JP2013156280A - Developing device and image forming device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a supply roller for supplying toner to a developing roller from being clogged with the toner.SOLUTION: A developing device includes: a developing roller for supplying one-component developer to a photoreceptor; a supply roller provided in contact with the developing roller to supply toner to the developing roller and removing the toner from the developing roller; a stabilization roller provided in contact with the supply roller to rotate in the same direction with the supply roller; and a first power source that applies a voltage to attract the toner from the supply roller to the stabilization roller, between the stabilization roller and the supply roller.

Description

  The present invention relates to a developing device, and more particularly, to a one-component developing device and an image forming apparatus for developing an electrostatic latent image formed on an electrostatic latent image carrier with toner.

  In an electrophotographic image forming apparatus, the surface of a photoconductor is charged, and an electrostatic latent image is formed by exposing the charged area according to image information, and the electrostatic latent image is developed and visualized (development). ) Is used.

  As such a developing method, there is a one-component developing method in which only a toner is used as a developer without using a carrier. The developing device of the one-component developing system mainly includes a developing roller for supplying toner to a photoconductor, a supply roller made of foam for supplying and removing toner from the developing roller, and a supply roller And a toner layer regulating blade for adding a charge amount while regulating the toner supplied to the developing roller to a predetermined amount.

  When the developing device of the one-component developing system is used for a long period of time, the toner enters the air layer portion of the foam, and the air layer inside the foam is clogged by the entered toner. Both performance and toner stripping performance deteriorate. In such a state, problems such as a ghost appearing in the formed image and an unstable toner charge amount are likely to occur.

  Therefore, a rotating member is disposed in contact with the supply roller and rotated in the forward direction with the supply roller at the contact portion, thereby preventing the supply roller from being clogged with toner and preventing toner deterioration and improving toner circulation. A developing device is known (see, for example, Patent Document 1).

JP 2003-330272 A

  Such a developing device adopts a configuration in which the toner is conveyed in the horizontal direction and in the opposite direction to the developing roller by the supply roller and the rotating member, thereby improving the circulation performance in the horizontally long developing tank. Yes.

However, if this configuration is applied to a vertically long developing tank, there is no space for creating a toner circulation path, and it is impossible to achieve both prevention of clogging of the supply roller and improvement of circulation performance.
The present invention has been made in view of such circumstances, and provides a developing device capable of improving the toner circulation performance while maintaining the performance of the supply roller in a vertically long developing tank.

  The present invention provides a developing roller for supplying a one-component developer to a photosensitive member, a supply roller provided to be in contact with the developing roller, for supplying toner to the developing roller and for peeling the toner from the developing roller, and for contacting the supply roller And a developing device that includes a stabilizing roller that rotates in the same direction as the supply roller, and a first power source that applies a voltage that attracts toner from the supply roller to the stabilizing roller between the stabilization roller and the supply roller. Is to provide.

  According to the present invention, the stabilizing roller is provided so as to contact the supply roller that supplies the toner to the developing roller and peels off the toner, and the voltage is applied between the stabilization roller and the supply roller. Since the toner is attracted from the roller to the stabilizing roller, the supply roller is prevented from being clogged, and good development can be stably performed.

1 is a configuration explanatory view showing an image forming apparatus according to the present invention. FIG. 2 is a configuration explanatory view showing a developing device of the present invention. FIG. 3 is a waveform diagram showing an example of an output waveform of a power supply of the developing device of FIG. 2. FIG. 10 is a configuration explanatory view showing a modification of the developing device shown in FIG. 2.

  The developing device of the present invention includes a developing roller for supplying a one-component developer to the photosensitive member, a supply roller provided in contact with the developing roller, for supplying toner to the developing roller, and for peeling the toner from the developing roller, and supply A stabilizing roller provided in contact with the roller and rotating in the same direction as the supply roller, and a first power source for applying a voltage for attracting toner from the supply roller to the stabilization roller between the stabilization roller and the supply roller. A developing device is provided.

The first power source may apply a positive DC voltage to the stabilizing roller and a negative DC voltage to the supply roller when the toner is charged to a negative polarity.
The first power supply may output a pulsed DC voltage that repeatedly turns on and off at regular intervals.

A toner circulation roller provided above the supply roller, and a second power source that applies a DC voltage between the toner circulation roller and the stabilization roller may be further provided.
The second power source is preferably connected to the toner circulation roller and the stabilization roller with a polarity that allows the charged toner to be drawn toward the toner circulation roller.

