JP2008076525A - Image forming apparatus and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of restraining the scattering of toner and carrier, and its control method. <P>SOLUTION: The image forming apparatus is equipped with: a photoreceptor drum 14 forming an image on a printing medium 15 by transferring toner; a developing roller 16 supplying the toner to the photoreceptor drum 14; a supply roller 24 holding two-component developer composed of toner and carrier and supplying the toner to the developing roller 16; a collecting roller 30 holding the toner collected from the developing roller 16; and a potential adjusting part 31 adjusting the potential of the developing roller 16, the supply roller 24 and the collecting roller 30. The potential adjusting part 31 sets the potential of the developing roller 16 higher than the potential of the supply roller 24 when an image is formed, sets the potential of the supply roller 24 higher than the potential of the developing roller 16 when the image is not formed, and sets the potential of the collecting roller 30 higher than the potential of the developing roller 16 when the image is formed and when the image is not formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a method for controlling the image forming apparatus.

  In an electrophotographic image forming apparatus such as a laser printer, a laser fax machine, or a digital copying machine, the photosensitive drum is charged almost uniformly, and the photosensitive drum is exposed to form an electrostatic latent image corresponding to the image signal. After formation, the toner charged by the developing device is supplied onto the photosensitive drum to be visualized, and the developer image is transferred to a printing medium such as transfer paper, and then fixed by the fixing device to form an image. Yes.

In an image forming apparatus, a method using a magnet roller is known as a method for supplying toner onto a photosensitive drum. For example, in Patent Document 1, in an apparatus using a two-component developer composed of toner and a carrier, two magnet rollers are used, toner is supplied to the toner carrier using one magnet roller, and the other magnet is used. A device for discharging excess toner from a toner carrier using a roller is described.

JP-A-10-319708 JP 2005-221938 A JP 2005-227506 A Japanese Patent No. 3356948

  However, in the above conventional technique, since toner is always supplied onto the toner carrier, the toner adhering to the toner carrier is easily detached, and the toner is scattered in the apparatus and contaminates the inside of the apparatus. There is a problem of end.

  In particular, the toner is negatively charged and adheres to the surface of the photosensitive member. However, when a predetermined time elapses while the toner is attached to the toner carrying member, the toner is uncharged. Accordingly, when the operation of the image forming apparatus is stopped, there is a problem that the toner is likely to be detached with time. Further, when the image forming apparatus is moved or the image forming apparatus is vibrated while the toner is attached to the toner carrier, there is a problem that the toner is detached from the toner carrier.

  Further, in an image forming apparatus using a two-component developer, when the carrier held by the magnet roller is detached from the magnet roller, the carrier adheres on the photosensitive drum and the carrier development is performed, so that the image is deteriorated. The problem also arises.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved image forming apparatus capable of suppressing scattering of toner and carrier in the apparatus, and An object of the present invention is to provide a method for controlling an image forming apparatus.

  In order to solve the above problems, according to an aspect of the present invention, an electrostatic latent image carrier that forms an image on a medium by transferring toner supplied according to an electrostatic latent image, and the electrostatic A developer carrier for supplying toner to the latent image carrier; a first magnetic roller for holding a two-component developer comprising toner and carrier; and supplying the toner to the developer carrier; and the developer carrier A second magnetic roller for holding the toner collected from the toner, and a potential adjusting unit for adjusting the potential of the developing carrier, the first magnetic roller, and the second magnetic roller, and the potential adjusting unit includes: The potential of the developer carrier is set higher than the potential of the first magnetic roller during image formation by the electrostatic latent image carrier, and the potential of the first magnetic roller is set to the developer during non-image formation. Set higher than the potential of the carrier, before During image formation and during the non-image forming, the image forming apparatus is provided which is set higher than the potential of the potential of the second magnetic roller the developer carrier.

  According to the above configuration, since the potential of the developer carrier is set higher than the potential of the first magnetic roller during image formation by the electrostatic latent image carrier, the first magnetic roller to the developer carrier. Negatively charged toner can be supplied. Further, during non-image formation, since the potential of the first magnetic roller is set higher than the potential of the developer carrier, the supply of toner from the first magnetic roller to the developer carrier is stopped. Further, during image formation and non-image formation, the potential of the second magnetic roller is set higher than the potential of the holding portion of the developer carrier, so that excess toner on the developer carrier is Recovered to magnetic roller. Accordingly, the toner is supplied onto the developer carrying member only at the time of image formation, and at the time of non-image formation, the supply of toner to the developer carrying member is stopped and the toner on the developer carrying member is collected. Thereby, the toner can be supplied onto the developing carrier only at a necessary timing, and the scattering of the toner from the developer carrier can be surely suppressed.

  The potential adjusting unit may be configured to set the potential of the first magnetic roller to be equal to or higher than the potential of the second magnetic roller during the image formation and the non-image formation. According to such a configuration, since the potential of the first magnetic roller is equal to or higher than the potential of the second magnetic roller, the toner supplied from the first magnetic roller is directly sent to the developing carrier without being sent to the developing carrier. Can be prevented from being sent to the magnetic roller.

  Further, the first magnetic roller is disposed downstream of the second magnetic roller with respect to the rotation direction of the developer carrier, and the outer diameter of the first magnetic roller is the second magnetic roller. It may be larger than the outer diameter of the magnetic roller. According to this configuration, since the outer diameter of the first magnetic roller can be increased to increase the magnetic force, it is possible to reliably prevent the carrier from being sent to the downstream side of the first magnetic roller. This makes it possible to suppress print deterioration due to the carrier adhering to the electrostatic latent image carrier. In addition, since the diameter of the second magnetic roller can be minimized, the image forming apparatus can be reduced in size and the manufacturing cost can be reduced.

