drawings is considered the vertically upward direction, and the direction indicated by the arrow DW is considered the vertically downward direction. Furthermore, the direction indicated by the arrow LH is considered the horizontal direction and the left direction of the device, and the direction indicated by the arrow RH is considered the horizontal direction and the right direction of the device. These arrows are provided for ease of explanation, and the device's posture does not necessarily correspond to them.

[0028] <<First Implementation>>

[0029] Hereinafter, an image forming apparatus according to a first embodiment will be described.

[0030] Overall Structure

[0031] Figure 1 1 is a schematic diagram showing the structure of the image forming apparatus 10 according to the first embodiment as viewed from the front. Figure 1 As shown, the image forming apparatus 10 includes a transport device 50 , an image forming unit 12 , a power supply 68 , and a control unit 80 that controls the operations of the various units of the image forming apparatus 10 .

[0032] (Transmission device)

[0033] like Figure 1 As shown, the transport device 50 transports the paper P. The transport device 50 includes a container 51 for accommodating the paper P and a plurality of transport rollers 52 and 53 for transporting the paper P from the container 51 to the secondary transfer position NT. The transport device 50 also includes a transport belt 58 for transporting the paper P from the secondary transfer position NT to the fixing device 40 described later.

[0034] (Image Forming Unit)

[0035] The image forming section 12 forms an image on the paper P using an electrophotographic method. The image forming section 12 includes a toner image forming section 20 , a transfer device 30 , and a fixing device 40 .

[0036] (Toner Image Forming Section)

[0037] The colorant image forming unit 20 forms a toner image. A plurality of toner image forming units 20 are provided to form toner images for each color. In the first embodiment, the toner image forming units 20 (20(Y), 20(C), 20(M), and 20(K)) of the base colors are formed from a total of four colors, namely yellow (Y), cyan (C), magenta (M), and black (K). In addition, in the first embodiment, in addition to the toner image forming units 20 of the base colors, a toner image forming unit 20 (20(V)) of a special color is provided, which is formed from one color selected from the group consisting of gold, silver, custom red, fluorescent pink, transparent, and white.

[0038] The toner image forming units 20 for the reference colors (20(Y), 20(C), 20(M), and 20(K)) are arranged in the order of yellow (Y), cyan (C), magenta (M), and black (K) in the left-right direction of the apparatus, from the upstream side to the downstream side in the direction of transport of the intermediate transfer belt 31 (described later). Furthermore, the toner image forming units 20 for the special colors (20(V)) are arranged upstream (in the right direction of the apparatus) of the toner image forming unit 20(Y) for yellow (Y) in the direction of transport of the intermediate transfer belt 31.

[0039] Figure 1 The (Y), (C), (M), (K), and (V) shown represent the structural parts corresponding to the above-mentioned colors. In addition, in the description of this specification, the brackets of (Y), (C), (M), (K), and (V) may be omitted and recorded as Y, M, C, K, V.

[0040] The toner image forming units 20 of each color are basically identical in configuration except for the toner used. Specifically, each color toner image forming unit 20 includes a photosensitive drum 21 that rotates clockwise as indicated by an arrow, a charging device 22 , an exposure device 23 , a developing device 24 , and a cleaning device 25 .

[0041] The charging device 22 charges the surface (photosensitive layer) of the photoconductive drum 21 to negative polarity by applying a voltage in which an AC component is superimposed on a DC component. The charging device 22 includes a charging roller.

[0042] For example, in the toner image forming unit 20(Y) for the base color, the charging device 22Y charges the surface of the photosensitive drum 21Y, while in the toner image forming unit 20(V) for the special color, the charging device 22V charges the surface of the photosensitive drum 21V. The charging devices 22Y and 22V are examples of a first charging unit and a second charging unit, respectively. Furthermore, the photosensitive drum 21Y and the photosensitive drum 21V are examples of a first image holder and a second image holder, respectively.

[0043] like Figure 2 As shown, the charging device 22 is powered by a power source 68. The power source 68 will be described later.

[0044] The exposure device 23 exposes the surface of the photosensitive drum 21, which has been charged to a negative polarity by the charging device 22, to form an electrostatic latent image on the photosensitive drum 21. Specifically, the exposure device 23 forms an electrostatic latent image on the surface of the photosensitive drum 21 by causing the portion of the surface of the photosensitive drum 21 irradiated with the exposure light L to assume a positive polarity. The electrostatic latent image is an example of a latent image.