  An image forming apparatus according to the present invention includes an exposure unit that forms an electrostatic latent image on a photoreceptor, a developing device that develops the formed electrostatic latent image into a toner image, and a toner image that is transferred to a recording medium and fixed. The image forming apparatus includes a transfer fixing unit, and the developing device is the developing device of the present invention.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIG. 1 is an explanatory diagram showing a configuration of an image forming apparatus according to the present invention.
The image forming apparatus 100 includes four image forming station units 50Y, 50M, 50C, and 50B for a yellow image, a magenta image, a cyan image, and a black image, and is a tandem color image capable of forming a color image. Forming device.

  The image forming apparatus 100 applies a color image or a color image to a sheet as a transfer material (recording medium) based on image data transmitted via a network or image data read by a document reading device such as a scanner. A monochrome image is formed.

  As shown in FIG. 1, the image forming apparatus 100 includes image forming station units 50Y, 50M, 50C, and 50B that form toner images on a sheet, a fixing device 40 that fixes a toner image formed on the sheet, and a sheet. A transport unit 30 having a function of transporting paper from the supply tray 60 to the image forming station units 50Y, 50M, 50C, 50B and the fixing device 40 is provided.

  The image forming station portions 50Y, 50M, 50C, and 50B are arranged in this order from the supply tray 60 side between the supply tray 60 and the fixing device 40.

  These image forming station units 50Y, 50M, 50C, and 50B have substantially the same configuration except for the type of toner. Yellow, magenta, and cyan are based on image data corresponding to each color. , And a black toner image is formed, and finally transferred onto a sheet as a recording medium.

  Note that the reference numerals of the components of the image forming station units 50Y, 50M, 50C, and 50B in FIG. The reference numerals of the component parts are omitted.

  Each of the image forming station units 50Y, 50M, 50C, and 50B includes a photoconductor 51 serving as a latent image carrier on which an electrostatic latent image is formed, and a charging device 52 is provided around the photoconductor 51 in the circumferential direction. An exposure device 53, a developing device 1, a transfer roller 55, and a cleaning device 56 are disposed.

The photoconductor 51 has a cylindrical drum shape having a photosensitive material such as OPC (Organic Photoconductor) on the surface, and is disposed below the exposure device 53. The photoconductor 51 is driven in a predetermined direction by a drive unit and a control unit. It is controlled so as to be rotationally driven (in the direction of arrow F in the figure).
The charging device 52 is a charging means for uniformly charging the surface of the photoconductor 51 to a predetermined potential, and is disposed above the photoconductor 51 and in proximity to the outer peripheral surface thereof.

  The exposure device 53 receives image data corresponding to yellow, magenta, cyan, or black according to each of the image forming station units 50Y, 50M, 50C, and 50B, and thereby electrostatics corresponding to the corresponding color. Each latent image is formed. As the exposure device 53, a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror can be used.

  The developing device 1 has a developing roller 4 that carries a developer. The developing roller 4 is disposed close to the photoconductor 51 so that the developer is conveyed to the photoconductor 51. The developing device 1 is a so-called one-component developing device that uses only toner as a developer, and develops an electrostatic latent image formed on the surface of the photoreceptor 51 by an exposure device 53 to develop a toner image (visible image). Form.

  The developing device 1 contains yellow, magenta, cyan, or black toner according to image formation at each image forming station. These toners are charged with the same polarity as the surface potential of the charged photoreceptor 51. It should be noted that the polarity of the surface potential of the photoconductor 51 and the charging polarity of the toner to be used may be positive or negative, but in this embodiment, it is negative (negative).

The transfer roller 55 transfers the toner image formed on the photosensitive member 51 onto the surface of the paper transported by the transport belt 33. The transfer roller 55 has a polarity opposite to the toner charging polarity (in this embodiment, the normal polarity). (Plus) polarity) bias voltage is applied.
The cleaning device 56 removes and collects the toner remaining on the outer peripheral surface of the photoreceptor 51 after the toner image is transferred onto the paper.

  The conveyance unit 30 includes a drive roller 31, a driven roller 32, and a conveyance belt 33, and conveys a sheet on which toner images of each color are transferred in the image forming station units 50Y, 50M, 50C, and 50B. The transport unit 30 has a configuration in which an endless transport belt 33 is stretched between the driving roller 31 and the driven roller 32 and moves in the direction of arrow Z, and the paper fed from the supply tray 60 is image-formed. Transport to station units 50Y, 50M, 50C, 50B in order.

  The fixing device 40 includes a heating roller 41 and a pressure roller 42, and conveys the paper to a fixing nip portion where these abut, thereby fixing the toner image transferred onto the paper by thermocompression.

  In the image forming apparatus 100 configured as described above, the sheet conveyed by the conveyance unit 30 passes through the position opposed to the photoconductor 51 of the image forming station units 50Y, 50M, 50C, and 50B. The toner images on the photoconductors 51 are sequentially transferred onto the paper by the action of the transfer electric field by the transfer roller 55 disposed below via the conveyor belt 33.