  The distance between the developer carrier and the first magnetic roller is equal to or greater than the distance between the first magnetic roller and the second magnetic roller, and the developer carrier and the second magnetic roller. May be greater than or equal to the distance between the first magnetic roller and the second magnetic roller. According to such a configuration, when the potential is adjusted by the first and second potential adjusting means, the voltage leaks between the first magnetic roller and the second magnetic roller, and the first magnetic roller and the first magnetic roller The toner can be prevented from moving between the two magnetic rollers. Therefore, it is possible to prevent the toner from moving to an unnecessary area and causing contamination in the apparatus.

  Further, an entry preventing member that prevents entry of toner or carrier between the first magnetic roller and the second magnetic roller is provided between the first magnetic roller and the second magnetic roller. It may be provided. According to such a configuration, it is possible to prevent the toner and carrier from entering the space between the first magnetic roller and the second magnetic roller, and development ghosts due to the toner and carrier entering, or printing deterioration can be prevented. It becomes possible to deter.

  In order to solve the above problems, according to another aspect of the present invention, an electrostatic latent image carrier that forms an image on a medium by transferring toner supplied according to an electrostatic latent image; A developer carrier that supplies toner to the electrostatic latent image carrier, a first magnetic roller that holds a two-component developer composed of toner and carrier, and supplies toner to the developer carrier; and the development A second magnetic roller for holding the toner collected from the agent carrier, and the potential of the developer carrier is set higher than the potential of the first magnetic roller, and the potential of the second magnetic roller is set to the development. A potential adjusting unit that sets the potential higher than the potential of the developer carrier, and the first magnetic roller is disposed downstream of the second magnetic roller with respect to the rotation direction of the developer carrier. The outer diameter of the first magnetic roller is Image forming apparatus is provided which is equal to or greater than the outer diameter of the magnetic roller.

  According to the above configuration, since the potential of the developer carrier is set higher than the potential of the first magnetic roller, negatively charged toner is supplied from the first magnetic roller to the developer carrier, and the second Since the potential of the magnetic roller is set to be higher than the potential of the developer carrier, excess toner on the developer carrier is collected by the second magnetic roller. Since the outer diameter of the first magnetic roller is greater than or equal to the outer diameter of the second magnetic roller, the magnetic force of the first magnetic roller can be increased, and the carrier is provided downstream of the first magnetic roller. Can be reliably suppressed, and printing deterioration due to the carrier adhering to the electrostatic latent image carrier can be suppressed. In addition, since the diameter of the second magnetic roller can be minimized, the image forming apparatus can be reduced in size and the manufacturing cost can be reduced.

  In order to solve the above problems, according to another aspect of the present invention, an electrostatic latent image carrier that forms an image on a medium by transferring toner supplied according to an electrostatic latent image; A developer carrier that supplies toner to the electrostatic latent image carrier, a first magnetic roller that holds a two-component developer composed of toner and carrier, and supplies toner to the developer carrier; and the development A second magnetic roller for holding the toner collected from the agent carrier, and the potential of the developer carrier is set higher than the potential of the first magnetic roller, and the potential of the second magnetic roller is set to the development. A potential adjusting unit that is set to be higher than the potential of the agent carrier, and the distance between the developer carrier and the first magnetic roller is the distance between the first magnetic roller and the second magnetic roller. That is the above, the developer carrier and the second carrier The distance between the gas rollers image forming apparatus is provided at least a distance between the second magnetic roller and the first magnetic roller.

  According to the above configuration, since the potential of the developer carrier is set higher than the potential of the first magnetic roller, negatively charged toner is supplied from the first magnetic roller to the developer carrier, and the second Since the potential of the magnetic roller is set to be higher than the potential of the developer carrier, excess toner on the developer carrier is collected by the second magnetic roller. The distance between the developer carrier and the first magnetic roller is greater than or equal to the distance between the first magnetic roller and the second magnetic roller, and the distance between the developer carrier and the second magnetic roller is the first. Since the distance between the first magnetic roller and the second magnetic roller is equal to or greater than the distance between the first magnetic roller and the second magnetic roller, a voltage leaks between the first magnetic roller and the second magnetic roller when the potential is adjusted by the potential adjusting means. It is possible to prevent the toner from moving between the first magnetic roller and the second magnetic roller. Therefore, it is possible to prevent the toner from moving to an unnecessary area and causing contamination in the apparatus.

  In order to solve the above problems, according to another aspect of the present invention, an electrostatic latent image carrier that forms an image on a medium by transferring toner supplied according to an electrostatic latent image; A developer carrier that supplies toner to the electrostatic latent image carrier, a first magnetic roller that holds a two-component developer composed of toner and carrier, and supplies toner to the developer carrier; and the development A second magnetic roller for holding the toner collected from the agent carrier, and the potential of the developer carrier is set higher than the potential of the first magnetic roller, and the potential of the second magnetic roller is set to the development. A potential adjustment unit that sets the potential higher than the potential of the agent carrier, and the first magnetic roller and the second magnetic roller between the first magnetic roller and the second magnetic roller, To prevent toner or carrier from entering between Image forming apparatus entrance block member is provided is provided.