[0045] The developing device 24 develops the electrostatic latent image formed on the photosensitive drum 21 to form a toner image. In this embodiment, the electrostatic latent image is developed by a voltage having an AC component superimposed on a DC component. The developing device 24 includes a developing roller.

[0046] For example, in the base color toner image forming unit 20(Y), the developing device 24Y develops the electrostatic latent image formed on the photosensitive drum 21Y to form a yellow toner image. In the special color toner image forming unit 20(V), the developing device 24V develops the electrostatic latent image formed on the photosensitive drum 21V to form a special color toner image. The developing device 24Y and the developing device 24V are examples of a first developing unit and a second developing unit, respectively.

[0047] like Figure 2 As shown, the developing device 24 is powered by a power supply 68. The power supply 68 will be described later.

[0048] The cleaning device 25 removes the toner remaining on the surface of the photosensitive drum 21 after the toner image is transferred to the transfer device 30. The cleaning device 25 includes a scraper 25A that contacts the surface of the photosensitive drum 21 and scrapes off the toner remaining on the surface of the photosensitive drum 21.

[0049] As described above, in the toner image forming section 20 , a toner image is formed on the surface (outer peripheral surface) of the photosensitive drum 21 .

[0050] ((Transfer device))

[0051] The transfer device 30 transfers the toner image formed by the toner image forming unit 20 onto the paper P. The transfer device 30 performs primary transfer by superimposing the toner images of the respective colors on the photosensitive drums 21 onto the intermediate transfer belt 31, and then performs secondary transfer of the superimposed toner images onto the paper P at the secondary transfer position NT. Specifically, the transfer device 30 includes the intermediate transfer belt 31, a primary transfer roller 33, and a secondary transfer unit 34.

[0052] (((Intermediate Transfer Belt)))

[0053] like Figure 1 As shown, the intermediate transfer belt 31 is endless and is wound around a drive roller 32D, a tensioning roller 32T, and an opposing roller 32B, with its posture determined. In the first embodiment, the intermediate transfer belt 31 assumes the shape of an inverted obtuse triangle that is long in the left-right direction of the apparatus when viewed from the front. Alternatively, other rollers around which the intermediate transfer belt 31 is wound may be provided.

[0054] The drive roller 32D, powered by a motor (not shown), causes the intermediate transfer belt 31 to revolve in the direction indicated by arrow A. By revolving in the direction indicated by arrow A, the intermediate transfer belt 31 conveys the primary transferred toner image to the secondary transfer position NT. For example, the drive roller 32D is positioned upstream of the five primary transfer rollers 33 in the direction of revolving the intermediate transfer belt 31. The tensioning roller 32T applies tension to the intermediate transfer belt 31.

[0055] The opposing roller 32B is a roller that opposes the secondary transfer roller 60, described later. The top portion of the obtuse lower end of the intermediate transfer belt 31, which is arranged in the shape of an inverted obtuse triangle as described above, is wound around the opposing roller 32B. The upper edge of the intermediate transfer belt 31, extending in the left-right direction of the apparatus in the aforementioned position, contacts the photoreceptor drums 21 of each color from below.

[0056] A cleaning device 35 for removing toner remaining on the intermediate transfer belt 31 is provided downstream of the secondary transfer position NT and upstream of the primary transfer position T(K) in the circling direction of the intermediate transfer belt 31 .

[0057] (((Primary Transfer Roller)))

[0058] like Figure 1 As shown, the primary transfer rollers 33 are rollers that transfer the toner images on the photoreceptor drums 21 to the intermediate transfer belt 31. They are located inside the intermediate transfer belt 31. Each primary transfer roller 33 is positioned opposite the photoreceptor drum 21 of the corresponding color, with the intermediate transfer belt 31 interposed therebetween. A primary transfer voltage having a polarity opposite to that of the toner is applied to the primary transfer rollers 33 by a power supply unit (not shown). This application of the primary transfer voltage transfers the toner images formed on the photoreceptor drums 21 to the intermediate transfer belt 31 at the primary transfer position T between the photoreceptor drums 21 and the primary transfer rollers 33.

