JP2011007993A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent magnetic powder, which grinds the surfaces of image carriers, such as an intermediate transfer body and photoreceptor, from deteriorating due to long use, resulting in reduction in grinding capability, and prevents reduction in image quality due to a cleaning failure of the image carriers.SOLUTION: The grinding device can be set to a first state in which magnetic powder is in contact with the image carrier and a second state in which the magnetic powder is separated from the image carrier. The magnetic powder slides over the image carriers only when necessary.

Description

  The present invention relates to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus provided with a polishing device for polishing an image carrier that carries a toner image, such as a photoconductor and an intermediate transfer member.

  In an electrophotographic image forming apparatus, it is known that a phenomenon called filming that contaminates the surface of an image carrier occurs when an image forming process is performed for a long time.

  Filming is a phenomenon in which toner, a substance separated from the toner, paper dust, discharge generation, and the like adhere to the surface of the image carrier, and image quality degradation such as image blurring, image flow, and background smearing occurs due to filming. A technique for preventing filming by polishing the surface of an image carrier has been developed.

  In Patent Document 1, it is proposed to use a magnetic brush cleaning device as a polishing device. That is, the amount of stay in the cleaning area of the magnetic brush that cleans the image carrier is increased when polishing than when it is cleaned.

  It is described that means for increasing the staying amount of the magnetic brush include stopping the sleeve that supports the magnetic brush, moving the magnet that forms the magnetic brush, and the like.

  Patent Document 1 discloses an invention relating to preventing the toner concentration in the cleaning agent (magnetic brush) from being lowered during polishing.

  In Patent Document 2, it is proposed that a polishing device for polishing the surface of the image carrier with magnetic powder is provided downstream of the cleaning device with respect to the moving direction of the image carrier.

JP-A-5-72950 JP 2004-333967 A

  It has been found that a polishing apparatus that polishes the surface of an image carrier using magnetic powder can prevent filming and maintain a high-quality image. However, when the surface of the image bearing member is polished with magnetic powder for a long period of time, toner, external additives contained in the developer, paper powder, discharge products, etc. accumulate in the magnetic powder and become magnetic. It was found that the polishing ability of the powder was reduced.

  In Patent Document 2, since the magnetic powder constantly rubs the image carrier, the magnetic powder is rapidly deteriorated and the polishing ability is quickly reduced.

  Also in Patent Document 1, the magnetic powder rubs the image carrier during cleaning for cleaning the image carrier and during polishing for polishing the image carrier. Decreases early.

  When the polishing ability of the polishing apparatus is lowered, the deposits causing filming are not removed from the image carrier, and image quality is generated due to poor cleaning or transfer failure.

  The present invention solves the above-described problems in the conventional polishing apparatus using magnetic powder, can maintain the polishing ability of the polishing apparatus well over a long period of time, and can form a high-quality image. An object is to provide a forming apparatus.

  The object is achieved by the following invention.

1. In an image forming apparatus having a polishing apparatus for polishing the surface of the image carrier with an image carrier and magnetic powder,
The polishing apparatus comprises:
The magnetic powder,
A container for containing the magnetic powder; and
A magnetic powder moving unit for setting a first state in which the magnetic powder is brought into contact with the image carrier to polish the surface of the image carrier and a second state in which the magnetic powder is separated from the image carrier;
An image forming apparatus comprising:

2. The magnetic powder moving part is
A permanent magnet disposed opposite the container across the image carrier; and
The permanent magnet is brought close to the image carrier to attract the magnetic powder, is brought into contact with the image carrier, the first state is set, and the permanent magnet is separated from the image carrier to thereby form the magnetic powder. A magnet drive unit that sets the second state by dropping / separating the image carrier from the image carrier;
2. The image forming apparatus as described in 1 above, comprising:

3. The magnetic powder moving part is
Electromagnets and
The electromagnet is configured to attract the magnetic powder to the image carrier, contact the image carrier to set the first state, and separate the magnetic powder from the image carrier to set the second state. The magnet drive power supply unit that operates the
2. The image forming apparatus as described in 1 above, comprising:

  4). 4. The image forming apparatus according to any one of 1 to 3, wherein the magnetic powder moving unit stirs the magnetic powder by repeating the first state and the second state.

  5. The image forming apparatus according to 3 above, wherein the electromagnet includes a plurality of electromagnet elements divided in the width direction of the image, and the magnet driving power source unit includes a magnet driving power source that individually operates the electromagnet elements. apparatus.