  According to the above configuration, since the potential of the developer carrier is set higher than the potential of the first magnetic roller, negatively charged toner is supplied from the first magnetic roller to the developer carrier, and the second Since the potential of the magnetic roller is set to be higher than the potential of the developer carrier, excess toner on the developer carrier is collected by the second magnetic roller. In addition, since an entry preventing member that prevents the toner or carrier from entering between the first magnetic roller and the second magnetic roller is provided, a space between the first magnetic roller and the second magnetic roller is provided. Intrusion of toner and carrier can be suppressed, and development ghosting can be suppressed.

  In order to solve the above problems, according to another aspect of the present invention, an electrostatic latent image carrier that forms an image on a medium by transferring toner supplied according to an electrostatic latent image; And a developer carrying member for supplying toner to the electrostatic latent image carrying member, wherein the potential of the developer carrying member is formed during image formation by the electrostatic latent image carrying member. Setting the potential higher than the potential of the first magnetic roller for supplying toner to the developing carrier, and setting the potential of the first magnetic roller higher than the potential of the developer carrier during non-image formation. And a step of setting a potential of a second magnetic roller that holds toner collected from the developer carrying member higher than a potential of the developer carrying member during the image formation and the non-image formation, For controlling image forming apparatus equipped with There is provided.

  According to the above configuration, since the potential of the developer carrier is set higher than the potential of the first magnetic roller during image formation by the electrostatic latent image carrier, the first magnetic roller to the developer carrier. Negatively charged toner can be supplied. Further, during non-image formation, since the potential of the first magnetic roller is set higher than the potential of the developer carrier, the supply of toner from the first magnetic roller to the developer carrier is stopped. In addition, the potential of the second magnetic roller is set higher than the potential of the holding portion of the developer carrying member during both image formation and non-image formation, so that excess toner on the developer carrying member Recovered to the second magnetic roller. Therefore, the toner can be supplied onto the developer carrying member only during image formation, and the toner on the developer carrying member can be recovered during non-image formation. Thereby, it is possible to reliably prevent the toner from scattering from the developer carrying member.

  According to the present invention, it is possible to provide an image forming apparatus and a control method for the image forming apparatus that can suppress scattering of toner and carrier in the apparatus.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

(First embodiment)
First, a first embodiment of the present invention will be described. FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus 10 according to the first embodiment.

  The image forming apparatus 10 according to the present embodiment scans and exposes a photosensitive drum 14 with a laser beam 12 modulated according to an image signal, and performs printing on a printing medium 15 such as paper or a plastic sheet by a dry electrophotographic method. Is what you do. The image forming apparatus 10 can be used as a laser printer, a laser fax, a digital copying machine, or a part thereof.

The image forming apparatus 10 performs printing or the like using a two-component developer composed of toner and carrier, and functions as a high-speed printing machine capable of printing at a speed of about 60 ppm (pages / minute) on A4 paper, for example. To do.

  The image forming apparatus 10 includes a laser exposure unit (not shown) that emits a laser beam 12. The laser exposure unit scans the laser beam 12 focused on a minute spot in a fixed direction on a straight line parallel to the rotation axis of the photosensitive drum 14 at the exposure position A on the photosensitive drum 14. In the following description, when expressing the relative position on the rotating body such as the photosensitive drum 14 and the developing roller 16, the rotation direction side is referred to as the downstream side, and the counter rotation direction side is referred to as the upstream side. When the laser beam 12 is scanned on the surface of the photosensitive drum 14, the exposed portion of the photosensitive drum 14 becomes a positive potential relative to the non-exposed portion.

  A developing roller 16 is disposed on the downstream side of the exposure position A on the photosensitive drum 14. A developing unit 18 is disposed adjacent to the developing roller 16. In the developing unit 18, a two-component developer composed of toner and carrier is stored. The toner in the developing unit 18 is supplied to the surface of the developing roller 16 by the supply roller 24 in the developing unit 18 and is supplied to the surface of the photosensitive drum.

  In the developing unit 18, a two-component developer T composed of powder toner having a predetermined color and a metal powder carrier is stored. The toner contains polyester particles having a diameter of about 7 to 8 μm and pigments, CCA, PMMA and the like. Further, the carrier is obtained by applying a silicon coating to ferrite particles having a diameter of about 35 to 60 nm.

  The developing unit 18 is provided with a magnetic permeability sensor (not shown), and the toner is supplied to the developing unit 18 so that the weight percentage of the toner with respect to the total weight of the two-component developer T is 6 to 10%. The amount is adjusted. In the developing unit 18, a stirrer 20 and a stirrer 22 are provided to stir the toner and the carrier.

  In the developing unit 18, a supply roller 24 and a collection roller 30 are provided at positions close to the developing roller 16. FIG. 2 is a schematic view showing the vicinity of the supply roller 24 and the collection roller 30 in detail. Both the supply roller 24 and the collection roller 30 are composed of magnet rollers. That is, the supply roller 24 includes a magnet body 26 that is fixed in a non-rotating state, and a sleeve 28 that is provided around the magnet body 26 and that is driven to rotate in the direction of the arrow. The collection roller 30 includes a magnet body 32 that is fixed in a non-rotating state and a sleeve 34 that is provided around the magnet body 32 and that is driven to rotate in the direction of the arrow.

  As shown in FIG. 2, a plurality of magnetic poles (S 1, N 1, S 2) are formed in the rotation direction on the outer periphery of the magnet body 26 of the supply roller 24. A plurality of magnetic poles (S1, N1) are formed in the rotation direction on the outer periphery of the magnet body 32 of the recovery roller 30.

