JP2010107916A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus configured to transfer a toner image carried on a toner image carrying belt to a transfer target member and form an image on the transfer target member, which is excellent in removal efficiency of removing residual toner remaining on the toner image carrying belt after performing transfer processing with respect to the transfer target member, and then, capable of forming high-definition images over a long period. <P>SOLUTION: A belt cleaning part 60 for removing the residual toner remaining on the outer circumferential surface of the intermediate transfer belt 311 after transferring the toner image to the recording sheet in a secondary transfer station part 32 includes: a counter roller 601 around which the intermediate transfer belt 311 is stretched; an electrode member 602 facing the counter roller 601 with leaving a gap therebetween; a power source 603 for applying a voltage having a prescribed frequency to the electrode member 602; and a cleaning blade 604 for removing the residual toner in contact with the intermediate transfer belt 311. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile machine. More specifically, the present invention relates to a toner image carrier after a toner image formed on a toner image carrier belt is transferred to a transfer member. The present invention relates to an image forming apparatus including a cleaning unit that cleans a belt.

  In an electrophotographic image forming apparatus, an electrostatic latent image on an electrostatic latent image holding member is developed with toner to obtain a toner image, and the toner image is transferred to a transfer member and transferred onto the transfer member. A method of forming a toner image is employed. As a transfer method in the image forming apparatus, a toner image formed on an electrostatic latent image holding member is transferred, and a transfer opposite to a toner image carrying member that carries and carries the toner image via a member to be transferred. A transfer method is used in which the toner image is transferred to the transfer member by moving the toner image by electrostatic force. A cleaning unit is provided to remove residual toner remaining on the toner image carrying member after the transfer of the toner image to the transfer member.

  As a cleaning method in such an image forming apparatus, a cleaning unit is brought into contact with a toner image carrying member that carries and transports residual toner, and the residual toner is mechanically scraped off from the toner image carrying member, or a voltage is applied to the cleaning unit. A cleaning method is used in which residual toner is removed from the toner image carrying member by moving the residual toner from the toner image carrying member with an electrostatic force generated by the operation.

  In such a cleaning method, in order to remove residual toner from the toner image carrying member, it is desirable that the adhesion force of the toner to the toner image carrying member is low. In particular, when toner with high sphericity remains on the toner image carrying member as residual toner, it is difficult to scrape and remove the residual toner efficiently even if the cleaning means is brought into contact with the toner image carrying member to remove it. It is important to reduce the adhesion force of the toner to the toner image carrying member.

  Patent Documents 1 and 2 disclose image forming apparatuses capable of reducing the adhesion force of toner to a toner image carrying belt that is a toner image carrying member. According to the image forming apparatus disclosed in Patent Document 1, a cleaning unit uses a cleaning unit in a transfer unit that transfers a toner image carried on a photosensitive drum that is an electrostatic latent image holding member to a recording sheet that is a transfer target member. The adhesive force between the transfer belt and the toner can be reduced by placing a piezo element in contact with the inner surface of the transfer belt so as to face a certain cleaning bias roller and applying a mechanical vibration by the piezo element to the transfer belt.

  Further, according to the image forming apparatus disclosed in Patent Document 2, in the intermediate transfer belt which is a toner image carrying belt for transferring the toner image carried on the photosensitive drum to the recording paper, cleaning is performed on the inner surface of the intermediate transfer belt. An ultrasonic generator is pressed against the small diameter part of the end of the metal roller facing the cleaning blade, and the intermediate transfer belt is mechanically vibrated by the ultrasonic generator, thereby improving the adhesion between the intermediate transfer belt and the toner. Can be reduced.

JP 2000-112267 A JP 2007-47587 A

  However, in the image forming apparatus disclosed in Patent Document 1, since an ultrasonic transducer such as a piezo element is rubbed against the transfer belt, wear occurs at a contact portion between the piezo element and the transfer belt. For this reason, the contact resistance between the inner surface of the transfer belt and the transfer electrode fluctuates, the transfer electric field becomes non-uniform, transfer efficiency decreases, and a uniform and high-quality image cannot be formed on the recording paper. Even if such a technique for reducing the adhesion force of the toner by the piezo element is applied to a portion where the residual toner is removed from the intermediate transfer belt, which is a toner image carrying member, it does not occur at the contact portion of the intermediate transfer belt with the piezo element. Since uniform wear occurs, the vibration imparted to the intermediate transfer belt by the piezo element becomes non-uniform, and the effect of reducing the adhesion of toner to the intermediate transfer belt by the piezo element is reduced. Therefore, the removal efficiency of removing the residual toner from the intermediate transfer belt is not excellent, and the toner remains on the intermediate transfer belt after the transfer process to the recording paper, and the image is formed on the next recording paper. The influence of the residual toner appears, and a high-quality image cannot be formed.

  Further, in the image forming apparatus disclosed in Patent Document 2, since the ultrasonic generator is brought into pressure contact with the small diameter portion at the end of the metal roller and vibrated, wear occurs at the pressure contact portion of the ultrasonic generator. In addition, the vibration generated by the ultrasonic generator pressed against the small diameter part of the end of the metal roller is transmitted in the width direction of the belt through the surface of the intermediate transfer belt contacting the metal roller, but corresponds to the radial direction of the metal roller. The intermediate transfer belt cannot be vibrated in the direction in which it moves. Therefore, the transmission of vibration generated at the pressure contact portion at the small diameter portion of the end portion of the metal roller is not stable, and the intermediate transfer belt cannot be vibrated in a direction corresponding to the radial direction of the metal roller. It cannot be said that the adhesion reducing effect is sufficient. Therefore, the removal efficiency of removing the residual toner from the intermediate transfer belt is not excellent, and the toner remains on the intermediate transfer belt after the transfer process to the recording paper, and the image is formed on the next recording paper. The influence of the residual toner appears, and a high-quality image cannot be formed.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus for forming an image on a member to be transferred by transferring the toner image carried on the toner image carrying belt to the member to be transferred. It is an object of the present invention to provide an image forming apparatus that has excellent removal efficiency for removing residual toner remaining on a belt and can form a high-quality image over a long period of time.

