JP2008076619A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus designed such that even if a secondary pre-transfer means is provided with a cleaning means for cleaning a grid electrode, floating of toner, resulting from cleaning, or reattaching of floating toner are restrained and, moreover, the performance of the secondary pre-transfer means can be adequately maintained for a long time. <P>SOLUTION: The secondary pre-transfer discharge means is disposed. Before a cleaning member is moved, a prescribed toner image is formed on an intermediate transfer body. Only when the prescribed toner image is located opposite the secondary pre-transfer discharge means, the movement of the intermediate transfer body is discontinued to perform the cleaning operation of the cleaning device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a pre-secondary transfer static elimination means, and more particularly to an electrode cleaning apparatus.

  In general, in an electrophotographic color image forming method used for a copying machine, a printer, or the like, primary toner images of different colors are formed on a plurality of image forming bodies, and the primary toner images are sequentially formed on an intermediate transfer body. A color toner image is formed by transferring and stacking, and then this color toner image is secondarily transferred to a transfer material, and then a fixing process is performed on the transfer material, thereby forming a color image. Has been done.

  The height of the potential of the color toner image on the intermediate transfer member varies depending on the amount of toner attached, and the height of the potential of the portion where the color toner images are superimposed on the color toner image is higher than that of the one-color toner image. If the distribution of the potential in the color toner image formed in this way is wide, various transfer defects occur in the secondary transfer process, and as a result, the image in the resulting color image is higher. There is a problem that defects occur.

  For example, specifically, when negative toner is used, the negative toner of each color is superimposed on the intermediate transfer member, and the surface potential of the intermediate transfer member eventually becomes −150V to −200V. In order to transfer the toner image onto the transfer material by the secondary transfer means in this state, the transfer voltage must be set high. If it does so, it will become easy to generate | occur | produce in a low-temperature, low-humidity environment, and a white spot-like defect will generate | occur | produce in an image. Therefore, in order to keep the transfer voltage low, a scorotron band electrode is provided at a position downstream of the primary transfer region at the most downstream position in the moving direction of the intermediate transfer member and upstream of the position of the secondary transfer means. It is necessary to provide the above-mentioned secondary pre-transfer charge eliminating means.

  In order to perform charge removal before secondary transfer, a voltage of about +5 kV is applied to the discharge electrode (main wire) in the scorotron band electrode, and a voltage of about −50 V is applied to the grid member (also referred to as grid electrode). As a result, the toner on the outermost surface on the intermediate transfer member becomes a plus toner, which causes a problem that the plus toner adheres to the grid electrode. In order to clean the adhering toner, a cleaning device is provided in the pre-secondary transfer neutralization unit. However, a new problem arises that the toner floats by further cleaning.

  In order to solve such a problem, for example, Patent Document 1 discloses a method for applying a stain-preventing bias voltage to the grid electrode constituting the secondary pre-transfer charge eliminating unit. In the method of applying a bias voltage, it is difficult to sufficiently prevent the pre-secondary transfer static elimination means of this content from being contaminated.

Further, in Patent Document 2, a secondary pre-transfer charge eliminating unit is provided to lower the potential on the intermediate transfer body before performing the secondary transfer. The pre-secondary transfer static elimination means can move between an operation position that is close to and faces the intermediate transfer member and a retracted position that is separated from the intermediate transfer member, and the image to be formed is black. Although it is described that means that the secondary pre-transfer neutralization means moves to the retracted position and does not stain the electrode as much as possible when it is a black monochrome image only with toner, the electrode cannot be actively cleaned, When a large number of sheets are printed, the electrodes become dirty, and the performance of the grid electrodes and the discharge wires may be impaired as described above.
Japanese Patent Laid-Open No. 11-143255 JP 2006-138904 A

  The present invention has been made on the basis of the above circumstances, and its object is to suppress the floating of toner and the reattachment of floating toner caused by cleaning the grid electrode of the pre-secondary transfer static elimination means. It is another object of the present invention to provide an image forming apparatus having a cleaning unit that can sufficiently maintain the performance of the secondary transfer pre-charge neutralizing unit over a long period of time.