  As a result, the toner images of the respective colors are transferred so as to overlap each other on the same sheet, and a desired full-color toner image is formed on the sheet. The sheet onto which the toner image has been transferred in this way is subjected to a toner image fixing process by the fixing device 40 and then sent to a paper discharge tray (not shown).

FIG. 2 is an explanatory diagram showing a configuration of the developing device 1 provided in each of the image forming station units 50Y, 50M, 50C, and 50B shown in FIG.
The developing roller 4 includes a central shaft, an elastic layer formed by molding around the central shaft, and an outermost coating layer, and is in contact with the photoreceptor 2. The main purpose of the coating layer is to adjust the hardness and work function, and to adjust the charge amount of the toner. Here, a coating mainly made of acrylic resin is used.

  The supply roller 5 is in contact with the developing roller 4 at the nip portion, and is composed of a central shaft metal shaft 5b and a foamed elastic layer 5a made of foamed urethane resin around the center shaft metal shaft 5b. The rotation direction of the developing roller 4 and the supply roller 5 is set opposite to the rotation direction of the photosensitive member 2 (the direction of the arrow F).

  At the contact portion between the developing roller 4 and the supply roller 5, the peripheral speed of the supply roller 5 is set in a range of 0.6 to 1.0 times the peripheral speed of the developing roller 4. A toner regulating blade 9 is provided above the developing roller 4, which is a metal L-shaped blade using a stainless steel plate having a thickness of about 0.1 mm to 0.2 mm. Yes.

  Furthermore, the stabilizing roller 6 is disposed in contact with the supply roller 5 above. The stabilizing roller 6 may be composed of a single stainless steel shaft, or may be composed of a metal shaft such as urethane rubber or urethane foam.

  The stabilizing roller 6 rotates in the same direction as the supply roller 5, and moves in the opposite direction at the contact portion between the two. A first DC power supply 10 is connected between the stabilization roller 6 and the supply roller 5, and a potential difference is provided between the stabilization roller 6 and the supply roller 5.

  Basically, a potential difference in a direction in which the toner easily moves from the supply roller 5 side to the stabilization roller 6 side is provided. In this embodiment, since negatively charged toner is used as described above, a potential on the positive side of the supply roller 5 is applied to the stabilizing roller 6. That is, a DC voltage is applied between the stabilizing roller 6 and the supply roller 5 with the stabilizing roller 6 as a positive electrode. The effect is obtained if the potential difference (voltage) is about 50V.

  The circumferential speed of the stabilizing roller 6 is preferably equal to that of the supply roller 5. When the peripheral speed of the stabilizing roller 6 is slower than that of the supply roller 5, there is a possibility that toner adhering to the stabilizing roller 6 at the contact portion may be collected and scraped off by the supply roller 5 again. When rotating at the same peripheral speed, scraping hardly occurs. In addition, when the stabilizing roller 6 rotates too fast, the movement of the toner, which is powder, is not linked, and it becomes difficult to obtain a circulation effect.

  A toner replenishing unit 7 is provided in the upper part of the developing tank 3, and toner for replenishment is prepared. The toner contained therein falls below the developing tank 3 via the toner replenishing roller 8 and is used for development.

  In the case of such a vertically long developing tank 3, there is almost no space between the supply roller 5 and the side wall 3a. Therefore, in order to improve the circulation of the toner, it is necessary to circulate the toner upward along the side wall 3a. is there.

  When a potential on the positive side of the supply roller 5 is applied to the stabilization roller 6, the toner contained in the foamed elastic layer 5 a of the supply roller 5 can be drawn toward the stabilization roller 6. When the stabilizing roller 6 moves in the reverse rotation direction at the contact portion with the supply roller 5, the toner attracted to the stabilization roller 6 from the foamed elastic layer 5 a of the supply roller 5 rotates in the rotation direction of the stabilization roller 6. It moves downstream and is pulled away from the supply roller 5.

  Since the separated toner has adhesion with peripheral toner, the toner moves upward along the side wall 3a as indicated by the arrow 12 as the stabilizing roller 6 rotates.

  The toner that has moved upward along the side wall 3 a reaches the upper part while being mixed with the peripheral toner, and falls in front of the blade 9 along the rotation direction of the stabilizing roller 6. By such movement, the toner near the developing roller 4 is agitated.

  If not stirred, only the toner around the supply roller 5 is supplied to the developing roller 4, and the toner peeled off by the supply roller 5 is supplied again to the developing roller 4. Charge reduction and toner fusion to the blade are likely to occur.

