JP2010176108A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device configured to prevent toner clogging without excessively increasing a compression force applied to the toner upon toner supply, and to provide an image forming apparatus with the same. <P>SOLUTION: The developing device 2 includes: a developing tank 111 for storing developer containing toner and magnetic carrier; a toner supply port 115a for receiving the supplied toner; a toner supply path 102 for guiding the supplied toner to the developing tank 111; and a toner supply path cleaning means 101 for cleaning the inside of the toner supply path 102. The toner supply path cleaning means 101 includes: a magnet 118 disposed outside the toner supply path 102; and magnetic particles to be attraacted by the magnet 118 in the toner supply path 102. By moving the magnet 118 along the toner supply path 102, the magnetic particles rub the inside of the toner supply path 102. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developing apparatus and an image forming apparatus that perform image formation with a two-component developer containing toner and a magnetic carrier.

  2. Description of the Related Art Conventionally, electrophotographic image forming apparatuses are often used as image forming apparatuses such as copying machines and printers. An electrophotographic image forming apparatus forms an electrostatic latent image on the surface of a photoreceptor (toner image carrier), develops the electrostatic latent image with toner supplied from a developing device, and develops the developed toner image. Is transferred and fixed on a sheet such as paper. In recent years, a two-component developer having excellent toner charging stability has been used as a developer for the purpose of achieving color and high image quality. The two-component developer includes toner and a magnetic carrier, and appropriately charged toner is obtained by stirring them in the developing device. When the charged toner is consumed by developing the electrostatic latent image formed on the surface of the photosensitive member, the replenishment toner is replenished from the toner replenishing device to the developing device.

  FIG. 11 shows an outline of a conventional developing device having a toner supply path. In the developing device 500 shown in FIG. 11, a conveying member 502 made of an auger screw that rotates in a shaft is disposed in a developing tank 501 that stores developer D containing toner, and a removable developing tank cover is disposed above the developing tank 501. 503 is provided. Further, a toner supply port 504 for supplying unused toner T is formed in the developing tank cover 503, and a cylindrical toner supply path 505 extending upward is connected to the toner supply port 504. Yes. In such a developing device 500, the toner in the developer D is designed to be quickly charged by mixing with the magnetic carrier, and therefore the toner supply path 505 for guiding the supply toner T to the developing device 500 is provided. There is a problem in that the toner easily adheres to the inner wall, forms a toner bridge as shown in FIG. 11, and the toner supply path 505 is completely clogged with the aggregated toner T.

  In order to solve such a problem, for example, in Patent Document 1, a belt-like toner transfer mechanism is provided in the toner transport path, and this is driven in the toner transport direction, so that the toner is moved in the toner transport path. A developing device is disclosed in which clogging is prevented.

JP 2006-163207 A

  However, the developing apparatus disclosed in Patent Document 1 has a drawback that the apparatus becomes large, and a driving component (toner transfer mechanism) is provided inside the toner replenishing path to add mechanical propulsive force to the toner. Therefore, there is a problem that the toner aggregates due to the compressive force received from the driving component.

  The present invention has been made in view of such circumstances, and a developing device capable of preventing toner clogging without excessively increasing the compressive force applied to the toner when replenishing the toner, and an image forming apparatus including the developing device The purpose is to provide.

The present invention includes a developer tank containing a developer containing toner and a magnetic carrier and provided with a toner replenishing port for receiving replenished toner, and a toner replenishment that communicates with the toner replenishing port and guides the replenished toner to the developing tank. A toner replenishment path cleaning means for cleaning the interior of the toner replenishment path,
The toner replenishment path cleaning means includes:
A magnet provided outside the toner supply path;
In the toner replenishment path, the magnetic particles are magnetically attracted by the magnet through the toner replenishment path,
In the developing device, the magnetic particles are rubbed in the toner supply path by moving the magnet along the toner supply path.

  In the invention, it is preferable that the magnet is composed of two magnets and arranged so that the N pole and the S pole face each other toward the toner supply path.

  In the invention, it is preferable that the magnet is a ring-shaped magnet having a magnetic field forming portion in which the north and south poles face each other toward the toner supply path.

In the invention, it is preferable that the magnetic particle is a magnetic carrier accommodated in the developing tank.
According to the present invention, the magnet is an electromagnet.

According to another aspect of the present invention, there is provided a developer tank containing a developer containing toner and a magnetic carrier and provided with a toner replenishing port for receiving replenished toner; A developing device comprising a replenishment path and a toner replenishment path cleaning means for cleaning the toner replenishment path,
The toner replenishment path cleaning means includes:
A plurality of electromagnets provided outside along the toner supply path;
Magnetic particles that are in the toner supply path and are magnetically attracted by the electromagnet through the toner supply path;
In the developing device, the plurality of electromagnets are alternately energized to rub the toner supply path with the magnetic particles.

The present invention also provides a photosensitive drum, a charging device for charging the surface of the photosensitive drum, an exposure device for forming an electrostatic latent image on the surface of the photosensitive drum, and a static image formed on the surface of the photosensitive drum. Image forming comprising: a developing device that forms a toner image by developing an electrostatic latent image; a transfer device that transfers the toner image onto a recording medium; and a fixing device that fixes the transferred toner image onto the recording medium. In the device
An image forming apparatus, wherein the developing device is a developing device having the configuration of each of the inventions.