The above object can be achieved by the following configuration.
1. The toner images of different colors electrostatically formed on the plurality of image forming bodies are sequentially moved in each primary transfer region to the intermediate transfer body contacting the plurality of image forming bodies. An intermediate toner image that forms an intermediate toner image on the transfer material by transferring and secondarily transferring a color toner image formed by stacking the toner images of each color on the intermediate transfer body onto the transfer material Forming means;
A color toner image formed on the intermediate transfer member is positioned downstream of the primary transfer region at the most downstream position in the moving direction of the intermediate transfer member and upstream of the position of the secondary transfer unit. Disposing a pre-secondary transfer neutralization means having a scorotron band electrode for neutralizing,
A cleaning device having a cleaning member that contacts the grid member in the scorotron band electrode and moves in the longitudinal direction;
An image forming apparatus comprising:
Before moving the cleaning member, a toner image having a predetermined pattern is formed on the intermediate transfer member, and the cleaning device performs a cleaning operation in a state where the toner image is opposed to the pre-secondary transfer neutralization unit. An image forming apparatus.
2. 2. The image forming apparatus according to 1, wherein the toner image of the predetermined pattern is a solid image having one or more layers of toner.
3. 3. The cleaning device according to 1 or 2, wherein the cleaning device performs cleaning by stopping the movement of the intermediate transfer member in a state where the toner image of the predetermined pattern is opposed to the pre-secondary transfer neutralization unit. Image forming apparatus.
4). The size of the toner image of the predetermined pattern is as follows:
4. The image forming apparatus according to any one of 1 to 3, wherein A> the width of the image area.
5. The size of the toner image of the predetermined pattern is such that the length in the rotation direction of the intermediate transfer member is B,
a ≦ B ≦ a + 50 (mm),
4. The image forming apparatus according to any one of 1 to 3, wherein
Where a is
a = the width of the neutralizing means before secondary transfer.

  According to the present invention, in order to neutralize the color toner image formed on the intermediate transfer member, the secondary pre-transfer neutralization unit having the scorotron band electrode is disposed, and the cleaning member slidingly contacting the grid member is arranged in the longitudinal direction. When the cleaning device is configured to move, the toner image is formed on the intermediate transfer body before the cleaning member is moved, and the toner image is at a position facing the pre-secondary transfer neutralization unit. By stopping the movement of the intermediate transfer member and performing the cleaning operation of the cleaning device, the floating of the toner and the reattachment of the floating toner caused by the cleaning are suppressed, and the performance of the pre-secondary transfer static elimination means can be improved over a long period of time. Sufficiently maintain.

An embodiment of the present invention will be described. In addition, although this invention is demonstrated based on embodiment of illustration, this invention is not restricted to this embodiment. In addition, the following assertive description in the embodiment of the present invention shows the best mode, and does not limit the meaning or technical scope of the terms of the present invention.
<Embodiment>
FIG. 1 is an explanatory diagram showing an example of the configuration of the color image forming apparatus of the present invention according to the first embodiment. FIG. 2 is an explanatory diagram schematically showing an example of the configuration around the secondary transfer pre-charge neutralizing unit in the color image forming apparatus of FIG. 1 in a state where the secondary pre-transfer neutralization unit is in the operating position.

  This color image forming apparatus is an image forming apparatus that forms a color image, and sequentially transfers toner images of different colors formed on a plurality of image forming bodies to a common intermediate transfer body in sequence. A so-called intermediate toner image is formed on the transfer material by superimposing the toner images of the respective colors on the intermediate transfer member and then collectively transferring the color toner images formed on the intermediate transfer member onto the transfer material. An intermediate transfer method.

  The color image forming apparatus includes an intermediate transfer member 17 which is an endless belt and is circulated and moved in the direction of the arrow in FIG. 1. A toner image forming unit arrangement provided in an outer peripheral surface region of the intermediate transfer member 17 is provided. In the region, four toner image forming units 30Y, 30M, 30C, and 30K that respectively form a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are sequentially arranged along the moving direction of the intermediate transfer body 17. Are arranged so as to be spaced apart from each other. The intermediate transfer member 17 circulates while being in contact with each of the image forming members 10Y, 10M, 10C, and 10K by the primary transfer units 14Y, 14M, 14C, and 14K in the toner image forming units 30Y, 30M, 30C, and 30K. It is stretched around a group of rollers including intermediate rollers 17a, 17b, 17c and a backup roller 17d described later so as to be moved.

The intermediate transfer member 17 is, for example, an endless belt having a single layer structure made of a semiconductive belt base having a volume resistivity of 1 × 10 ⁴ to 1 × 10 ¹² Ωcm, and has a surface resistivity of 1. × 10 ⁹ to 1 × 10 ¹³ Ω / □, more preferably 1 × 10 ¹⁰ to 1 × 10 ¹² Ω / □. The surface resistivity of the intermediate transfer member 17 is 100 V in a normal temperature and normal humidity (temperature 20 ± 1 ° C., humidity 50 ± 2%) environment using a resistance measuring instrument “Hi-Lester IP” (manufactured by Yuka Denshi). It is the value measured by applying for 10 seconds.

  Examples of the material constituting the belt substrate of the intermediate transfer body 17 include resin materials such as thermosetting polyimide and modified polyimide, ethylene-propylene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), and polyurethane. Examples thereof include those obtained by dispersing a conductive filler such as carbon in a rubber material such as rubber, or those containing an ionic conductive material.

