JP2010204580A - Cleaning device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning device and an image forming apparatus which do not form a film such as toner and talc on a photoreceptor surface for a long period, prevent a damage by a carrier or the like, maintain successful cleaning nature, and obtain an even and high-definition image. <P>SOLUTION: An electrode member 264 is arranged adjacent to a cleaning brush 261 in which a brush fiber 268 is provided so as to extend to the outside of the radial direction of a cleaning brush support 262 by making an opposite surface 269 face the cleaning brush 261. When a power source 265 applies voltage having a predetermined frequency and predetermined amplitude to the electrode member 264, an oscillating electric field is formed in a gap between the electrode member 264 and the cleaning brush 261. By the oscillating electric field, the brush fiber 268 vibrates, and developer remaining in a photoreceptor 21 which abuts on the brush fiber 268 is collected. When the predetermined frequency is made into a natural frequency of the brush fiber 268, the brush fiber 268 resonates to more greatly vibrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning device and an image forming apparatus that remove deposits such as toner remaining on the surface of a photoreceptor, and more specifically, is used in the field using electrophotographic methods such as copying machines, laser printers, and facsimiles. In an image forming apparatus, an electrostatic latent image formed on a photoconductor is developed with toner and the like, and after the developed toner image is transferred to a transfer body, cleaning that removes deposits such as toner remaining on the surface of the photoconductor The present invention relates to an apparatus and an image forming apparatus including the apparatus.

  Image forming apparatuses such as copying machines and printers using an electrophotographic system form an electrostatic latent image on a photosensitive member by exposing the charged photosensitive member based on acquired image data. A toner image is formed by supplying toner (hereinafter also referred to as “developer”) to the electrostatic latent image. The toner image formed on the photoreceptor is transferred to a transfer material and fixed to form an image on the transfer material.

  The image forming apparatus includes a cleaning device that transfers a toner image formed on a photoconductor to a transfer material, and then sequentially removes and collects the developer remaining on the photoconductor. In the repeated toner image forming process, if the toner remains on the photoconductor, it is difficult to uniformly charge the surface of the photoconductor. Therefore, it is necessary to remove the residual toner reliably.

The cleaning device has, as a cleaning member, a cleaning blade or a cleaning brush that contacts the surface of the photoconductor and collects toner remaining on the surface of the photoconductor. The cleaning blade is generally composed of a rubber member, and collects toner while rubbing the surface of the photoreceptor. The cleaning brush is made of a brush member or a fiber made of a nylon material having an electrical resistance of about 1.0 × 10 ^{6.5 to} 1.0 × 10 ^9.5 Ω · cm, and is disposed on the surface of the photoreceptor. The toner is collected while in contact. By charging the cleaning brush to a predetermined potential, toner and carrier charged at opposite potentials can be adsorbed to the cleaning brush, so that the surface of the photoreceptor can be more efficiently cleaned.

  In the cleaning mechanism of the image forming apparatus described in Patent Document 1, an ultrasonic generator is provided between the transfer unit and the cleaning unit. This ultrasonic generator generates an ultrasonic wave having the same frequency as the natural frequency of the toner, vibrates the toner with the ultrasonic wave, weakens the adhesion to the photoconductor, and makes the toner easy to peel off from the photoconductor. Is.

JP-A-5-313539

  A cleaning device that uses a cleaning member that abuts on the surface of the photoconductor, such as a cleaning blade, needs to make the abutting portion sufficiently hard to collect toner and abut on the surface of the photoconductor with a relatively large load. is there. Therefore, a film such as toner or talc may be formed on the surface of the photoconductor, or the surface of the photoconductor may be damaged by coarse grained paper powder, resulting in deterioration of image quality and shortening the life of the photoconductor. There is.

In order to vibrate the toner with the ultrasonic generator described in Patent Document 1, a high frequency that is the same level as the natural frequency of the toner, for example, a frequency of 2.8 × 10 ⁴ kHz with 6 μm toner is required. In addition to concern about heat generation, since the toner on the photoconductor is irradiated with ultrasonic waves, vibration is also propagated to the photoconductor, and there is a concern that the toner image formed on the photoconductor may be disturbed.

  The object of the present invention is to form a uniform and high-quality image without forming a film such as toner and talc on the surface of the photoreceptor over a long period of time and preventing damage due to a carrier, etc., maintaining good cleaning properties. It is an object to provide a cleaning device and an image forming apparatus capable of obtaining

The present invention has a columnar shape, and is composed of a brush body supported so as to be movable in the radial direction, and brush fibers implanted in the outer circumference of the brush body over the entire circumference, and the central axis of the brush body is a cylinder. A conductive outer circumference arranged parallel to the central axis of the object to be cleaned, in which a virtual outer circumference circle in contact with the tip of the brush fiber contacts the outer circumference of the object to be cleaned, and rotates in the direction opposite to the rotation direction of the object to be cleaned. Brush and
An opposing surface formed in the vicinity of the virtual outer circumference and facing the virtual outer circle, and an electrode member serving as an electrode with respect to the brush;
And a voltage applying means for applying a voltage changing at a predetermined frequency to the electrode member.

  According to the present invention, the predetermined frequency is any one of a natural frequency of brush fibers provided in the brush body and an n-th normal vibration frequency of the natural frequency when n is a natural number. It is characterized by being.

  In the present invention, the voltage applied to the electrode member by the voltage applying means is a voltage obtained by superimposing an AC voltage having a predetermined amplitude on a DC voltage having a predetermined voltage value.

  In the present invention, the line of intersection between the facing surface and a plane perpendicular to the central axis of the brush body is a concentric circle with an outer circumference when the brush body is cut along a plane perpendicular to the central axis of the brush body. It is a part of a circle.

  In the invention, it is preferable that the electrode member has a coating layer made of an insulating material on the facing surface.

In the invention, it is preferable that the electrode member is coated with a fluororesin on the facing surface.
In addition, the present invention is an image forming apparatus including the cleaning device.