The present invention is an endless belt member that is stretched by a plurality of support rollers and is rotationally driven as the support rollers rotate, and a toner image carrying belt that carries a toner image;
A cleaning unit which is one of the plurality of supporting rollers and is opposed to the opposing roller formed in a hollow cylindrical shape via the toner image carrying belt;
An electrode member facing the opposing roller with a predetermined gap;
A power source for applying a voltage having a predetermined frequency to the electrode member;
When the toner remaining on the toner image carrying belt after the toner image carried on the toner image carrying belt is transferred to the transfer member is removed by contact with the toner image carrying belt, In the image forming apparatus, a power source applies a voltage to the electrode member to vibrate the toner image carrying belt via the counter roller.

  Further, the invention is characterized in that a coating layer made of an insulating material is provided on a portion of the electrode member that faces the counter roller.

  Further, the invention is characterized in that the bending rigidity of the electrode member in the facing direction with respect to the facing roller is higher than the bending rigidity in the radial direction of the cylindrical surface of the facing roller.

  In the invention, it is preferable that the power source applies a natural vibration voltage, which is a voltage having a frequency that is an integral multiple of the natural frequency of the cylindrical surface of the counter roller, to the electrode member.

  According to the present invention, when the power source applies the natural vibration voltage to the electrode member, the cleaning means contacts the portion of the toner image carrying belt corresponding to the antinode of vibration in the resonance mode generated in the facing roller. Then, the residual toner is removed.

  In the invention, it is preferable that the frequency of the voltage applied to the electrode member by the power source is 20 kHz or more.

  According to the present invention, the belt member is an endless belt member that is stretched by a plurality of support rollers and is driven to rotate in accordance with the rotation of the support roller, and includes a toner image carrying belt that carries a toner image and a plurality of support rollers. A cleaning means that is opposed to the opposing roller formed in a hollow cylindrical shape via a toner image carrying belt, an electrode member that is opposed to the opposing roller with a predetermined gap, An image forming apparatus including a power source that applies a voltage having a predetermined frequency to an electrode member. When the cleaning unit contacts the toner image carrying belt and removes residual toner remaining on the toner image carrying belt after the toner image carried on the toner image carrying belt is transferred to the transfer member, the power supply A voltage having a predetermined frequency is applied to the electrode member. As described above, when a voltage is applied to the electrode member, a vibration electric field is formed in the gap between the electrode member and the counter roller, and the counter roller vibrates by the vibration electric field, and the toner image is suspended on the counter roller. The belt vibrates. As the toner image carrying belt vibrates, the adhesive force between the residual toner remaining on the toner image carrying belt and the toner image carrying belt is reduced by the inertial force caused by the mass of the toner itself. This provides excellent removal efficiency for removing residual toner remaining on the toner image carrying belt after the transfer process to the transfer member, and prevents the influence of the residual toner during the next image formation on the transfer member. High-quality images can be formed.

  In the prior art, since the ultrasonic vibrator is brought into contact with the toner image carrying belt and vibrated, wear occurs at the contact portion between the ultrasonic vibrator and the toner image carrying belt due to long-term use. However, in the image forming apparatus of the present invention, the toner image carrying belt is vibrated in a non-contact manner by an oscillating electric field generated in the gap between the electrode member and the opposing roller. In each of the support belts, wear due to vibration does not occur over a long period of time. Therefore, after the transfer process on the transfer member over a long period of time, the removal efficiency that removes the residual toner remaining on the toner image carrying belt is maintained at a high level, and the influence of the residual toner at the time of image formation on the next transfer member Can be prevented, and a high-quality image can be formed.

  According to the invention, the coat layer made of an insulating material is provided on the portion of the electrode member facing the counter roller. As described above, the coating layer made of an insulating material is provided on the surface of the electrode member, so that a higher voltage can be applied to the electrode member than when the portion facing the counter roller is made of a conductor. The occurrence of air discharge can be prevented. For this reason, a high voltage can be applied to the electrode member to generate a large oscillating electric field in the gap between the opposing roller and the electrode member.

  Further, according to the present invention, the bending rigidity of the electrode member in the facing direction with respect to the facing roller is configured to be higher than the bending rigidity in the radial direction of the cylindrical surface of the facing roller. Thus, when an attractive force due to an oscillating electric field generated in the gap between the electrode member and the opposing roller is applied, the opposing roller can be vibrated while suppressing the deflection of the electrode member. In addition, when the electrode member is bent, the gap width between the electrode member and the opposing roller is reduced by this bending, and air discharge is likely to occur. By suppressing the bending of the electrode member by increasing the bending rigidity of the electrode member, even if a high voltage is applied to the electrode member, the gap width between the electrode member and the counter roller is prevented from becoming too small. Can be greatly vibrated to give a large vibration to the toner image carrying belt.

  According to the invention, the power source applies a natural vibration voltage, which is a voltage having a frequency that is an integral multiple of the natural frequency of the cylindrical surface of the opposing roller, to the electrode member. Thereby, the cylindrical surface of the opposing roller can be resonated. For this reason, the vibration amplitude of the opposing roller is increased, and the residual toner on the toner image carrying belt can be vibrated greatly. Accordingly, the inertial force acting on the residual toner is increased, and the adhesion of the residual toner to the toner image carrying belt can be reduced.

  Further, according to the present invention, when the power source applies a natural vibration voltage to the electrode member, the cleaning unit contacts and remains on the portion of the toner image carrying belt corresponding to the antinode of vibration in the resonance mode generated in the opposing roller. It is configured to remove toner. Large vibration is applied to the portion of the toner image carrying belt corresponding to the antinode of vibration in the resonance mode generated in the opposing roller. Therefore, the residual toner on the toner image carrying belt can be vibrated greatly, the inertial force acting on the residual toner is increased, and the adhesion force of the residual toner to the toner image carrying belt can be reduced.