  The toner image forming unit 30Y related to the yellow toner image includes an image forming body 10Y made of a rotating drum-shaped photoconductor, and the rotation direction of the image forming body 10Y in the outer peripheral surface area of the image forming body 10Y. On the other hand, a charging device 11Y, an exposure device 12Y, and a developing device 13Y that performs development with a developer relating to a yellow toner image are arranged in this order, and are downstream of the developing device 13Y in the rotation direction of the image forming body 10Y. An image forming body cleaning means 20Y provided with an image forming body cleaning blade is provided at a position downstream of the primary transfer means 14Y provided at the position.

  The image forming body 10Y has, for example, a photosensitive layer made of a resin containing an organic photoconductor on the outer peripheral surface of a drum-shaped metal substrate, and is arranged in a state extending in a direction perpendicular to the paper surface in FIG. Has been.

  The charging device 11Y is made of, for example, a scorotron charger having a grid electrode and a charging electrode, and the exposure device 12Y is made of, for example, a laser irradiation device.

  The developing unit 13Y includes, for example, a developing sleeve that contains a magnet and rotates while holding the developer, and a voltage applying unit (not shown) that applies a DC or AC bias voltage between the image forming body 10Y and the developing sleeve. Is provided.

  The primary transfer unit 14Y includes a primary transfer roller 141Y disposed so as to form a primary transfer region while being pressed against the surface of the image forming body 10Y via the intermediate transfer body 17, and the primary transfer roller. 141Y is connected to a transfer current supply device (not shown) made of, for example, a constant current power source, and the transfer current supply device supplies a current to the primary transfer roller 141Y, thereby forming an image forming body. This is a so-called contact transfer method in which the yellow toner image on 10Y is transferred to the intermediate transfer member 17.

  The image forming body cleaning blade of the image forming body cleaning means 20Y is made of, for example, an elastic body such as urethane rubber. The base end portion of the image forming body cleaning blade is supported by a support member and the front end portion is in contact with the surface of the image forming body 10Y. The direction extending from the base end side of the image forming body cleaning blade is a so-called counter direction, which is the direction opposite to the moving direction of the image forming body 10Y at the contact portion.

  In each of the other toner image forming units 30M, 30C, and 30K, the developer includes magenta toner, cyan toner, and black toner instead of yellow toner, respectively. It is the same composition.

  In this color image forming apparatus, each of the image forming bodies 10Y in the toner image forming units 30Y, 30M, and 30C relating to the yellow, magenta, and cyan toner images among the toner image forming units 30Y, 30M, 30C, and 30K. An image forming member separation mechanism (not shown) for releasing the contact state between 10M and 10C and the intermediate transfer member 17 is provided.

  Specifically, the primary transfer rollers 141Y, 141M, and 141C in the toner image forming units 30Y, 30M, and 30C are integrally pressed by, for example, a cam or the like (upward in FIG. 1). The primary transfer area is formed by pressing the image forming bodies 10Y, 10M, and 10C through the intermediate transfer body 17 at the contact position, and the pressing state in the cam is released, and the primary transfer roller 141Y. , 141M, 141C are moved downward by their own weight, and the intermediate transfer body 17 is deformed according to the positions of the moved primary transfer rollers 141Y, 141M, 141C, whereby each of the toner image forming units 30Y, 30M, 30C. The contact state between the image forming bodies 10Y, 10M, and 10C and the intermediate transfer body 17 is released.

  A secondary transfer unit 14S is provided at a position downstream of the toner image forming unit 30K related to black toner, which is a toner image forming unit at the most downstream position in the moving direction of the intermediate transfer body 17, and this secondary transfer unit 14S is provided. The means 14S includes a secondary transfer roller 141S that forms a secondary transfer region by pressing the backup roller 17d via the intermediate transfer body 17, and a transfer current supply device (not shown) connected to the secondary transfer roller 141S. And a transfer current P is supplied to the secondary transfer roller 141S by the transfer current supply device, whereby the color toner image formed on the intermediate transfer body 17 is transferred to the transfer material P that has been conveyed. In the so-called contact transfer system, an intermediate toner image is formed on the transfer material P by secondary transfer. Here, the toner image forming units 30Y, 30M, 30C, and 30K and the secondary transfer unit 14S constitute an intermediate toner image forming unit.

  In FIG. 1, reference numeral 18 denotes a fixing device that forms an image by fixing an intermediate toner image on a transfer material P conveyed from a secondary transfer region, and includes, for example, a heating roller 181 having a heating source therein, The heating roller 181 and a pressure roller 182 provided in pressure contact with each other to form a fixing nip portion.