6). A control unit for controlling the magnetic powder moving unit;
The control unit sets the first state when there is an instruction from the user, when the moving distance of the image carrier exceeds a predetermined value, or when the image forming process is completed. The image forming apparatus according to any one of 1 to 5, wherein the magnetic powder moving unit is controlled so as to be set.

  7. When the first state is set, in the case of patch detection for detecting the density of a patch image or when releasing the recording material jam, the control unit sets the second state so as to set the second state. 7. The image forming apparatus according to 6, wherein the moving unit is controlled.

  In the present invention, the polishing apparatus is set to a first state in which the magnetic powder is brought into contact with the image carrier and a second state in which the magnetic powder is separated from the image carrier. Thus, polishing with magnetic powder is performed only when polishing is necessary, and magnetic powder is separated from the image carrier when not required. As a result, a decrease in the polishing ability of the magnetic powder is suppressed, and the image carrier is sufficiently polished for a long period. Thereby, a high quality image is formed over a long period of time.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a first example of a polishing apparatus 100. FIG. 2 is a diagram illustrating a configuration example of an electromagnet 101. FIG. 2 is a block diagram of a control system of the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a flowchart of polishing / non-polishing control of the intermediate transfer body 70 using the polishing apparatus 100. 6 is a flowchart of control in which a step of stirring magnetic powder 102 is added to the control shown in FIG. 5. 5 is a flowchart of control for preventing toner from being brought into an intermediate transfer member 70 into a polishing apparatus. It is a figure which shows the 2nd example of the grinding | polishing apparatus. It is a graph which shows the evaluation result of cleaning property. It is a graph which shows the evaluation result of cleaning property. It is a graph which shows the evaluation result of cleaning property.

<Image forming apparatus>
FIG. 1 is a diagram showing an overall configuration of an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus is a digital color printer that forms a monochrome image or a color image based on an image signal.

  The image forming apparatus includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K called tandem color image forming units, an intermediate transfer member 70 as an image carrier, a paper feeding unit 80, a fixing device 77, and a paper discharge tray. 79 etc. The paper feed unit 80 includes a paper feed tray 81 for storing recording materials, a paper feed roller 82, and the like. The tandem color image forming unit includes an image forming unit 10Y that forms a yellow (Y) image, an image forming unit M that forms a magenta (M) image, and an image forming unit that forms a cyan (C) color image. A unit C and an image forming unit K for forming a black (K) color image are included.

  An image forming unit 10Y for forming a yellow (Y) color image has a cylindrical photosensitive drum 1Y, and a charging unit 2Y, an exposing unit 3Y, a developing unit 4Y, and 1 arranged around the photosensitive drum 1. It has a next transfer portion 5Y and a cleaning portion 6Y. An image forming unit 10M that forms a magenta (M) color image includes a cylindrical photosensitive drum 1M, and a charging unit 2M, an exposure unit 3M, a developing unit 4M, and 1 arranged around the photosensitive drum 1M. It has a next transfer portion 5M and a cleaning portion 6M. An image forming unit 10C for forming a cyan (C) color image includes a cylindrical photosensitive drum 1C, and a charging unit 2C, an exposure unit 3C, a developing unit 4C, and 1C disposed around the photosensitive drum 1C. It has a next transfer portion 5C and a cleaning portion 6C. The image forming unit 10K that forms a black (K) color image includes a cylindrical photosensitive drum 1K, and a charging unit 2K, an exposure unit 3K, a developing unit 4K, and 1 arranged around the photosensitive drum 1K. It has a next transfer portion 5K and a cleaning portion 6K. When color image data is input to the image forming apparatus, toner images of respective colors are formed from the image forming units 10Y, 10M, 10C, and 10K. When monochrome image data is input to the image forming apparatus, the image forming unit 10K A black toner image is formed. The intermediate transfer body 70 is stretched around two rollers 71, and the transfer roller constituting the secondary transfer unit 72 is in contact with the right end of the intermediate transfer body 70. The left end portion of the intermediate transfer body 70 faces the belt cleaning unit 74. The intermediate transfer member 70 is formed of a nonmagnetic endless belt made of a semiconductive resin belt.

  The belt cleaning unit 74 has a brush cleaner as a cleaning unit for cleaning the intermediate transfer member 70. In addition, as a cleaning means, it is also possible to use a blade cleaner made of a rubber blade, or to use these cleaners in combination.

