JP2011013248A - Developing apparatus and image forming apparatus equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing apparatus and an image forming apparatus equipped with the developing apparatus which can always form a stable toner layer on a developing roller by efficiently recovering toner accumulated on a downstream side face of an ear-breaking blade.SOLUTION: A magnetic roller side magnetic pole 22b in a magnetic roller 22 is rotated counterclockwise by a predetermined amount when not forming an image. A carrier pole 37 of the same polarity thereby faces a developing roller side magnetic pole 23b to generate a repulsive magnetic field at the facing parts of the magnetic roller 22 and developing roller 23. As a result, the movement of a developer at the facing parts of the magnetic roller 22 and developing roller 23 is regulated, and a developer reservoir 45 is formed between the ear-breaking blade 25 and the facing parts of the magnetic roller 22 and developing roller 23.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device mounted on an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and an image forming apparatus including the developing device, and in particular, uses a two-component developer composed of a magnetic carrier and toner, and carries a toner. The present invention relates to a developing device that develops an electrostatic latent image on an image carrier while holding only toner charged on the body.

  Conventionally, as a developing method using dry toner in an image forming apparatus using an electrophotographic process, a one-component developing method using no carrier and a non-magnetic toner using a magnetic carrier (hereinafter also simply referred to as a carrier) are used. There is known a two-component developing system that uses a two-component developer to be charged and develops an electrostatic latent image on a photosensitive member with a magnetic brush composed of toner and a carrier formed on a developing roller.

  The one-component development method is suitable for high image quality because the electrostatic latent image on the image carrier is not disturbed by the magnetic brush, but toner adheres to the regulating blade, resulting in non-uniform layer formation. It sometimes caused image defects.

  In the case of color printing in which color superposition is performed, since the color toner is required to be transparent, it needs to be a non-magnetic toner. Therefore, in a full-color image forming apparatus, a two-component development system in which toner is charged and conveyed using a carrier is often employed. However, the two-component development method can maintain a stable charge amount for a long time and is suitable for extending the life of the toner, but is disadvantageous in terms of image quality due to the influence of the magnetic brush described above.

  As one means for solving these problems, a magnetic roller (toner supply member) is used to transfer the developer onto a developing roller (toner carrier) installed in a non-contact manner with respect to the photoreceptor (image carrier). When developing, a non-magnetic toner is transferred onto the developing roller while leaving the magnetic carrier on the magnetic roller to form a thin toner layer, and the toner is attached to the electrostatic latent image on the photosensitive member by an alternating electric field. A scheme has been proposed.

  In the case of the above developing method, since a pressure is applied when the developer passes through the pan blade that regulates the developer layer on the magnetic roller, toner agglomerates may be generated. There is a problem that streaky white spots occur in an image due to clogging between rollers.

  In addition, the toner is transferred from the magnetic roller to the developing roller at a portion where the magnetic roller and the developing roller are opposed to each other. In this case, the toner separated from the magnetic brush is likely to be scattered, and the scattered toner is deposited on the spike cutting blade.

  In particular, in a developing device having a configuration in which the blade cutting blade is disposed substantially horizontally and the magnetic roller is positioned below the developing roller, when the toner accumulated on the blade falls on the magnetic roller, the toner that is not stirred with the carrier Moves to the developing roller side, which may affect the toner layer on the developing roller. Further, when toner accumulation on the blade becomes significant, the accumulated toner comes into contact with the developing roller and disturbs the toner layer on the developing roller.

  Patent Document 1 discloses a method of rotating the developing sleeve reversely as a method of removing toner aggregates clogged in the gap between the doctor blade and the developing sleeve.

Japanese Patent Laid-Open No. 3-103882

  When the method of Patent Document 1 is applied to the above-described developing method using a magnetic roller and a developing roller, the toner deposited on the spike cutting blade can be recovered to some extent. However, since the toner collection efficiency is not sufficient, the toner layer on the developing roller due to the scattered toner cannot be completely prevented.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a developing device capable of always forming a stable toner layer on a developing roller by efficiently recovering toner deposited on a pan blade, and an image forming apparatus including the developing device. The purpose is to do.