  An intermediate transfer body cleaning means 20S having a cleaning blade for removing untransferred toner on the intermediate transfer body 17 is provided at a position downstream of the secondary transfer means 14S in the moving direction of the intermediate transfer body 17. Yes.

  Then, on the downstream side of the primary transfer means 14K at the most downstream position in the moving direction of the intermediate transfer body 17 and on the upstream side of the secondary transfer means 14S, for example, a secondary pre-transfer charge eliminating means comprising a scorotron charger having a grid electrode, for example. 24 are provided in this order along the moving direction of the intermediate transfer member 17.

  The secondary pre-transfer charge eliminating unit 24 is close to and opposed to the intermediate transfer body 17 and has a function of discharging the color toner image by applying a charge to the color toner image. A discharge electrode 241 made of a discharge wire extending along the width direction of the body 17 (the direction perpendicular to the paper surface in FIG. 1), and the amount of charge applied to the color toner image from the discharge electrode 241 is regulated to control the color toner image. The grid electrode 242 for controlling the height of the electric potential and the back plate 243 which is a shield of a metal frame for making the discharge direction constant.

  The grid electrode 242 is provided in a state of facing the surface of the intermediate transfer body 17 separated from the surface of the intermediate transfer body 17 by, for example, a separation distance h 1, and the grid electrode 242 is disposed on the back surface of the intermediate transfer body 17 through the intermediate transfer body 17. A counter electrode 244 made of a conductive brush that slidably rubs the metal plate and the intermediate transfer body 17 is provided. The separation distance h1 is 1 mm, for example.

  The counter electrode 244 is maintained in a grounded state, and the back plate 243 is maintained at the same potential as the grid electrode 242.

  The discharge electrode 241 and the grid electrode 242 are respectively charged with respect to the color toner image by a discharge voltage applying device 241A for discharging, for example, a constant voltage power source and a grid voltage applying device 242A for discharging, for example, a constant voltage power source. Each of the bias voltages is applied so that Specifically, for example, the discharge electrode 241 has a uniform distribution of the charge amount of the color toner image in an appropriate range for performing the secondary transfer process in order to obtain a highly uniform transfer performance. Is +3 to +5 kV, and a bias voltage of −50 to −300 V is applied to the grid electrode 242.

  In this color image forming apparatus, an image forming operation is performed as follows. That is, when forming a full color image composed of toner images of a plurality of colors, for example, four colors, the image forming bodies 10Y, 10M, 10C, and 10K are rotationally driven in each of the toner image forming units 30Y, 30M, 30C, and 30K. The image forming bodies 10Y, 10M, 10C, and 10K are charged to a predetermined polarity, for example, negative polarity by the charging devices 11Y, 11M, 11C, and 11K, and then a toner image is to be formed on the surface of the image forming body. By exposing the formation area by the exposure devices 12Y, 12M, 12C, and 12K, the potential of the irradiated portion (exposure area) is lowered, and electrostatic latent images corresponding to the original image are formed on the image forming bodies 10Y, 10M, and 10C. Formed on the surface of 10K and charged with the same polarity as the surface potential of the image forming bodies 10Y, 10M, 10C, and 10K, for example, negative polarity. Over the image forming members 10Y, 10M, 10C, reversal development adhere to the electrostatic latent image 10K performed, thereby a toner image of each color is formed.

  Further, the color toner images are formed on the intermediate transfer member 17 by sequentially transferring and superimposing the respective color toner images in the respective primary transfer regions by the primary transfer units 14Y, 14M, 14C, and 14K. It is formed.

  Charges are applied by the pre-secondary transfer neutralization means 24 positioned at the operating position so that the entire color toner image is in a uniform potential state in an appropriate range for the secondary transfer process.

  After the color toner image having the uniform potential state as described above is transferred to the secondary transfer roller 141S of the secondary transfer unit 14S, the transfer current controlled to an appropriate magnitude by the transfer current supply device is then supplied. The color toner image on the intermediate transfer body 17 is secondarily transferred to the transfer material P that has been conveyed, and then a fixing process is performed by the fixing device 18, thereby forming a color image.

  In the toner image forming units 30Y, 30M, 30C, and 30K, untransferred toner that passes through the primary transfer region and remains on the image forming bodies 10Y, 10M, 10C, and 10K is transferred to the image forming body cleaning units 20Y, 20M, and It is removed by the image forming body cleaning blade of 20C and 20K.

Further, untransferred toner that passes through the secondary transfer region and remains on the intermediate transfer member 17 is removed by the cleaning blade of the intermediate transfer member cleaning unit 20S.
<Static removal means before secondary transfer>
Next, the pre-secondary transfer static elimination means and the grid electrode cleaning device of the present invention will be described.