  According to the present invention, since the magnet moves along the toner supply path in a state where the magnetic particles are magnetically attracted, the inner wall of the toner supply path is rubbed by the magnetic particles. As a result, even if toner adheres to the inner wall of the toner replenishment path, it is immediately removed, so that toner gradually accumulates in the toner replenishment path and suppresses the formation of a bridge composed of toner aggregates in the toner replenishment path. , Toner clogging can be prevented. Further, since there is no need to provide a moving part such as a screw in the toner supply path, it is possible to prevent the toner from being compressed and aggregated. Further, since vibration does not occur, it is possible to prevent toner from dropping from the toner replenishing device due to vibration.

  According to the present invention, the magnetic flux density formed in the toner replenishment path can be made uniform, so that it is possible to prevent uneven toner scraping that adheres to the inner wall of the toner replenishment path.

  Further, according to the present invention, a magnetic field can be effectively formed in the toner replenishment path, so that magnetic leakage to the outside can be suppressed and magnetic particles can be held more strongly even when the magnetic force is small.

  In addition, according to the present invention, even when the magnetic particles fall and are mixed in the developer, the magnetic particles play the role of a magnetic carrier, thereby preventing the occurrence of image defects.

  According to the invention, the magnetic carrier is dropped by dropping the magnetic carrier into the developing tank by stopping the energization of the electromagnet, and starting the energization of the electromagnet at a position close to the developer contained in the developing tank. As a result, the magnetic particles can be exchanged, and the toner scraping effect can be maintained over a long period of time.

  Further, according to the present invention, the magnetic particles can be moved along the toner replenishment path only by controlling the energization timing without moving the electromagnet, and the inner wall of the toner replenishment path is rubbed with the magnetic particles. . As a result, even if toner adheres to the inner wall of the toner replenishment path, it is immediately removed, so that toner gradually accumulates in the toner replenishment path and suppresses the formation of a bridge composed of toner aggregates in the toner replenishment path. , Toner clogging can be prevented. Furthermore, since no means for moving the magnet is required, the developing device can be miniaturized.

  According to the invention, the electrostatic latent image formed on the surface of the photosensitive drum is developed by the developing device to be a toner image. This toner image is transferred onto a recording medium by a transfer device, and fixed on the recording medium as a permanent image by a fixing device. The toner replenishment path for replenishing toner to the developing tank of the developing device is always maintained in a state free of toner clogging by the toner replenishment path cleaning means, so that the toner replenishment is reliably performed and the toner concentration Is stable and an image having no density unevenness can be obtained.

1 is a schematic diagram illustrating an overall configuration of an image forming apparatus A in which a developing device 2 according to a first embodiment of the present invention is used. 2 is a cross-sectional view showing a configuration of a developing device 2. FIG. It is sectional drawing seen from the cut surface line III-III of FIG. It is sectional drawing seen from the cut surface line IV-IV of FIG. 3 is a plan view of the developing device 2. FIG. 2 is an enlarged perspective view of an electromagnet 118. FIG. FIG. 2 is a cross-sectional view illustrating a configuration of a toner supply device 22 illustrated in FIG. 1. FIG. 8 is an enlarged cross-sectional view of the periphery of the toner discharge member shown in FIG. In the developing device 2 according to the first embodiment of the present invention, the toner replenishment path 102 is rubbed with magnetic particles, and the toner T starts to adhere to the inner wall of the toner replenishment path 102. The state shows the state where the electromagnet 118 is moved to the position (lowermost part) closest to the developer D in the developing tank 111 without being energized. In the same diagram, energization of the electromagnet 118 moved to the position closest to the developer D (lowermost part) is started, the magnetic carrier accommodated in the developing tank 111 is attracted by the electromagnet 218a, and the magnetic brush DJ is moved. The state of forming is shown. It is the same schematic diagram, and shows a state in which the electromagnet 118 is moved to the top by rotating the magnet drive screw 102a while the magnetic carrier is attracted. It is the same schematic diagram, and shows a state in which the electromagnet 118 is moved to the lowest position by rotating the magnet drive screw 102a while the magnetic carrier is attracted. It is the same figure, Comprising: When the electromagnet 118 moved to the lowest part is stopped, the magnetic carrier which has formed the magnetic brush DJ is returned to the developer D in the developing tank. FIG. 5 is a cross-sectional view showing a configuration of a developing device 202 according to a second embodiment of the present invention, corresponding to FIG. 4. FIG. 10 is a cross-sectional view showing a configuration of a conventional developing device 500.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the overall configuration of an image forming apparatus A in which the developing device according to the first embodiment of the present invention is used.

  An image forming apparatus A shown in FIG. 1 is a printer or a printing machine, and is an image forming apparatus that forms an image using toner by an electrophotographic method. That is, the image forming apparatus A shown in FIG. 1 includes a photosensitive drum 3 on which an electrostatic latent image is formed, a charger (charging device) 5 that charges the surface of the photosensitive drum 3, and the photosensitive drum 3. An exposure unit (exposure device) 1 for forming an electrostatic latent image on the surface of the toner, a developing device 2 for supplying toner to the electrostatic latent image formed on the surface of the photosensitive drum 3 to form a toner image, and development A toner replenishing device 22 for replenishing toner to the device 2, an intermediate transfer belt unit (transfer device) 8 for transferring the toner image developed on the surface of the photosensitive drum 3 to a recording medium, and fixing the toner image on the recording medium. And a fixing unit (fixing device) 12. The developing device 2 employs the configuration of the developing device according to the present invention.

  This image forming apparatus A forms a multicolor image on a predetermined sheet (recording paper, recording medium) in accordance with image data transmitted from the outside, but forms a single color image. Also good. Note that a scanner or the like may be provided above the image forming apparatus A and configured as a copying machine, a facsimile machine, or a multifunction machine.