  The photosensitive drums 1Y, 1M, 1C, and 1K and the primary transfer portions 5Y, 5M, 5C, and 5K press the intermediate transfer body 70 together. The toner images formed on the photosensitive drums 1Y, 1M, 1C, and 1K are sequentially transferred to the intermediate transfer member 70, and a toner image is formed on the intermediate transfer member 70.

  In the image forming units 10Y, 10M, 10C, and 10K, the formed single color toner images are transferred to the intermediate transfer member 70 by the primary transfer portions 5Y, 5C, 5M, and 5K, and a color toner image is formed on the intermediate transfer member 70. Is done.

  The recording material P is separated from the sheet feed tray 81 by the sheet feed roller 82 and is conveyed to the secondary transfer unit 72. The color toner image on the intermediate transfer body 70 is transferred to the recording material P by the secondary transfer unit 72.

  The color toner image on the recording material P is fixed by the fixing device 77, and the recording material P subjected to the fixing process is discharged to a discharge tray 79 by a discharge roller 78.

  The image forming apparatus has a polishing apparatus 100. The polishing apparatus 100 removes substances affecting the image quality, such as paper dust, toner, toner separation, and discharge products generated by discharge, from the intermediate transfer pair 70.

  The image forming apparatus described above is an example having the intermediate transfer member 70, but the present invention can also be applied to an image forming apparatus having no intermediate transfer member.

  In an image forming apparatus that does not have an intermediate transfer member, a toner image is formed on a photoreceptor as an image carrier by electrostatic latent image formation and development, and the toner image is transferred from the photoreceptor to a recording material.

In such an image forming apparatus, the polishing apparatus 100 in FIG. 1 is used to polish the surface of the photoreceptor.
<Polishing device>
FIG. 2 shows a first example of the polishing apparatus 100.

  In the example shown in FIG. 1, the polishing apparatus 100 is a primary transfer unit that is a primary transfer unit that is the most upstream primary transfer unit downstream of the belt cleaning unit 74 with respect to the movement direction indicated by the arrow W <b> 3 of the intermediate transfer body 70. Although it arrange | positions upstream of the part 5Y, the installation position of a grinding | polishing apparatus is not limited to this position. That is, it may be disposed in a space where it can be installed upstream of the secondary transfer unit 72 such as upstream of the belt cleaning unit 74.

  The polishing apparatus 100 includes an electromagnet 101, a container 103, and magnetic powder 102. The electromagnet 101 and the container 103 are disposed to face each other with the intermediate transfer body 70 interposed therebetween, and the magnetic powder 102 is accommodated in the container 103. The electromagnet 101 attracts the magnetic powder 102 and presses it against the intermediate transfer member 70. Reference numeral 103 denotes a container made of a non-magnetic material. A sealing member 104 prevents the magnetic powder 102 from leaking out of the container 103, and is made of a resin or rubber sheet. As described later, the first state shown in FIG. 2A, that is, the state in which the magnetic powder 102 is attracted by the electromagnet 101 and rubs against the intermediate transfer body 70, and the second state shown in FIG. In other words, the seal member 104 is in the state shown in FIG. 2A, while preventing the magnetic powder 102 from leaking out of the container 103, while being separated from the intermediate transfer body 70, and FIG. ) To prevent the magnetic powder 102 adhering to the intermediate transfer body 70 from leaking out of the container 103 with a force other than the magnetic force. Reference numeral 106 denotes a magnet driving power source for driving the electromagnet 101, and 107 denotes a magnetic material.

  The electromagnet 101 includes a magnetic body 101B and a coil 101C, and generates a magnetic flux indicated by an arrow W1 or a magnetic flux indicated by an arrow W2 depending on the direction of the drive current of the magnet drive power supply unit 106. The magnetic powder 102 moves upward by the magnetic flux indicated by the arrow W <b> 1 and comes into pressure contact with the intermediate transfer body 70.

  The first state shown in FIG. 2A is a state in which the magnetic powder 102 is pressed against the intermediate transfer body 70 by forming the magnetic flux indicated by the arrow W1 by turning on the magnet drive power supply unit 106.

  The second state shown in FIG. 2B is a state in which the magnet drive power supply unit 106 is turned off and the magnetic powder 102 is dropped on the bottom of the container 103.