  According to the color image forming apparatus, basically, the surface potential of the color toner image formed on the intermediate transfer member 17 is determined by the product of the toner amount and the Coulomb force per unit. In the present embodiment, the surface potential is −150V to −200V.

  In view of this, a secondary pre-transfer charge eliminating means for removing the surface potential is provided, and a voltage of about +5 kV and a voltage of about −50 V are applied to the discharge electrode 241 and the grid electrode 242. However, at this time, the toner on the outermost surface on the intermediate transfer member is positively charged, and a phenomenon that the electric field is drawn in the direction of the grid electrode 242 to which a negative voltage is applied occurs. As a result, the plus toner adheres to the grid electrode 242 and does not have the function as the pre-secondary transfer charge removal unit 24. Therefore, a means for automatically cleaning the grid electrode 242 of the secondary pre-transfer charge eliminating means is provided periodically at the time of initial system check, for example, when the image forming apparatus is turned on.

  FIG. 3 is a view showing the secondary pre-transfer charge eliminating means 24 that holds the cleaning device according to the present invention.

  FIG. 3A is a view as seen from the back surface (side facing the irradiated body) of the pre-secondary transfer static elimination means 24, and FIG. 3B shows the cleaning device attached to the secondary pre-transfer static elimination means 24. It is the figure which expanded the VV cross section.

  3A, the pre-secondary transfer static elimination means 24 includes a back plate 243, a discharge electrode 241, a wire stopper block (front) 303, a wire stopper block (rear) 304, a grid electrode 242, a cleaning device 50, and the like. Has been.

  As shown in FIG. 4, the grid electrode 242 has a large number of holes H formed in a mesh shape on the surface of a thin metal plate, and a negative voltage is applied thereto.

  The material of the back plate 243 is formed of a U-shaped SUS (stainless steel) material, and a PC (polycarbonate) wire stop block (front) 303 and a wire stop block (rear) 304 are attached to both ends in the longitudinal direction. ing. In addition, a discharge electrode 241 of a tungsten wire is stretched between both wire stopper blocks, and one end of the discharge electrode 241 is attached to an electrode plug (not shown) on the wire block 304 side, and is connected to a high voltage power source.

  Both ends of the grid electrode 242 are fixed and stretched by a support member (not shown) across the longitudinal direction of the opening of the discharge electrode 241.

  In FIG. 3B, the cleaning device 50 includes a brush 54 that contacts the discharge electrode 241, a block 51 that is a brush holding member in which a brush 53 that contacts the grid electrode 242 is implanted, and a brush for cleaning the discharge electrode 241. The slide member 52 etc. which hold | maintain the brush board which implants 57 are comprised.

  The slide member 52 is dropped into the recess of the back plate 243, and a guide pin 56 is attached to the slide member 52 from the bottom of the back plate 243 through the guide groove 306, and slides in the longitudinal direction along the grid electrode 242 and moves. It is possible. The block 51 collides with the discharge electrode 241 so as to be integrated with the slide member 52. Further, a brush 53 is implanted in the block 51. The cleaning device 50 is located outside the discharge image area (position Q, see FIG. 3A) during image formation.

Next, a means for cleaning the grid electrode of the cleaning device will be described.
FIG. 5 shows driving means for reciprocating the slide member 52 integral with the block 51 in the longitudinal direction from the position Q.

  In FIG. 5, the screw shaft 310 is supported on the upper portion of the back plate 243 by the support protrusions 303 a and 304 a of the wire stopper block (front) 303 and the wire stopper block (rear) 304, and on the block (rear) 304 side. FIG. 5 is a perspective view showing a place where a gear 313 is provided at an end of a screw shaft 310. Further, the block (rear) 304 is provided with a motor M1 for rotating the screw shaft 310 and a worm 312 attached to the rotation shaft of the motor M1, and the worm 312 and the gear 313 are engaged with each other.

  Reference numeral 311 denotes an upper slide that is provided with a screw groove so as to mesh with the screw shaft 310, and is movable in the longitudinal direction by the rotation of the motor M1. Further, the upper slide base 311 is attached with a guide pin 56 attached to the slide member 52 interposed therebetween.

In the cleaning device 50 having such a configuration, the brush 53 rubs the surface of the grid electrode 242 when the motor M1 is operated in accordance with an instruction from a control unit (not shown) that controls the image forming apparatus, and the grid electrode Remove the adhering toner.
<Predetermined toner image>
Next, a description will be given of means for suppressing toner floating and reattachment of the floating toner caused by cleaning the grid electrode according to the present invention.