  First, the overall configuration of the image forming apparatus A will be described. As shown in FIG. 1, the illustrated image forming apparatus A handles image data for each color component of black (K), cyan (C), magenta (M), and yellow (Y). A magenta image and a yellow image are formed, and a color image is formed by superimposing the respective color component images. Therefore, in the image forming apparatus A, as shown in FIG. 1, the developing device 2 (2a, 2b, 2c, 2d) and the photosensitive drum 3 (3a, 3b, 3c) are formed so that an image of each color component is formed. , 3d), four chargers 5 (5a, 5b, 5c, 5d), four cleaner units 4 (4a, 4b, 4c, 4d) and four toner replenishing devices 22 (22a, 22b, 22c, 22d). ing. In other words, four image forming stations (image forming units) each including the developing device 2, the photosensitive drum 3, the charger 5, the cleaner unit 4, and the toner replenishing device 22 are provided.

  In addition, a to d included in the reference numerals attached to the respective parts constituting the four image forming units are a for a black image forming member, b for a cyan image forming member, and c for a magenta image. It shows that the forming member d is a yellow image forming member. In addition, the image forming apparatus A includes an exposure unit 1, a fixing unit 12, a sheet conveyance path S, a paper feed tray 10, and a paper discharge tray 15.

  The charger 5 (5a, 5b, 5c, 5d) uniformly charges the surface of each photosensitive drum 3 (3a, 3b, 3c, 3d) to a predetermined potential. As the charger 5, in addition to the contact roller type charger shown in FIG. 1, a contact brush type charger or a non-contact charger type charger may be used. As shown in FIG. 1, the exposure unit 1 is a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror. However, in addition to the laser scanning unit, the exposure unit 1 may be an EL (electroluminescence) in which light emitting elements are arranged in an array or an LED writing head. The exposure unit 1 exposes the charged photosensitive drum 3 according to the input image data, thereby forming an electrostatic latent image corresponding to the image data on the surface of the photosensitive drum 3.

  The developing device 2 (2a, 2b, 2c, 2d) visualizes (develops) the electrostatic latent image formed on the photosensitive drum 3 with any of K, C, M, and Y toners. is there. The developing device 2 includes a developing tank 111 (111a, 111b, 111c, 111d), and a toner supply path 102 and a toner supply device 22 (22a, 22b, 22c, 22d) are provided above each developing tank 111. is set up. The cleaner unit 4 (4a, 4b, 4c, 4d) removes and collects the toner remaining on the surface of the photosensitive drum 3 after the development and image transfer steps.

  An intermediate transfer belt unit 8 is disposed above the photosensitive drum 3. The intermediate transfer belt unit 8 includes an intermediate transfer roller 6 (6a, 6b, 6c, 6d) corresponding to the four image forming units, an intermediate transfer belt 7, an intermediate transfer belt driving roller 71, an intermediate transfer belt driven roller 72, an intermediate transfer belt A transfer belt tension mechanism 73 and an intermediate transfer belt cleaning unit 9 are provided. The intermediate transfer belt 6, the intermediate transfer belt drive roller 71, the intermediate transfer belt driven roller 72, and the intermediate transfer belt tension mechanism 73 stretch the intermediate transfer belt 7 and rotationally drive the intermediate transfer belt 7 in the direction of arrow B in FIG. It is something to be made. The intermediate transfer roller 6 is rotatably supported by an intermediate transfer roller mounting portion in the intermediate transfer belt tension mechanism 73 of the intermediate transfer belt unit 8. A transfer bias for transferring the toner image on the photosensitive drum 3 onto the intermediate transfer belt 7 is applied to the intermediate transfer roller 6.

  The intermediate transfer belt 7 is provided so as to be in contact with each photosensitive drum 3. A color toner image (multicolor toner image) is formed on the intermediate transfer belt 7 by sequentially superimposing and transferring the toner images of the respective color components formed on the photosensitive drum 3. The intermediate transfer belt 7 is formed in an endless shape using a film having a thickness of, for example, about 100 μm to 150 μm. Transfer of the toner image from the photosensitive drum 3 to the intermediate transfer belt 7 is performed by the intermediate transfer roller 6 in contact with the back side of the intermediate transfer belt 7. A high voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 6 in order to transfer the toner image.

  The intermediate transfer roller 6 is formed based on a metal (for example, stainless steel) shaft having a diameter of, for example, 8 to 10 mm, and the surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). With this conductive elastic material, the intermediate transfer roller 6 can uniformly apply a high voltage to the intermediate transfer belt 7. In this embodiment, a roller-shaped electrode is used as the transfer electrode, but a brush-shaped electrode can also be used.

  As described above, the electrostatic latent images on the respective photosensitive drums 3 are visualized with toners corresponding to the respective color components to become toner images, and these toner images are superimposed on the intermediate transfer belt 7 and stacked. As described above, the stacked toner images are moved to a contact position (transfer portion) between the sheet conveyed on the sheet conveyance path S and the intermediate transfer belt 7 by the rotation of the intermediate transfer belt 7, and are moved to this position. The image is transferred onto the paper by the arranged transfer roller 11. In this case, the intermediate transfer belt 7 and the transfer roller 11 are pressed against each other at a predetermined nip, and a voltage for transferring the toner image onto the sheet is applied to the transfer roller 11. This voltage is a high voltage having a polarity (+) opposite to the charging polarity (−) of the toner.