  In order to achieve the above object, the present invention uses a two-component developer containing at least a carrier and a toner, a developing roller disposed opposite to the image carrier, a magnetic roller disposed opposite to the developing roller, A magnetic or non-magnetic ear cutting blade disposed opposite to the upstream side of the developing roller with respect to the rotation direction of the magnetic roller, a main pole disposed inside the magnetic roller and facing the developing roller, and the ear cutting A magnetic roller side magnetic pole having a plurality of magnetic poles including a regulating pole facing the blade, and a developing roller side magnetic pole arranged opposite to the magnetic roller inside the developing roller and having a different polarity from the main pole, In a developing device that develops an electrostatic latent image on an image carrier by supplying toner to the developing roller using a magnetic brush formed on a magnetic roller, during non-image formation At least one of the magnetic roller side magnetic pole and the development roller side magnetic pole is moved so that a developer pool is generated between the developing roller and the facing portion of the magnetic roller and the spike cutting blade. .

  According to the present invention, in the developing device configured as described above, the magnetic roller side magnetic pole is rotated so that the magnetic pole having the same polarity faces the developing roller side magnetic pole.

  According to the present invention, in the developing device having the above-described configuration, the magnetic roller side magnetic pole includes a pumping pole having a polarity different from that of the regulation pole positioned upstream of the regulation pole with respect to the rotation direction of the magnetic roller, and the main pole. The magnetic roller side magnetic pole has a main pole located on the downstream side and a transport pole of different polarity, and the magnetic roller side magnetic pole is rotated so that the transport pole faces the developing roller side magnetic pole.

  According to the present invention, in the developing device configured as described above, the magnetic pole on the developing roller side is rotationally moved toward the blade cutting blade.

  According to the present invention, in the developing device configured as described above, the magnetic pole of the developing roller side is rotated and the magnetic roller is rotated in the reverse direction.

  In the developing device having the above-described configuration, the reverse rotation speed of the magnetic roller is slower than the rotation speed of the magnetic roller during image formation.

  According to the present invention, in the developing device configured as described above, the magnetic roller is disposed below the developing roller.

  The present invention also provides an image forming apparatus equipped with the developing device having the above-described configuration.

  According to the first configuration of the present invention, the panning blade using the developer pool generated between the developing roller and the facing portion of the magnetic roller and the panning blade due to the movement of the magnetic roller side magnetic pole or the developing roller side magnetic pole. By efficiently collecting the toner deposited thereon, a stable toner thin layer can always be formed on the developing roller.

  Further, according to the second configuration of the present invention, in the developing device of the first configuration, the magnetic roller side magnetic pole is rotated and moved so that the magnetic pole of the same polarity faces the magnetic pole of the developing roller. Since a repelling magnetic field is generated between the roller and the magnetic roller to restrict the passage of the developer, a developer reservoir can be easily formed between the developing roller and the facing portion of the magnetic roller and the spike cutting blade. Can do.

  According to the third configuration of the present invention, in the developing device of the second configuration, the magnetic roller side magnetic pole has a polarity different from that of the regulation pole located upstream of the regulation pole with respect to the rotation direction of the magnetic roller. It has regulation by rotating the magnetic roller side magnetic pole so that the conveyance pole is opposed to the developing roller side magnetic pole. Since the pole is disposed at the position of the original pumping pole, the developer pumping force onto the magnetic roller does not decrease. Therefore, a sufficient developer pool can be formed between the facing portion of the developing roller and the magnetic roller and the spike cutting blade.

  Further, according to the fourth configuration of the present invention, in the developing device of the first configuration, by rotating the developing roller side magnetic pole to the panning blade side, the direction of the magnetic force lines near the panning blade downstream side is changed. Therefore, the developer pool can be easily formed between the facing portion of the developing roller and the magnetic roller and the spike cutting blade.

  Further, according to the fifth configuration of the present invention, in the developing device of the fourth configuration, the developer pool moving with the magnetic roller is spiked by moving the magnetic pole of the developing roller and rotating the magnetic roller in the reverse direction. Since it is pressed against the downstream side surface of the cutting blade, the toner on the cutting blade can be collected more effectively.

  According to the sixth configuration of the present invention, in the developing device of the fifth configuration, the reverse rotation speed of the magnetic roller is made slower than the rotation speed at the time of image formation, thereby generating the rotation of the magnetic roller. Toner scattering efficiency due to wind pressure can be prevented and toner recovery efficiency can be increased.