As described above, by cleaning the grid electrode, the positively charged toner floats around the pre-secondary transfer static elimination means 24. The floating toner stays inside the image layer forming apparatus and stains the inside of the apparatus, and further enters the respective toner image forming units 30 inside each of them to cause a problem that toners of different colors are mixed. Therefore, in the present invention, at the time of initial operation check performed when the power of the image forming apparatus is turned on, a solid image (predetermined toner image) of one or more layers is created on the intermediate transfer member before moving the cleaning member. When the predetermined toner image is at a position facing the pre-secondary transfer neutralization means 24, the movement of the intermediate transfer member 17 is stopped. In such a state, the floating positive toner adheres to a predetermined negatively charged toner image on the intermediate transfer member. The predetermined toner image size is A> the width of the image area, where A is the axial length.
When the length of the intermediate transfer member 17 in the rotation direction is B, a ≦ B ≦ a + 50 (mm)
Here, a is the width of the neutralizing means before secondary transfer.
<flowchart>
The grid electrode cleaning process will be described with reference to the flowchart of FIG.
Step S01: An electrode cleaning operation button is pressed from an operation unit (not shown), and an electrode cleaning ON signal is instructed from a control unit (not shown) of the image forming apparatus.
Step S02: An image forming operation for cleaning is started.
Step S03: A yellow solid image is formed on the intermediate transfer member.

The size of the image at this time is wider than the width of the image area with respect to the axial direction of the intermediate transfer member, and about 50 mm wider than the width of the neutralizing means before secondary transfer with respect to the rotational direction of the intermediate transfer member. It has become.
Step S04: The timing at which the yellow solid image comes to a position facing the pre-secondary transfer static elimination means is detected.
Step S05: The rotation of the intermediate transfer member is stopped.
Step S06: The cleaning operation is started.
Step S07: End of the cleaning operation By passing through the above steps, the yellow solid image on the intermediate transfer member is a negative toner image, so the positive toner floating around the pre-secondary transfer neutralization means is negative toner. It can be attracted by the toner and can suppress contamination inside the machine due to toner.
<Example>
A color image forming apparatus according to the present invention was manufactured according to the configuration of FIG. The specific configuration is as shown below.
(1) As an image forming body, a photosensitive drum having a thickness of 25 μm made of a phthalocyanine pigment dispersed in polycarbonate, an aluminum drum having an outer diameter of 60 mm, an axial length of 335 mm, and a wall thickness of 1 mm Using an organic photoreceptor having a negative charging characteristic formed on the outer peripheral surface of the metal substrate, the linear velocity when the image forming body was rotated was set to 220 mm / sec.
(2) As the charging device, a device composed of a scorotron charger having negative discharge characteristics was used, and the organic photoreceptor was negatively charged.
(3) As an exposure apparatus, an exposure apparatus comprising a semiconductor laser irradiation apparatus having a surface standard output of 300 μW was used.
(4) A two-component developing system was used as the developing device.
(5) As the developer, a toner containing negatively charged toner having a mass average particle diameter of 6.5 μm and a sphericity of 9.70, contained at a concentration of 7% by mass was used.
(6) The distance between the rotation axes of the image forming bodies in adjacent toner image forming units is 95 mm.
(7) As the primary transfer means, a contact transfer type using a primary transfer roller is used, and the primary transfer roller is made of stainless steel with a coating layer made of semiconductive acrylonitrile-butadiene rubber (NBR). It is formed on the outer peripheral surface of a cylindrical conductive core bar having an outer diameter of 9 mm, and has an outer diameter of 20 mm, a resistance value of 1 × 10 ⁷ Ω · cm, and an Asker C hardness of 27 °. . The pressing force of the primary transfer roller against the image forming body was set to 4.9 N, and the current value supplied to the primary transfer roller by the transfer current applying device was set to 35 μA.
(8) The cleaning blade of the image forming body cleaning means is made of urethane rubber, and the material constituting the cleaning blade has a rubber hardness of JIS A hardness of 70 °, a rebound resilience coefficient of 40%, a thickness of 2 mm, and free. A cleaning blade having a length of 9 mm is used. The effective contact angle of the cleaning blade with respect to the intermediate transfer member is set to 17 °. The cleaning blade is contacted in the counter direction with respect to the moving direction by the rotation of the intermediate transfer member. It was set to 196 mN / cm.
(9) As an intermediate transfer member, from an endless semiconductive resin belt made of polyimide having a surface resistivity of 1 × 10 ¹¹ Ω / □, a volume resistivity of 1 × 10 ⁹ Ωcm, and a circumference of 861 mm. The belt tension was set to 49N.
(10) As the charge removal means before secondary transfer, a scorotron charger composed of a discharge electrode made of a discharge wire, a grid electrode and a back plate was used, and the separation distance between the intermediate transfer member and the grid electrode was set to 1 mm. A high voltage power source was connected to the discharge tungsten wire, a voltage of +5 kV was applied, and a negative voltage polarity was applied to the grid electrode, and a voltage of -50 V was applied. The side plate of the electrode was set to the same potential as the grid electrode.
(11) As the grid electrode cleaning brush, a fluorine fiber having a hair length of 2 mm, a wire diameter of 10 T, and a density of 30 K / inch ² was used.
(12) As the secondary transfer means, a contact transfer type using a secondary transfer roller is used, and the secondary transfer roller is made of stainless steel with a coating layer made of semiconductive acrylonitrile-butadiene rubber (NBR). It is formed on the outer peripheral surface of a cylindrical metal core having an outer diameter of 16 mm, and has an outer diameter of 30 mm, a resistance value of 1 × 10 ⁸ Ω · cm, and an Asker C hardness of 64 °. . The pressing force of the secondary transfer roller against the intermediate transfer member was set to 98 N, and a transfer current of −50 μA was supplied to the secondary transfer roller by the transfer current supply device.
(13) The cleaning blade of the intermediate transfer member cleaning means is made of urethane rubber, and the material constituting the cleaning blade has a rubber hardness of JIS A hardness of 70 °, a rebound resilience coefficient of 40%, a thickness of 2 mm, and free. A cleaning blade having a length of 9 mm is used. The effective contact angle of the cleaning blade with respect to the intermediate transfer member is set to 17 °. The cleaning blade is contacted in the counter direction with respect to the moving direction by the rotation of the intermediate transfer member. It was set to 196 mN / cm.
(14) As the fixing device, a heat roller fixing type constituted by a heating roller and a pressure roller was used, and the fixing temperature was set to 200 ° C.
(15) A conductive acrylic brush (raw yarn resistance value 1 × 10 ² Ω, wire diameter 3d (denier), density 200K / inch ² , hair length 4 mm) is placed inside the intermediate transfer member facing the electrode removal electrode. It installed so that it might contact lightly with a transfer body.

