JP5887796B2 - Developing device and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus using the developing device.

  Conventionally, various image forming apparatuses having a plurality of developing rolls have been proposed as developing apparatuses for developing an electrostatic latent image formed on an image carrier. As a technique related to a developing device having a plurality of developing rolls, for example, there is one disclosed in Japanese Patent Laid-Open No. 2003-270956.

  The electrophotographic apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 2003-270956 is an electrophotographic apparatus including a photoconductor and a developing machine having a plurality of developing rolls including a sleeve and a magnet roll, and at least one having a rotating magnet roll. A magnetic shielding plate is provided between the developing roll, another developing roll adjacent to the developing roll having the rotating magnet roll, and the developing roll having the rotating magnet roll and the other developing roll.

JP 2003-270956 A

  By the way, the problem to be solved by the present invention is that other developer holders are held via a guide member that guides the developer peeled off from one developer holder to a transport unit among a plurality of developer holders. An object of the present invention is to provide a developing device capable of suppressing the formation of a magnetic circuit between itself and an image forming apparatus using the same.

In other words, the invention described in claim 1 is provided with a plurality of developer holders having a magnetic roll that is arranged above and below the image carrier and magnetized with a plurality of magnetic poles.
A conveying member that is arranged adjacent to one developer holding body among the plurality of developer holding bodies and conveys the developer held by the plurality of developer holding bodies via the one developer holding body. When,
A separating member that is disposed between the plurality of developer holders and separates the developer conveyed by the conveying member into the plurality of developer holders;
Of the plurality of developer holders, at least a surface in contact with the developer that guides the developer peeled from the developer holder disposed relatively above to the transport member is made of a non-magnetic material. A guide member;
Development that is arranged along the axial direction of the developer holder other than the separation member on the opposite side of the surface of the guide member that contacts the developer, and that is adjacent to the developer holder that is disposed relatively upward. A developing device comprising: a magnetic circuit suppressing member made of a magnetic material that suppresses formation of a magnetic circuit passing through the guide member between the agent holding member and the agent holding member.

  According to a second aspect of the present invention, the magnetic roll of the developer holding body and the magnetic roll of the adjacent developer holding body, which are disposed relatively above, have opposite polarities at positions facing each other. The developing device according to claim 1, wherein the magnetic pole is magnetized.

  Furthermore, the invention described in claim 3 is the developing device according to claim 1 or 2, wherein the magnetic circuit suppressing member is set to a thickness of 0.1 to 0.3 mm. is there.

  According to a fourth aspect of the present invention, the surface of the developer holding member disposed relatively above moves in a direction opposite to the moving direction of the image holding member. The developer holder disposed relatively below is rotated such that the surface facing the image holder moves in the same direction as the moving direction of the image holder. The developing device according to claim 1, wherein the developing device is a developing device.

Furthermore, the invention described in claim 5 is an image holding body for holding an electrostatic latent image;
Developing means for developing the electrostatic latent image held on the image carrier with toner;
Transfer means for transferring the toner image developed on the image holding member to a recording medium directly or via an intermediate transfer member,
An image forming apparatus using the developing device according to claim 1 as the developing unit.

  According to the first aspect of the present invention, among the plurality of developer holders, the other developer holding is performed via the guide member that guides the developer separated from the one developer holding body to the transport unit. The formation of a magnetic circuit between the body and the body can be suppressed.

  According to the second aspect of the present invention, the developer can be separated between a plurality of adjacent developer holders without imposing a load on the developer.

  Furthermore, according to the third aspect of the present invention, it is possible to suppress a secondary failure that occurs when the magnetic circuit suppressing member is magnetized.

  According to the invention described in claim 4, the development efficiency can be improved.

  Furthermore, according to the fifth aspect of the present invention, among the plurality of developer holders, the other development is performed via the guide member that guides the developer peeled from one developer holder to the transport unit. It is possible to suppress the formation of a magnetic circuit with the agent holding body, and it is possible to avoid deterioration in image quality.