  Further, according to the seventh configuration of the present invention, in the developing device having any one of the first to sixth configurations, the magnetic roller on which toner easily accumulates is located below the developing roller. Therefore, it is possible to efficiently collect the accumulated toner and prevent the accumulated toner from dropping onto the magnetic roller.

  Further, according to the eighth configuration of the present invention, by mounting the developing device of any one of the first to seventh configurations, the toner thin layer on the developing roller by the toner accumulated on the pan blade is formed. Thus, the image forming apparatus can obtain a good image over a long period of time without causing any disturbance.

1 is a schematic diagram showing the overall configuration of an image forming apparatus equipped with a developing device of the present invention. Side surface sectional drawing which shows the structure of the image development apparatus concerning 1st Embodiment of this invention. The figure which shows an example of the bias waveform applied to a developing roller and a magnetic roller Schematic diagram showing the state where toner has accumulated on the spike cutting blade In the developing device of the first embodiment, a schematic diagram showing how the toner accumulated on the spike blade is removed by rotating the magnetic pole in the magnetic roller. In the developing device of 2nd Embodiment, the schematic which shows a mode that the magnetic pole in a developing roller is rotated, and the toner deposited on the spike cutting blade is removed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of an image forming apparatus equipped with the developing device of the present invention. Here, a tandem color image forming apparatus is shown. In the main body of the color image forming apparatus 100, four image forming portions Pa, Pb, Pc, and Pd are sequentially arranged from the upstream side in the transport direction (the right side in FIG. 1). These image forming portions Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow, and black), and cyan, magenta, and yellow are respectively performed by charging, exposure, development, and transfer processes. And a black image are sequentially formed.

  The image forming portions Pa to Pd are provided with photosensitive drums 1a, 1b, 1c, and 1d that carry visible images (toner images) of the respective colors, and are further driven by a driving unit (not shown). The intermediate transfer belt 8 that rotates clockwise is provided adjacent to the image forming portions Pa to Pd. The toner images formed on the photosensitive drums 1a to 1d are sequentially transferred onto the intermediate transfer belt 8 that moves while being in contact with the photosensitive drums 1a to 1d. The image is transferred onto P at a time, and further fixed on the transfer paper P in the fixing unit 7 and then discharged from the apparatus main body. An image forming process for each of the photosensitive drums 1a to 1d is executed while rotating the photosensitive drums 1a to 1d counterclockwise in FIG.

  The transfer paper P onto which the toner image is transferred is accommodated in a paper cassette 16 at the lower part of the apparatus, and is conveyed to the secondary transfer roller 9 via a paper feed roller 12a and a registration roller pair 12b. A sheet made of a dielectric resin is used for the intermediate transfer belt 8, and a belt in which both ends thereof are overlapped and joined to form an endless shape, or a belt without a seam (seamless) is used. A blade-shaped belt cleaner 19 for removing toner remaining on the surface of the intermediate transfer belt 8 is disposed on the downstream side of the secondary transfer roller 9.

  Next, the image forming units Pa to Pd will be described. There are chargers 2a, 2b, 2c, and 2d for charging the photosensitive drums 1a to 1d and image information on the photosensitive drums 1a to 1d around and below the photosensitive drums 1a to 1d that are rotatably arranged. The exposure unit 4 for exposing the toner, the developing devices 3a, 3b, 3c and 3d for forming toner images on the photosensitive drums 1a to 1d, and the developer (toner) remaining on the photosensitive drums 1a to 1d are removed. Cleaning units 5a, 5b, 5c and 5d are provided.

  When the image formation start is input by the user, first, the surfaces of the photosensitive drums 1a to 1d are uniformly charged by the chargers 2a to 2d, and then light is irradiated by the exposure unit 4 to each of the photosensitive drums 1a to 1d. An electrostatic latent image corresponding to the image signal is formed on the top. Each of the developing devices 3a to 3d is filled with a predetermined amount of cyan, magenta, yellow, and black toner by a replenishing device (not shown). The toner is supplied onto the photosensitive drums 1a to 1d by the developing devices 3a to 3d and electrostatically attached, whereby a toner image corresponding to the electrostatic latent image formed by exposure from the exposure unit 4 is formed. It is formed.