Using the color image forming apparatus as described above, the following implementation test was performed.
<Example 1>
Durability image output test was performed with an image pattern that mixed solid images, halftone images, character images, etc., and after confirming that a large amount of toner had adhered to the grid after 10,000 copies, the cleaning member was reciprocated once. The grid cleaning operation was performed. Thereafter, toner adhesion (electrode contamination) to the grid electrode was observed, and the surface potential before and after neutralization of the halftone part was measured to evaluate the image quality of the halftone image.

  Before the cleaning device was driven, a Y-color solid image having a length of 50 mm and a width of 300 mm was output on the intermediate transfer member, and the intermediate transfer member was stopped so that the toner image was at a position opposite to the electrode removal. Thereafter, the grid potential was set to 0 V, and the cleaning device was driven.

After cleaning, no toner adheres to the grid. The toner scattered during the cleaning was transferred onto the intermediate transfer body, but could be removed by the downstream intermediate transfer body cleaning device. After neutralization on the intermediate transfer member in the halftone part, the toner layer potential was the same as before the neutralization, and the halftone output image was good.
<Example 2>
As in Example 1, after performing a grid cleaning operation after 10,000 copies of the durable image output test, the toner adhesion (electrode contamination) to the grid electrode was observed, the surface potential before and after neutralization of the halftone part was measured, and the halftone The image quality was evaluated.

  Before driving the cleaning device, a solid superimposed image of Y color and M color with a length of 50 mm and a width of 300 mm is output on the intermediate transfer member, and the intermediate transfer member is placed so that the toner image comes to a position facing the electrode removal. Stopped. Thereafter, the grid potential was set to 0 V, and the cleaning device was driven.

After cleaning, no toner adheres to the grid. The toner layer potential after neutralization on the intermediate transfer member in the halftone portion was the same as that before the neutralization, and the halftone output image was good.
<Example 3>
Durability image output test was performed with an image pattern that mixed solid images, halftone images, character images, etc., and after confirming that a large amount of toner had adhered to the grid after 10,000 copies, the cleaning member was reciprocated once. The grid cleaning operation was performed. Thereafter, toner adhesion (electrode contamination) to the grid electrode was observed, and the surface potential before and after neutralization of the halftone part was measured to evaluate the image quality of the halftone image.

  Before the cleaning device was driven, a Y-color solid image having a length of 50 mm and a width of 300 mm was output on the intermediate transfer member, and the intermediate transfer member was stopped so that the toner image was at a position opposite to the electrode removal. Thereafter, a grid potential of −50 V was applied to drive the cleaning device.