1 is a cross-sectional configuration diagram illustrating a developing device according to a first embodiment of the present invention. 1 is a configuration diagram illustrating an image forming apparatus to which a developing device according to Embodiment 1 of the present invention is applied. FIG. It is a block diagram which shows the magnetic pole arrangement | positioning of the developing roll of the developing device which concerns on Embodiment 1 of this invention. It is a graph which shows magnetic flux distribution of the 1st magnet roll of the image development apparatus concerning Embodiment 1 of this invention. It is a graph which shows magnetic flux distribution of the 2nd magnet roll of the developing device which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows magnetic flux distribution between the 1st and 2nd image development roll. It is a schematic diagram showing a developer staying on the guide chute. FIG. 2 is a cross-sectional configuration diagram illustrating a main part of the developing device according to the first embodiment of the present invention. It is a schematic diagram which shows magnetic flux distribution between the 1st and 2nd image development roll. It is a model block diagram which shows the developing device which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows magnetic flux distribution between the 1st and 2nd image development roll. It is a graph which shows each the actual value of the magnetic flux density of the developing device which concerns on Embodiment 1 of this invention, and the numerical value by a magnetic field analysis. It is a graph which shows the magnetic force on a guide chute. It is a schematic diagram showing a developer staying on the guide chute. It is a graph which shows the magnetic force on a guide chute. It is a schematic diagram showing a developer staying on the guide chute. It is a graph which shows the magnetic force on a guide chute. It is a schematic diagram showing a developer staying on the guide chute. It is a block diagram which shows the developing device which concerns on Embodiment 2 of this invention. It is a block diagram which shows a paddle. It is a block diagram which shows the image forming apparatus to which the developing device which concerns on Embodiment 3 of this invention is applied.

  Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1
FIG. 2 shows a tandem full-color image forming apparatus as an image forming apparatus to which the developing device according to Embodiment 1 of the present invention is applied. The tandem full-color image forming apparatus includes an image reading apparatus and is configured to function as a full-color copying machine. However, the image reading apparatus may be omitted. Further, this full-color image forming apparatus is set to be highly productive, which is the number of recording sheets on which image formation is possible per unit time. For example, per full minute on an A4 size LEF (Long Edge Feed) recording sheet. An image of about 100 to 140 sheets (PPM) can be formed. However, the present invention is not limited to a high-speed tandem image forming apparatus, and can be applied to a single-color image forming apparatus having only one photosensitive drum.

  In FIG. 2, reference numeral 1 denotes a main body of the image forming apparatus, and an image reading device 4 that reads an image of the document 2 is disposed at one upper end (left end in the illustrated example) of the image forming apparatus main body 1. ing. The image reading device 4 illuminates a document 2 placed on a platen glass 5 while being pressed by a document pressing member 3 with a light source 6, and reflects a reflected light image from the document 2 with a full rate mirror 7 and a half rate mirror 8. The image reading element 11 reads the image of the document 2 at a predetermined dot density by performing scanning exposure on the image reading element 11 made of a CCD or the like through a reduction optical system including the image forming lens 10 and the image forming lens 10. It is configured.

  The image of the document 2 read by the image reading device 4 includes, for example, an image processing device as image data of three colors of red (R), green (G), and blue (B) (for example, 8 bits each). The control device 12 determines in advance the image data of the document 2 such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color / moving editing, and the like. The processed image processing is performed. In addition, the image data that has been subjected to the predetermined image processing by the control device 12 as described above is converted into four colors of cyan (C), magenta (M), yellow (Y), and black (K). Converted to image data. Note that the number of colors of image data converted by the control device 12 is not limited to image data of four colors of cyan (C), magenta (M), yellow (Y), and black (K), as will be described later. The color may be converted into six colors including high saturation cyan (HC) and high saturation magenta (HM), and the number of colors is arbitrary. Of course, the image data input to the control device 12 may be sent from a personal computer or the like via a communication line (not shown).