  After an electric field is applied to the intermediate transfer belt 8 at a predetermined transfer voltage, the cyan, magenta, yellow, and black toner images on the photosensitive drums 1a to 1d are transferred to the intermediate transfer belt 8 by the primary transfer rollers 6a to 6d. Transcribed above. These four color images are formed with a predetermined positional relationship predetermined for forming a predetermined full-color image. Thereafter, the toner remaining on the surfaces of the photosensitive drums 1a to 1d is removed by the cleaning units 5a to 5d in preparation for the subsequent formation of a new electrostatic latent image.

  The intermediate transfer belt 8 is stretched over a plurality of stretching rollers including an upstream conveying roller 10 and a downstream driving roller 11, and the intermediate transfer belt 8 is intermediated as the driving roller 11 is rotated by a driving motor (not shown). When the transfer belt 8 starts to rotate clockwise, the transfer paper P is conveyed from the registration roller pair 12b to the secondary transfer roller 9 provided adjacent to the intermediate transfer belt 8 at a predetermined timing, and the full color image is transferred. The The transfer paper P onto which the toner image is transferred is conveyed to the fixing unit 7.

  The transfer paper P conveyed to the fixing unit 7 is heated and pressurized by the fixing roller pair 13 so that the toner image is fixed on the surface of the transfer paper P, and a predetermined full color image is formed. The transfer paper P on which the full-color image is formed is distributed in the transport direction by the branching portion 14 that branches in a plurality of directions. When an image is formed on only one side of the transfer paper P, the image is directly discharged onto the discharge tray 17 by the discharge roller pair 15.

  On the other hand, when images are formed on both sides of the transfer paper P, a part of the transfer paper P that has passed through the fixing unit 7 is once protruded from the discharge roller pair 15 to the outside of the apparatus. Thereafter, the transfer paper P is distributed to the paper conveyance path 18 by the branching section 14 by rotating the discharge roller pair 15 in the reverse direction, and is re-conveyed to the registration roller pair 12b with the image surface reversed. Then, after the next image formed on the intermediate transfer belt 8 is transferred to the surface of the transfer paper P on which the image is not formed by the secondary transfer roller 9 and conveyed to the fixing unit 7 to fix the toner image. The paper is discharged from the discharge roller pair 15 to the discharge tray 17.

  FIG. 2 is a side sectional view showing the configuration of the developing device according to the first embodiment of the present invention. Here, the developing device 3a disposed in the image forming unit Pa of FIG. 1 will be described, but the configuration of the developing devices 3b to 3d disposed in the image forming units Pb to Pd is basically the same, and thus described. Is omitted.

  As shown in FIG. 2, the developing device 3a includes a developing container 20 in which a two-component developer (hereinafter also simply referred to as a developer) is accommodated. The developing container 20 is divided into a first wall and a second wall by a partition wall 20a. The first and second agitating chambers 20b and 20c are divided into agitating chambers 20b and 20c, and a toner (positively charged toner) supplied from a toner container (not shown) is mixed with a carrier and agitated and charged. The stirring screw 21a and the second stirring screw 21b are rotatably arranged.

  Then, the developer is conveyed in the axial direction while being stirred by the first stirring screw 21a and the second stirring screw 21b, and the first and second are passed through developer passages (not shown) formed in the partition wall 20a. It circulates between the stirring chambers 20b and 20c. In the illustrated example, the developing container 20 extends obliquely upward to the left, a magnetic roller 22 is disposed in the developing container 20 above the second stirring screw 21b, and the developing roller 20 is disposed obliquely upward to the left of the magnetic roller 22. Rollers 23 are arranged opposite to each other. The developing roller 23 faces the photosensitive drum 1a on the opening side (left side in FIG. 2) of the developing container 20, and the magnetic roller 22 and the developing roller 23 rotate clockwise in the drawing.

  The developing container 20 is provided with a toner concentration sensor (not shown) facing the first stirring screw 21a, and a replenishing device (not shown) according to the toner concentration detected by the toner concentration sensor. Then, toner is supplied into the developing container 20 through the toner supply port 20d.