  According to the present invention, a conductive brush comprising a brush body that is cylindrical and supported so as to be movable in the radial direction, and brush fibers that are planted on the outer circumference of the brush body over the entire circumference thereof, The central axis of the brush body is arranged in parallel to the central axis of the cylindrical object to be cleaned, and the virtual outer circumference circle where the tip of the brush fiber is inscribed contacts the outer peripheral surface of the object to be cleaned and is opposite to the rotation direction of the object to be cleaned. Rotate in the direction. The electrode member is formed with an opposing surface that is close to the virtual outer circumference and faces the brush, and serves as an electrode with respect to the brush. Then, a voltage changing at a predetermined frequency is applied to the electrode member by the voltage applying means.

  That is, when the voltage applied to the electrode member changes at a predetermined frequency, the electric field formed around the brush body changes, and the brush body vibrates. When the brush body vibrates, the tip of the brush fiber that contacts the photoconductor that is the object to be cleaned also vibrates, reducing the adhesive force such as residual developer remaining on the photoconductor surface after transfer, and weakly scraping the brush. Even with a force (rubbing force), the deposits can be removed and recovered. Therefore, a film such as toner and talc is not formed on the surface of the photoreceptor over a long period of time, and it is possible to prevent damage caused by a carrier and maintain a good cleaning property and obtain a uniform and high-quality image. Can do.

  According to the invention, the predetermined frequency is any one of the natural frequency of the brush fiber provided in the brush body and the n-th normal vibration frequency of the natural frequency when n is a natural number. Because of the frequency, the brush fiber resonates, the vibration amplitude of the brush fiber becomes larger, the residual developer that comes into contact with the brush fiber is vibrated more, and the adhesion force can be reduced, improving the cleaning property. Can be achieved.

  According to the present invention, the voltage applied to the electrode member by the voltage applying means is a voltage obtained by superimposing a DC voltage having a predetermined voltage value on a DC voltage having a predetermined amplitude, and thus applying a voltage to be applied. A strong electric field can be formed around the brush body by the DC voltage included in the, thereby increasing the electrostatic attraction force. Therefore, the brush can be removed from the photoreceptor, and the residual developer attached to the brush can be efficiently peeled off from the brush. Further, since the tip of the brush fiber is attracted toward the electrode member by the electrostatic attraction force of the electrode member, it is possible to cause the brush fiber to fall down due to contact with the photosensitive member.

  According to the invention, the line of intersection between the facing surface and a plane perpendicular to the central axis of the brush body is concentric with an outer circumference when the brush body is cut along a plane perpendicular to the central axis of the brush body. Is a part of a circle. Therefore, since the gap between the opposing surface of the electrode member and the outer circumference of the brush body is constant, the electric field formed around the brush body is uniformly propagated to the outer circumference of the brush body, causing the brush body to vibrate uniformly. And efficient cleaning performance can be maintained over a long period of time.

  According to the present invention, since the electrode member is formed with a coating layer made of an insulating material on the facing surface, even if a high voltage is applied to the electrode member, generation of atmospheric discharge can be prevented. . Therefore, a high voltage can be applied to the electrode member, the brush can be vibrated more greatly, and the electrostatic attractive force can be further increased. Therefore, it is possible to more efficiently prevent the residual developer from being cleaned, the brush from being clogged by the residual developer, and the brush from falling down.

  According to the invention, the electrode member is coated with a fluororesin on the facing surface. That is, the surface coated with the fluororesin has an effect of suppressing the residual developer peeled off from the brush from adhering to the electrode member, thereby preventing the electrode member from being contaminated and forming a stable electric field. It is possible to stabilize the recovery of the residual developer by the brush and to maintain the brush falling over a long period of time.

  Moreover, according to this invention, the said cleaning apparatus is provided. That is, since the cleaning device that improves the recovery efficiency of the residual developer and prevents the brush fibers from falling down is provided, high print quality can be maintained over a long period of time.

1 is a diagram illustrating a configuration of an image forming apparatus 1 including a photoconductor cleaning device 26 according to an embodiment of the present invention. 2 is a diagram illustrating a configuration of a photoconductor cleaning device 26. FIG. 5 is a diagram showing developer recovery by brush fibers 268 and deformation of brush fibers 268. It is a figure for demonstrating the normal vibration of the brush fiber 268. FIG. It is a figure which shows the structure of the photoreceptor cleaning apparatus 26a which is the other form of implementation of this invention.

  FIG. 1 is a diagram illustrating a configuration of an image forming apparatus 1 including a photoreceptor cleaning device 26 according to an embodiment of the present invention. The image forming apparatus 1 is a tandem color image forming apparatus that can form a color image. The image forming apparatus 1 forms a recording medium P serving as a recording medium on the basis of image data transmitted from a personal computer or terminal device connected via a network, or image data read by a document reading device such as a scanner. On the other hand, it has a printer function for forming a color image or a monochrome image.

  The image forming apparatus 1 includes a photoconductor 21 as an image carrier, a charger 22, an exposure device 23, a developer 24 using a two-component developer composed of toner and a carrier, a primary transfer roller 25, and a photoconductor cleaning device 26. The image forming station unit 2 including the image forming station 2, the secondary transfer unit 3, the fixing unit 4, the paper supply unit 5, and the paper discharge unit 6 constitute a main part.

  The image forming station unit 2 corresponds to the image information of each color of yellow (y), magenta (m), cyan (c), and black (k) included in the color image information representing the color image. And four image forming stations for magenta image, cyan image and black image. Then, image forming stations for yellow image, magenta image, cyan image, and black image are arranged in this order in the advancing direction A of the intermediate transfer belt 31 described later.

  The four image forming stations for yellow image, magenta image, cyan image and black image have substantially the same configuration, and based on the image data corresponding to each color, yellow, magenta Then, cyan and black images are formed, superimposed on the intermediate transfer belt 31 to form an image composed of four colors of toner, and the secondary transfer unit 3 transfers the toner image onto the recording paper P. Then, the toner image on the recording paper P is heated and fixed by the fixing unit 4 to form a full-color image on the recording paper P.