  As described above, the polishing apparatus 100 is set to the first state in which the magnetic powder 102 is brought into contact with the intermediate transfer body 70 and the second state in which the magnetic powder 102 is separated from the intermediate transfer body 70. The magnet drive power supply unit 106 constitutes a magnetic powder moving unit that contacts / separates the magnetic powder 102 intermediate transfer body 70.

  Note that the second state can be formed by changing the direction of the output current of the magnet drive power supply unit 106 to form the magnetic flux indicated by the arrow W2.

The magnetic powder used is as follows.
Material As the magnetic powder, iron, magnetite, magnetic powder of various ferrites, magnetic powder obtained by coating magnetic particles with resin, or magnetic powder made of a resin dispersion of magnetic material is used. As the ferrite, a light metal ferrite containing at least one of a ferrite containing a heavy metal such as copper, zinc, nickel and manganese, an alkali metal and an alkaline earth metal can be used.

  Iron-based ferromagnetic fine particles are preferable for obtaining highly magnetized magnetic powder. Ferromagnetic materials such as magnetite and gamma-iron oxide containing spinel ferrite and barium ferrite such as magnetobrampite type ferrite are preferred for obtaining chemically stable magnetic powder.

  Resins for coating magnetic particles include various polyolefin resins, various polyvinyl resins, various polyvinylidene resins, vinyl chloride-vinyl acetate copolymers, styrene-acrylic copolymers, organosiloxane bonds, etc. A silicone resin having a silane, a modified resin of the silicone resin, a fluororesin, an amino resin, an epoxy resin, or the like can be used.

  A copolymer such as a polyacrylate resin or a styrene-acrylic copolymer is preferred from the viewpoint of preventing spent deterioration due to the toner.

As the resin coating method, a conventionally known wet coating method or dry coating method is used.
-Particle shape The particle shape of the magnetic powder may be any of a spherical shape, a needle shape, and a shape having irregularities on the surface. A spherical shape is preferable in that it does not cause local scratches on the surface of the image carrier.
-Particle size The volume average particle size is preferably 1000 µm or less. If the particle size exceeds 1000 μm, uniform polishing becomes difficult. 100 μm or less is particularly preferable.

The volume average particle diameter is a volume-based average particle diameter measured using a laser analysis type flow rate distribution measuring device HEROS (manufactured by Sympatech).
Magnetization characteristics Saturation magnetization of 2.5 × 10 ⁻⁵ Wb · m / kg or more is preferable. The saturation magnetization is a value measured by a DC magnetization characteristic automatic recording device 3257-35 (manufactured by Yokogawa Electric Corporation). When the saturation magnetization is less than 2.5 × 10 ⁻⁵ Wb · m / kg, the holding force by the magnetic holding portion becomes weak, magnetic powder spills and the polishing effect decreases.
Amount of adhesion The amount of magnetic powder that adheres to the intermediate transfer member 70 during polishing is preferably 0.001 kg / m ^{2 to} 10 kg / m ² . If less than 0.001 kg / ^{m 2,} the polishing effect is not sufficient, when it is more than 10 kg / ^{m 2,} the leakage of the magnetic powder is liable to occur.

  As described below, the polishing apparatus 100 shown in FIG. 2 is set to the first state shown in FIG. 2A at the time of polishing and polishes the intermediate transfer body 70. The second state shown in FIG. 2B is set and polishing is not performed.

  A preferable configuration, shape, and arrangement of the electromagnet 101 are as follows.

  The electromagnet 101 is preferably one that forms a magnetic flux having a high magnetic flux density and has a low frictional resistance with the intermediate transfer member 70. Examples of magnetic materials that are preferably used include neodymium, alnico, ferrite, and saccharum. In order to reduce the frictional resistance between the intermediate transfer member 70 and the electromagnet 101, it is preferable to coat the surface of the magnetic member 101B that contacts the intermediate transfer member 70 with a low friction material.

  The electromagnet 101 has a length longer than the width of the recording material in a direction perpendicular to the paper surface of FIG. 2, which is the width direction of the image, and the width of the electromagnet 101, that is, along the arrow W3 in FIG. The width in which the magnetic powder 102 contacts the intermediate transfer member 70 is determined by the length in the direction. The width of the electromagnet 101 is preferably 1 mm to 200 mm. When the width is shorter than 1 mm, it is difficult to obtain a polishing effect. When the width is longer than 200 mm, the apparatus becomes large and excessive polishing may occur.