  The magnetic roller 22 includes a nonmagnetic rotating sleeve 22a and a magnetic roller side magnetic pole 22b having a plurality of magnetic poles contained in the rotating sleeve. In the present embodiment, the magnetic roller side magnetic pole 22 b has a five-pole configuration including a main pole 35, a regulation pole (head cutting pole) 36, a transport pole 37, a peeling pole 38, and a pumping pole 39. The magnetic roller side magnetic pole 22b is rotatably arranged in a state where the relative positions of the magnetic poles 35 to 39 are held with the central axis as a support shaft.

  Further, a spike cutting blade 25 is attached to the developing container 20 along the longitudinal direction of the magnetic roller 22 (front and back direction in FIG. 2), and the spike cutting blade 25 rotates in the rotational direction of the magnetic roller 22 (clockwise in the figure). Around the opposite position between the developing roller 23 and the magnetic roller 22. A slight gap (gap) is formed between the front end of the spike cutting blade 25 and the surface of the magnetic roller 22.

  The developing roller 23 includes a cylindrical developing sleeve 23a and a developing roller-side magnetic pole 23b fixed in the developing sleeve 23a. The magnetic roller 22 and the developing roller 23 are predetermined at a facing position (opposed position). It is facing with a gap of. The developing roller side magnetic pole 23b has a different polarity from the opposing magnetic pole (main pole) 35 of the magnetic roller side magnetic pole 22b.

  The developing roller 23 is connected to a first bias circuit 30 that applies a DC voltage (hereinafter referred to as Vslv (DC)) and an AC voltage (hereinafter referred to as Vslv (AC)). A second bias circuit 31 for applying a voltage (hereinafter referred to as Vmag (DC)) and an alternating voltage (hereinafter referred to as Vmag (AC)) is connected. The first bias circuit 30 and the second bias circuit 31 are grounded to a common ground.

  A voltage variable device 33 is connected to the first bias circuit 30 and the second bias circuit 31, and Vslv (DC), Vslv (AC) applied to the developing roller 23 and Vmag (DC) applied to the magnetic roller 22. ), Vmag (AC) can be varied.

  As described above, the first stirring screw 21a and the second stirring screw 21b circulate in the developing container 20 while the developer is being stirred to charge the toner, and the second stirring screw 21b causes the developer to move to the magnetic roller 22. Be transported. Since the regulating pole 36 of the magnetic roller side magnetic pole 22b is opposed to the ear cutting blade 25, a non-magnetic material or a magnetic material having a polarity different from that of the regulation pole 36 is used as the ear cutting blade 25. A magnetic field is generated in a direction attracting the gap with the rotating sleeve 22a.

  Due to this magnetic field, a magnetic brush is formed between the ear cutting blade 25 and the rotating sleeve 22a. Then, after the layer thickness of the magnetic brush on the magnetic roller 22 is regulated by the cutting blade 25, when the magnetic brush moves to a position facing the developing roller 23, it attracts by the main pole 35 of the magnetic roller side magnetic pole 22b and the developing roller side magnetic pole 23b. Since the magnetic field is applied, the magnetic brush contacts the surface of the developing roller 23. Then, a toner thin layer is formed on the developing roller 23 by a potential difference ΔV between Vmag (DC) applied to the magnetic roller 22 and Vslv (DC) applied to the developing roller 23 and a magnetic field.

  The thickness of the toner layer on the developing roller 23 varies depending on the resistance of the developer and the rotational speed difference between the magnetic roller 22 and the developing roller 23, but can be controlled by ΔV. When ΔV is increased, the toner layer on the developing roller 23 is thickened, and when ΔV is decreased, the toner layer is thinned. The range of ΔV at the time of development is generally about 100V to 350V.

  FIG. 3 is a diagram illustrating an example of a bias waveform applied to the developing roller 23 and the magnetic roller 22. As shown in FIG. 3A, the developing roller 23 has a combined waveform Vslv (solid line) in which a rectangular wave Vslv (AC) having a peak-to-peak value of Vpp1 superimposed on Vslv (DC) is a first bias circuit. 30 applied. Further, the magnetic roller 22 has a second combined waveform Vmag (broken line) in which Vmag (DC) has a peak-to-peak value of Vpp2 and a rectangular wave Vmag (AC) having a phase different from Vslv (AC). Applied from the bias circuit 31.