  When the two-component developer T is stirred in the developing unit 18, the toner is negatively charged and the carrier is positively charged. At this time, the charge amount of the toner is, for example, about −25 to −15 [μC / g]. Thereby, the negatively charged toner adheres to the surface of the positively charged carrier. At this time, if the weight percentage of the toner stored in the developing unit 18 is about 6 to 10%, the toner adheres to about 60 to 80% of the surface area of the carrier.

  The carrier to which the toner is attached is sent to the vicinity of the supply roller 24 by the rotation of the stirrer 22. Then, the carrier to which the toner adheres adheres to the sleeve 28 of the supply roller 24 by the magnetic force of the magnet body 26 of the supply roller 24. As a result, the carrier adheres in layers to the sleeve 28 of the supply roller 24, and a so-called magnetic brush is formed by the carrier layer.

   The sleeve 28 of the supply roller 24 and the sleeve 34 of the collection roller 30 rotate in the arrow direction shown in FIGS. The carrier attached on the sleeve 28 of the supply roller 24 is sent to the developing roller 16 side by the rotation of the sleeve 24.

   As shown in FIG. 1, the developing roller 16, the supply roller 24, and the collection roller 30 are connected to a potential adjustment unit 31. The potential adjusting unit 31 can adjust the potentials of the developing roller 16, the supply roller 24, and the collection roller 30.

   FIG. 3 is a schematic diagram illustrating how the potentials of the developing roller 16, the supply roller 24, and the collection roller 30 are adjusted by the potential adjusting unit 31. Here, FIG. 3A shows the potential of each roller during image formation, and FIG. 3B shows the potential of each roller during image non-formation.

   3A and 3B, V0 and V1 indicate the potential of the photosensitive drum, V1 indicates the potential of the portion exposed by the laser beam 12, and V0 indicates the potential of the non-exposed portion. Yes. Vsp represents the potential of the sleeve 26 of the supply roller 24, Vmid represents the potential of the developing roller 16, and Vwi represents the potential of the sleeve 34 of the collection roller 30.

   In the present embodiment, a predetermined gap is provided between the surface of the developing roller 16 and the surface of the photosensitive drum 14, and the toner on the developing roller 16 is provided by applying a high-frequency voltage to the developing roller 16. The toner is caused to fly to the photosensitive drum 14 side to adhere toner to the exposed portion of the photosensitive drum 14. Vmid shown in FIG. 3 indicates a direct current component of the potential of the developing roller 16.

   In the examples of FIGS. 3A and 3B, the values of V0, V1, Vmid, and Vwi are the same values both during image formation and during non-image formation. On the other hand, the value of Vsp is different between image formation and non-image formation. As described above, in this embodiment, by supplying different potentials during image formation and non-image formation, the toner is appropriately supplied to the developing roller 16 and the toner is recovered from the developing roller 16. Yes.

   First, a case where toner is supplied to the developing roller 16 during image formation will be described. As shown in FIG. 3A, at the time of image formation, the potential of the developing roller 16 is set higher than the potential of the supply roller 24, and Vsp = −500 [V] and Vmid = −350 [V].

   As described above, the carrier attached to the sleeve 28 of the supply roller 24 together with the toner is sent to the developing roller 16 side by the rotation of the sleeve 28. When the toner and the carrier approach the developing roller 16, the potential of the developing roller 16 (−350 [V]) is higher than the potential of the sleeve 28 (−500 [V]). Separate and adhere to the surface of the developing roller. On the other hand, the carrier continues to adhere to the sleeve 28 by the magnetic force of the magnet body 26. In this way, by making the potential Vmid of the developing roller 16 higher than the potential Vsp of the supply roller 24, the toner can be reliably supplied to the surface of the developing roller 16.

   1 and 2, the photosensitive drum 14 and the developing roller 16 rotate in the direction of the arrow. The toner attached on the developing roller 16 is supplied to the photosensitive drum 14 side as the developing roller 16 rotates. In the photosensitive drum 14, the potential V1 of the portion exposed by the laser beam 12 is set to −50 [V], which is higher than the potential Vmid (= −350 [V]) of the developing roller 16, and therefore adheres to the developing roller 16. Among the toners, the toner corresponding to the exposed portion of the photosensitive drum 14 flies and adheres to the exposed portion on the photosensitive drum 14. Accordingly, when the photosensitive drum 14 that has been supplied with toner in the exposed portion comes into contact with the print medium 15, printing corresponding to the exposed portion can be performed.

   On the developing roller 16, toner attached at a position corresponding to the exposed portion is supplied onto the photosensitive drum 14, so that toner at a portion corresponding to the non-exposed portion of the photosensitive drum 14 remains on the developing roller 16. To do. The remaining toner is sent to the collection roller 30 side as the developing roller 16 rotates.

  On the other hand, after the toner is supplied from the supply roller 24 to the developing roller 16, the carrier remaining on the sleeve 28 of the supply roller 24 is sent to the collection roller 30 side as the sleeve 28 rotates. Here, as shown in FIGS. 1 and 2, in the direction along the outer periphery of the developing roller 16, the S1 pole of the magnet body 32 is formed at a position facing the N1 pole of the magnet body 26. A magnetic field is generated in the direction connecting the N1 pole of the magnet and the S1 pole of the magnet body 32.

  Therefore, the carrier remaining on the sleeve 28 of the supply roller 24 approaches the sleeve 34 side as the sleeve 28 rotates, and flies over the magnetic field connecting the N1 pole of the magnet body 26 and the S1 pole of the magnet body 32. Sent onto the sleeve 34.