  By the way, this embodiment is configured to include a plurality of image forming means for forming images using toners having different colors.

  That is, inside the image forming apparatus main body 1 according to this embodiment, as shown in FIG. 2, as a plurality of image forming means, cyan (C), magenta (M), high chroma cyan (HC), high chroma magenta Six image forming units 13C, 13M, 13HC, 13HM, 13Y, and 13K corresponding to the colors (HM), yellow (Y), and black (K) are arranged in parallel at regular intervals along the horizontal direction. Has been placed. Note that high chroma cyan (HC) is a high chroma cyan color having a cyan hue and having a brighter tone and relatively higher chroma than the cyan (C) color. The high saturation magenta (HM) is a high saturation magenta color having a magenta color hue and a brighter tone and a relatively higher saturation than the magenta (M) color.

  Further, the cyan (C), magenta (M), high chroma cyan (HC), high chroma magenta (HM), yellow (Y), and black (K) image forming units 13C, 13M, 13HC, 13HM, 13Y, The arrangement order of 13K is not limited to that shown in the figure, and may be arranged in a different order. Further, the cyan (C), magenta (M), high chroma cyan (HC), high chroma magenta (HM), yellow (Y), and black (K) image forming units 13C, 13M, 13HC, 13HM, 13Y, 13K is individually integrated into a unit, and each of the image forming units 13C, 13M, 13HC, 13HM, 13Y, and 13K is independently attached to the image forming apparatus main body 1 in a replaceable manner.

  These six image forming units 13C, 13M, 13HC, 13HM, 13Y, and 13K are basically configured in the same manner except for the type (color) of the toner to be used, as shown in FIG. Broadly speaking, a photosensitive drum 15 as an image holding member driven at a predetermined rotational speed along the direction of arrow A, and a scorotron 16 as primary charging means for uniformly charging the surface of the photosensitive drum 15. An image exposure device 14 serving as a latent image forming unit that exposes an image corresponding to each color on the surface of the photosensitive drum 15 to form an electrostatic latent image, and an electrostatic latent image formed on the photosensitive drum 15. The image forming apparatus includes a developing device 17 as a developing unit according to the present exemplary embodiment that develops an image with a corresponding color toner, and a cleaning device 18 that removes transfer residual toner remaining on the photosensitive drum 15. There.

  As shown in FIG. 2, the image exposure device 14 modulates the semiconductor laser 19 according to the image data, and emits a laser beam LB from the semiconductor laser 19 according to the image data. The laser beam LB emitted from the semiconductor laser 19 is deflected and scanned by the rotary polygon mirror 22 via the reflecting mirrors 20 and 21, and the focal length is adjusted according to the scanning angle by an unshown f-θ lens. Then, scanning exposure is performed on the photosensitive drum 15 as an image holding member through a plurality of reflecting mirrors 23 and 24 and the like. The image exposure apparatus 14 is not limited to an apparatus that performs image scanning by deflecting and scanning the laser beam LB. For example, an LED eyelet in which a large number of LED light emitting elements are arranged along the axial direction of the photosensitive drum 15 is used. You may use the equipment that was used. In the case of the image exposure device 14 using the LED eyelet, the image exposure device 14 can be significantly reduced in size compared to the image exposure device 14 that performs image exposure by deflecting and scanning the laser beam LB, and image formation is possible. The entire apparatus can be reduced in size, which is desirable.

  From the control device 12, image forming units 13C, 13M, 13HC for cyan (C), magenta (M), high saturation cyan (HC), high saturation magenta (HM), yellow (Y), and black (K) are provided. The image data of each color is sequentially output to the 13HM, 13Y, and 13K image exposure apparatuses 14C, 14M, 14HC, 14HM, 14Y, and 14K. The laser beams LB emitted from the image exposure apparatuses 14C, 14M, 14HC, 14HM, 14Y, and 14K according to the image data are the surfaces of the corresponding photosensitive drums 15C, 15M, 15HC, 15HM, 15Y, and 15K. Then, scanning exposure is performed along the main scanning direction (the axial direction of the photosensitive drum 15) to form an electrostatic latent image. The electrostatic latent images formed on the photosensitive drums 15C, 15M, 15HC, 15HM, 15Y, and 15K are converted into cyan (C) and magenta (magenta) by the developing devices 17C, 17M, 17HC, 17HM, 17Y, and 17K, respectively. M), high chroma cyan (HC), high chroma magenta (HM), yellow (Y), and black (K) toner images.