  FIG. 3 shows a configuration example of the electromagnet 101. In FIG. 3A, the electromagnet 101 is configured by bundling plate-like electromagnet elements 1011 to 101n having a length substantially equal to the width of the image. In the example of FIG. 3B, the electromagnet 101 is configured by bundling the electromagnet elements 1011a to 101na and the electromagnet elements 1011d to 101nd divided also in the width direction of the image. In the example of FIG. 3B, the electromagnet elements 1011a to 101na are driven by the magnet driving power source 106a, the electromagnet elements 1011b to 101nb are driven by the magnet driving power source 106b, and the electromagnet elements 1011c to 101nc are driven by the magnet driving power source 106c. The electromagnet elements 1011d to 101nd are driven by a magnet driving power source 106d. Thus, by providing the magnet drive power supplies 106a to 106d for each block divided in the image width direction, it becomes possible to perform polishing / non-polishing with different widths in the image width direction. That is, it is possible to prevent deterioration of the intermediate transfer body 70 by performing polishing according to the width of the image.

  In the present invention, the intermediate transfer body 70 is polished only when polishing is necessary, and the polishing apparatus 100 is set to the second state, which is a non-polishing state, during execution of the image forming process. This avoids unnecessary deterioration of the magnetic powder 102 and extends its life.

  FIG. 4 is a block diagram of a control system of the image forming apparatus according to the embodiment of the present invention.

  200 is a control unit that controls the entire apparatus, 201 is an operation unit, 202 is formed at an end of the intermediate transfer body 70, an encoder for measuring the moving distance of the intermediate transfer body 70, and 203 is the image of FIG. A paper discharge sensor 204 is installed in the paper discharge unit of the forming apparatus to detect the discharge of the recording material, and 204 is a sensor for detecting the recording material that is set at various positions on the recording material conveyance path in the image forming apparatus in FIG. The sensor 204 includes a plurality of sensor elements, and the recording material jam, that is, jam is detected by the sensor 204. A belt drive motor 205 drives the intermediate transfer member 70.

  The control unit 200 controls the magnet drive power supply unit 106 and the belt drive motor 205 based on information from the operation unit 201, the encoder 202, the paper discharge sensor 203, the sensor 204, and the like, so that the magnetic powder 102 in FIG. Control such as polishing of the transfer body 70 is performed.

  FIG. 5 is a flowchart of polishing / non-polishing control of the intermediate transfer body 70 using the polishing apparatus 100.

  The control in FIG. 5 is started when the main switch of the image forming apparatus is turned on, continues during the period when the main switch is turned on, and ends when the main switch is turned off, that is, when the control is finished at step ST7. To do. In the control of FIG. 5, the first state and the second state are repeated alternately.

  In step ST1, if there is polishing by the user's instruction (Y in ST1), the belt moving distance in step ST2, that is, the moving distance of the intermediate transfer body 70 exceeds 5 km (Y in ST2), or printing in step ST3. At the end of the job (Y in ST3), the electromagnet 101 is turned on to generate a magnetic flux in the direction of arrow W1 in FIG.

  The determination of the user instruction in ST1 is determined based on the information from the operation unit 201, the moving distance of the intermediate transfer body 70 in S2 is determined based on the information from the encoder 202, and the job end in ST3 is the discharge sensor 204. Is determined on the basis of information detected that the last recording material has been discharged.

  Based on these pieces of information, control unit 200 operates magnet drive power supply unit 106 to turn on electromagnet 101 (ST4).

  When the electromagnet 101 is turned on, the magnetic powder 102 is attracted upward, and the first state shown in FIG. At the same time as the operation of the magnet drive power supply unit 106, the control unit 200 drives the belt drive motor 205 to move the intermediate transfer member 70 (ST5). As the intermediate transfer member 70 moves, the surface of the intermediate transfer member 70 is rubbed and polished by the magnetic powder 102. As a result, paper dust, toner, toner separations, discharge products, and the like attached to the surface of the intermediate transfer member 70 are removed.

  The first state is continued for a certain period of time, and when the intermediate transfer body 70 has moved a distance necessary for polishing, the magnet drive power supply unit 106 stops outputting, the electromagnet 101 is turned off (ST6), and FIG. The second state shown in FIG. In the second state, the belt drive motor 205 is stopped, but the operation of the belt drive motor 205 may be continued and the intermediate transfer member 70 may be moved continuously.