  Each member constituting the image forming station unit 2 corresponds to the image information of each color of black (k), cyan (c), magenta (m), and yellow (y) included in the color image information. Four are provided.

  The photoreceptor 21 to be cleaned has a substantially cylindrical drum shape having a photosensitive material such as an organic photoreceptor (abbreviated as “OPC”) on its surface, and is disposed above the exposure unit 23. It is controlled to rotate in the rotational direction B by the drive means and the control means that do not. The charger 22 is a scorotron charger for uniformly charging the surface of the photoconductor 21 to a predetermined potential, and is disposed in the vicinity of the outer peripheral surface of the photoconductor 21.

  The exposure device 23 irradiates the surface of the photosensitive member 21 charged by the charger 22 by irradiating it with a laser beam based on image data output from an image processing unit (not shown), thereby exposing the photosensitive member 21. It has a function of reducing the potential of the exposed portion on the surface and writing and forming an electrostatic latent image corresponding to the image data on the surface. The exposure unit 23 forms an electrostatic latent image corresponding to the corresponding color by inputting image data corresponding to yellow, magenta, cyan, or black according to the image forming station corresponding to each color. It has become. As the exposure unit 23, in addition to a laser scanning unit (abbreviated as “LSU”) including a laser irradiation unit and a reflecting mirror, electroluminescence (abbreviated as “EL”) or light emitting diode (abbreviated as “EL”). A writing device in which light-emitting elements such as “LED”) are arranged in an array, for example, a writing head can be used.

  The developing device 24 includes a developing roller serving as a developer latent image that carries the developer, and a developing tank that stores the developer. Here, in the embodiment of the present invention, using a two-component developer, the electrostatic latent image formed on the surface of the photoreceptor 21 by the exposure device 23 is reversely developed with the toner to form a toner image. . The developer is not limited to a two-component developer, and a one-component developer can also be used. Further, the developing device 24 includes a toner bottle 27 that accommodates each toner corresponding to each color and replenishes the developing tank with toner according to the amount of toner consumed. The developing roller is configured to convey the developer to a developing area where toner can move to the photoreceptor 21. Further, the toner in the developer stored in the developing tank is charged with the same polarity as the surface potential charged on the photoreceptor 21. Here, the polarity of the surface potential charged on the photoconductor 21 and the charging polarity of the toner used are both negative.

  The intermediate transfer belt 31 is stretched by a transfer roller 32 which is one member of the secondary transfer unit 3 and an opposing roller 35 which faces a belt cleaner 34 described later, thereby forming an endless movement path. A belt member that is driven to rotate as the counter roller 35 rotates.

  When the intermediate transfer belt 31 passes through the photoconductor 21 while being in contact with the photoconductor 21, charging of the toner on the surface of the photoconductor 21 from the primary transfer roller 25 disposed opposite to the photoconductor 21 via the intermediate transfer belt 31 is performed. A transfer bias having a polarity opposite to the polarity, here positive polarity, is applied, and the toner image formed on the photoreceptor 21 is transferred onto the intermediate transfer belt 31 and carried.

  After the toner image transfer process is completed, the photosensitive member 21 is adhered to the surface of the photosensitive member 21, that is, the photosensitive member 21 described later includes a developer (hereinafter also referred to as “residual developer”) remaining on the surface of the photosensitive member 21. It is removed and collected by the body cleaning device 26.

  In the secondary transfer unit 3, the secondary transfer roller 33 performs intermediate transfer via the recording paper P supplied and conveyed by the paper supply means 5 in synchronization with the conveyance of the toner image carried on the intermediate transfer belt 31. Press contact with the belt 31. A pressure contact portion between the secondary transfer roller 33 and the intermediate transfer belt 31 becomes a transfer nip portion. When the toner image carried on the intermediate transfer belt 31 and the recording paper P pass through the transfer nip at the same time, a positive potential (transfer electric field) that attracts toner is applied to the secondary transfer roller 33, The toner image on the intermediate transfer belt 31 is transferred to the recording paper P.

  The fixing unit 4 is provided downstream of the secondary transfer unit 3 in the conveyance direction of the recording paper P, and includes a heating roller 41 and a pressure roller 42. The heating roller 41 is rotatably provided by a driving means (not shown), and heats and melts the toner constituting the unfixed toner image transferred and carried on the recording paper P, and fixes it on the recording paper P. A heating means (not shown) is provided inside the heating roller 41 and heats the heating roller 41 so that the surface of the heating roller 41 has a predetermined temperature. For example, a heater or a halogen lamp can be used as the heating means.

  The pressure roller 42 is provided so as to be in pressure contact with the heating roller 41, and is supported so as to be driven to rotate by the rotational drive of the pressure roller 42. The pressure roller 42 assists fixing of the toner image on the recording paper P by pressing the toner and the recording medium when the toner is melted and fixed on the recording paper P by the heating roller 41. A pressure contact portion between the heating roller 41 and the pressure roller 42 is a fixing nip portion. According to the fixing unit 4, the recording paper P onto which the toner image has been transferred is sandwiched between the heating roller 41 and the pressure roller 42 in the secondary transfer unit 3, and the toner image is transferred when passing through the fixing nip unit. By being pressed against the recording paper P under heating, the toner image is fixed on the recording paper P and an image is formed.

  The paper supply unit 5 includes a paper supply tray 51, a pickup roller 52, a registration roller 53, a transport roller 54, and a paper guide 55. The paper supply tray 51 is a container-like member that is provided in the lower part of the image forming apparatus 1 in the vertical direction and stores the recording paper P. Examples of the recording paper P include plain paper, color copy paper, overhead projector sheets, and postcards.

  The pickup roller 52 takes out the recording paper P stored in the paper supply tray 51 one by one and feeds it toward the registration roller 53. The registration rollers 53 are a pair of roller members provided so as to be in pressure contact with each other, and the toner image carried on the intermediate transfer belt 31 is conveyed to the transfer nip portion on the recording paper P fed from the pickup roller 52. In synchronism with the recording paper P, the recording paper P is fed to a paper guide 55 that defines the conveyance path of the recording paper P so as to be fed to the transfer nip portion. The recording paper P fed to the paper guide 55 is transported to a transport roller 54 which is a pair of roller members provided so as to be pressed against each other, and transported to a transfer nip portion.