[0059] (((Secondary transfer section)))

[0060] like Figure 1 As shown, the secondary transfer section 34 includes a secondary transfer belt 36, a secondary transfer roller 60, a driven roller 61, an opposing roller 32B, and a cleaning device 62. The secondary transfer section 34 also includes a contact roller (not shown) that supplies power to the opposing roller 32B by contacting the opposing roller 32B. In the secondary transfer section 34, a voltage composed of a DC component superimposed with an AC component is applied between the opposing roller 32B and the secondary transfer roller 60 via the contact roller, thereby forming a transfer electric field. This transfer electric field transfers the toner image superimposed on the intermediate transfer belt 31 to the paper P conveyed between the intermediate transfer belt 31 and the secondary transfer belt 36.

[0061] The secondary transfer belt 36 is endless and is wound around a secondary transfer roller 60 and a driven roller 61. The secondary transfer roller 60 circumferentially supports the secondary transfer belt 36 and is rotationally driven by a motor (not shown). The driven roller 61 is driven as the secondary transfer belt 36 circulates.

[0062] The secondary transfer roller 60 is positioned to sandwich the intermediate transfer belt 31 and the secondary transfer belt 36 between it and the opposing roller 32B (described later). The secondary transfer belt 36 is in contact with the intermediate transfer belt 31 with a predetermined load. The area between the secondary transfer belt 36 and the intermediate transfer belt 31 in this contact forms the secondary transfer position NT. Sheets of paper P are supplied from the container 51 to this secondary transfer position NT at an appropriate time. The secondary transfer belt 36 is driven to rotate by the secondary transfer roller 60, thereby circulating in the direction indicated by arrow B.

[0063] The opposing roller 32B faces the secondary transfer roller 60 via the intermediate transfer belt 31 and the secondary transfer belt 36 .

[0064] The cleaning device 62 removes toner from the surface of the secondary transfer belt 36 .

[0065] ((Fixing Device 40))

[0066] The fixing device 40 heats and pressurizes the toner image transferred to the paper P, thereby fixing the toner image to the paper P. The fixing device 40 includes a heating roller 40A and a pressure roller 40B pressed against the heating roller 40A. The paper P to which the toner image has been transferred passes through the nip between the heating roller 40A and the pressure roller 40B, whereby the toner image is fixed to the paper P.

[0067] (power supply)

[0068] like Figure 2 As shown, the power supply 68 supplies power to at least the toner image forming unit 20 of the image forming unit 12. Specifically, the power supply 68 applies a voltage having an AC component with a specific frequency superimposed on a DC component to the charging device 22 and the developing device 24. Figure 2 , for convenience of explanation, illustration of the toner image forming units 20 (M), 20 (C), and 20 (K) of the reference color other than the toner image forming unit 20 (Y) of the reference color and the toner image forming unit 20 (V) of the special color is omitted.

[0069] The power supply 68 is supported by a housing (not shown) of the image forming apparatus 10 on the rear side of the image forming apparatus 10. The power supply 68 and the toner image forming units 20 are connected by wirings 72 and 74.

[0070] The power supply 68 includes a power supply 68A and a power supply 68B. The power supply 68A is connected to the charging device 22V by a wiring 72V (72), and the power supply 68B is connected to the developing device 24V by a wiring 74V (74). The wiring 72V and the wiring 74V are examples of first wiring and second wiring, respectively.

[0071] The wiring 72V and the wiring 74V are each supported by the housing of the image forming apparatus 10. For example, the wiring 72V and the wiring 74V are supported on the housing by a plurality of band clips.

[0072] [Charging-related frequencies]

[0073] exist Figure 3 , frequencies f1 to f4 set for productivity P1, P2, P3, and P4 of different numbers of images formed per unit time in the image forming apparatus 10 are shown. Furthermore, productivity is shown to increase from P1 to P4.

[0074] First, the charging device 22 will be described. Figure 3 As shown, under any of the production rates P1, P2, P3, and P4, the frequency f1 of the voltage applied to the charging device 22Y and the frequency f2 of the voltage applied to the charging device 22V are different. Frequency f1 and frequency f2 are examples of the first and second frequencies, respectively. Specifically, frequency f2 is set higher than frequency f1. For example, frequency f1 is 1 to 3 kHz, while frequency f2 is 2 to 6 kHz. Under any of the corresponding production rates P1, P2, P3, and P4, frequency f2 is set higher than frequency f1.