  Accordingly, the voltage applied between the magnetic roller 22 and the developing roller 23 (hereinafter referred to as MS) is a composite waveform Vmag-Vslv having Vpp (max) and Vpp (min) as shown in FIG. Become. Note that Vmag (AC) is set so that the duty ratio is larger than Vslv (AC). Actually, an AC voltage having a partially distorted shape is applied instead of a complete rectangular wave as shown in FIG.

  The toner thin layer formed on the developing roller 23 by the magnetic brush is conveyed to a facing portion between the photosensitive drum 1 a and the developing roller 23 by the rotation of the developing roller 23. Since Vslv (DC) and Vslv (AC) are applied to the developing roller 23, the toner flies due to a potential difference with the photosensitive drum 1a, and the electrostatic latent image on the photosensitive drum 1a is developed. .

  When the rotating sleeve 22a further rotates clockwise, the magnetic brush is now separated from the surface of the developing roller 23 by the horizontal (roller circumferential direction) magnetic field generated by the opposite polarity transport pole 37 adjacent to the main pole 35, and the developing roller 23a develops. The remaining toner that is not used for is collected from the developing roller 23 onto the rotating sleeve 22a. When the rotating sleeve 22a further rotates, a repulsive magnetic field is applied by the peeling pole 38 of the magnetic roller side magnetic pole 22b and the scooping pole 39 having the same polarity, so that the toner separates from the rotating sleeve 22a in the developing container 20. Then, after being stirred and conveyed by the second agitating screw 21b, a magnetic brush is again formed on the rotating sleeve 22a by the scooping pole 39 as a two-component developer uniformly charged with an appropriate toner concentration, It is conveyed to 25.

  By the way, in the developing device 3a of FIG. 2, since the ear cutting blade 25 is disposed substantially horizontally, scattered toner is likely to accumulate on the ear cutting blade 25. FIG. 4 is a schematic diagram showing a state where toner is deposited on the spike cutting blade. In FIG. 4, only the magnetic roller 22, the developing roller 23, and the ear cutting blade 25 are shown for convenience of explanation. Further, hatching of each of the magnetic poles 35 to 39 (magnetic roller side magnetic pole 22b) and the developing roller side magnetic pole 23b in the magnetic roller 22 indicates a difference in polarity. That is, the main pole 35, the peeling pole 38, and the scooping pole 39 indicated by diagonal lines have the same polarity (for example, N pole), and the regulation pole 36, the transport pole 37, and the developing roller side magnetic pole 23b indicated by dots have the same polarity (for example, S pole). (Hereinafter, the same applies to FIGS. 5 and 6).

  As shown in FIG. 4, when the developing device 3a is driven, the magnetic brush 40 formed on the rotating sleeve 22a comes into contact with the developing roller 23, so that the toner moves on the developing sleeve 23a and the toner thin layer 41 is formed. Is done. On the other hand, a part of the toner separated from the magnetic brush 40 is scattered at a portion facing the developing roller 23 and accumulates on the downstream side surface 25a of the spike cutting blade 25 with respect to the rotation direction (clockwise) of the rotating sleeve 22a. 43 is produced. When the toner reservoir 43 becomes large, it falls on the magnetic roller 22 or comes into contact with the toner thin layer 41, thereby preventing the stable formation of the toner thin layer 41.

  Therefore, in the developing device 3a of this embodiment, as shown in FIG. 5, the magnetic roller side magnetic pole 22b in the magnetic roller 22 is rotated and moved by a predetermined amount counterclockwise during non-image formation. As a result, the conveying pole 37 having the same polarity is opposed to the developing roller side magnetic pole 23b, and therefore a magnetic force line G (shown by a broken line in FIG. 5) is generated between the developing roller side magnetic pole 23b and the main pole 35. As a result, a repulsive magnetic field is generated at the opposing portion of the magnetic roller 22 and the developing roller 23, the movement of the developer at the opposing portion of the magnetic roller 22 and the developing roller 23 is restricted, and the opposing portion of the magnetic roller 22 and the developing roller 23 A developer reservoir 45 is formed between the blade and the cutting blade 25.

  Then, the developer reservoir 45 rotates with the rotary sleeve 22a while being in contact with the toner reservoir 43 on the spike cutting blade 25, whereby the toner reservoir 43 is taken into the developer. Since the developer reservoir 45 gradually increases as the rotary sleeve 22a rotates, the rotary sleeve 22a is rotated for a predetermined time to sufficiently collect the toner reservoir 43, and then the magnetic roller side magnetic pole 22b is rotated clockwise. Then, the image forming process is started after returning to the original position and eliminating the developer reservoir 45.