  Moreover, according to this invention, the frequency of the voltage which a power supply applies to an electrode member is 20 kHz or more. When the counter roller vibrates due to the oscillating electric field generated in the gap between the electrode member and the counter roller, the air vibration generated by the vibration of the counter roller exceeds the human audible frequency and prevents discomfort during operation. Can do.

  FIG. 1 is a diagram illustrating a configuration of an image forming apparatus 1 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 includes a recording medium and a recording medium based on image data transmitted from various terminal devices such as a PC (Personal Computer) connected via a network and image data read by a document reading device such as a scanner. A recording paper having a printer function for forming a color image or a monochrome image.

  The image forming apparatus 1 includes an image forming station unit 2 having a toner image forming unit 20 and a primary transfer unit 31, a secondary transfer station unit 32, a fixing unit 4, a paper supply unit 5, and a paper discharge unit 6. It is comprised including. The image forming station unit 2 uses a yellow image and a magenta image in order to correspond to the image information of each color of yellow (y), magenta (m), cyan (c), and black (k) included in the color image information. And four image forming stations for cyan image and black image. Further, image forming stations for yellow image, magenta image, cyan image, and black image are arranged in this order in the rotation direction of an intermediate transfer belt 311 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 , Cyan, and black images are formed, superimposed on the intermediate transfer belt 311 to form an image composed of four colors of toner, and the secondary transfer station unit 32 transfers the toner image onto the recording paper. Then, the toner image on the recording paper is heated and pressed by the fixing unit 4 to form a full-color image on the recording paper.

  Each member constituting the image forming station unit 2 corresponds to image information of each color of black (k), cyan (c), magenta (m), and yellow (y) included in the color image information. It is provided one by one. Here, each member provided by four according to each color is distinguished by attaching an alphabet representing each color to the end of the reference symbol, and when referring collectively, only the reference symbol is used.

  The image forming station unit 2 includes a toner image forming unit 20 and a primary transfer unit 31. The toner image forming unit 20 includes a photosensitive drum 21, a charging unit 22, an exposure unit 23, a developing unit 24, and a cleaner 25. The charging unit 22, the developing unit 24, and the cleaner 25 are arranged in this order around the rotation direction of the photosensitive drum 21.

  The photosensitive drum 21 has a substantially cylindrical drum shape having a photosensitive material such as OPC (Organic Photoconductor) on the surface, and is disposed above the exposure unit 23. By the driving means and the control means, It is controlled to rotate in a predetermined direction. The charging unit 22 is a scorotron charger for uniformly charging the surface of the photosensitive drum 21 to a predetermined potential, and is disposed in the vicinity of the outer peripheral surface of the photosensitive drum 21.

The exposure unit 23 irradiates the surface of the photosensitive drum 21 charged by the charging unit 22 with laser light based on the image data output from the image processing unit (not shown), thereby exposing the photosensitive member. It has a function of lowering the potential of the exposed portion on the surface of the drum 21 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 (LSU) provided with a laser irradiation unit and a reflection mirror, EL (Electro Luminescence) or LED (Light
A writing device (for example, a writing head) in which light emitting elements such as Emitting Diodes are arranged in an array can be used.

  The developing unit 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 this embodiment, an electrostatic latent image formed on the surface of the photosensitive drum 21 by the exposure unit 23 is reversely developed with the toner using a two-component developer including toner and carrier. A toner image is formed. The developer is not limited to two-component development, and a one-component developer can also be used. Further, the developing unit 24 includes a toner bottle 241 that stores 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 the toner can move to the photosensitive drum 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 photosensitive drum 21. Here, both the polarity of the surface potential charged on the photosensitive drum 21 and the charging polarity of the toner to be used are negative.

  The cleaner 25 removes and collects the toner remaining on the outer peripheral surface of the photosensitive drum 21 after the toner image is transferred to the intermediate transfer belt 311, and a cleaning blade made of urethane rubber is used as a surface of the photosensitive drum 21. Abut.

  The primary transfer unit 31 includes an intermediate transfer belt 311 that is a toner image carrying belt, a driving roller 312, a primary transfer roller 313, and a belt cleaning unit 60. The intermediate transfer belt 311 is stretched and looped by a transfer roller 321 which is a member of the secondary transfer station unit 32 and a counter roller 601 which is a member of the belt cleaning unit 60 described later. This is an endless belt member that forms a moving path of the roller, and is driven to rotate as the counter roller 601 rotates. The opposing roller 601 includes a rubber layer on the surface of the cylindrical portion in order to increase the frictional force with the intermediate transfer belt 311, and is mechanically connected to a motor (not shown) provided in the apparatus main body and is driven to rotate.

  When the intermediate transfer belt 311 passes through the photosensitive drum 21 while being in contact with the photosensitive drum 21, the surface of the photosensitive drum 21 from the primary transfer roller 313 arranged to face the photosensitive drum 21 via the intermediate transfer belt 311. A transfer bias having a polarity opposite to the charging polarity of the toner (here, positive polarity) is applied, and the toner image formed on the surface of the photosensitive drum 21 is transferred onto the intermediate transfer belt 311 and carried.

The intermediate transfer belt 311 superimposes the toner images formed on the photosensitive drums 21 of the image forming stations for the respective colors at the same position so that a toner image composed of four color toners is formed on the surface of the toner image carrying region. It is carried inside. The intermediate transfer belt 311 is made of semiconductive polyimide having a thickness of 80 μm, a volume resistivity of 10 ¹⁰ Ω · cm, and a surface resistivity of 10 ¹⁰ Ω / □. Then, when the intermediate transfer belt 311 rotates, a toner image composed of four color toners is conveyed to the secondary transfer station unit 32.

  Although details will be described later, the belt cleaning unit 60 removes residual toner remaining on the outer peripheral surface of the intermediate transfer belt 311 after the transfer of the toner image to the recording paper serving as the transfer material in the secondary transfer station unit 32. As with the cleaner 25 described above, a cleaning blade 604 that is a cleaning means made of urethane rubber is in contact with the intermediate transfer belt 311.