  In order to obtain the nip constantly, either the transfer roller 11 or the intermediate transfer belt drive roller 71 is formed of a hard material such as metal, and the other is a soft material such as an elastic roller (elastic rubber roller or foamable resin roller). Etc.). The toner adhering to the intermediate transfer belt 7 due to the contact between the intermediate transfer belt 7 and the photosensitive drum 3 and the toner image remaining on the intermediate transfer belt 7 without being transferred when the toner image is transferred from the intermediate transfer belt 7 to the sheet. The toner is removed and collected by the intermediate transfer belt cleaning unit 9 because it causes toner color mixing in the next step. The intermediate transfer belt cleaning unit 9 includes a cleaning blade (cleaning member) that contacts the intermediate transfer belt 7. The portion of the intermediate transfer belt 7 that is in contact with the cleaning blade is supported by the intermediate transfer belt driven roller 72 from the back side.

  The paper feed tray 10 is for storing sheets (for example, recording paper) used for image formation, and is provided below the image forming unit and the exposure unit 1. On the other hand, a paper discharge tray 15 provided in the upper part of the image forming unit is for placing printed sheets face down. Further, the image forming apparatus A is provided with a sheet conveyance path S for guiding the sheet of the paper feed tray 10 and the sheet of the manual feed tray 20 to the paper discharge tray 15 via the transfer unit and the fixing unit 12. . The transfer unit is located between the intermediate transfer belt driving roller 71 and the transfer roller 11. Further, a pickup roller 16 (16a, 16b), a registration roller 14, a transfer unit, a fixing unit 12, a conveyance roller 25 (25a to 25h), and the like are arranged in the sheet conveyance path S.

  The conveyance rollers 25 are small rollers for promoting and assisting conveyance of the sheet, and a plurality of conveyance rollers 25 are provided along the sheet conveyance path S. The pickup roller 16 a is a pull-in roller that is provided at the end of the paper feed tray 10 and supplies sheets one by one from the paper feed tray 10 to the sheet conveyance path S. The pickup roller 16 b is a drawing roller that is provided near the manual feed tray 20 and supplies sheets from the manual feed tray 20 to the sheet conveyance path S one by one. The registration roller 14 temporarily holds the sheet conveyed in the sheet conveyance path S, and conveys the sheet to the transfer unit at a timing when the leading edge of the toner image on the intermediate transfer belt 7 and the leading edge of the sheet are aligned.

  The fixing unit 12 includes a heat roller 81, a pressure roller 82, and the like. The heat roller 81 and the pressure roller 82 rotate with the sheet interposed therebetween. The heat roller 81 is controlled by a control unit (not shown) so as to have a predetermined fixing temperature. This control unit controls the temperature of the heat roller 81 based on a detection signal from a temperature detector (not shown). The heat roller 81 heat-presses the sheet together with the pressure roller 82 to melt, mix, and press the color toner images transferred to the sheet, and heat-fix the sheet. Note that the sheet on which the multicolor toner image (each color toner image) is fixed is conveyed to the reverse sheet discharge path of the sheet conveyance path S by the plurality of conveyance rollers 25, and is in the reversed state (the fixed multicolor toner image The sheet is discharged onto the sheet discharge tray 15 in a state of being directed downward.

  Next, the sheet conveying operation by the sheet conveying path S will be described. As shown in FIG. 1, the image forming apparatus A is provided with a paper feed tray 10 that stores sheets in advance and a manual feed tray 20 that is used when printing a small number of sheets as described above. Pick-up rollers 16 (16a, 16b) are arranged on the trays 10 and 20, respectively, and the pick-up rollers 16 feed sheets one by one to the sheet conveyance path S. In the case of single-sided printing, the sheet conveyed from the sheet feeding tray 10 is conveyed to the registration roller 14 by the conveyance roller 25a in the sheet conveyance path S, and is stacked on the leading edge of the sheet and the intermediate transfer belt 7 by the registration roller 14. Then, the toner image is conveyed to a transfer portion (contact position between the transfer roller 11 and the intermediate transfer belt 7) at a timing when the leading edge of the toner image is aligned. In the transfer portion, a toner image is transferred onto the sheet, and this toner image is fixed on the sheet by the fixing unit 12. Thereafter, the sheet is discharged onto the discharge tray 15 from the discharge roller 25c via the conveyance roller 25b. Further, the sheet conveyed from the manual feed tray 20 is conveyed to the registration roller 14 by a plurality of conveying rollers 25 (25f, 25e, 25d). Subsequent sheet conveyance operations are discharged to the sheet discharge tray 15 through a process similar to that for the sheets supplied from the sheet feed tray 10 described above.

  On the other hand, in the case of double-sided printing, the trailing edge of the sheet that has completed single-sided printing and passed through the fixing unit 12 as described above is chucked by the paper discharge roller 25c. Next, the sheet is switched back and guided to the transport rollers 25g and 25h by the reverse rotation of the paper discharge roller 25c. After the back side printing is performed again through the registration roller 14, the sheet is placed on the paper discharge tray 15. Discharged.

  Next, the developing device 2 will be described with reference to FIGS. 2 is a cross-sectional view showing the configuration of the developing device 2, FIG. 3 is a cross-sectional view taken along the section line III-III in FIG. 2, and FIG. 4 is seen from the section line IV-IV in FIG. FIG. 5 is a plan view of the developing device 2, and FIG. 6 is an enlarged perspective view of the electromagnet 118. As illustrated in FIG. 2, the developing device 2 includes a developing roller 114 disposed in the developing tank 111 so as to face the photosensitive drum 3 (see FIG. 1). In this device, toner is supplied to the surface of the photosensitive drum 3 and the electrostatic latent image formed on the surface of the photosensitive drum 3 is developed (visualized). In addition to the developing roller 114, the developing device 2 includes a developing tank 111, a removable developing tank cover 115, a toner supply port 115a, a doctor blade 116, a first conveying member 112, a second conveying member 113, a partition plate (partition wall). ) 117, a toner density detection sensor 119 and a toner supply path 102 are provided.