  The paper discharge unit 6 includes a discharge roller 61. The discharge roller 61 is provided on the downstream side of the fixing nip portion of the fixing unit 4 in the sheet conveyance direction, and the recording sheet P on which the image is fixed by the fixing unit 4 is provided on the upper surface in the vertical direction of the image forming apparatus 1. Do not discharge to the discharge tray. The discharge tray stores the recording paper P on which the image is fixed.

  FIG. 2 is a diagram illustrating the configuration of the photoconductor cleaning device 26. The photoconductor cleaning device 26 that is a cleaning device includes a cleaning brush 261, a power source 263, an electrode member 264, a power source 265, a toner fall prevention lower seal 266, and a waste toner case 267.

  A cleaning brush 261 that is a brush includes a cleaning brush support 262 and brush fibers 268. The cleaning brush support 262, which is a brush body, has a cylindrical shape with a diameter of 10 mm, for example, and is supported so as to be movable in the radial direction. The brush fibers 268 are provided so as to extend outward in the radial direction of the cleaning brush support 262, and have a length of, for example, 5 mm.

  A shaft (hereinafter also referred to as “axis”) of the cleaning brush support 262 is, for example, Φ6 mm stainless steel (abbreviated as “SUS”) or aluminum, and is passed through a bearing (not illustrated) of the waste toner case 267. It is supported. The inner diameter of the bearing is, for example, 6.1 mm, and the clearance with the shaft is 0.1 mm. Accordingly, when the cleaning brush 261 vibrates, it is possible to vibrate and separate the photosensitive member 21 with a width of 0.1 mm, and the residual developer can be vibrated.

  The cleaning brush 261 is arranged such that a virtual outer circumference inscribed in the tip of the brush fiber 268 is in contact with the photoconductor 21 and rotates at a high speed in a rotation direction C opposite to the rotation direction B of the photoconductor 21. The cleaning brush 261 rotates at a peripheral speed equal to or higher than the peripheral speed of the photoconductor 21. However, since the diameter of the cleaning brush 261 is shorter than the diameter of the photoconductor 21, the cleaning brush 261 rotates at a higher speed than the photoconductor 21. Will do. The cleaning brush 261 contacts the photoconductor 21 after the toner image transfer process is completed, weakens the adhesion between the photoconductor 21 and the residual developer, and scrapes off the residual developer.

  The cleaning brush 261 has a certain amount of biting with respect to the photosensitive member 21, and this biting amount is set in consideration of the performance of the cleaning brush 261 and the influence on the photosensitive member 21. Specifically, when the cleaning performance is poor, the contact is made with a large biting amount, that is, a high contact pressure, and when the cleaning performance is good, the contact is made with a small biting amount, that is, a low contact pressure. In the present embodiment, the amount of biting is set to about 0.5 to 2.0 mm, for example, but depending on the selection of the material of the brush fibers 268 of the cleaning brush 261 and the like, the influence on the photoreceptor 21 and the cleaning capability It is possible to widen the range of selection of the biting amount to improve both.

  As the material of the brush fibers 268, fibers such as rayon, acetate, nylon, polyester, acrylic, polypropylene, polyethylene, polyurethane, fluorine, cotton, or wool, or glass or metal processed into fibers are used. .

The fiber thickness is, for example, 5 to 15 denier / filament. The density of the brush fiber is suitably 10,000 to 100,000 / inch ² , and the length of the brush is suitably 1 to 10 mm. Further, when the brush fiber 268 is non-conductive, a conductive cleaning brush 261 is obtained by performing a conductive process.

The cleaning brush 261 is configured by directly fixing the brush fibers 268 on the cleaning brush support 262 or by bonding a fabric of the brush fibers 268 on the cleaning brush support 262. That is, the brush fibers 268 are implanted on the outer circumference of the cleaning brush support 262 over the entire circumference. The tip of the brush fiber 268, that is, the hair tip, may have a shape after the brush fiber 268 is cut or may have a loop shape. In this embodiment, a nylon fiber obtained by conductive processing is used, the thickness of the brush fiber is 6 denier / filament, the density of the brush is 50,000 / inch ² , and the length of the brush fiber is 5 mm.

  The power source 263 is a DC power source, and applies a DC bias voltage having a polarity opposite to the transfer bias, that is, a negative polarity, to the cleaning brush 261. The applied bias voltage is preferably −200 V to −400 V, and is set to −250 V in the present embodiment. By applying a bias voltage to the cleaning brush 261, the cleaning brush 261 applies an electrostatic attraction to the photoconductor 21, and can efficiently collect the positively charged toner and carrier remaining after the transfer from the photoconductor 21. it can. The electrostatic attraction force is an attraction force due to the tension of electric lines of force generated between the electrodes, and is proportional to the square of the applied voltage and inversely proportional to the square of the distance between the electrodes.

  The electrode member 264 is not particularly limited as long as it is made of a material such as stainless steel (SUS), aluminum (Al), copper (Cu), brass, or carbon, but is made of stainless steel in the present embodiment. Is done. The electrode member 264 has a facing surface 269 that faces the cleaning brush 261, and is disposed in close proximity with the facing surface 269 facing the cleaning brush 261.

  More specifically, when the opposed surface 269 is cut along a virtual plane orthogonal to the axis of the cleaning brush support 262, the cut portion of the cut opposed surface 269 is an arc FG as shown in FIG. That is, the line of intersection between the facing surface 269 and the virtual plane is an arc FG. The arc FG is concentric with the outer circumference of the cut portion where the cleaning brush support 262 is cut along a virtual plane. The electrode member 264 is disposed at a position in the fourth quadrant with respect to the center of the concentric circle with a gap E from a virtual outer circumferential circle in which the facing surface 269 is inscribed in the tip of the brush fiber 268. In the present embodiment, the gap E is set to 200 μm.