  By the above procedure, it is possible to eliminate the toner reservoir 43 on the ear cutting blade 25 and form a stable toner thin layer 41 at all times. Since the amount of toner deposited on the spike cutting blade 25 increases in proportion to the number of printed sheets, that is, the driving time of the developing device, the magnetic roller according to the cumulative number of printed sheets or the cumulative driving time of the developing devices 3a to 3d. What is necessary is just to determine the timing which rotationally moves the side magnetic pole 22b.

  In FIG. 5, the magnetic roller side magnetic pole 22b is rotated counterclockwise so that the developing roller side magnetic pole 23b faces the transporting pole 37 having the same polarity. However, the magnetic roller side magnetic pole 22b is rotated clockwise. The regulating pole 36 having the same polarity may be opposed to the developing roller side magnetic pole 23b. Also in this case, similarly to FIG. 5, the toner reservoir 43 on the spike cutting blade 25 can be efficiently collected using the developer reservoir 45 formed on the magnetic roller 22.

  However, when the developing roller side magnetic pole 23b and the regulating pole 36 are made to face each other, the magnetic pole is not present at the position of the drawing top pole 39 in FIG. 4, so the pumping force of the developer onto the rotating sleeve 22a is reduced, This is disadvantageous for the formation of the developer reservoir 45. On the other hand, when the developing roller side magnetic pole 23b and the conveying pole 37 are opposed to each other, the regulating pole 36 is disposed at the position of the drawing top pole 39 in FIG. 4 as shown in FIG. The pumping power of the agent does not decrease. Therefore, it is preferable to rotate the magnetic roller side magnetic pole 22b so that the developing roller side magnetic pole 23b and the transport pole 37 face each other.

  Next, the developing device according to the second embodiment of the present invention will be described. In the present embodiment, the magnetic roller side magnetic pole 22b is fixed, and instead, the developing roller side magnetic pole 23b is disposed so as to be rotatable about the central axis. The configuration of other parts and the operation of the developing device are the same as those of the first embodiment shown in FIG.

  In the developing device 3a of the present embodiment, as shown in FIG. 6, the developing roller side magnetic pole 23b in the developing roller 23 is rotated and moved by a predetermined amount toward the ear cutting blade 25 (clockwise) during non-image formation. As a result, the magnetic lines of force between the developing roller side magnetic pole 23b and the main pole 35 are greatly curved, and magnetic lines of force G as indicated by broken lines are generated. As a result, similarly to FIG. 5, a developer reservoir 45 is formed between the facing portion of the magnetic roller 22 and the developing roller 23 and the spike cutting blade 25.

  By rotating the rotary sleeve 22a in this state, the toner reservoir 43 on the ear cutting blade 25 can be efficiently collected using the developer reservoir 45 as in the first embodiment.

  Further, in the present embodiment, it is preferable to rotate the rotating sleeve 22a in the reverse direction (counterclockwise in FIG. 6) while collecting the toner reservoir 43 using the developer reservoir 45. In this case, the developer pumped up on the rotary sleeve 22a by the peeling pole 38 moves together with the rotary sleeve 22a by the magnetic force of the transport pole 37 and the main pole 35, and is downstream of the spike cutting blade 25 (upstream side during reverse rotation). ).

  Therefore, it is advantageous for forming the developer reservoir 45 as compared with the case where the rotating sleeve 22a is rotated forward (clockwise in FIG. 6). Further, since the developer reservoir 45 is pressed against the downstream side surface 25a of the pan blade 25 by the reverse rotation of the rotary sleeve 22a, the toner reservoir 43 can be collected more effectively. Furthermore, an effect of removing toner aggregates clogged in the gap between the spike cutting blade and the magnetic roller can be expected.

  At this time, if the reverse rotation speed of the rotating sleeve 22a is too high, the toner accumulated on the ear cutting blade 25 is scattered by the wind pressure generated by the rotation of the rotating sleeve 22a, and the collection efficiency of the toner reservoir 43 is lowered. Therefore, it is preferable that the reverse rotation speed of the rotation sleeve 22a is slower than the rotation speed at the time of image formation.