  On the other hand, in the magnet body 26 of the supply roller 24, the N2 pole is formed on the downstream side in the rotation direction of the sleeve 28 with respect to the N1 pole. Further, the N1 pole of the magnet body 32 is formed at a position facing the magnet body 26N2 pole. For this reason, a repulsive magnetic field is generated between the N1 pole and N2 pole of the magnet body 26, and a repelling magnetic field is also generated between the N2 pole of the magnet body 26 and the N1 pole of the magnet body 32.

  For this reason, the carrier adhering to the sleeve 28 can be prevented from entering these repulsive magnetic field regions. Therefore, the carrier adhering to the sleeve 28 is reliably sent onto the sleeve 34 without being sent to the stirrer 22 side.

  After the toner is supplied to the photosensitive drum 14, the toner remaining on the developing roller 16 is sent to the collection roller 30 side as the developing roller 16 rotates. Here, as shown in FIG. 3A, the potential of the sleeve 34 is 0 [V], and the potential of the developing roller 16 is −350 [V]. Accordingly, since the potential of the sleeve 34 is higher than the potential of the developing roller 16, the toner that remains on the developing roller 16 and is negatively charged moves to the sleeve 34 side having a high potential and is positively charged on the sleeve 34. It adheres to the carrier. At this time, since the toner has not already adhered to the carrier sent from the sleeve 28 to the sleeve 34, the toner on the developing roller 16 reliably adheres to the carrier on the sleeve 34.

  The carrier to which the toner sent from the developing roller 16 adheres on the sleeve 34 moves in the rotation direction as the sleeve 34 rotates. Then, the carrier on the sleeve 34 is detached from the sleeve 34 together with the adhered toner at a rotational position where the magnetic force of the magnet body 32 is weakened, and returned to the developing unit 18. The toner and carrier returned into the developing unit 18 are stirred again and sent to the supply roller 24.

  As described above, at the time of image formation, by setting Vsp> Vmid> Vwi, it is possible to supply the toner from the supply roller 24 to the developing roller 16 and to reliably collect the toner from the developing roller 16 to the collecting roller 30. It becomes.

  In particular, if toner collection from the developing roller 16 becomes insufficient, residual toner passes on the developing roller 16 through the position of the collecting roller 30 and is sent to the supply roller 24 side. In this case, the toner remaining on the developing roller 16 and the toner newly supplied from the supply roller 24 are mixed on the developing roller 16 and the charged state of the toner becomes unstable. The toner is not accurately supplied to the 14 exposed portions, and a development ghost is likely to occur. In this embodiment, since the potential of the collection roller 30 is higher than the potential of the developing roller 16, it is possible to reliably collect the toner remaining on the developing roller 16, and to suppress the development ghost. Can do.

  Next, operations performed during non-image formation will be described. If toner remains on the developing roller 16 during non-image formation, it can be assumed that the toner on the developing roller 16 scatters due to vibration or the like and adheres to or around the photosensitive drum 14. For example, if the toner adheres to the photoconductive drum 14, image irregularities and the like are likely to occur during the next printing. For this reason, during non-image formation, the supply of toner from the supply roller 24 to the development roller 16 is stopped by making the potential of the supply roller 24 higher than the potential of the development roller 16 as shown in FIG. Like to do.

  That is, as shown in FIG. 3B, during non-image formation, the potential Vsp of the sleeve 28 of the supply roller 24 is −200 [V], and the potential Vmid of the developing roller 16 is −350 [V]. Is done. For this reason, even when the toner adhering to the sleeve 28 together with the carrier is sent to the vicinity of the surface of the developing roller 16 by the rotation of the sleeve 28, the negatively charged toner is developed with a lower potential than the sleeve 28. The toner supply from the supply roller 24 to the developing roller 16 is stopped without moving onto the roller 16.

  On the other hand, the potential Vwi of the collection roller 30 is set to 0 [V], and the potentials of the developing roller 16 and the collection roller 30 are maintained at the same setting as in FIG. Therefore, the toner remaining on the developing roller 16 moves to the collecting roller 30 side having a higher potential, and is collected in the developing unit 18 together with the carrier.

  Therefore, all the toner on the developing roller 16 is collected in the developing unit 18 by rotating the developing roller 16, the supply roller 24, and the collecting roller 30 by a predetermined amount with the potential shown in FIG. be able to.

  As described above, at the time of non-image formation, by setting Vmid> Vsp ≧ Vwi, the toner supply from the supply roller 24 to the developing roller 16 can be stopped and the toner can be recovered from the developing roller 16 to the recovery roller 30. It becomes possible, and all the toner on the developing roller 16 can be collected. At this time, by setting Vsp ≧ Vwi, it is possible to suppress the movement of the toner directly from the supply roller 24 toward the collection roller 30, and to prevent the toner supply efficiency to the developing roller 16 from being lowered.

  When a predetermined time elapses while the toner is attached to the developing roller 16, it is assumed that the charge charged in the toner disappears and the toner is scattered from the developing roller 16 to contaminate the inside of the apparatus. In the present embodiment, since all the toner on the developing roller 16 can be collected during non-image formation, it is possible to reliably prevent such contamination.

  Further, it is preferable to supply the toner onto the developing roller 16 in accordance with the timing at which printing or the like is performed on the printing medium 15. For example, when printing is continuously performed on several printing media 15, the toner is supplied onto the developing roller 16 so that the toner is supplied to the exposed portion of the photosensitive drum 14 at the timing when each printing medium 15 contacts the photosensitive drum 14. It is desirable to supply the toner. Therefore, for example, after the contact between the print medium 15 sent first and the photosensitive drum 14 is released, until the next print medium 15 sent comes into contact with the photosensitive drum 14, the photosensitive drum 14. Therefore, it is not necessary to supply toner on the developing roller 16.