  In the secondary transfer station unit 32, the secondary transfer roller 322 is disposed to face the transfer roller 321 that suspends the intermediate transfer belt 311 with the intermediate transfer belt 311 interposed therebetween. The intermediate transfer belt 311 is rotationally driven by the rotation of the transfer roller 321. In order to increase the frictional force with the intermediate transfer belt 311, the transfer roller 321 includes a rubber layer on the surface of the cylindrical portion, and is connected to a drive motor (not shown) provided in the apparatus main body and is rotationally driven. The secondary transfer roller 322 is in pressure contact with the intermediate transfer belt 311 through a recording sheet supplied and conveyed by the sheet supply unit 5 in synchronization with the conveyance of the toner image carried on the intermediate transfer belt 311. A pressure-contact portion between the secondary transfer roller 322 and the intermediate transfer belt 311 becomes a transfer nip portion. When the toner image carried on the intermediate transfer belt 311 and the recording paper pass through the transfer nip portion at the same timing, a positive potential (transfer electric field) that attracts the toner is applied to the secondary transfer roller 322, so that the intermediate The toner image on the transfer belt 311 is transferred to a recording sheet.

  The fixing unit 4 is provided downstream of the secondary transfer station unit 32 in the recording sheet conveyance direction, and includes a heating roller 41 and a pressure roller 42. The heating roller 41 is provided so as to be rotationally driven by a driving unit (not shown), and heats and melts the toner constituting the unfixed toner image transferred and carried on the recording paper, and fixes it on the recording paper. A heating means (not shown) is provided inside the heating roller 41. The heating means heats the heating roller 41 so that the surface of the heating roller 41 reaches a predetermined temperature (heating 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 rotation drive of the pressure roller 42. The pressure roller 42 assists the fixing of the toner image onto the recording paper by pressing the toner and the recording medium when the toner is melted and fixed on the recording paper 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 sheet onto which the toner image is transferred in the secondary transfer station unit 32 is sandwiched between the heating roller 41 and the pressure roller 42, and the toner image is heated when passing through the fixing nip unit. The toner image is fixed on the recording paper by being pressed down against the recording paper, and an image is formed.

  The paper supply unit 5 includes a paper feed tray 51, a pickup roller 52, a registration roller 53, a transport roller 54, and a paper guide 55. The paper feed 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 recording paper. Examples of the recording paper include plain paper, color copy paper, overhead projector sheet, postcard, and the like. In particular, when plain paper with rough surfaces (bad paper) is used, in the present invention described later. The improvement in transfer efficiency, which is an excellent effect, is noticeable.

  The pick-up roller 52 takes out the recording paper stored in the paper feed 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 311 is conveyed to the transfer nip portion on the recording paper fed from the pickup roller 52. In synchronism with this, the sheet is fed to a sheet guide 55 that defines the conveyance path of the recording sheet so that the sheet is fed to the transfer nip portion. The recording sheet fed to the sheet guide 55 is conveyed to a conveying roller 54 which is a pair of roller members provided so as to be in pressure contact with each other, and is conveyed 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 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. To discharge. The discharge tray stores recording paper on which an image is fixed.

  FIG. 2 is a diagram illustrating a configuration of the belt cleaning unit 60 according to the first embodiment of the present invention. The belt cleaning unit 60 includes a counter roller 601, an electrode member 602, a power source 603, a cleaning blade 604 that is a cleaning unit, a rake seal 605, and a waste toner case 606.

  The counter roller 601 is a support roller that suspends the intermediate transfer belt 311 together with the transfer roller 321 described above, and is formed in a hollow cylindrical shape. The opposing roller 601 has an outer diameter of 30 mm, an axial length of 310 mm, and a cylindrical resin end made of aluminum (A5052) with a thickness of 0.8 mm, and a conductive resin flange provided via a ball bearing. It is supported so as to be rotatable around the rotation axis. The opposing roller 601 rotates following the rotation of the intermediate transfer belt 311. The opposing roller 601 is electrically grounded via the rotating shaft.

  The electrode member 602 is disposed inside the intermediate transfer belt 311 so as to face the opposing roller 601 with a predetermined gap. The material constituting the electrode member 602 is not particularly limited as long as it is a conductive material such as stainless steel (SUS), aluminum (Al), copper (Cu), brass, and carbon, but in this embodiment, it is made of SUS. Further, in this embodiment, the electrode member 602 is formed in a rectangular parallelepiped shape, the cut surface cut by a plane orthogonal to the axis of the opposing roller 601 is rectangular, and the dimension thereof is in the direction A facing the opposing roller 601. The corresponding dimension L is 20 mm, and the dimension H corresponding to the direction orthogonal to the facing direction A is 10 mm, which is smaller than the diameter of the facing roller 601. Here, the facing direction A is a direction from the electrode member 602 toward the facing roller 601. The length of the electrode member 602 extending in the axial direction of the counter roller 601 is 300 mm. In the present embodiment, the gap width G of the gap between the electrode member 602 and the opposing roller 601 is set to 200 μm. Here, the surface of the electrode member 602 facing the peripheral surface of the facing roller 601 is a flat surface, but the gap width G is the shortest distance between the surfaces facing each other.

  The power source 603 applies a voltage having a predetermined frequency and amplitude to the electrode member 602. In the present embodiment, the power supply 603 applies a voltage having a frequency of 2.2 kHz and a sinusoidal waveform with an amplitude of 4 kVpp to the electrode member 602, and the offset voltage is 0V. After the toner image carried on the intermediate transfer belt 311 is transferred to the recording paper in the secondary transfer station unit 32, the power source 603 removes the leading edge of the residual toner remaining on the intermediate transfer belt 311 from the belt cleaning unit 60. The supply of voltage to the electrode member 602 is started in accordance with the timing when the upstream reaches a predetermined position (for example, a position 100 mm upstream from the belt cleaning unit 60), and the rear end of the residual toner image is downstream of the belt cleaning unit 60. When a predetermined position (for example, a position 100 mm downstream from the belt cleaning unit 60) is reached, voltage supply to the electrode member 602 is stopped.