[0075] [Frequencies related to development]

[0076] Next, the developing device 24 will be described. Figure 3 As shown, under any of the production rates P1, P2, P3, and P4, the frequency f3 of the voltage applied to the developing device 24Y and the frequency f4 of the voltage applied to the developing device 24V are different. Frequency f3 and frequency f4 are examples of the third and fourth frequencies, respectively. Specifically, frequency f4 is set lower than frequency f3. For example, frequency f3 is 12 to 14 kHz, while frequency f4 is 9 to 10 kHz, setting frequency f4 lower than frequency f3.

[0077] <Function and Effect>

[0078] Next, the operation and effects of the first embodiment will be described.

[0079] The image forming apparatus 10 includes a charging device 22Y for applying a voltage having an AC component at a frequency f1 to a photosensitive drum 21Y to charge the photosensitive drum 21Y; a developing device 24Y for developing a latent image formed on the photosensitive drum 21Y with a toner of a reference color; a charging device 22V for applying a voltage having an AC component at a frequency f2 different from the frequency f1 to the photosensitive drum 21V to charge the photosensitive drum 21V; and a developing device 24V for developing the latent image formed on the photosensitive drum 21V with a toner of a special color. This improves the quality of the output image compared to a configuration in which the AC component frequency of the voltage applied to the charging units for charging the photosensitive drums of the reference color and the special color is the same, in which case the electrostatic latent images formed on the plurality of photosensitive drums 21 are developed separately with the toner of the reference color and the toner of the special color.

[0080] Furthermore, a higher frequency of the voltage applied to the charging device can more effectively prevent disturbances in the output image quality, such as interference fringes. However, this also increases wear on the photoreceptor being charged by the charging device. Furthermore, toners of specific colors have a relatively low wear rate on the photoreceptor drum. Therefore, in the image forming apparatus 10, the charging device 22V applies a voltage at a frequency f2, which is higher than the frequency f1, to the photoreceptor drum 21V. This reduces wear on the photoreceptor drum 21Y and improves the quality of the output image, compared to a case where the frequency f1 is higher than the frequency f2.

[0081] Furthermore, in the image forming apparatus 10, the developing device 24Y develops the electrostatic latent image by applying a voltage having an AC component frequency of f3, while the developing device 24V develops the electrostatic latent image by applying a voltage having an AC component frequency of f4, which is different from the frequency f3. This reduces wear on the photoconductive drum 21Y or the photoconductive drum 21V compared to a configuration in which the frequencies f3 and f4 are the same.

[0082] To prevent background blur, the frequency of the voltage applied to the developing device is set relatively high. Setting the development frequency for a specific color toner to a relatively high frequency requires a corresponding power source, limiting the flexibility in selecting a power source. Therefore, in the image forming apparatus 10, the developing device 24V develops the latent image by applying a voltage at a frequency f4, which is lower than the frequency f3. This reduces wear on the photoreceptor drum 21Y compared to a case where the frequency f3 is lower than the frequency f4, and provides greater flexibility in selecting the power source 68B that applies the voltage to the developing device 24V.

[0083] Second Embodiment

[0084] Next, an image forming apparatus according to a second embodiment will be described. Components identical to those in the first embodiment are denoted by the same reference numerals, and their description will be omitted.

[0085] Overall Structure

[0086] like Figure 4 As shown, in the image forming apparatus 110, an image is formed in the image forming unit 112. During image formation, the toner image forming unit 20 for the reference and special colors transfers the black, yellow, cyan, magenta, and special color images in this order (in the left-right direction of the apparatus) onto the intermediate transfer belt 31. The toner images of each color on the intermediate transfer belt 31 are then transferred onto the paper P by the secondary transfer unit 34. The positions of the reference and special colors can be changed by user settings.

[0087] Furthermore, in the image forming apparatus 110, since the position of the special color toner image forming unit 20 (20(V)) in the image forming unit 112 is different from that in the first embodiment, the positions of the wiring 72 and the wiring 74 supported by the frame of the image forming unit 112 are different.

[0088] Furthermore, in the image forming apparatus 110, a shield 70 is disposed around the wiring 74. The shield 70 will be described later.

[0089] The rest of the structure of the image forming apparatus 110 is the same as that of the image forming apparatus 10 according to the first embodiment.