  According to the configuration of the present embodiment, the timing of supplying and collecting the toner can be freely controlled by controlling the potential of each roller, so that it corresponds to the timing when printing or the like is performed on the print medium 15. Thus, the toner can be supplied onto the developing roller 16. As a result, the supply of toner onto the developing roller 16 can be minimized, and contamination in the apparatus due to toner scattering from the surface of the developing roller 16 can be reliably suppressed.

  Next, processing performed at the time of image formation and non-image formation will be described based on the timing charts of FIGS. FIG. 4 shows one print mode for printing on one sheet. FIG. 5 shows a two-print mode in which continuous printing is performed on two sheets.

  First, one print mode will be described with reference to FIG. First, at time t1, the main motor is turned on, and driving parts such as the photosensitive drum 14, the developing roller 16, the supply roller 24, and the collection roller 30 are driven.

  At time t2, the charging device for uniformly charging the photosensitive drum 14 is turned on. The charging device includes a charging roller that contacts the photosensitive drum 14. At time t3, the developing roller 16, the supply roller 24, and the collection roller 30 are set to a predetermined potential. Here, Vmid = −350 [V], Vsp = Vs2 = −200 [V], Vwi = Vw2 = 0 [V] are set, and the potential of each roller is set at the time of non-image formation shown in FIG. Set to state. Prior to time t3, the potentials to the developing roller 16, the supply roller 24, and the collection roller 30 are turned off.

  At time t4, exposure to the photosensitive drum 14 is performed by the laser beam 12. At time t5, Vsp = Vs1 = −500 [V] and Vwi = Vw1 [V] are set. Here, Vs2 is set to a potential equal to or lower than Vmid (Vs2 ≦ Vmid). As a result, the magnitude relationship among Vmid, Vsp, and Vwi becomes the same as that shown in FIG. 3A, and the toner is supplied from the supply roller 24 to the developing drum 30 and the toner remaining on the developing drum 14 is removed by the collecting roller 30. Collected. Accordingly, the toner supplied onto the developing drum 14 adheres to the exposed portion of the photosensitive drum 14 and image formation on the print medium 15 is performed.

  At time t6, exposure to the photosensitive drum 14 is completed. At time t7, Vsp = Vs2 = −200 [V] and Vwi = Vw2 = 0 [V] are set, and the potential of each roller is set to the state during non-image formation shown in FIG.

  At time t8, the charging device is turned off. At time t9, the potentials of the developing roller 16, the supply roller 24, and the collection roller 30 are turned off, and at time t10, the main motor is turned off.

  As described above, in the one print mode in which only one sheet is printed, the magnitude-related potential shown in FIG. 3A is set only at the timing of image formation on the sheet, and at the timings before and after that, FIG. The magnitude-related potential shown in B) is set. Therefore, the toner can be supplied onto the developing roller 16 only at the timing of image formation.

  Next, the 2-print mode will be described with reference to FIG. First, at time t11, the main motor is turned on, and driving parts such as the photosensitive drum 14, the developing roller 16, the supply roller 24, and the collection roller 30 are driven.

  At time t12, the charging device for uniformly charging the photosensitive drum 14 is turned on. At time t13, the developing roller 16, the supply roller 24, and the collection roller 30 are set to a predetermined potential. Here, Vmid = −350 [V], Vsp = Vs2 = −200 [V], Vwi = Vw2 = 0 [V] are set, and the potential of each roller is set at the time of non-image formation shown in FIG. Is set to the state. Prior to time t13, the potentials to the developing roller 16, the supply roller 24, and the collection roller 30 are turned off.

  At time t14, exposure to the photosensitive drum 14 is performed by the laser beam 12. At time t15, Vsp = Vs1 = −500 [V] and Vwi = Vw1 [V] are set. Here, Vs2 is set to a potential equal to or lower than Vmid (Vs2 ≦ Vmid). As a result, the magnitude relationship among Vmid, Vsp, and Vwi becomes the same as that shown in FIG. 3A, and the toner is supplied from the supply roller 24 to the developing drum 30 and the toner remaining on the developing drum 14 is removed by the collecting roller 30. To be recovered. Therefore, the toner supplied onto the developing drum 14 adheres to the exposed portion of the photosensitive drum 14 and image formation is performed on the first sheet (print medium 15).

  When the image formation on the first sheet is completed, the exposure to the photosensitive drum 14 ends at time t16. At time t17, Vsp = Vs2 = −200 [V] and Vwi = Vw2 = 0 [V] are set, and the potential of each roller is set to the state during non-image formation shown in FIG.

  At time t18, in order to form an image on the second sheet, the photosensitive drum 14 is exposed by the laser beam 12 (exposure). At time t19, Vsp = Vs1 = −500 [V] and Vwi = Vw1 [V] are set. As a result, the magnitude relationship among Vmid, Vsp, and Vwi becomes the same as that shown in FIG. 3A, and the toner is supplied from the supply roller 24 to the developing drum 30 and the toner remaining on the developing drum 14 is removed by the collecting roller 30. Collected. Therefore, the toner supplied onto the developing drum 14 adheres to the exposed portion of the photosensitive drum 14 and image formation is performed on the first sheet (print medium 15).

  At time t20, the exposure to the photosensitive drum 14 corresponding to the image formation on the second sheet is completed. At time t21, Vsp = Vs2 = −200 [V] and Vwi = Vw2 = 0 [V] are set, and the potential of each roller is set to the state at the time of non-image formation shown in FIG.