  In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in each of the embodiments described above, the developing device using positively charged toner whose charging direction is positive (plus side) is described as an example. However, the developing device using negatively charged toner whose charging direction is negative (minus side). The same applies to the above.

  In each of the above-described embodiments, either the magnetic roller side magnetic pole 22b or the developing roller side magnetic pole 23b is rotationally moved to generate the developer pool 45. However, both the magnetic roller side magnetic pole 22b and the developing roller side magnetic pole 23b are used. May be rotated. Further, the method of moving the magnetic pole is not limited to rotational movement, and for example, the developing roller side magnetic pole 23b can be moved in parallel to the ear cutting blade 25 side.

  The present invention is not limited to the tandem type color printer shown in FIG. 1, but a digital carrier or an analog type monochrome copying machine, a monochrome printer, a rotary developing type color printer and a color copying machine, a facsimile, etc. It is applicable to various image forming apparatuses provided with a developing device that uses a two-component developer composed of the above, and develops an electrostatic latent image on an image carrier by holding only a charged toner on a developing roller.

  INDUSTRIAL APPLICABILITY The present invention can be used for a developing device that develops an electrostatic latent image on an image carrier by holding only the charged toner on the developing roller using a magnetic roller, and the developing roller and the magnetic roller at the time of non-image formation At least one of the magnetic roller-side magnetic pole and the developing roller-side magnetic pole is moved so that a developer pool is generated between the facing portion and the cutting blade.

  Accordingly, it is possible to provide a developing device capable of efficiently collecting the toner accumulated on the cutting blade by generating a developer pool in the vicinity of the downstream side of the cutting blade.

1a to 1d Photosensitive drum (image carrier)
3a to 3d Developing device 21a First agitating screw 21b Second agitating screw 22 Magnetic roller 22a Rotating sleeve 22b Magnetic roller side magnetic pole 23 Developing roller 23a Developing sleeve 23b Developing roller side magnetic pole 25 Ear cutting blade 35 Main pole 36 Regulating pole 37 Conveying pole 38 Peeling pole 39 Floating pole 40 Magnetic brush 41 Thin toner layer 43 Toner reservoir 45 Developer reservoir 100 Image forming apparatus

Claims (8)

A two-component developer containing at least a carrier and a toner is used, and a developing roller disposed opposite to the image carrier;
A magnetic roller disposed opposite to the developing roller;
A magnetic or non-magnetic hob cutting blade disposed opposite to the upstream side of the developing roller with respect to the rotation direction of the magnetic roller;
A magnetic roller-side magnetic pole having a plurality of magnetic poles including a main pole disposed inside the magnetic roller and facing the developing roller and a regulating pole facing the spike cutting blade;
A developing roller side magnetic pole disposed opposite to the magnetic roller in the developing roller and having a polarity different from that of the main pole,
In a developing device for developing an electrostatic latent image on an image carrier by supplying toner to the developing roller using a magnetic brush formed on the magnetic roller,
At the time of non-image formation, at least one of the magnetic roller side magnetic pole and the developing roller side magnetic pole is moved so that a developer pool is generated between a portion facing the developing roller and the magnetic roller and the spike cutting blade. A developing device.   The developing device according to claim 1, wherein the magnetic roller side magnetic pole is rotationally moved so that the magnetic pole of the same polarity is opposed to the developing roller side magnetic pole.   The magnetic roller side magnetic poles are different in polarity from the restricting pole located upstream of the restricting pole with respect to the rotation direction of the magnetic roller, and in the opposite polarity to the main pole located downstream of the main pole. The developing device according to claim 2, wherein the magnetic roller side magnetic pole is rotationally moved so that the conveyance pole faces the developing roller side magnetic pole.   The developing device according to claim 1, wherein the developing roller side magnetic pole is rotated and moved toward the spike cutting blade.   The developing device according to claim 4, wherein the developing roller side magnetic pole is rotated and the magnetic roller is reversely rotated.   The developing device according to claim 5, wherein the reverse rotation speed of the magnetic roller is slower than the rotation speed of the magnetic roller during image formation.   The developing device according to claim 1, wherein the magnetic roller is disposed below the developing roller.   An image forming apparatus on which the developing device according to claim 1 is mounted.