  The cleaning blade 604 is arranged in a state where one edge abuts on the outer peripheral surface of the intermediate transfer belt 311 in a region that contacts the opposing roller 601 and is elastically bent, and the outer periphery of the intermediate transfer belt 311 after the transfer process. The residual toner remaining on the surface is mechanically scraped to clean the outer peripheral surface of the intermediate transfer belt 311. In the present embodiment, the cleaning blade 604 is made of urethane rubber having a thickness of 2 mm.

  The waste toner case 606 is a container-like member for storing the residual toner scraped from the intermediate transfer belt 311 by the cleaning blade 604 as waste toner. The waste toner stored in the waste toner case 606 is transported to a waste toner disposal bottle (not shown) by a waste toner transport screw (not shown). The other edge of the cleaning blade 604 is connected to the open end of the waste toner case 606.

  The rake seal 605 slightly contacts the outer peripheral surface of the intermediate transfer belt 311 in an area where the rake seal 605 is in contact with the counter roller 601 of the intermediate transfer belt 311 to scrape residual toner on the outer peripheral surface of the intermediate transfer belt 311. It passes through the contact portion of the cleaning blade 604 without dropping. The scoop seal 605 prevents waste toner scraped by the cleaning blade 604 and stored in the waste toner case 606 from leaking out of the waste toner case 606. In the present embodiment, the rake seal 605 is made of a urethane rubber sheet having a thickness of 0.1 mm. The other edge of the rake seal 605 is connected to the open end of the waste toner case 606.

  According to the belt cleaning unit 60, when a voltage having a predetermined frequency and amplitude is applied to the electrode member 602 disposed so as to face the opposing roller 601, vibration is generated in the gap G between the electrode member 602 and the opposing roller 601. An electric field is formed, and the oscillating electric field vibrates the cylindrical surface of the opposed roller 601 in the opposed direction A, and vibrates in the opposed direction A in a region where the intermediate transfer belt 311 is suspended from the opposed roller 601. When the intermediate transfer belt 311 vibrates in the facing direction A, the residual toner remaining on the outer peripheral surface of the intermediate transfer belt 311 vibrates in the facing direction A, and the residual toner intermediate transfer belt 311 is caused by the inertia force generated by the vibration. Adhesive strength against is reduced. As a result, the residual toner remaining on the intermediate transfer belt 311 after the transfer process on the recording paper is excellent in removal efficiency by the cleaning blade 604, and the influence of the residual toner is expressed at the time of image formation on the next recording paper. And a high-quality image can be formed.

  In the prior art, since the ultrasonic vibrator is brought into contact with the intermediate transfer belt 311 and vibrated, wear occurs at the contact portion between the ultrasonic vibrator and the intermediate transfer belt 311 due to long-term use. However, the image forming apparatus 1 according to the present invention is configured to vibrate the intermediate transfer belt 311 in a non-contact manner by an oscillating electric field generated in the gap G between the electrode member 602 and the opposing roller 601. In each of the facing roller 601 and the intermediate transfer belt 311, wear due to vibration does not occur over a long period of time. Therefore, after the transfer process on the recording paper for a long time, the residual toner remaining on the intermediate transfer belt 311 is maintained at a high removal efficiency by the cleaning blade 604, and the residual toner is formed at the time of image formation on the next recording paper. It is possible to prevent the occurrence of the influence of the above and to form a high-quality image.

  Further, when toner having a high sphericity remains on the intermediate transfer belt 311 as residual toner, it is difficult to remove the toner from the intermediate transfer belt 311 by the mechanical scraping action of the cleaning blade 604. In the image forming apparatus 1, since the intermediate transfer belt 311 vibrates in the facing direction A, the adhesion of residual toner to the intermediate transfer belt 311 is reduced, and the removal efficiency removed by the cleaning blade 604 is maintained in a high state. .

  Next, matters to be considered in order to improve the removal efficiency of removing the residual toner remaining on the intermediate transfer belt 311 in the facing direction A by reducing the adhesion force to the intermediate transfer belt 311 and removing it by the cleaning blade 604. explain. Important matters to consider when the intermediate transfer belt 311 is vibrated to reduce the adhesion of residual toner to the intermediate transfer belt 311 are: (a) vibration frequency and vibration amplitude of the intermediate transfer belt 311; (b). These are the size of the vibration area of the intermediate transfer belt 311 and (c) the distribution of the magnitude of vibration amplitude in the vibration area of the intermediate transfer belt 311.

(A) Vibration frequency and vibration amplitude of the intermediate transfer belt 311 The vibration frequency and vibration amplitude of the vibration in the facing direction A generated on the intermediate transfer belt 311 are generated by applying a voltage to the electrode member 602. Depends on the vibration.

First, the force that acts on the counter roller 601 from the electrode member 602 will be described. Considering a capacitor in which the electrode member 602 and the counter roller 601 are electrode plates, the attractive force F acting between the electrode plates is expressed by the following equation (1).
F = (1/2) × Q × E (1)
[Wherein 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. ]

The charge amount Q is expressed by the following formula (2).
Q = (εS / d) V (2)
[In the formula, ε represents the relative permittivity of vacuum, S represents the facing area, d represents the electrode spacing, and V represents the potential difference. ]

In formula (1) and formula (2), for example, S = 300 mm × 5 mm, d = 200 μm, ε = 8.85 × 10 ⁻¹² (s ⁴ · A ² · kg ⁻¹ · m ⁻³ ), V = When the attractive force F acting between the electrode plates is calculated by substituting 2 kV, F = 0.66N.

  That is, when a voltage is applied to the electrode member 602 from the power source 603, the above-described attractive force acts between the electrode member 602 and the opposing roller 601, and this attractive force is repeatedly generated at the frequency of the applied voltage. As a result, the cylindrical surface of the facing roller 601 vibrates in the facing direction A with a vibration amplitude corresponding to the attractive force and a vibration frequency corresponding to the frequency of the applied voltage. As the counter roller 601 vibrates, the intermediate transfer belt 311 vibrates in the facing direction A at the vibration amplitude and vibration frequency in the region suspended by the counter roller 601.