  If the control does not end in step ST7, the process proceeds to ST1 and the control described above is repeated.

  The control of FIG. 5 is executed independently of the image forming process. Therefore, even when the image forming process is being performed, if any of ST1 to ST3 is Y, the first state in which polishing is performed is set. When all the determinations of ST1 to ST3 are N, image formation is executed in the second state that is not polished. Therefore, unnecessary polishing of the intermediate transfer member 70 is not performed.

  FIG. 6 is a flowchart of the control in which the step of stirring the magnetic powder 102 is added to the control shown in FIG.

  That is, in step ST5A executed after step ST5, the output current of the magnet drive power supply unit 106 is reversed, and the electromagnet 101 forms magnetic fluxes in opposite directions indicated by arrows W1 and W2. Thereby, the magnetic powder 102 is stirred.

  If the polishing with the magnetic powder 102 is continued, the magnetic powder 102 on the side close to the intermediate transfer body 70 contains more polishing powder, and the polishing ability decreases.

  The control of FIG. 6 prevents such a decrease in the polishing force, and polishing is performed with a constant polishing effect.

  If polishing is performed in a state where toner is present on the intermediate transfer body 70, the toner is brought into the polishing apparatus 100, and the polishing power is reduced.

  In the example shown in FIG. 1, the polishing apparatus 100 is disposed downstream of the belt cleaning unit 74. When the belt cleaning unit 74 uses a brush as a cleaning unit, when a large amount of toner is in the intermediate transfer member 70, the toner may slip through the belt cleaning unit 74. Further, as described above, it is possible to set the polishing apparatus 100 upstream of the belt cleaning unit 74, but in this configuration, the polishing apparatus 100 without removing the toner on the intermediate transfer member 70. Brought to you. Thereby, the polishing power of the polishing apparatus 100 is reduced.

  FIG. 7 is a flowchart of control for preventing toner from being brought into the intermediate transfer member 70 into the polishing apparatus. The control of FIG. 7 is executed by interrupt control at a predetermined time interval in the control shown in FIGS.

  In step ST10, the presence / absence of patch detection for detecting the density of the patch image is checked. Patch detection is control in which a patch image, which is a toner image of a reference pattern, is formed on the intermediate transfer body 70, the density of the formed patch image is detected by a density sensor, and the detection result is fed back to image formation control. . Patch detection is performed at the start of the image forming process, when the image forming apparatus starts up, every time a predetermined number of images are formed, and the patch detection start signal is formed by the control unit 200.

  In step ST11, the presence / absence of jam release is checked. The jam is detected by the sensor 204, but the jam release starts when the jammed recording material is removed and the door of the image forming apparatus is closed. The jam release operation is an operation in which the intermediate transfer member 70 is moved by a predetermined distance after the door is closed, and the toner adhering to the intermediate transfer member 70 is removed by the jam.

  Based on the jam detection signal of the sensor 204, the control unit 200 executes the jam release operation, sets the polishing apparatus 100 to the second state during the jam release, and the toner is brought into the polishing apparatus 100. To prevent.

  When the determination in ST10 and ST11 is Y, the magnet drive power supply unit 106 stops and the electromagnet 101 is turned off. As a result, the polishing apparatus 100 is set to the second state in FIG. In the control start stage of FIG. 7, the electromagnet 101 is on, and the polishing apparatus 100 is in the first state shown in FIG.

  Based on the patch detection end signal in ST13 or the jam release end signal in ST14, the electromagnet 101 is activated in step ST15 to return to the first state.

  In the patch detection, the toner image of the patch image is not transferred, but is held on the intermediate transfer body 70, and the density of the toner image is detected. Then, the toner image that has passed through the detection unit is brought into the belt cleaning device 74. Further, when the jam of the recording material occurs, the intermediate transfer member 70 is forcibly rotated when the jam is released, so that the toner on the intermediate transfer member 70 is brought into the belt cleaning device 74 and further into the polishing device 100. Thus, when untransferred toner is brought into the belt cleaning device 74, there is toner that passes through the belt cleaning device 74, and the toner is also brought into the polishing device 100 disposed downstream of the belt cleaning device 74.

  The control shown in FIG. 7 prevents the deterioration of the polishing performance due to the toner brought into the polishing apparatus 100 at the time of patch detection and jam release.

  FIG. 8 is a view showing a second example of the polishing apparatus 100.

  The same parts as those in the example shown in FIG.