  The developing tank 111 is a tank that stores a two-component developer containing toner and a carrier. The developing tank 111 is provided with a developing roller 114, a first conveying member 112, a second conveying member 113, and the like. Note that the carrier of this embodiment is a magnetic carrier having magnetism. The developing roller 114 is a magnet roller that is driven to rotate about an axis by a driving unit (not shown), and conveys the two-component developer in the developing tank 111 to the photosensitive drum 3. The developing roller 114 is provided so as to face the photosensitive drum 3 and be separated from the photosensitive drum 3 with a gap. The two-component developer conveyed by the developing roller 114 comes into contact with the photosensitive drum 3 at the closest portion. This contact area is a development nip portion. In the development nip portion, a development bias voltage is applied to the development roller 114 from a power source (not shown) connected to the development roller 114, and the two-component developer on the surface of the development roller 114 is exposed to light. Toner is supplied to the electrostatic latent image on the surface of the body drum 3.

  The doctor blade 116 is a plate-like member extending parallel to the axial direction of the developing roller 114, and one end in the short direction is supported by the developing tank 111 and the other end is the developing roller 114 below the developing roller 114 in the vertical direction. It is provided so as to be separated from the surface of the surface with a gap. As the material of the doctor blade 116, stainless steel can be used, but aluminum or synthetic resin can also be used.

  The toner concentration detection sensor 119 is mounted on the bottom surface of the developing tank 111 below the second conveying member 113 in the vertical direction, and is provided so that the sensor surface is exposed inside the developing tank 111. The toner concentration detection sensor 119 is electrically connected to a toner concentration control means (not shown). The toner density control means rotates and drives a toner discharge member 122 (see FIGS. 7 and 8), which will be described later, in accordance with the toner density measurement value detected by the toner density detection sensor 119, and the toner discharge port 123 (see FIGS. 7 and 8). 8) to control the supply of toner into the developing tank 111. When the toner density control means determines that the measured toner density value by the toner density detection sensor 119 is lower than the toner density setting value, the toner density control means sends a control signal to the drive means for driving the toner discharge member 122 to rotate, thereby rotating the toner discharge member 122. Drive. As the toner concentration detection sensor 119, a general toner concentration detection sensor can be used, and examples thereof include a transmitted light detection sensor, a reflected light detection sensor, and a magnetic permeability detection sensor. Among these, a magnetic permeability detection sensor is preferably used.

  A power source (not shown) is connected to the magnetic permeability detection sensor. The power supply applies a drive voltage for driving the magnetic permeability detection sensor and a control voltage for outputting the detection result of the toner density to the control means. Application of a voltage to the magnetic permeability detection sensor by the power source is controlled by the control means. The permeability detection sensor is a type of sensor that receives the control voltage and outputs the toner density detection result as an output voltage value. Basically, the sensitivity near the median value of the output voltage is good. It is used by applying a control voltage to obtain a voltage. Such type of magnetic permeability detection sensors are commercially available, and examples thereof include TS-L, TS-A, TS-K (all are trade names, manufactured by TDK Corporation) and the like.

  Further, as shown in FIGS. 2 and 4, a detachable developing tank cover 115 is provided above the developing tank 111. Further, as shown in FIG. 4, the developer tank cover 115 is formed with a toner supply port 115 a for supplying unused toner to the developer tank 111. The first conveying member 112 is configured by an auger screw including a spiral first conveying blade 112a, a first rotating shaft 112b, and a first conveying gear 112c, and agitates and conveys the two-component developer by rotating. It is supposed to be. The second conveying member 113 is composed of an auger screw composed of a spiral second conveying blade 113a, a second rotating shaft 113b, and a first conveying gear 113c, and agitates and conveys the two-component developer by rotating. It is supposed to be.

  In the developing tank 111, a partition plate 117 is disposed between the first transport member 112 and the second transport member 113. The partition plate 117 extends in parallel with each axial direction (each rotational axis direction) of the first transport member 112 and the second transport member 113. The interior of the developing tank 111 is partitioned by a partition plate 117 into a first transport path P in which the first transport member 112 is disposed and a second transport path Q in which the second transport member 113 is disposed. The partition plate 117 is disposed away from the inner wall surface of the developing tank 111 at both axial ends of the first transport member 112 and the second transport member 113. As a result, in the developing tank 111, a communication path that connects the first transport path P and the second transport path Q is formed in the vicinity of both axial ends of the first transport member 112 and the second transport member 113. ing. In the following, as shown in FIG. 3, the communication path formed on the arrow X direction side is referred to as a first communication path a, and the communication path formed on the arrow Y direction side is referred to as a second communication path b.

  The first conveying member 112 and the second conveying member 113 are arranged in parallel so that their peripheral surfaces face each other via the partition plate 117 and their axes are parallel to each other, and rotate in opposite directions. Is set to As shown in FIG. 3, the first transport member 112 transports the two-component developer in the arrow X direction, and the second transport member 113 transports the two-component developer in the arrow Y direction opposite to the arrow X direction. Is set to carry. The toner replenishing port 115a is a region in the first transport path P and is formed at a position on the arrow X direction side from the second communication path b. That is, in the first transport path P, the toner is replenished downstream of the second communication path b.