  As described above, the vibration frequency of the intermediate transfer belt 311 can be adjusted by the frequency of the applied voltage applied to the electrode member 602. However, the adhesion force of the residual toner to the intermediate transfer belt 311 is reduced to reduce the residual toner. In order to improve the removal efficiency, it is necessary to adjust the frequency of the applied voltage to a predetermined value or more. That is, as described above, the adhesive force of the residual toner to the intermediate transfer belt 311 decreases due to the inertial force generated by the vibration of the residual toner. However, if the frequency of the applied voltage is too low, the inertia applied to the residual toner is low. Since the force becomes too small, the decrease in the adhesive force is small, and the improvement in the removal efficiency of the residual toner is not recognized. Therefore, in this embodiment, the frequency of the applied voltage applied to the electrode member 602 is set to 2.2 kHz.

  Moreover, it is preferable that the frequency of the applied voltage applied to the electrode member 602 is 20 kHz or more (for example, 22 kHz). As a result, the air vibration generated by the vibration of the facing roller 601 exceeds the human audible frequency, and uncomfortable feeling during operation can be prevented.

  In addition, the vibration amplitude of the intermediate transfer belt 311 corresponding to the attractive force generated between the electrode member 602 and the counter roller 601 clearly forms the electrode member 602 and the counter roller 601 from the equations (1) and (2). The dielectric constant of the material to be increased is increased, the opposing area between the electrode member 602 and the opposing roller 601 is increased, the applied voltage applied to the electrode member 602 is increased, and the gap width between the electrode member 602 and the opposing roller 601 is reduced. As a result, the vibration amplitude can be increased. As described above, when the vibration amplitude of the intermediate transfer belt 311 increases, the inertial force applied to the residual toner remaining on the intermediate transfer belt 311 increases, and the adhesion of the residual toner to the intermediate transfer belt 311 decreases. However, if the applied voltage applied to the electrode member 602 is too high, or if the gap width between the electrode member 602 and the opposing roller 601 is too small, an air discharge occurs, which is not preferable.

  Next, a configuration capable of efficiently increasing the vibration amplitude of the intermediate transfer belt 311 will be described.

  The applied voltage applied to the electrode member 602 by the power source 603 is a natural vibration voltage having a frequency that is an integral multiple of the natural frequency of the cylindrical surface of the opposed roller 601, thereby resonating the cylindrical surface of the opposed roller 601. Can be made. Specifically, the natural frequency f of the in-plane vibration in the radial direction of the cylindrical surface of the facing roller 601 is expressed by the following expression (3).

［式中、Ｒは対向ローラ６０１の半径を示し、ｎは振動次数を示し、Ｅはヤング率を示し、νはポアソン比を示し、Ｉは断面２次モーメントを示し、ρは周方向の単位長さ当りの質量を示す。］

[In the formula, R represents the radius of the opposing roller 601, n represents the vibration order, E represents the Young's modulus, ν represents the Poisson's ratio, I represents the cross-sectional secondary moment, and ρ represents the circumferential unit. Indicates mass per length. ]

  Moreover, the cross-sectional secondary moment I is represented by the following formula (4).

［式中、ｂは対向ローラ６０１の軸線方向長さを示し、ｈは対向ローラ６０１の肉厚を示す。］

[Wherein, b represents the axial length of the opposing roller 601, and h represents the thickness of the opposing roller 601. ]

Further, the mass ρ per unit length in the circumferential direction is expressed by the following formula (5).
ρ = γbh (5)
[In the formula, γ represents density, b represents the axial length of the opposing roller 601, and h represents the thickness of the opposing roller 601. ]

In the equations (3), (4) and (5), the radius R of the counter roller 601 is 15 mm, the thickness h of the counter roller 601 is 0.8 mm, the axial length b of the counter roller 601 is b = 300 mm, Young Substituting the rate E = 70 GPa, Poisson's ratio ν = 0.35, density γ = 2.7 × 10 ³ kg / m ³ and calculating the fundamental natural frequency (vibration order n = 2) f 1, f 1 = 2 .2 kHz. By applying a voltage having the fundamental natural frequency f 1 and a frequency that is an integral multiple of the fundamental natural frequency f 1 to the electrode member 602, the cylindrical surface of the facing roller 601 can resonate. Therefore, the vibration amplitude that vibrates in the facing direction A of the facing roller 601 increases, and the residual toner on the intermediate transfer belt 311 can be vibrated greatly. Accordingly, the inertia force acting on the toner is increased, and the adhesion force of the toner to the intermediate transfer belt 311 can be reduced.

  The electrode member 602 is preferably set so that the bending rigidity in the facing direction A with respect to the facing roller 601 is higher than the bending rigidity in the radial direction of the cylindrical surface of the facing roller 601. Thus, when an attractive force due to an oscillating electric field generated in the gap G between the electrode member 602 and the counter roller 601 is applied, the counter roller 601 can be vibrated while suppressing the deflection of the electrode member 602. 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 a secondary moment of section).

  The cut surface cut by the plane orthogonal to the axis of the opposing roller 601 is rectangular, and the dimension is 20 mm, the dimension L corresponding to the opposing direction A with respect to the opposing roller 601, and the dimension corresponding to the direction orthogonal to the opposing direction A. In the electrode member 602 where H is 10 mm, the cross-sectional secondary moment I1 is expressed by the following formula (6).

When the constituent material of the electrode member 602 is stainless steel, since the Young's modulus E of stainless steel is 170 GPa, the bending rigidity A1 of the electrode member 602 is A1 = E × I1 = 1.1 × 10 ³ N · m ^2. .

  On the other hand, in the cylindrical opposing roller 601 having an outer diameter D of 30 mm and a wall thickness of 0.8 mm (inner diameter d = 28.4 mm), the cross-sectional secondary moment I2 is expressed by the following equation (7).

When the material of the facing roller 601 is aluminum, the Young's modulus E of aluminum is 70 GPa, and therefore the bending rigidity A2 of the facing roller 601 is A2 = E × I2 = 5.5 × 10 ² N · m ^2. .