  A power source 265 that is a voltage applying unit applies a voltage having a predetermined frequency and a predetermined amplitude to the electrode member 264. The predetermined frequency is a frequency equal to or higher than the natural frequency of the brush fiber. In the present embodiment, power supply 265 applies a voltage having a sine wave waveform with a predetermined frequency of 198 Hz and a predetermined amplitude of 1.5 kVpp to electrode member 264. The offset voltage, which is a predetermined voltage value at this time, is −500V. Therefore, the amplitude of the voltage is −1250V to + 250V. When a voltage having a predetermined frequency and a predetermined amplitude is applied to the electrode member 264 by the power source 265, an oscillating electric field is formed in the gap between the electrode member 264 and the cleaning brush 261. Due to this oscillating electric field, the cleaning brush support 262 which is a constituent member of the cleaning brush 261 vibrates.

  FIG. 3 is a diagram illustrating the recovery of the developer by the brush fibers 268 and the deformation of the brush fibers 268. FIG. 3 schematically shows an exaggerated manner in which the deformed brush fiber 268 recovers while the cleaning brush 261 makes one rotation while vibrating.

  The cleaning brush 261 receives the action of an oscillating electric field formed between the electrode member 264, contacts the surface of the photoconductor 21 while vibrating, and floats the developer remaining on the surface of the photoconductor 21. They are attracted and recovered by electrostatic attraction by the DC bias voltage applied by the power supply 263.

  Subsequently, the portion of the brush fiber 268 that is in contact with the photoconductor 21 rotates 180 ° in the rotation direction C from the point H, that is, the position closest to the point F. . During this time, a part of the developer collected by the brush fibers 268 is separated from the brush fibers 268 due to the vibration of the brush fibers 268 and the adhesion between the brush fibers 268 and the developer being reduced. It is collected in the case 267.

  Next, while the portion of the brush fiber 268 that has reached the position closest to the point F reaches the position closest to the point G by subsequently making a quarter turn, the electrode member 264 and the cleaning brush support 262 are rotated. Since the brush fiber 268 receives an attractive force in the direction of the electrode member 264 while vibrating, the developer adhering to the brush fiber is recovered and pressed and deformed by contact with the photoreceptor 21. The shape of the brush fiber 268 can be restored to its original state before being deformed.

  Referring to FIG. 2, when a voltage having a predetermined frequency and a predetermined amplitude is applied to electrode member 264 by power supply 265, an oscillating electric field is formed in the gap between electrode member 264 and cleaning brush support 262. The The cleaning brush support 262 is a middle point perpendicular to the central axis of the cleaning brush support 262 and the center of the arc FG and the arc FG equally divided by the oscillating electric field of the electrode member 264 arranged in the fourth quadrant. Vibrates in the direction of a straight line connecting

  For example, when focusing on the point G, when the cleaning brush support 262 vibrates in the direction D opposite to the point G due to this oscillating electric field, the photosensitive member 21 at the point H among the brush fibers 268 fixed to the cleaning brush support 262. The brush fibers 268 in contact with the surface oscillate at the natural frequency of the brush fibers 268 or the n-th order normal frequency along the same direction as the facing direction D. A point G is a point H where the cleaning brush 261 and the photosensitive member 21 are in contact with each other, and is a point that is in the same opposing direction as the vibration direction for cleaning the photosensitive member 21.

  FIG. 4 is a diagram for explaining normal vibration of the brush fiber 268. Since one end of the brush fiber 268 is fixed to the cleaning brush support 262 and the other end is a free end, the vibration of the brush fiber 268 is a cantilever vibration as shown in FIG. FIG. 4 shows the shape of the brush fiber 268 having the maximum amplitude when each portion of the brush fiber 268 moves relative to the fixed position when vibration is applied to the cleaning brush support 262.

  FIG. 4A shows the shape of the brush fiber 268 when it vibrates at the natural frequency of the brush fiber 268. The natural frequency is a primary normal vibration frequency. FIG. 4B shows the shape of the brush fiber 268 when vibrating at the secondary normal vibration frequency. FIG. 4C shows the shape of the brush fiber 268 when oscillating at the third normal vibration frequency. FIG. 4D shows the shape of the brush fiber 268 when vibrating at the fourth-order normal vibration frequency. The secondary normal vibration has one node that does not vibrate except for the fixed position, and the tertiary normal vibration has two nodes except for the fixed position. The subnormal vibration has three nodes except for the fixed position. An equation for calculating the n-th order normal vibration frequency will be described later.

  The waste toner case 267 is a container-like member for storing the residual developer recovered from the photoreceptor 21 by the cleaning brush 261 as waste toner. The waste toner stored in the waste toner case 267 is conveyed to a waste toner disposal bottle (not shown) by a waste toner conveyance screw (not shown). The toner fall prevention lower seal 266 is for preventing the developer scraped by the cleaning brush 261 from leaking out of the waste toner case 267. In this embodiment, the toner fall prevention lower seal 266 is made of a urethane rubber sheet having a thickness of 0.1 mm.

  Since the image forming apparatus 1 is configured as described above, the image forming apparatus 1 has excellent cleaning performance, prevents the influence of the residual developer during image formation on the next recording paper P, and forms a high-quality image. be able to.

  Next, the developer remaining on the photoconductor 21 is vibrated in the facing direction D to vibrate the brush fibers 268 of the cleaning brush 261, and the surface of the photoconductor 21 is rubbed to clean the residual developer. Explain the points to consider to improve efficiency.

  Important matters to consider when vibrating the cleaning brush 261 and sliding the tip of the brush fiber 268 against the surface of the photoreceptor 21 are (a) the vibration frequency and vibration amplitude of the brush fiber 268, and (b) the cleaning brush 261. And (c) the distribution of the magnitude of the vibration amplitude in the vibration area of the cleaning brush 261.