  In the developing tank 111, the first transport member 112 and the second transport member 113 are rotationally driven by a first transport member drive motor (not shown) and a second transport member drive motor (not shown), respectively, and two-component development. Transport the agent. Specifically, in the first transport path P, the two-component developer is transported in the direction of arrow X while being stirred by the first transport member 112 and reaches the first communication path a. The two-component developer that has reached the first communication path a passes through the first communication path a and is conveyed to the second conveyance path Q. On the other hand, in the second transport path Q, the two-component developer is transported in the direction of the arrow Y while being stirred by the second transport member 113 and reaches the second communication path b. The two-component developer that has reached the second communication path b passes through the second communication path b and is conveyed to the first conveyance path P. That is, the first transport member 112 and the second transport member 113 transport the two-component developer in the opposite directions while stirring.

  In this way, the two-component developer passes through the first conveyance path P, the first communication path a, the second conveyance path Q, and the second communication path b in the developing tank 111 from the first conveyance path P to the first. Circulation movement is carried out in the order of communication path a → second transport path Q → second communication path b. Then, while the two-component developer is being conveyed on the second conveyance path Q, the developer roller 114 is carried on the surface by the rotation of the developing roller 114 and pumped up, and the toner in the two-component developer thus pumped is exposed to light. It moves to the body drum 3 and is consumed sequentially. In order to make up for the consumed toner, unused toner is replenished to the first transport path P from the toner replenishing port 115a. The replenished toner is mixed and agitated with the two-component developer existing in the first conveyance path P.

  Next, the toner supply path 102 and the toner supply path cleaning means 101 will be described. The toner replenishment path 102 is a hollow pipe having an outer shape that guides the toner T (see also FIG. 9A) supplied from the toner replenishing device 22 to the toner replenishing port 115a. An electromagnet 118 is provided outside the toner supply path 102 so as to move along the toner supply path 102. Outside the toner supply path 102, a magnet drive screw 102a for driving the electromagnet 118 up and down and a drive gear 102b for rotating the magnet drive screw 102a (see also FIGS. 9A to E) are provided. Thus, the magnet drive screw 102a is rotated.

  The electromagnet 118 is a ring-shaped electromagnet having a magnetic field forming portion in which the N pole and the S pole face each other toward the toner supply path 102, and is formed of a ferromagnetic body including a coil 118c. Further, the electromagnet 118 has a through hole 118p having nut-like irregularities inside, and the magnet drive screw 102a can be penetrated in a state of being screwed into the through hole 118p, and at the same time, the rotation of the magnet drive screw 102a. It moves up and down by the relative screwing and unscrewing action of the screwing part. The electromagnet 118 energizes the magnetic carrier (magnetic particles) accommodated in the developing tank 111 when energized at a position closest to the developer D (see also FIG. 9A) containing the magnetic carrier in the developing tank 111. It is arranged to be attracted, and moves along the toner replenishment path 102 while attracting the magnetic carrier (magnetic particles), thereby rubbing the toner replenishment path 102 with the magnetic particles. In the present embodiment, the electromagnet 118, the magnetic carrier (magnetic particles), and the magnet drive screw 102a constitute the toner replenishment path cleaning means 101.

  Further, a permanent magnet may be used in place of the electromagnet 118. At this time, if the permanent magnet keeps the magnetic carrier (magnetic particles) fully in the toner replenishment path, it becomes an obstacle when the replenishment toner falls, so when the permanent magnet reaches the top As shown in FIG. 4 for the sake of convenience, it is preferable to provide a nonmagnetic plate 102c above the toner supply path 102 so that the holding power of the magnetic carrier (magnetic particles) is reduced. In the case of an electromagnet, since the magnetic field disappears when energization is turned off, it is not necessary to provide such a nonmagnetic plate 102c.

  The magnetic particles that can be used in the present invention are not particularly limited as long as they are magnetic particles. However, even if the particles fall into the developing tank 111 and mix with the developer D, the image is not affected. The magnetic carrier used for the agent D is preferable. A magnetic carrier (sometimes simply referred to as a carrier) used as magnetic particles will be described below. A well-known thing can be used as a particle size of a carrier, for example, a magnetic body with a volume average particle diameter of 20-100 micrometers can be used. If the particle size of the carrier is too small, the carrier moves from the developing roller 114 to the photosensitive drum 3 at the time of development, thereby causing white spots in the obtained image. Moreover, since dot reproducibility will worsen and an image will become coarse when too large, it is more preferable that it is 30-60 micrometers as a volume average particle diameter of a carrier.

  The volume average particle diameter of the carrier is determined when a dry dispersion apparatus RODOS (manufactured by SYMPATEC) is used in a laser diffraction particle size distribution measuring apparatus HELOS (manufactured by SYMPATEC) under a dispersion pressure of 3.0 bar. Is the value of

  As such a carrier, a coated carrier in which a coating layer is provided on the surface of magnetic core particles is generally used. Known magnetic particles can be used as the core particles, but ferrite particles are preferred. Since ferrite particles have high saturation magnetization and low density carriers, carrier adhesion to the photoreceptor is unlikely to occur, and images with high dot reproduction due to soft spike formation can be obtained. Known ferrite particles can be used, such as zinc ferrite, nickel ferrite, copper ferrite, nickel-zinc ferrite, manganese-magnesium ferrite, copper-magnesium ferrite, manganese-zinc ferrite, Manganese-copper-zinc ferrite can be used.