After cleaning, no toner adheres to the grid electrode. The toner scattered during the cleaning was transferred onto the intermediate transfer body, but could be removed by the downstream intermediate transfer body cleaning device. After neutralization on the intermediate transfer member in the halftone part, the toner layer potential was the same as before the neutralization, and the halftone output image was good.
<Comparative example>
As in Example 1, after performing a grid cleaning operation after 10,000 copies of the durable image output test, the toner adhesion (electrode contamination) to the grid electrode was observed, the surface potential before and after neutralization of the halftone part was measured, and the halftone The image quality was evaluated. Here, the intermediate transfer member was stopped so that a position where there is no toner image comes to a position facing the electrode removal of the intermediate transfer member. Thereafter, the grid potential was set to 0 V, and the cleaning device was driven.

  After cleaning, a thin toner adheres to the entire grid electrode. The positively charged toner scraped off by the cleaning member is considered to have reattached to the grid electrode due to the electric field directed from the intermediate transfer member to the grid electrode. In addition, the toner layer potential after neutralization on the intermediate transfer member in the halftone portion was lower than that before neutralization, and image roughness occurred in the halftone output image. It is considered that the potential control performance of the electrode removal was lowered by the toner adhering to the grid electrode.

  From the above results, when the grid was cleaned, a voltage was applied to the grid electrode and the counter electrode, so that the positively charged toner formed an electric field from the grid electrode toward the intermediate transfer member, and was scraped and scattered by the cleaning member. Since the toner faces the intermediate transfer member and does not adhere again to the grid electrode, it is possible to stably obtain a good charge removal control performance and a good secondary transfer image quality.

  Table 1 shows the results of grid electrode contamination and halftone image quality in Examples 1 to 3 and Comparative Example.

1 is an explanatory diagram illustrating an example of a configuration of an image forming apparatus. FIG. 2 is an explanatory diagram schematically illustrating an example of a configuration around a secondary transfer pre-charge neutralizing unit in the image forming apparatus of FIG. 1. FIG. 3A is a view as seen from the back surface (side facing the irradiated body) of the secondary transfer pre-charger, and FIG. 3B is a VV cross section of the cleaning device attached to the pre-transfer secondary charge remover. FIG. It is explanatory drawing which showed typically the arrangement pattern of a grid electrode. It is a perspective view which shows the drive means to which a cleaning member is moved. It is a flowchart which shows the cleaning process of a grid electrode.

Explanation of symbols

10Y, 10M, 10C, 10K Image forming body 11Y, 11M, 11C, 11K Charging device 12Y, 12M, 12C, 12K Exposure device 13Y, 13M, 13C, 13K Developer 14Y, 14M, 14C, 14K Primary transfer means 141Y, 141M, 141C, 141K Primary transfer roller 14S Secondary transfer means 141S Secondary transfer roller 17 Intermediate transfer member 17a, 17b, 17c Intermediate roller 17d Backup roller 18 Fixing device 181 Heating roller 182 Pressure roller 20Y, 20M, 20C, 20K Image forming body cleaning means 20S Intermediate transfer body cleaning means 24 Pre-secondary transfer neutralization means 241 Discharge electrode 241A Discharge discharge voltage application device 242 Grid electrode 242A Discharge grid voltage application device 243 Back plate 244 Counter electrode 30Y, 30M, 30C, 30K toner image forming unit

Claims (5)

The toner images of different colors electrostatically formed on the plurality of image forming bodies are sequentially moved in each primary transfer region to the intermediate transfer body contacting the plurality of image forming bodies. An intermediate toner image that forms an intermediate toner image on the transfer material by transferring and secondarily transferring a color toner image formed by stacking the toner images of each color on the intermediate transfer body onto the transfer material Forming means;
A color toner image formed on the intermediate transfer member is positioned downstream of the primary transfer region at the most downstream position in the moving direction of the intermediate transfer member and upstream of the position of the secondary transfer unit. Disposing a pre-secondary transfer neutralization means having a scorotron band electrode for neutralizing,
A cleaning device having a cleaning member that contacts the grid member in the scorotron band electrode and moves in the longitudinal direction;
An image forming apparatus comprising:
Before moving the cleaning member, a toner image having a predetermined pattern is formed on the intermediate transfer member, and the cleaning device performs a cleaning operation in a state where the toner image is opposed to the pre-secondary transfer neutralization unit. An image forming apparatus. The image forming apparatus according to claim 1, wherein the toner image of the predetermined pattern is a solid image having one or more layers of toner. 3. The cleaning device according to claim 1, wherein the cleaning device performs the cleaning by stopping the movement of the intermediate transfer member in a state where the toner image of the predetermined pattern is opposed to the pre-secondary transfer neutralization unit. The image forming apparatus described. The size of the toner image of the predetermined pattern is as follows:
4. The image forming apparatus according to claim 1, wherein A> width of the image area. The size of the toner image of the predetermined pattern is such that the length in the rotation direction of the intermediate transfer member is B,
a ≦ B ≦ a + 50 (mm),
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.
Where a is
a = the width of the neutralizing means before secondary transfer.

Images