First, (a) the vibration frequency and vibration amplitude of the brush fiber 268 will be described. The vibration frequency and vibration amplitude of the vibration in the facing direction D generated on the brush fibers 268 depend on the vibration of the cleaning brush support 262 generated when a voltage is applied to the electrode member 264. The attractive force F acting on the cleaning brush support 262 from the electrode member 264 can be obtained by the equation (1) when considered as a capacitor using the electrode member 264 and the cleaning brush support 262 as electrode plates. F represents the attractive force acting between the electrode plates, Q represents the amount of charge, and E represents the strength of the electric field.
F = (1/2) × Q × E (1)

Further, the charge amount Q can be obtained by the equation (2). ε represents the relative permittivity of vacuum, S represents the facing area, d represents the electrode spacing, and V represents the potential difference.
Q = (εS / d) V (2)

For example, in Equation (1) and Equation (2), S = 300 mm × 5 mm, d = 200 μm, ε = 8.85 × 10 ⁻¹² (s ⁴ · A ² · kg ⁻¹ · m ⁻³ ), V = Substituting 2 kV to calculate the attractive force F acting between the electrode plates, F = 0.66N.

  That is, when a voltage is applied to the electrode member 264 from the power source 265, the above-described attractive force acts between the electrode member 264 and the cleaning brush support 262, and this attractive force repeatedly changes at the frequency of the applied voltage. To do. As a result, the cleaning brush support 262 vibrates in the facing direction D with a vibration amplitude corresponding to the attractive force and a vibration frequency corresponding to the frequency of the applied voltage. As the cleaning brush support 262 vibrates, the brush fibers 268 vibrate in the facing direction D at the vibration amplitude and vibration frequency at the point H where the cleaning brush 261 and the photosensitive member 21 come into contact with each other.

  The vibration frequency of the brush fiber 268 can be adjusted by changing the frequency of the voltage applied to the electrode member 264 (hereinafter referred to as “applied voltage”). In order to reduce the adhesion of the residual developer to the photoreceptor 21 and improve the recovery efficiency, it is necessary to adjust the frequency of the applied voltage to a predetermined value or more. That is, as described above, the vibrating brush fiber 268 vibrates the surface of the photoconductor 21, thereby reducing the adhesive force of the remaining developer to the photoconductor 21. However, if the frequency of the applied voltage is too low, The force that gives vibration to the residual developer on the surface of the body 21 is weak, and improvement in the recovery efficiency of the residual developer is not recognized. Therefore, in this embodiment, the frequency of the applied voltage applied to the electrode member 264 is set to be equal to or higher than the natural frequency of the brush fiber 268.

  In addition, the vibration amplitude corresponding to the attractive force generated between the electrode member 264 and the cleaning brush support 262 is obtained from the equations (1) and (2) based on the material constituting the electrode member 264 and the cleaning brush support 262. The dielectric constant is increased, the facing area between the electrode member 264 and the cleaning brush support 262 is increased, the applied voltage applied to the electrode member 264 is increased, and the gap width between the electrode member 264 and the cleaning brush support 262 is decreased. It can be enlarged by doing.

  Thus, when the vibration amplitude of the cleaning brush support 262 increases, the vibration amplitude by which the brush fibers 268 vibrate the surface of the photoconductor 21 increases, and the effect of rubbing the developer attached to the surface of the photoconductor 21 is obtained. Get higher. However, if the applied voltage applied to the electrode member 264 is too high, or if the gap width between the electrode member 264 and the cleaning brush support 262 is too small, an atmospheric discharge occurs, and therefore, the applied voltage is applied to the electrode member 264. It is not preferable to make the applied voltage too high and to make the gap width between the electrode member 264 and the cleaning brush support 262 too small.

Next, a configuration capable of efficiently increasing the vibration amplitude of the brush fiber 268 will be described. The applied voltage applied to the electrode member 264 by the power source 265 is a natural vibration voltage that is a voltage that changes at the natural frequency of the brush fiber 268 or the n-th order normal vibration frequency, so that the brush fiber 268 can resonate. . Specifically, the natural frequency f _i of the cantilever beam of the brush fiber 268 can be obtained by Expression (3). λ _i represents the frequency coefficient, l represents the length of the brush fiber, E represents the Young's modulus, I represents the second moment of section, ρ represents the density of the material, and A represents the sectional area.

For a cantilever beam, λ ₁ = 1.875, λ ₂ = 4.694, λ ₃ = 7.855, λ ₄ = 10.996.

  Moreover, the cross-sectional secondary moment I is represented by Formula (4). d shows the diameter of a brush fiber cross section.

In formula (3) and formula (4), the length l of brush fiber 268 is 5 mm, density ρ = 1.16 g / cm ³ , cross-sectional area A = 5.75 × 10 ⁻¹⁰ m ² , Young's modulus E = 0 Substituting 20 × 10 ¹⁰ kg / m · s to calculate the natural frequency, that is, the primary normal vibration frequency f ₁ , f ₁ = 198 Hz. The brush fiber 268 can be made to resonate by applying to the electrode member 264 a voltage that changes at the primary normal vibration frequency f ₁ or a normal vibration frequency of the second or higher order. When the brush fibers 268 resonate, the vibration amplitude that vibrates in the facing direction D of the brush fibers 268 becomes larger, and the developer remaining on the surface of the photoreceptor 21 can be rubbed greatly, thereby improving the cleaning efficiency. it can.

  The electrode member 264 is preferably set so that the bending rigidity in the facing direction D with respect to the cleaning brush support 262 is higher than the bending rigidity in the cross-sectional direction of the cleaning brush support 262. Accordingly, when an attractive force due to an oscillating electric field generated between the electrode member 264 and the cleaning brush support 262 is applied, the cleaning brush support 262 can be vibrated while suppressing the deflection of the electrode member 264. Specifically, when considering a beam extending in the axial direction, the bending rigidity A is represented by A = E × I. E is Young's modulus, and I is the secondary moment of section.

The cut surface obtained by cutting the electrode member 264 along a plane perpendicular to the axis of the cleaning brush support 262 has a shape that is a square shape cut out from a fan shape, and has a sectional moment of inertia of the electrode member 264 having a radius r of 10 mm. I ₁ is represented by the formula (5).