  A known resin material can be used as the covering material, for example, an acrylic resin or a silicone resin can be used. In particular, a coated carrier coated with a straight silicone resin (alkyl-substituted silicone resin) is preferable because the toner component (binder resin) is less likely to adhere (filming) to the surface, and the charge imparting ability of the toner can be maintained over a long period of time. .

  FIG. 7 is a cross-sectional view showing the configuration of the toner replenishing device 22 shown in FIG. FIG. 8 is an enlarged cross-sectional view of the vicinity of the toner discharge member shown in FIG. 7 as viewed from the section line VIII-VIII. In FIG. 7, the toner replenishing device 22 includes a toner container 121, a toner stirring member 125, a toner discharge member 122, and a toner discharge port 123. The toner replenishing device 22 is disposed on the upper side of the developing tank 111 and stores unused toner (powder toner) T. The toner T in the toner replenishing device 22 is supplied from the toner discharge port 123 to the developing tank 111 through the toner supply path 102 by rotating a toner discharge member (discharge screw) 122.

  The toner storage container 121 is a substantially semi-cylindrical container member having an internal space, and rotatably supports the toner stirring member 125 and the toner discharge member 122 to store the toner T. The toner discharge port 123 is a substantially rectangular opening provided at a lower portion of the toner discharge member 122 and from a central portion in the axial direction, and is disposed at a position facing the toner supply path 102. The toner stirring member 125 rotates around the rotation shaft 125 a to pump up the toner T in the toner container 121 and convey it to the toner discharge member 122 while stirring the toner T stored in the toner container 121. This is a plate-like member that has a toner pumping member 125b at the tip. The toner pumping member 125 b is made of a flexible polyethylene terephthalate (PET) sheet and is attached to both ends of the toner stirring member 125.

  The toner discharge member 122 supplies the toner T in the toner container 121 from the toner discharge port 123 to the developing tank 111, and includes an auger including a toner conveying blade 122a and a toner discharge member rotating shaft 122b as shown in FIG. It is comprised from the screw and the toner discharge member rotation gear 122c. The toner discharge member 122 is rotationally driven by a toner discharge member drive motor (not shown). The direction of the auger screw is set so that the toner is conveyed from both ends in the axial direction of the toner discharge member 122 toward the toner discharge port 123. A toner discharge member partition wall 124 is provided between the toner discharge member 122 and the toner stirring member 125. Accordingly, the toner pumped up by the toner stirring member 125 can hold an appropriate amount of toner around the toner discharge member 122.

  In FIG. 7, the toner stirring member 125 rotates in the direction of the arrow to stir the toner T and pumps it toward the toner discharge member 122. At this time, the toner scooping member 125 b rotates while sliding and deforming the inner wall of the toner container 121 due to its flexibility, and supplies the toner T to the toner discharge member 122. The toner discharge member 122 guides the supplied toner T to the toner discharge port 123 by its rotation.

  FIGS. 9A to 9E are schematic diagrams showing how the toner supply path 102 is rubbed with magnetic particles in the developing device 2 according to the embodiment of the present invention. FIG. 9A shows a state in which the toner T starts to adhere to the inner wall of the toner replenishment path 102, and the electromagnet 118 is moved to the position closest to the developer D (lowermost part) in the developing tank 111 without being energized. Indicates the state of being made. FIG. 9B shows that the electromagnet 118 moved to the position closest to the developer D (lowermost part) is energized, and the magnetic carrier accommodated in the developing tank 111 is attracted by the electromagnet 218a to form the magnetic brush DJ. Indicates the state. FIG. 9C shows a state in which the electromagnet 118 is moved to the top by rotating the magnet driving screw 102a while the magnetic carrier is attracted. FIG. 9D shows a state in which the electromagnet 118 is moved to the lowest position by rotating the magnet drive screw 102a while the magnetic carrier is attracted. FIG. 9E shows a state where energization of the electromagnet 118 moved to the bottom is stopped (turned off) and the magnetic carrier forming the magnetic brush DJ is returned to the developer D in the developing tank.

  That is, in the state of FIG. 9A, by energizing the electromagnet 118 at the bottom, the magnetic carrier is attracted from the developer D in the developing tank 111 to form the magnetic brush DJ (FIG. 9B). Thereafter, when the electromagnet 118 is energized while being raised along the toner supply path 102, the magnetic brush DJ also moves upward. At this time, the toner T adhering to the inner wall of the toner replenishment path 102 is scraped off by the rubbing action of the magnetic brush DJ, and the toner T is lifted to the top while being carried on the magnetic brush DJ (FIG. 9C). . Subsequently, when the electromagnet 118 is lowered in the energized state, the magnetic brush DJ carrying the toner T is also lowered to scrape and carry the remaining adhering toner T on the inner wall of the toner replenishment path 102 to reach the bottom (FIG. 9D). ). If the energization of the electromagnet 118 is turned off in this state, the magnetic action of the electromagnet 118 is lost, and the magnetic carrier forming the magnetic brush DJ falls into the developing tank 111 together with the toner T, and the development in the developing tank 111 is performed. The mixture is stirred and mixed with the agent D (FIG. 9E). In this way, the toner T adhering to the inner wall of the toner supply path 102 is scraped off by rubbing the inner wall of the toner supply path 102 with the magnetic brush DJ. Occurrence is prevented and toner clogging is prevented. Thereby, the supply of the unused toner T from the toner replenishing device 22 to the developing tank 111 is smoothly performed without stagnation.