[0090] (Shielding parts)

[0091] like Figure 5 As shown, shield 70 is disposed on a portion of wiring 74. Specifically, it is disposed on wiring 74V that connects the developing device 24V of the special color toner image forming unit 20 (V) to the power supply 68B. Furthermore, shield 70 is disposed on a portion of the section where wiring 72V and wiring 74V are arranged side by side in the left-right direction of the device.

[0092] On the other hand, the shield 70 is not wrapped around the wiring 72V connecting the charger 22V of the special color toner image forming unit 20(V) to the power supply 68A. Specifically, the shield 70 is positioned between the wiring 72V and the wiring 74V, shielding the wiring 74V by separating them by a predetermined distance or more. The shield 70 is an example of a spacer. Furthermore, the positional relationship between the shield 70, wiring 72V, and wiring 74V is an example of a separated structure.

[0093] like Figure 6As shown in (A), the shielding member 70A (70) is a resin formed into a cylindrical shape. In this embodiment, the shielding member 70A (70) is configured as a heat-insulating tube. The inner diameter of the shielding member 70A is larger than the outer diameter of the wiring 74. In other words, there is at least a gap between the inner peripheral surface of the shielding member 70A and the outer peripheral surface of the wiring 74.

[0094] Furthermore, shield 70A separates wiring 72V and wiring 74V by a predetermined distance D or greater. Distance D is the distance from outer surface 72VS of conductor portion 72VC in wiring 72V to outer surface 74VS of conductor portion 74VC in wiring 74V. For example, distance D is set to 3.5 mm or greater.

[0095] <Function and Effect>

[0096] Next, the operation and effects of the second embodiment will be described.

[0097] In the image forming apparatus 110 according to the second embodiment, in addition to the operations and effects based on the same configuration as the image forming apparatus 10 according to the first embodiment, the following operations and effects can be obtained.

[0098] When wiring 72 and wiring 74 are arranged side by side, an electrostatic induced voltage is generated from wiring 72 to wiring 74 corresponding to the length of the section where wiring 72 and wiring 74 are arranged. Furthermore, when wiring 72 and wiring 74 come close together within a distance D, an electrostatic induced voltage is generated from wiring 72 to wiring 74 corresponding to the distance of proximity. The generation of this electrostatic induced voltage generates induced noise, which may affect the output image (causing defects).

[0099] Therefore, the image forming apparatus 110 further includes: a wiring 72V connecting the power supply 68A outputting a voltage at the frequency f2 and the charging device 22V; a wiring 74V connecting the power supply 68B outputting a voltage at a frequency f4 different from the frequency f2 and the developing device 24V; and a separation structure separating the wiring 72V and the wiring 74V by at least a predetermined distance D. The image forming apparatus 10 according to the first embodiment suppresses degradation in image quality of special colors compared to a configuration in which the wiring 72V and the wiring 74V are close together within the predetermined distance D.

[0100] Furthermore, in the image forming apparatus 110 , the separation structure includes the shield 70 disposed between the wiring 72V and the wiring 74V. This allows the wiring 72V and the wiring 74V to be maintained separated from each other.

[0101] Furthermore, although the present invention has been described in detail with reference to specific embodiments, it is not limited to these embodiments, and it will be apparent to those skilled in the art that various other embodiments can be adopted within the scope of the present invention.

[0102] Modifications

[0103] The distance D between the wiring 72V and the wiring 74V in the image forming apparatus 110 can be maintained by supporting the wiring 72V and the wiring 74V on the frame with support members such as a belt clip, for example, while the wiring 72V and the wiring 74V are separated from each other. Alternatively, the thickness of the shield 70A can be set to be greater than D.

[0104] The shielding member 70 is a resin formed into a cylindrical shape, but is not limited thereto. Figure 6 As shown in FIG. 1B , the shielding member 70 may be a sheet-shaped shielding member 70B made of a plastic resin wrapped around the outer periphery of the wiring 74V, or a tape-shaped resin tape wrapped around the outer periphery of the wiring 74V. Furthermore, the shielding member 70 may be any structure as long as it separates the wiring 72V and the wiring 74V by a predetermined distance or more. For example, the shielding member 70 may be a spacer disposed between the wiring 72V and the wiring 74V.