When the constituent material of the electrode member 264 is stainless Since stainless Young's modulus ^{E = 17 × 10 10 kg /} m · s, flexural rigidity _{A 1} of the electrode member 264,
A ₁ = E × I ₁ = 13 N · m ²

On the other hand, in the cleaning brush support 262 having an outer diameter of 10 mm, the cross-sectional secondary moment I ₂ can be obtained by the above-described equation (4). When the constituent material of the cleaning brush support 262 is aluminum, since the Young's modulus E of aluminum is 7.0 × 10 ¹⁰ kg / m · s, the bending rigidity A ₂ of the cleaning brush support 262 is A ₂ = the ^{_{E × I 2 = 34N · m}} 2.

  Thus, when the bending rigidity of the electrode member 264 in the facing direction D of the electrode member 264 is set higher than the bending rigidity of the cleaning brush support 262 in the cross-sectional direction, the electrode member 264 and the cleaning brush support When an attractive force due to an oscillating electric field generated between the body 262 and the body 262 acts, the cleaning brush support 262 can be vibrated while suppressing the bending of the electrode member 264.

  Further, when the electrode member 264 is bent, the gap width between the electrode member 264 and the cleaning brush support 262 and further the brush fiber 268 fixed to the cleaning brush support 262 is small due to the bending of the electrode member 264. Therefore, discharge in the air is likely to occur. By suppressing the bending of the electrode member 264 by increasing the bending rigidity of the electrode member 264, the gap width between the electrode member 264 and the cleaning brush 261 is prevented from becoming too small even when a high voltage is applied to the electrode member 264. Then, a large vibration amplitude can be applied to the brush fibers 268 by greatly vibrating the cleaning brush support 262.

  Next, (b) the size of the vibration region of the cleaning brush 261 will be described. The vibration region is within the range of the maximum width of the vibration amplitude at each point of the cleaning brush 261. The electrode member 264 is formed such that a facing surface 269 that faces the outer peripheral surface of the cleaning brush support 262 is along the outer peripheral surface of the cleaning brush support 262. Therefore, in the region where the electrode member 264 and the cleaning brush support 262 face each other with a gap, the same gap width is obtained over the entire region. That is, when a voltage is applied to the electrode member 264, the oscillating electric field formed in the facing region where the electrode member 264 and the cleaning brush support 262 face each other is uniform over the entire facing region.

  Finally, (c) the distribution of the magnitude of the vibration amplitude in the vibration region of the cleaning brush 261 will be described. The distribution is the magnitude of the oscillating electric field between the arcs FG. In the electrode member 264, a facing surface 269 that faces the outer peripheral surface of the cleaning brush support 262 is formed along the outer peripheral surface of the cleaning brush support 262. Therefore, in the region where the electrode member 264 and the cleaning brush support 262 face each other, the electrode member 264 and the cleaning brush support 262 always face each other with a constant gap width. That is, when a voltage is applied to the electrode member 264, the oscillating electric field formed in the facing region is uniform, and the vibration amplitude has a constant magnitude.

  FIG. 5 is a diagram showing a configuration of a photoconductor cleaning device 26a according to another embodiment of the present invention. The photoconductor cleaning device 26a is similar to the photoconductor cleaning device 26, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. A characteristic configuration of the photoconductor cleaning device 26a is that a coating layer 601 made of an insulating material is provided on an opposing surface 269 of the electrode member 264 facing the cleaning brush support 262. The photoconductor cleaning device 26 a is configured in the same manner as the photoconductor cleaning device 26 except that the electrode member 264 is provided with a coat layer 601. Further, a fluororesin layer 602 may be provided on the electrode member 264 or the coat layer 601.

  The layer thickness of the coat layer 601 is, for example, in the range of 50 to 2000 nm. The layer thickness of the fluororesin layer 602 is, for example, in the range of 50 to 400 μm. Examples of the material constituting the coat layer 601 include barium titanate having a relative dielectric constant of “1200”, strontium titanate having a relative dielectric constant of “332”, or titanium oxide having a relative dielectric constant of “100”. As described above, an insulating material having a high dielectric constant is desirable.

  Thus, by providing the coat layer 601 made of an insulating material on the surface of the electrode member 264, a higher voltage is applied to the electrode member 264 than when the portion facing the cleaning brush 261 is made of a conductor. Even if it is applied, generation of atmospheric discharge can be prevented. Therefore, a large oscillating electric field can be generated in the gap between the cleaning brush support 262 and the electrode member 264, and the removal efficiency for removing the developer remaining on the photosensitive member 21 is excellent, and the image on the next recording sheet P is excellent. It is possible to prevent the influence of the developer remaining at the time of formation from appearing and to form a high-quality image.

  As mentioned above, although embodiment of this invention was described, description of this embodiment should be considered that it is an illustration and restrictive at no points. The scope of the present invention is shown not only by the above-described embodiments but also by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

  In this way, the conductive body is composed of the cleaning brush support 262 that is cylindrical and supported so as to be movable in the radial direction, and the brush fibers 268 that are implanted on the outer circumference of the cleaning brush support 262 over the entire circumference. In the cleaning brush 261, the central axis of the cleaning brush support 262 is arranged in parallel to the central axis of the cylindrical photosensitive member 21, and a virtual outer peripheral circle in which the tip of the brush fiber 268 is inscribed is formed on the outer peripheral surface of the photosensitive member 21. It contacts and rotates in the direction opposite to the rotation direction of the photosensitive member 21. The electrode member 264 has a facing surface 269 that is opposed to the virtual outer circumference in the vicinity, and serves as an electrode for the cleaning brush 261. Then, a voltage that changes at a predetermined frequency is applied to the electrode member 264 by the power source 265.