  Cyan (C), magenta (M), high chroma cyan formed in sequence on the photosensitive drums 15C, 15M, 15HC, 15HM, 15Y, and 15K of the image forming units 13C, 13M, 13HC, 13HM, 13Y, and 13K. (HC), high chroma magenta (HM), yellow (Y), and black (K) toner images are below the image forming units 13C, 13M, 13HC, 13HM, 13Y, and 13K, as shown in FIG. Primary transfer rolls 26C, 26M, 26HC, 26HM, 26Y, and 26K are primarily transferred onto the intermediate transfer belt 25 serving as an intermediate transfer member disposed in the state of being superposed on each other.

  The intermediate transfer belt 25 includes a driving roll 27, a driven roll 28, a tension applying roll 29, a driven roll 30, a back support roll 31 of the secondary transfer unit, and a plurality of rolls including a driven roll 32. It is stretched with the specified tension. Then, the intermediate transfer belt 25 is rotated along a direction indicated by an arrow B by a drive roll 27 that is rotated by a dedicated drive motor that is excellent in constant speed (not shown), and the photosensitive drums 15C, 15M, 15HC, 15HM, 15Y, and 15K. It is driven to circulate at a predetermined speed substantially equal to the rotational speed (circumferential speed). As the intermediate transfer belt 25, for example, a belt formed by adjusting the resistance value of a synthetic resin film such as polyimide or polyamideimide having flexibility to form an endless belt is used.

  The cyan (C), magenta (M), high chroma cyan (HC), high chroma magenta (HM), yellow (Y), and black (K) toner images transferred in multiple onto the intermediate transfer belt 25 are as follows: A secondary transfer bias applied to a secondary transfer roll 33 that is in pressure contact with the back support roll 31 via the intermediate transfer belt 25 is collectively transferred onto a recording paper 34 as a recording medium, and toners of these colors. The recording sheet 34 onto which the image has been transferred is transported to a fixing device 37 as a fixing unit by two transport belts 35 and 36. The recording paper 34 on which the toner images of the respective colors are transferred is subjected to a fixing process with heat and pressure by a heating belt 38 and a pressure roll 39 of a fixing device 37, and then a cooling unit 41 via a sheet conveying device 40. In the case of single-sided printing in a state where the curl is corrected by the curl correction unit 42, it is discharged as it is onto a discharge tray 43 provided outside the image forming apparatus main body 1.

  As shown in FIG. 2, the recording paper 34 is, for example, of a predetermined size or material from one of a plurality of paper feed trays 44, 45, a paper feed roll 46, and a paper transport roll. The paper is once transported to the resist roll 49 in a state of being separated one by one through the paper transport path 48 formed of the pair 47. The recording paper 34 supplied from either one of the paper feed trays 44 and 45 is synchronized with the toner image on the intermediate transfer belt 25 by a registration roll 49 that is rotationally driven at a predetermined timing. To be sent to.