  At time t22, the charging device is turned off. At time t23, the potentials of the developing roller 16, the supply roller 24, and the collection roller 30 are turned off, and at time t24, the main motor is turned off.

  As described above, even in the 3-print mode in which only two sheets are printed, the image is formed on each roller during the period from the image formation of the first sheet to the image formation of the second sheet. The magnitude-related potential shown in 3 (B) is set. Therefore, it is possible to supply toner onto the developing roller 16 only at the timing of image formation.

  Next, the magnitude relationship between the diameters of the supply roller 24 and the collection roller 30 will be described with reference to FIG. As shown in FIG. 6, in the present embodiment, a relationship of Ds ≧ Dw is established between the outer diameter Ds of the supply roller 24 and the outer diameter Dw of the collection roller 30.

  Thereby, the volume of the magnet body 26 can be increased compared to the magnet body 32, and the magnetic force of the magnet body 26 can be made stronger than the magnetic force of the magnet body 32. Therefore, the carrier can be reliably attached to the sleeve 28 of the supply roller 24. Therefore, the carrier can be prevented from being separated from the sleeve 28 and adhering to the developing roller 16, and the carrier can be reliably prevented from being supplied onto the photosensitive drum 14 and so-called carrier development. It becomes possible.

  On the other hand, as for the collection roller 30, it is sufficient that the magnet body 32 has a magnetic force that allows the carrier to adhere to the sleeve 34 and restrict the magnetic brush, and the outer diameter Dw may be smaller than the outer diameter Ds. it can. When the magnetic force of the magnet body 32 is minimized, even if the carrier is detached from the sleeve 34, the outer diameter Ds is increased on the downstream side in the rotation direction of the developing roller 16 to strengthen the magnetic force. Since the supply roller 24 having the magnet body 26 is arranged, the carrier detached from the sleeve 34 is attracted to the sleeve 26 of the supply roller 24 and the carrier is further prevented from being sent to the downstream side photosensitive drum 14 side. Is done. Therefore, it is possible to reliably suppress the carrier from being sent to the photosensitive drum 14 and causing the carrier development.

  Therefore, by setting Ds ≧ Dw, it is possible to reliably prevent the carrier from being sent to the downstream side of the supply roller 24, and as a result, printing deterioration due to the carrier adhering to the photosensitive drum 14. Can be suppressed. Further, since the diameter of the collection roller 30 can be minimized, the image forming apparatus 10 can be downsized. Moreover, since the magnetic force of the magnet body 26 and the magnet body 32 can be minimized, the manufacturing cost can be reduced.

Next, based on FIG. 7, the relationship of the mutual gap of the developing roller 16, the supply roller 24, and the collection | recovery roller 30 is demonstrated. As shown in FIG. 7, the gap between the developing roller 16 and the supply roller 24 is Gs-d, the gap between the development roller 16 and the collection roller 30 is Gw-d, and the gap between the supply roller 24 and the collection roller 30 is Assuming Gs-w, in the present embodiment, the following relationship is established.
Gs−w ≧ Gs−d
Gs−w ≧ Gw−d

  That is, the gap Gs-w between the supply roller 24 and the collection roller 30 is greater than or equal to the gap Gs-d between the development roller 16 and the supply roller 24, and the gap Gw− between the development roller 16 and the collection roller 30. d or more. When the potential shown in FIG. 3 is applied to each roller by setting the gap between the supply roller 24 and the collection roller 30 to be greater than the other gap Gs-w, the voltage between the supply roller 24 and the collection roller 30 is a voltage. Can be prevented from leaking and the toner moving between the supply roller 24 and the collection roller 30. Accordingly, it is possible to move the toner only between the supply roller 24 and the developing roller 16 or between the developing roller 16 and the collecting roller 30, and the toner moves to an unnecessary area, causing contamination in the apparatus. Can be prevented.

  Next, a configuration for avoiding the supply of the carrier and the toner to the space between the supply roller 24 and the collection roller 30 will be described with reference to FIG. Between the supply roller 24 and the collection roller 30, a magnetic field due to the N2 pole of the magnet body 26 and a magnetic field due to the N1 pole of the magnet body 32 are generated in the space on the stirrer 22 side. For this reason, when a carrier scatters toward this magnetic field from the stirrer 22 side, it is assumed that the carrier is sent to the vicinity of the developing roller 16. In this case, since the toner adheres to the carrier, the toner is supplied onto the developing roller 16 upstream of the supply roller 24. If toner is further supplied from the supply roller 24 to the developing roller 16 in this state, the charged state of the toner becomes unstable, causing development ghosting.

  In the configuration shown in FIG. 8, the developer intrusion prevention member 36 is provided in the space between the supply roller 24 and the collection roller 30. More specifically, the developer intrusion prevention member 36 is provided at a position corresponding to the repulsive magnetic field between the N2 pole of the magnet body 26 and the N1 pole of the magnet body 32. Thereby, the movement of the toner and the carrier that enter the developing roller 16 through the space between the supply roller 24 and the collection roller 30 from the stirrer 22 side is blocked by the developer intrusion prevention member 36. Accordingly, it is possible to prevent the toner from entering the space between the supply roller 24 and the collection roller 30, and to prevent the development ghost from being generated due to the toner adhering to the development roller 16.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. It is a schematic diagram which shows the vicinity of a supply roller and a collection | recovery roller in detail. It is a schematic diagram which shows a mode that each electric potential of a developing roller, a supply roller, and a collection | recovery roller is adjusted by an electric potential adjustment part. It is a timing chart which shows the process performed at the time of image formation and non-image formation, Comprising: It is a timing chart which shows 1 print mode which prints on one paper. It is a timing chart which shows the process performed at the time of image formation and non-image formation, Comprising: It is a timing chart which shows 2 print mode which performs continuous printing on two paper. It is a schematic diagram which shows the magnitude relationship of the diameter of a supply roller and a collection | recovery roller. It is a schematic diagram which shows the relationship of the mutual gap of a developing roller, a supply roller, and a collection | recovery roller. FIG. 4 is a schematic diagram illustrating a configuration in which a developer intrusion prevention member is provided in a space between a supply roller and a collection roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 14 Photosensitive drum 16 Developing roller 24 Supply roller 30 Recovery roller 31 Potential adjustment part 36 Developer penetration | inhibition prevention member