  That is, when the voltage applied to the electrode member 264 changes at a predetermined frequency, the electric field formed around the cleaning brush support 262 changes, and the cleaning brush support 262 vibrates. As the cleaning brush support 262 vibrates, the tip of the brush fiber 268 that contacts the photoconductor 21 also vibrates, reducing the adhesion of residual developer and the like remaining on the surface of the photoconductor 21 after transfer, and the cleaning brush 261. Even with a weak scraping force (sliding force), the deposits can be removed and recovered. Therefore, a film such as toner and talc is not formed on the surface of the photoconductor 21 over a long period of time, and damage due to a carrier or the like is prevented to maintain a good cleaning property, and a uniform and high-quality image can be obtained. Obtainable.

  Further, the predetermined frequency is any one of the natural frequency of the brush fibers 268 provided on the cleaning brush support 262 and the n-th normal vibration frequency of the natural frequency when n is a natural number. As a result, the brush fiber 268 resonates and the vibration amplitude of the brush fiber 268 becomes larger, and the residual developer in contact with the brush fiber 268 is vibrated more greatly, thereby reducing the adhesive force and improving the cleaning performance. Improvements can be made.

  Further, the voltage applied to the electrode member 264 by the power source 265 is a voltage obtained by superimposing an AC voltage that is a voltage value having a predetermined amplitude on a DC voltage that is a predetermined voltage value. Therefore, depending on the DC voltage included in the applied voltage, A strong electric field can be formed around the cleaning brush support 262 to increase the electrostatic attractive force. Therefore, the cleaning agent 261 removed from the photoreceptor 21 and the residual developer attached to the cleaning brush 261 can be efficiently peeled from the cleaning brush 261. Further, since the tip of the brush fiber 268 is attracted toward the electrode member 264 by the electrostatic attraction force of the electrode member 264, the brush fiber 268 that has fallen due to contact with the photoreceptor 21 can be raised.

  Furthermore, the line of intersection between the facing surface 269 and the plane orthogonal to the central axis of the cleaning brush support 262 is the outer circle when the cleaning brush support 262 is cut along the plane orthogonal to the central axis of the cleaning brush support 262. Part of a circle that is a concentric circle. Accordingly, the gap between the facing surface 269 of the electrode member 264 and the outer circumferential circle of the cleaning brush support 262 is constant, so that the electric field formed around the cleaning brush support 262 is uniform on the outer peripheral surface of the cleaning brush support 262. Therefore, the cleaning brush support 262 can be vibrated uniformly, and an efficient cleaning performance can be maintained over a long period of time.

  Furthermore, since the electrode member 264 is formed with the coat layer 601 made of an insulating material on the opposing surface 269, even if a high voltage is applied to the electrode member 264, generation of atmospheric discharge can be prevented. Therefore, a high voltage can be applied to the electrode member 264, and the cleaning brush 261 can be vibrated further and the electrostatic attraction force can be further increased. Therefore, it is possible to more efficiently prevent the cleaning performance of the residual developer, the clogging of the cleaning brush 261 due to the residual developer, and the hair fall of the cleaning brush 261.

  Further, the electrode member 264 is coated with a fluororesin on the facing surface 269. That is, the surface coated with the fluororesin has an effect of suppressing the residual developer peeled off from the cleaning brush 261 from adhering to the electrode member 264, so that the electrode member 264 is prevented from being contaminated and stabilized. An electric field can be formed, the recovery of the residual developer by the cleaning brush 261 can be stabilized, and the falling of the cleaning brush 261 can be maintained for a long time.

  Further, the image forming apparatus 1 includes a photoconductor cleaning device 26 or a photoconductor cleaning device 26a. That is, since the photoconductor cleaning device 26 or the photoconductor cleaning device 26a, which is a cleaning device that can improve the recovery efficiency of the residual developer and prevent the brush fibers from falling down, is provided, high print quality can be obtained over a long period of time. Can be maintained.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming station part 3 Secondary transfer part 4 Fixing means 5 Paper supply means 6 Paper discharge means 21 Photoconductor 22 Charger 23 Exposure device 24 Developer 25 Primary transfer roller 26, 26a Photoconductor cleaning device 27 Toner Bottle 31 Intermediate transfer belt 32 Transfer roller 33 Secondary transfer roller 34 Belt cleaner 35 Opposed roller 41 Heating roller 42 Pressure roller 51 Paper feed tray 52 Pickup roller 53 Registration roller 54 Conveyance roller 55 Paper guide 61 Discharge roller 261 Cleaning brush 262 Cleaning brush support 263, 265 Power source 264 Electrode member 266 Lower seal for preventing toner fall 267 Waste toner case 268 Brush fiber 269 Opposing surface P Recording paper

Claims (7)

It is cylindrical and consists of a brush body that is supported so as to be movable in the radial direction, and brush fibers that are implanted on the outer circumference of the brush body over the entire circumference, and the central axis of the brush body is cylindrical. A conductive brush that is arranged in parallel to the center axis of the body, a virtual outer circumference circle in contact with the tip of the brush fiber is in contact with the outer circumferential surface of the object to be cleaned, and rotates in a direction opposite to the rotation direction of the object to be cleaned;
An opposing surface formed in the vicinity of the virtual outer circumference and facing the virtual outer circle, and an electrode member serving as an electrode with respect to the brush;
And a voltage applying means for applying a voltage changing at a predetermined frequency to the electrode member.   The predetermined frequency is any one of a natural frequency of a brush fiber provided in the brush body and an n-order normal vibration frequency of the natural frequency when n is a natural number. The cleaning device according to claim 1.   3. The voltage applied to the electrode member by the voltage applying means is a voltage obtained by superimposing an alternating voltage having a predetermined amplitude voltage value on a direct current voltage having a predetermined voltage value. Cleaning equipment.   A line of intersection between the facing surface and a plane perpendicular to the central axis of the brush body is a part of a circle that is concentric with an outer circumference when the brush body is cut along a plane perpendicular to the central axis of the brush body. The cleaning apparatus according to claim 1, wherein the cleaning apparatus is provided.   The cleaning device according to claim 1, wherein a coating layer made of an insulating material is formed on the facing surface of the electrode member.   The cleaning device according to claim 1, wherein the electrode member is coated with a fluororesin on the facing surface. An image forming apparatus comprising the cleaning device according to claim 1.

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