[0105] The shield 70 may be disposed in the entire section where the wiring 72V and the wiring 74V are arranged in parallel, or may be disposed in a part or the entire section in a state where the section is divided into a plurality of small sections.

[0106] [Note] (1)

[0108] An image forming apparatus comprising:

[0109] a first charging unit for applying a voltage having an AC component with a first frequency to the first image holding member to charge the first image holding member;

[0110] a first developing unit for developing the latent image formed on the first image holding member using a toner of a reference color;

[0111] a second charging unit for applying a voltage having an AC component with a second frequency different from the first frequency to a second image holding member to charge the second image holding member; and

[0112] The second developing section develops the latent image formed on the second image holding member using a toner of a specific color. (2)

[0114] The image forming apparatus according to (1), wherein

[0115] The second charging section applies a voltage having a second frequency higher than the first frequency to the second image holding member. (3)

[0117] The image forming apparatus according to (1) or (2), wherein

[0118] The first developing unit develops the latent image by applying a voltage having an AC component with a third frequency.

[0119] The second developing section develops the latent image by applying a voltage having an AC component with a fourth frequency that is different from the third frequency. (4)

[0121] The image forming apparatus according to (3), wherein

[0122] The second developing section develops the latent image by applying a voltage having a fourth frequency lower than the third frequency. (5)

[0124] The image forming apparatus according to any one of (1) to (4), further comprising:

[0125] a first wiring connecting a power source outputting a voltage of the second frequency and the second charging unit;

[0126] a second wiring connecting a power source outputting a voltage of a fourth frequency different from the second frequency and the second developing unit; and

[0127] The separation structure separates the first wiring and the second wiring by a predetermined distance or more. (6)

[0129] The image forming apparatus according to (5), wherein

[0130] The separation structure includes a spacer disposed between the first wiring and the second wiring.

[0131] According to the image forming device described in (1), the quality of the output image is improved compared with the case where the frequency of the AC component of the voltage applied to the charging part for charging each image holding body is the same in a structure in which latent images formed on multiple image holding bodies are developed separately using a colorant of a base color and a colorant of a special color.

[0132] According to the image forming apparatus described in (2), compared with a case where the first frequency is higher than the second frequency, wear of the first image holding member is suppressed and the quality of the output image is improved.

[0133] According to the image forming apparatus described in (3), compared with the structure in which the third frequency and the fourth frequency are the same, wear of the first image holding member or the second image holding member is suppressed.

[0134] According to the image forming apparatus described in (4), compared with a case where the third frequency is lower than the fourth frequency, wear of the first image holding member is suppressed and the degree of freedom in selecting a power source for applying a voltage to the second developing unit is improved.

[0135] According to the image forming apparatus described in (5), degradation of image quality of special colors can be suppressed compared to a configuration in which the first wiring and the second wiring are close to each other within a predetermined distance.

[0136] According to the image forming apparatus described in (6), the first wiring and the second wiring can be maintained in a state of being separated from each other.

[0137] 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. An image forming apparatus comprising: a first charging unit for applying a voltage having an AC component with a first frequency to the first image holding member to charge the first image holding member; a first developing unit for developing the latent image formed on the first image holding member using a toner of a reference color; a second charging unit for applying a voltage having an AC component with a second frequency different from the first frequency to a second image holding member to charge the second image holding member; and The second developing section develops the latent image formed on the second image holding member using a toner of a specific color.

2. The image forming apparatus according to claim 1, wherein The second charging section applies a voltage having a second frequency higher than the first frequency to the second image holding member.

3. The image forming apparatus according to claim 1 or 2, wherein: The first developing unit develops the latent image by applying a voltage having an AC component with a third frequency. The second developing section develops the latent image by applying a voltage having an AC component with a fourth frequency that is different from the third frequency.

4. The image forming apparatus according to claim 3, wherein The second developing section develops the latent image by applying a voltage having a fourth frequency lower than the third frequency.

5. The image forming apparatus according to any one of claims 1 to 4, further comprising: a first wiring connecting a power source outputting a voltage of the second frequency and the second charging unit; a second wiring connecting a power source outputting a voltage having a fourth frequency different from the second frequency and the second developing unit; and The separation structure separates the first wiring and the second wiring by a predetermined distance or more.

6. The image forming apparatus according to claim 5, wherein The separation structure includes a spacer disposed between the first wiring and the second wiring.

Images