  Thus, when the bending rigidity of the electrode member 602 in the facing direction A is set higher than the bending rigidity of the cylindrical surface of the facing roller 601 in the radial direction, the electrode member 602 and the facing roller 601 When the attractive force due to the oscillating electric field generated in the gap G is applied, the counter roller 601 can be vibrated while suppressing the bending of the electrode member 602.

  In addition, when the electrode member 602 is bent, the gap width between the electrode member 602 and the opposing roller 601 is reduced by this bending, and air discharge is likely to occur. By suppressing the bending of the electrode member 602 by increasing the bending rigidity of the electrode member 602, even if a high voltage is applied to the electrode member 602, the gap width between the electrode member 602 and the opposing roller 601 is prevented from becoming too small. Thus, the counter roller 601 can be vibrated greatly to impart a vibration having a large vibration amplitude to the intermediate transfer belt 311.

  When the power supply 603 applies the above-described natural vibration voltage to the electrode member 602, the cleaning blade 604 comes into contact with the portion of the intermediate transfer belt 311 corresponding to the antinode of vibration in the vibration mode generated in the facing roller 601. It is preferably configured to scrape and remove residual toner. A portion of the intermediate transfer belt 311 corresponding to the antinode portion of the vibration in the vibration mode generated in the facing roller 601 is given a vibration having a large vibration amplitude. Therefore, the residual toner on the transfer belt 311 can be vibrated with a large vibration amplitude, the inertial force acting on the residual toner is increased, and the adhesion force of the residual toner to the intermediate transfer belt 311 can be reduced.

  Specifically, this will be described below with reference to FIG. FIG. 3 is a diagram for explaining the vibration mode of the facing roller 601. When the voltage having the above-described basic natural frequency f1 is applied to the electrode member 602, the vibration mode of the facing roller 601 is the primary vibration mode (n = 2) as shown in FIG. At this time, the amplitude in the abdomen 11 which is a part hitting the antinode of vibration is the maximum. Also, in the secondary vibration mode (n = 3) shown in FIG. 3B and the tertiary vibration mode (n = 4) shown in FIG. 3C, the amplitude of vibration in the abdomen 11 is maximum. The cleaning blade 604 may be brought into contact with the portion of the intermediate transfer belt 311 corresponding to the vibration abdomen 11 of the facing roller 601.

(B) The size of the vibration area of the intermediate transfer belt 311 The vibration area in which the intermediate transfer belt 311 vibrates is a portion that is suspended from and touches the counter roller 601 that vibrates. However, in order to reduce the adhesion of residual toner remaining on the outer peripheral surface of the intermediate transfer belt 311, it is important that the toner image carrying area on the surface of the intermediate transfer belt 311 where the residual toner may remain in the axial direction. It vibrates over the entire extending range. The length in which the toner image carrying area on the surface of the intermediate transfer belt 311 extends in the axial direction is set slightly smaller than the axial length of the recording paper to be conveyed. The length of the electrode member 602 extending in the axial direction is preferably set such that the toner image carrying region is longer than the length extending in the axial direction and the opposing roller 601 is shorter than the length extending in the axial direction. As a result, the adhesive force of all residual toner remaining in the toner image carrying area on the surface of the intermediate transfer belt 311 can be reduced by vibration.

(C) Distribution of magnitude of vibration amplitude in vibration region of intermediate transfer belt 311 In the electrode member 602 formed in a rectangular parallelepiped shape, the facing surface facing the peripheral surface of the facing roller 601 is a flat surface. Therefore, in the facing region where the electrode member 602 and the facing roller 601 are opposed to each other with a gap, the gap width is narrow at the center of the facing region when viewed from the axial direction, and at the both ends of the facing region. The width is wide. Therefore, the oscillating electric field formed in the opposing region when a voltage is applied to the electrode member 602 is large at the center of the opposing region and small at both ends of the opposing region when viewed from the axial direction. As a result, when viewed from the axial direction, the intermediate transfer belt 311 can be vibrated with a large vibration amplitude at a portion corresponding to the central portion of the opposed region and with a small vibration amplitude at portions corresponding to both ends of the opposed region. Accordingly, it is possible to prevent the vibration amplitude of the region other than the contact region with the cleaning blade 604 in the intermediate transfer belt 311 from becoming excessively large, and the residual toner is separated from the region other than the contact region with the cleaning blade 604. Can be prevented.

FIG. 4 is a diagram illustrating another configuration of the electrode member included in the belt cleaning unit 60.
In the electrode member 602 described above, the facing surface facing the peripheral surface of the facing roller 601 is a flat surface. The electrode member 602 a shown in FIG. 4A is formed so that the facing surface facing the circumferential surface of the facing roller 601 is along the circumferential surface of the facing roller 601. Therefore, in the facing region where the electrode member 602a and the facing roller 601 face each other with a gap, the same gap width is obtained over the entire region. Therefore, the oscillating electric field formed in the opposing region when a voltage is applied to the electrode member 602a becomes uniform over the entire opposing region. As a result, the narrow range of the gap between the facing portions of the electrode member 602a and the facing roller 601 is widened. For this reason, the charge amount Q in the above equation (2) increases, and the seismic force in the above equation (1) increases. Therefore, the residual toner on the intermediate transfer belt 311 in contact with the opposing roller 601 can be vibrated greatly, and an effect that the adhesion force between the intermediate transfer belt 311 and the residual toner can be further reduced can be obtained.

  Moreover, the electrode member 602b shown in FIG.4 (b) is formed in a column shape, and the opposing surface facing the surrounding surface of the opposing roller 601 becomes an arc-shaped surrounding surface. In the electrode member 602b formed in this way, as in the electrode member 602 described above, in the facing region where the electrode member 602b and the facing roller 601 face each other with a gap, the gap width is viewed from the axial direction. In this case, the gap width is narrow at the center of the opposing area, and the gap width is wide at both ends of the opposing area. The difference between the electrode member 602 b and the electrode member 602 is that the electrode member 602 b has a wider gap width at both ends of the opposing region than the electrode member 602. Accordingly, it is possible to further prevent the vibration amplitude in the region other than the contact region with the cleaning blade 604 in the intermediate transfer belt 311 from being excessively increased, and the residual toner is peeled off in a region other than the contact region with the cleaning blade 604. Can be further prevented.