Claims (9)

An electrostatic latent image carrier that forms an image on a medium by transferring toner supplied according to the electrostatic latent image; and
A developer carrier for supplying toner to the electrostatic latent image carrier;
A first magnetic roller for holding a two-component developer comprising a toner and a carrier and supplying the toner to the development carrier;
A second magnetic roller for holding toner collected from the developer carrier;
A potential adjusting unit that adjusts the potentials of the developing carrier, the first magnetic roller, and the second magnetic roller;
The potential adjustment unit includes:
The potential of the developer carrier is set higher than the potential of the first magnetic roller during image formation by the electrostatic latent image carrier, and the potential of the first magnetic roller is set to the developer carrier during non-image formation. Set higher than the body potential,
An image forming apparatus, wherein the potential of the second magnetic roller is set higher than the potential of the developer carrying member during the image formation and the non-image formation.   2. The image according to claim 1, wherein the potential adjusting unit sets the potential of the first magnetic roller to be equal to or higher than the potential of the second magnetic roller during the image formation and the non-image formation. Forming equipment.   The first magnetic roller is disposed downstream of the second magnetic roller with respect to the rotation direction of the developer carrying member, and the outer diameter of the first magnetic roller is the second magnetic roller. The image forming apparatus according to claim 1, wherein the image forming apparatus has an outer diameter equal to or greater than an outer diameter of the image forming apparatus.   An interval between the developer carrier and the first magnetic roller is equal to or greater than an interval between the first magnetic roller and the second magnetic roller, and the developer carrier and the second magnetic roller The image forming apparatus according to claim 1, wherein the interval is equal to or greater than the interval between the first magnetic roller and the second magnetic roller.   An entry preventing member is provided between the first magnetic roller and the second magnetic roller to prevent the toner or carrier from entering between the first magnetic roller and the second magnetic roller. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. An electrostatic latent image carrier that forms an image on a medium by transferring toner supplied according to the electrostatic latent image; and
A developer carrier for supplying toner to the electrostatic latent image carrier;
A first magnetic roller for holding a two-component developer comprising a toner and a carrier and supplying the toner to the development carrier;
A second magnetic roller for holding toner collected from the developer carrier;
A potential adjusting unit that sets the potential of the developer carrier higher than the potential of the first magnetic roller and sets the potential of the second magnetic roller higher than the potential of the developer carrier. ,
The first magnetic roller is disposed downstream of the second magnetic roller with respect to the rotation direction of the developer carrier, and the outer diameter of the first magnetic roller is the second magnetic roller. An image forming apparatus having an outer diameter equal to or larger than the outer diameter. An electrostatic latent image carrier that forms an image on a medium by transferring toner supplied according to the electrostatic latent image; and
A developer carrier for supplying toner to the electrostatic latent image carrier;
A first magnetic roller for holding a two-component developer comprising a toner and a carrier and supplying the toner to the development carrier;
A second magnetic roller for holding toner collected from the developer carrier;
A potential adjusting unit that sets the potential of the developer carrier higher than the potential of the first magnetic roller and sets the potential of the second magnetic roller higher than the potential of the developer carrier. ,
An interval between the developer carrier and the first magnetic roller is equal to or greater than an interval between the first magnetic roller and the second magnetic roller, and the developer carrier and the second magnetic roller The image forming apparatus, wherein the interval is equal to or greater than the interval between the first magnetic roller and the second magnetic roller. An electrostatic latent image carrier that forms an image on a medium by transferring toner supplied according to the electrostatic latent image; and
A developer carrier for supplying toner to the electrostatic latent image carrier;
A first magnetic roller for holding a two-component developer comprising a toner and a carrier and supplying the toner to the development carrier;
A second magnetic roller for holding toner collected from the developer carrier;
A potential adjusting unit that sets the potential of the developer carrier higher than the potential of the first magnetic roller and sets the potential of the second magnetic roller higher than the potential of the developer carrier. ,
An entry preventing member is provided between the first magnetic roller and the second magnetic roller to prevent entry of toner or carrier between the first magnetic roller and the second magnetic roller. An image forming apparatus. An electrostatic latent image carrier that forms an image on a medium by transferring toner supplied according to the electrostatic latent image; and a developer carrier that supplies toner to the electrostatic latent image carrier. An image forming apparatus control method comprising:
At the time of image formation by the electrostatic latent image carrier, setting the potential of the developer carrier higher than the potential of the first magnetic roller that supplies toner to the developer carrier;
Setting a potential of the first magnetic roller higher than a potential of the developer carrier during non-image formation;
Setting the potential of the second magnetic roller holding the toner collected from the developer carrying member higher than the potential of the developer carrying member during the image formation and the non-image formation;
An image forming apparatus control method comprising:

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