  Further, when images are formed on both sides of the recording paper 34 by the image forming apparatus, the recording paper 34 on which the image is fixed on one side by the fixing device 37 is not discharged out of the apparatus as it is, but is switched by the switching gate 51. Then, the conveyance path of the recording paper 34 is switched downward, and the recording paper 34 is temporarily stored in the intermediate tray 53 by the paper feed roller 54 via the reverse paper conveyance path 52. The recording paper 34 accommodated in the intermediate tray 53 is turned upside down through the double-sided paper transport path 55 and the normal paper transport path 48 with the transport direction reversed by the paper feed roller 54. In this state, the sheet is conveyed again to the secondary transfer position 50 of the intermediate transfer belt 25, and after the image is transferred to the back surface, the fixing process is performed with heat and pressure by the heating belt 38 and the pressure roll 39 of the fixing device 37. The sheet is conveyed to the cooling unit 41 via the sheet conveying device 40 and cooled, and is discharged onto a discharge tray 43 provided outside the image forming apparatus main body 1 in a state where the curl correction unit 42 corrects the curl. Is done.

  The surface of the photosensitive drum 15 after the primary transfer of the toner image is cleaned by the cleaning device 18. The intermediate transfer belt 25 after the secondary transfer of the toner image is cleaned by a belt cleaning device 56 whose surface is disposed in the vicinity of the drive roll 27.

  In FIG. 2, reference numeral 57 denotes a user interface through which the user inputs image forming conditions and the like.

  FIG. 1 is a sectional view showing developing devices 17C to 17K applied to the image forming apparatus configured as described above.

  As shown in FIG. 1, the developing device 17 has a developer accommodating portion 102 for accommodating a two-component developer 101 composed of a carrier and a toner, and a side surface (on the left side in the illustrated example). A developing device main body 104 having an opening 103 is provided. Inside the opening 103 of the developing device main body 104, first and second two developing rolls 105 and 106 serving as a plurality of developer holders are defined with respect to the surface of the photosensitive drum 15 in a predetermined gap ( (Approx. 0.2 to 1.0 mm) so as to face each other in close proximity to each other, and adjacent to each other via a short gap in the vertical direction. The first and second developing rolls 105 and 106 are basically configured in the same manner, and the magnet rolls 107 and 108 as magnetic rolls arranged in a fixed state inside the magnet rolls 107 and 108. The developing sleeves 109 and 110 are arranged on the outer periphery of the sleeve so as to be rotatable along the arrow direction.

  The magnet rolls 107 and 108 are formed in a cylindrical shape from a magnetic material made of a ferromagnetic material or the like, and are attached to the developing device main body 104 in a fixed state. Of the magnet rolls 107 and 108, the first magnet roll 107 of the first developing roll 105 located on the upstream side in the rotation direction of the photosensitive drum 15 is, as shown in FIG. The third N3 pole 112 is provided as a development pole in the development area 111 that is in close proximity to and opposite to the third N3 pole 112, on the downstream side in the rotation direction of the development sleeve 109 with respect to the third N3 pole 112. A first S1 pole 113 as a magnetic pole for conveying the agent 101 is magnetized. On the downstream side of the first S1 pole 113 in the rotation direction of the developing sleeve 107, a first N1 pole 114 as a transport magnetic pole for transporting the developer 101 is also magnetized, and the first S1 pole 113 is magnetized. A second N2 pole 115 constituting a peeling magnetic pole for peeling the developer 101 from the surface of the developing sleeve 107 together with the first N2 pole 114 is provided downstream of the N2 pole 114 in the rotation direction of the developing sleeve 107. Magnetized. Further, at a position downstream of the second N2 pole 115 along the rotation direction of the developing sleeve 107 and facing the other developing roll 104, the second N2 pole 115 serves as a transport magnetic pole for transporting the developer 101. The second S2 pole 116 is magnetized, and the second S2 pole 116 constitutes a transport magnetic pole with the third N3 pole 112 as a developing pole.

  The third N3 pole 112, the first S1 pole 113, the first N1 pole 114, the second N2 pole 115, and the second S2 pole 116 are used as developing poles as shown in FIG. The position slightly upstream of the third N3 pole 112 along the rotation direction of the developing sleeve 107 is set as a reference (0 °) at a predetermined angle along the circumferential direction of the magnet roll 107. It is magnetized so as to have a high magnetic flux density.