  However, when the facing region where the electrode member and the facing roller 601 face each other is configured to be extremely narrow, the facing area between the electrode member and the facing roller 601 becomes small, and the charge amount Q in the above equation (2) becomes small. The seismic force in equation (1) is reduced. For this reason, a problem that the residual toner on the intermediate transfer belt 311 in contact with the counter roller 601 cannot sufficiently vibrate occurs, which is not preferable.

  FIG. 5 is a diagram illustrating a configuration of the belt cleaning unit 70 according to the second embodiment of the present invention. The belt cleaning unit 70 is similar to the belt cleaning unit 60, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. A characteristic configuration of the belt cleaning unit 70 is that a coating layer 701 made of an insulating material is provided on a portion of the electrode member 602 facing the facing roller 601. The belt cleaning unit 70 is configured in the same manner as the belt cleaning 60 except that the electrode member 602 is provided with a coat layer 701.

  Examples of the material constituting the coat layer 701 include a high dielectric constant such as barium titanate (relative permittivity: 1200), strontium titanate (relative permittivity; 332), and titanium oxide (relative permittivity; 100). Insulating materials are desirable. As described above, the coating layer 701 made of an insulating material is provided on the surface of the electrode member 602, so that a higher voltage is applied to the electrode member 602 than when the portion facing the opposing roller 601 is made of a conductor. Even if it is applied, generation of air discharge can be prevented. Therefore, the voltage applied to the electrode member 602 of the belt cleaning unit 70 is set higher than the discharge voltage of Paschen in the air, which is higher than the voltage applied to the electrode member 602 of the belt cleaning unit 60. In this way, a large oscillating electric field can be generated in the gap between the opposing roller 601 and the electrode member 602.

  Further, since the coat layer 701 made of an insulating material has a high dielectric constant, a larger oscillating electric field can be generated in the gap between the opposing roller 601 and the electrode member 602. For this reason, the counter roller 601 can be vibrated greatly to apply a large vibration to the intermediate transfer belt 311. Accordingly, the adhesive force between the residual toner and the intermediate transfer belt 311 can be reduced, and after the transfer process to the recording paper, the removal efficiency of removing the residual toner remaining on the intermediate transfer belt 311 is excellent. It is possible to prevent the influence of residual toner from appearing during image formation and to form a high-quality image.

  The present embodiment as described above is merely an example of the invention, and the configuration can be changed within the scope of the invention. For example, the configuration in which the intermediate transfer belt is vibrated when residual toner remaining on the intermediate transfer belt is removed has been described. However, the present invention is not limited to this. For example, the toner image is transferred from the photosensitive belt to the intermediate transfer belt, and the toner image transferred onto the intermediate transfer belt is transferred to the recording paper to form an image. In the image forming apparatus configured to perform the above configuration, the photosensitive belt and the intermediate transfer belt are vibrated to remove residual toner, and the toner image carried on the photosensitive belt is directly transferred to a recording sheet to form an image. In the image forming apparatus configured as described above, a configuration in which the residual belt is removed by vibrating the photosensitive belt is also within the scope of the present invention.

  In addition, the cleaning blade is brought into contact with the outer peripheral surface of the intermediate transfer belt and the residual toner remaining on the intermediate transfer belt is scraped and removed, but an electric field that attracts residual toner is applied instead of the cleaning blade. The present invention can also be applied to configurations using other cleaning means such as the bias cleaning roller and fur brush cleaning means.

1 is a diagram illustrating a configuration of an image forming apparatus 1 according to an embodiment of the present invention. It is a figure which shows the structure of the belt cleaning part 60 which is 1st Embodiment of this invention. It is a figure explaining the vibration mode of the opposing roller. It is a figure which shows the other structure of the electrode member which the belt cleaning part 60 has. It is a figure which shows the structure of the belt cleaning part 70 which is 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming station part 4 Fixing means 5 Paper supply means 6 Paper discharge means 20 Toner image forming part 31 Primary transfer part 32 Secondary transfer station part 60, 70 Belt cleaning part 311 Intermediate transfer belt 601 Opposing roller 602 Electrode member 603 Power supply 604 Cleaning blade 701 Coat layer

Claims (6)

An endless belt member that is stretched by a plurality of support rollers and is driven to rotate as the support rollers rotate, and a toner image carrying belt that carries a toner image;
A cleaning unit which is one of the plurality of supporting rollers and is opposed to the opposing roller formed in a hollow cylindrical shape via the toner image carrying belt;
An electrode member facing the opposing roller with a predetermined gap;
A power source for applying a voltage having a predetermined frequency to the electrode member;
When the toner remaining on the toner image carrying belt after the toner image carried on the toner image carrying belt is transferred to the transfer member is removed by contact with the toner image carrying belt, An image forming apparatus, wherein a power source applies a voltage to the electrode member to vibrate the toner image carrying belt via the counter roller.   The image forming apparatus according to claim 1, wherein a coating layer made of an insulating material is provided on a portion of the electrode member facing the facing roller.   3. The image forming apparatus according to claim 1, wherein a bending rigidity of the electrode member in a facing direction with respect to the facing roller is higher than a bending rigidity of a cylindrical surface of the facing roller in a radial direction.   The said power supply applies the natural vibration voltage which is a voltage which has a frequency which becomes an integral multiple of the natural frequency of the cylindrical surface of the said opposing roller to the said electrode member, The any one of Claims 1-3 characterized by the above-mentioned. The image forming apparatus described in 1.   When the power source applies the natural vibration voltage to the electrode member, the cleaning means comes into contact with the portion of the toner image carrying belt corresponding to the anti-vibration portion in the resonance mode generated in the counter roller, and residual toner is removed. The image forming apparatus according to claim 4, wherein the image forming apparatus is removed.   The image forming apparatus according to claim 1, wherein a frequency of a voltage applied by the power source to the electrode member is 20 kHz or more.

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