  101A is a permanent magnet, and 108 is a magnet drive motor that sets the permanent magnet 101A to the first state shown in FIG. 8 (a) and the second state shown in FIG. 8 (b).

  In the first state of FIG. 8A, the permanent magnet 101A is close to the intermediate transfer member 70, the magnetic powder 102 is attracted by the permanent magnet 101A and pressed against the intermediate transfer member 70, and the intermediate transfer member is moved to an arrow. By moving like W3, the surface of the intermediate transfer body 70 is polished.

  In the second state of FIG. 8B, since the permanent magnet 101A is separated from the intermediate transfer body 70, the magnetic powder 102 falls and is separated from the intermediate transfer body 70, and the polishing action on the polishing apparatus 100 is lost.

  As described above, in the embodiment shown in FIG. 8, the permanent magnet 101A and the magnet drive motor 108 as the magnet drive unit constitute a magnetic powder moving unit.

Image forming apparatus G1:
A laser printer bizhub C650 (manufactured by Konica Minolta Business Technologies, Inc.) was used after being modified to dispose the polishing apparatus 100 shown in FIG. 8 downstream of the belt cleaning unit.
Magnet 101A: Width (length in the moving direction of the intermediate transfer member) 20 mm, length (length in the width direction of the image) 330 mm, height 30 mm, magnetic flux density 100 mT The lower surface of the magnet 101A is brought into contact with the intermediate transfer member during polishing. When not polished, the lower surface of the magnet 101A was separated from the intermediate transfer member by 30 mm.

The amount of magnetic powder adhering to the intermediate transfer member when the magnet 101A was raised was 200 g / m ² .
Image forming apparatus G2:
Bizhub C650 (manufactured by Konica Minolta Business Technologies Co., Ltd.) was used after being modified to dispose the polishing apparatus 100 shown in FIG. 2 downstream of the belt cleaning unit.
Electromagnet 101: 800 coils of enameled wire were wound on a steel material having a width (length in the moving direction of the intermediate transfer member) of 20 mm, a length (length in the width direction of the image) of 330 mm, and a height of 30 mm. When a current of 2 A was supplied to the coil, a magnetic flux with a magnetic flux density of 100 mT was generated.

The amount of magnetic powder adhering to the intermediate transfer member when the electromagnet 101 was turned on was 200 g / m ² .
Example 1:
Using the image forming apparatus G1, the polishing apparatus was set to the first state every 100 prints and polishing was performed for 5 minutes.
Example 2:
Using the image forming apparatus G2, the polishing apparatus was set to the first state every 100 prints and polishing was performed for 5 minutes.
Example 3:
In addition to the polishing of Example 1, magnetic powder stirring control shown in FIG. 6 was performed. The magnetic powder agitation interval was set to a period during which the intermediate transfer member moved 5 km.
Example 4:
In addition to the polishing in Example 2, magnetic powder stirring control shown in FIG. 5 was performed. The magnetic powder agitation interval was set to a period during which the intermediate transfer member moved 5 km.
Example 5:
Using the image forming apparatus G1, the state corresponding to the occurrence of the jam is controlled so that the blue toner image is brought into the belt cleaning unit without being transferred every 1000 prints, and when the blue toner layer is brought into FIG. The control shown was implemented.
Example 6:
The image forming apparatus G2 is used to control the state corresponding to the occurrence of the jam so that the blue toner image is not transferred to the belt cleaning unit every 1000 prints, and when the blue toner layer is brought into FIG. The control shown was implemented.
Comparative Example 1:
A laser printer bizhub C650 was used. That is, an image forming apparatus without a polishing apparatus was used.
Comparative Example 2: The polishing apparatus was always set to the first state using the image forming apparatus G1.
Comparative Example 3: An image was formed in the same manner as in Comparative Example 1, and as in Example 5, the blue toner image was controlled so that it was not transferred to the belt cleaning section every 1000 prints.

Comparative Example 4: An image was formed in the same manner as in Comparative Example 2 and, as in Example 5, control was performed so that a blue toner image was not transferred to the belt cleaning unit every 1000 prints.
Rating:
Using an A4 size recording material on which a line image with a printing rate of 10% is formed, longitudinal paper with the short side of the recording material as the transport direction is performed,
The cleaning performance was evaluated at 50 kp, 100 kp, 200 kp, 400 kp, 800 kp, and 1000 kp. Note that kp represents kiloprints, that is, 1000 prints.