  However, since the whole toner is mixed by stirring and only the specific toner circulates, the entire toner can be circulated, so that the toner charge reduction and toner fusion can be suppressed.

  When only specific toner is used, a difference in toner on the developing roller 4 is likely to occur between when the toner is consumed and when it is not consumed, so that a development history (ghost) is likely to occur. By stabilizing the surface of the supply roller 5 by the stabilizing roller 6 and improving the circulation, the change of the toner layer on the developing roller 4 can be suppressed, and the development history can be suppressed.

  Further, the toner of the supply roller 5 is attracted toward the stabilizing roller 6, so that the toner can be prevented from entering the supply roller 5, and the toner is hardened inside the supply roller 5. Can be prevented.

  FIG. 3 shows voltage waveforms when a DC voltage is intermittently output from the first power supply 10 in the developing device 1 shown in FIG. This waveform is a pulse waveform having a peak value V that repeats an on time (t1) and an off time (t2) with a period T. That is, the voltage V is intermittently applied between the stabilizing roller 6 and the supply roller 5 with a period T.

  The period T is set to a time for approximately two rotations of the stabilizing roller 6. By doing so, the stabilizing roller 6 makes one round during the time t1 during which the voltage is applied, and makes one round while the toner is strongly attracted to the stabilizing roller 6. In this state, the toner falls in front of the toner regulating blade 9 by entering a period t2 when the voltage is turned off.

  Since the toner on the side of the side wall 14 is moving upward when the voltage is turned off, the toner does not immediately fall down and still rises up. Therefore, the toner can be surely dropped into the toner regulating blade 9 while the circulation flow remains unchanged.

  In FIG. 3, the potential during the period t2 is set to zero. However, a positive potential may be left, or conversely, a negative potential may be applied.

FIG. 4 is an explanatory diagram showing a modification of the developing device shown in FIG.
The developing device 1 a shown in FIG. 4 further includes a toner circulation roller 13 above the stabilizing roller 6. The other structure is the same as that of FIG. The toner circulation roller 13 may have a screw configuration or a paddle configuration.

  The entire toner circulation roller 13 may be conductive, or only the shaft may be a conductive member, and the blade portion of the screw or paddle may be non-conductive resin.

  A voltage is applied between the toner circulation roller 13 and the stabilization roller 6 in the direction in which the toner moves from the stabilization roller 6 toward the toner circulation roller 13 by the second DC power supply 14. That is, when the toner is negatively charged, the positive polarity is connected to the toner circulation roller 13.

  According to this configuration, the toner on the supply roller 5 is peeled off by the stabilization roller 6 and moved upward along the side wall 3 a, and further upward due to the potential difference between the toner circulation roller 13 and the stabilization roller 6. Move the toner.

  The toner moving direction is rotated by the rotation of the toner circulation roller 13, and then the toner is dropped before the toner regulating blade 9. Therefore, more effective circulation performance can be obtained with this configuration.

DESCRIPTION OF SYMBOLS 1, 1a Developing device 2 Photoconductor 3 Developing tank 3a Side wall 4 Developing roller 5 Supply roller 5a Foam elastic layer 5b Metal shaft 6 Stabilizing roller 7 Toner replenishing portion 8 Toner replenishing roller 9 Toner regulating blade 10 First DC power supply 12 Arrow 13 Toner circulation roller 14 Second DC power supply

Claims (6)

  A developing roller that supplies a one-component developer to the photosensitive member, a supply roller that is provided in contact with the developing roller, supplies toner to the developing roller, and peels off the toner from the developing roller, and is provided in contact with the supply roller A developing device comprising: a stabilizing roller that rotates in the same direction as the supply roller; and a first power source that applies a voltage that attracts toner from the supply roller to the stabilization roller between the stabilization roller and the supply roller.   The developing device according to claim 1, wherein the first power source applies a positive DC voltage to the stabilizing roller and a negative DC voltage to the supply roller when the toner is charged to a negative polarity.   The developing device according to claim 1, wherein the first power source outputs a pulsed DC voltage that repeatedly turns on and off at a constant cycle.   The development according to claim 1, further comprising: a toner circulation roller provided above the supply roller; and a second power source that applies a DC voltage between the toner circulation roller and the stabilization roller. apparatus.   The developing device according to claim 4, wherein the second power source is connected to the toner circulation roller and the stabilization roller with a polarity such that the charged toner is attracted toward the toner circulation roller.   An exposure unit that forms an electrostatic latent image on a photoreceptor; a developing device that develops the formed electrostatic latent image into a toner image; and a transfer fixing unit that transfers and fixes the toner image onto a recording medium. An image forming apparatus, wherein the apparatus is the developing apparatus according to claim 1.