  Next, the developing device 202 according to the second embodiment of the present invention will be described with reference to FIG. FIG. 10 is a cross-sectional view showing a configuration of the developing device 202 according to the second embodiment of the present invention, and is a cross-sectional view corresponding to FIG. 4 in the developing device 2 of the first embodiment described above. In addition to the developing roller 114 (see FIG. 2), the developing device 202 according to the second embodiment shown in FIG. 10 includes a developing tank 111, a developing tank cover 115, a toner supply port 115a, a doctor blade 116 (see FIG. 2), A first transport member 112, a second transport member 113 (see FIG. 2), a partition plate (partition wall) 117 (see FIG. 2), a toner concentration detection sensor 119 (see FIG. 2), and a toner supply path 102 are provided. .

  Outside the toner supply path 102, a plurality of electromagnets 218a to 218i are provided along the toner supply path 102, and are sequentially energized alternately by a power source (not shown). The order of energizing each electromagnet 218a-i is, for example, by first energizing the lowermost electromagnet 218a closest to the developer, thereby attracting the magnetic carrier in the developer D (see FIG. 9B) by the electromagnet 218a. A magnetic brush DJ (not shown) similar to the above is formed. Next, the magnetic carrier is attracted to the electromagnet 218b by energizing the second stage electromagnet 218b after 1 second and simultaneously stopping energization of the electromagnet 218a after 2 seconds. Next, the magnetic carrier is attracted to the electromagnet 218c by energizing the third stage electromagnet 218c after 1 second and simultaneously stopping energization of the electromagnet 218b after 2 seconds. By repeating this operation sequentially, the magnetic carrier is attracted to the uppermost electromagnet 218i, thereby moving the magnetic brush DJ upward along the toner supply path 102. During this time, the toner T (see FIGS. 9A and 9B) adhering to the inner wall of the toner replenishment path 102 is scraped off, carried on the magnetic brush DJ, and lifted to the top. Thereafter, when energization of the electromagnet 218i is stopped, the magnetic action of the electromagnet 218i is lost, and the magnetic carrier falls into the developing tank 111 together with the toner T, and is agitated and mixed with the developer D in the developing tank 111. As a result, the toner adhering to the inner wall of the toner replenishing path 102 is removed, and the supply of unused toner T from the toner replenishing device 22 to the developing tank 111 is smoothly performed.

  The developing device 202 in this embodiment has the same configuration as the developing device 2 in the first embodiment described above except that it does not have a drive mechanism for moving the electromagnet 118 up and down. Members having the same configuration other than the electromagnet 118 in the embodiment are denoted by the same reference numerals, and description thereof is omitted. Further, the number of electromagnets 218 is not limited to nine as shown in the figure, and is appropriately determined according to the height of the toner supply path 102 and the like.

  FIG. 1 shows an example of the image forming apparatus A in which the image forming unit is based on a plurality of color electrophotographic systems, but a color in which four developing devices are arranged around one photosensitive drum. It may be an image forming unit. Further, as described above, a monochrome electrophotographic method may be used, and in this case, the present invention is applied to one developing device.

DESCRIPTION OF SYMBOLS 1 Exposure apparatus 2 Developing apparatus 3 Photosensitive drum 11 Transfer apparatus 12 Fixing apparatus 111 Developing tank 115a Toner replenishment port 101 Toner replenishment path cleaning means 102 Toner replenishment path 118 Magnet (electromagnet)
118a-i Electromagnet A Image forming apparatus

Claims (7)

A developer tank containing a developer containing toner and a magnetic carrier and provided with a toner replenishing port for receiving replenished toner; a toner replenishing path that communicates with the toner replenishing port and guides the replenished toner to the developer tank; A developing device comprising: a toner replenishment path cleaning means for cleaning the toner replenishment path;
The toner replenishment path cleaning means includes:
A magnet provided outside the toner supply path;
In the toner replenishment path, the magnetic particles are magnetically attracted by the magnet through the toner replenishment path,
2. A developing device according to claim 1, wherein the magnet particles are moved along the toner replenishment path to cause the magnetic particles to rub in the toner replenishment path.   The developing device according to claim 1, wherein the magnet is composed of two magnets, and is arranged so that an N pole and an S pole face each other toward the toner supply path.   The developing device according to claim 1, wherein the magnet is a ring-shaped magnet having a magnetic field forming portion in which an N pole and an S pole face each other toward the toner supply path.   The developing device according to claim 1, wherein the magnetic particles are a magnetic carrier accommodated in the developing tank.   The developing device according to claim 4, wherein the magnet is an electromagnet. A developer tank containing a developer containing toner and a magnetic carrier and provided with a toner replenishing port for receiving replenished toner; a toner replenishing path that communicates with the toner replenishing port and guides the replenished toner to the developer tank; A developing device comprising: a toner replenishment path cleaning means for cleaning the toner replenishment path;
The toner replenishment path cleaning means includes:
A plurality of electromagnets provided outside along the toner supply path;
Magnetic particles that are in the toner supply path and are magnetically attracted by the electromagnet through the toner supply path;
A developing device, wherein the plurality of electromagnets are alternately energized to rub the toner replenishment path with the magnetic particles. Developing a photosensitive drum, a charging device for charging the surface of the photosensitive drum, an exposure device for forming an electrostatic latent image on the surface of the photosensitive drum, and developing the electrostatic latent image formed on the surface of the photosensitive drum An image forming apparatus including: a developing device that forms a toner image; a transfer device that transfers the toner image onto a recording medium; and a fixing device that fixes the transferred toner image onto the recording medium.
An image forming apparatus, wherein the developing device is the developing device according to claim 1.

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