  The evaluation procedure is as follows.

  Using a laser printer bizhub C650, a cyan image with the highest density is formed, and without transferring the image from the intermediate transfer member to the recording material, toner is rushed into the belt cleaning unit, and on the intermediate transfer member that has passed through the belt cleaning unit. The toner amount was measured using a reflection densitometer, CM2002 (manufactured by Minolta Co., Ltd.).

  The toner amount is measured by attaching an adhesive tape to the intermediate transfer member, transferring the toner on the intermediate transfer member to the adhesive tape, peeling off the adhesive tape, and measuring the concentration of the adhesive tape with the reflection densitometer. went.

  When the output of the reflection densitometer exceeded 0.5V, the cleaning failure was determined, and the number of printed sheets exceeding 0.5V was determined as the durable number.

  The evaluation results of the cleaning property are shown in FIGS. 10 shows the scale of the vertical axis of FIG. 9, FIG. 12 shows the scale of the vertical axis of FIG. 11, and FIG. 14 shows the scale of the vertical axis of FIG.

A curve CV1 in FIG. 9 shows the cleaning property of Example 1,
Curve CV2 in FIG. 9 shows the cleaning property of Example 2,
Curve CV3 in FIG. 9 shows the cleaning property of Comparative Example 1,
Curve CV4 in FIG. 9 shows the cleaning property of Comparative Example 2,
Curve CV1 in FIG. 10 shows the cleaning property of Example 3,
Curve CV2 in FIG. 10 shows the cleaning performance of Example 4,
A curve CV1 in FIG. 11 shows the cleaning property of Example 5,
A curve CV2 in FIG. 11 shows the cleaning property of Example 6,
A curve CV3 in FIG. 11 shows the cleaning property of Comparative Example 3,
A curve CV4 in FIG. 11 shows the cleaning property of Comparative Example 4.

  As is apparent from FIGS. 9 to 11, all of Examples 1 to 6 showed good cleaning properties at a reflection densitometer output of 0.5 V or less through 1200 kp from the initial stage, but Comparative Examples 1 to 4 had 1200 kp. The cleaning performance was poor before reaching.

70 Intermediate transfer body 100 Polishing device 101 Electromagnet 101A Magnet 102 Magnetic powder 103 Container 104 Seal member 106 Magnet drive power supply section 101B, 107 Magnetic body 108 Magnet drive motor 200 Control section

Claims (7)

In an image forming apparatus having a polishing apparatus for polishing the surface of the image carrier with an image carrier and magnetic powder,
The polishing apparatus comprises:
The magnetic powder,
A container for containing the magnetic powder; and
A magnetic powder moving unit for setting a first state in which the magnetic powder is brought into contact with the image carrier to polish the surface of the image carrier and a second state in which the magnetic powder is separated from the image carrier;
An image forming apparatus comprising: The magnetic powder moving part is
A permanent magnet disposed opposite the container across the image carrier; and
The permanent magnet is brought close to the image carrier to attract the magnetic powder, is brought into contact with the image carrier, the first state is set, and the permanent magnet is separated from the image carrier to thereby form the magnetic powder. A magnet drive unit that sets the second state by dropping / separating the image carrier from the image carrier;
The image forming apparatus according to claim 1, further comprising: The magnetic powder moving part is
Electromagnets and
The electromagnet is configured to attract the magnetic powder to the image carrier, contact the image carrier to set the first state, and separate the magnetic powder from the image carrier to set the second state. The magnet drive power supply unit that operates the
The image forming apparatus according to claim 1, further comprising:   The image forming apparatus according to claim 1, wherein the magnetic powder moving unit stirs the magnetic powder by repeating the first state and the second state. .   4. The image according to claim 3, wherein the electromagnet includes a plurality of electromagnet elements divided in the width direction of the image, and the magnet drive power supply unit includes a magnet drive power supply that individually operates the electromagnet elements. 5. Forming equipment. A control unit for controlling the magnetic powder moving unit;
The control unit sets the first state when there is an instruction from the user, when the moving distance of the image carrier exceeds a predetermined value, or when the image forming process is completed. The image forming apparatus according to claim 1, wherein the magnetic powder moving unit is controlled so as to be set.   When the first state is set, in the case of patch detection for detecting the density of a patch image or when releasing the recording material jam, the control unit sets the second state so as to set the second state. The image forming apparatus according to claim 6, wherein the moving unit is controlled.

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