  On the other hand, among the magnet rolls 107 and 108, the magnet roll 108 of the developing roll 106 located on the downstream side in the rotation direction of the photosensitive drum 15 is connected to the photosensitive drum 15 as shown in FIGS. A first S1 pole 117 is provided as a developing pole in a developing area that is closely opposed to the developing area, and the developer 101 is located downstream of the first S1 pole 117 in the rotation direction of the developing sleeve 110. The first N1 pole 118 as the transport magnetic pole for transporting the magnet is magnetized. On the downstream side of the first N1 pole 118 in the rotation direction of the developing sleeve 110, a third N3 that forms a peeling magnetic pole that peels the developer 101 from the surface of the developing sleeve 110 together with the first N1 pole 118. The pole 119 is magnetized. A second S2 pole 120 serving as a transport magnetic pole for transporting the developer 101 is magnetized on the downstream side of the third N3 pole 119 along the rotation direction of the developing sleeve 110. Further, a downstream side of the second S2 pole 120 in the rotation direction of the developing sleeve 110 and a position facing the other developing roll 105 in the vicinity thereof is a conveying magnetic pole for conveying the developer 101. The second N2 pole 121 is magnetized, and the second N2 pole 121 constitutes a transport magnetic pole with the first S1 pole 117 as a developing pole.

  As shown in FIG. 5, the first S1 pole 117, the first N1 pole 118, the third N3 pole 119, the second S2 pole 120, and the second N2 pole 121 are the first development pole. The S1 pole 117 is slightly upstream along the rotation direction of the developing sleeve 110 as a reference (0 °), and the magnetic flux is determined at a predetermined angle along the circumferential direction of the magnet roll 108. It is magnetized to a density.

  In the above embodiment, the case where five magnetic poles are arranged along the circumferential direction of the magnet rolls 107 and 108 has been described. However, the number of magnetic poles arranged along the circumferential direction of the magnet rolls 107 and 108 is as follows. It is not limited to five, and may be, for example, seven poles.

  Further, as shown in FIG. 1, the developing sleeves 109 and 110 are formed in a cylindrical shape by a nonmagnetic material such as aluminum or stainless steel, and are rotatably attached to the developing device main body 104. One developing sleeve 109 is rotationally driven at a predetermined speed along the same direction as the rotation direction of the photosensitive drum 15 (the arrow direction in FIG. 1). The other developing sleeve 110 is rotationally driven at a predetermined speed along the direction opposite to the rotational direction of the photosensitive drum 15. As a result, one of the developing sleeves 109 moves in a direction opposite to the moving direction of the surface of the photosensitive drum 15 at a position where the surface of the developing sleeve 109 faces the photosensitive drum 15, and the other developing sleeve 110 has a surface of the photosensitive drum. It is configured to move in the same direction as the moving direction of the surface of the photosensitive drum 15 at a position facing the drum 15. Further, in the first developing sleeve 109 and the second developing sleeve, the rotational speed (peripheral speed) of the first developing sleeve 109 is set to be higher than that of the second developing sleeve 110, and the first and second developing sleeves 109 and 109 are set. The speed ratio of the developing sleeves 109 and 110 is set to about 1.2 to 1.8 times, for example.

  As a result, the first and second developing rolls 105 and 106 have a ratio that contributes to developing the electrostatic latent image formed on the surface of the photosensitive drum 15 along the rotation direction of the photosensitive drum 15. The first developing roll 105 positioned on the upstream side is set to be approximately 70%, and the second developing roll 106 positioned on the downstream side in the rotation direction of the photosensitive drum 15 is set to be approximately 30%. The first developing roll 105 mainly contributes to improving the reproducibility of fine lines by improving the developing performance, and the second developing roll 106 mainly contributes to improving the reproducibility of gradation.

  Further, a trimmer member 123 made of a nonmagnetic metal flat plate or the like as a layer thickness regulating member for regulating the amount of the developer 101 supplied to the surface of the developing sleeve 110 is provided on the surface of the second developing sleeve 110. The second magnet roll 108 is disposed in the vicinity of the position facing the second S2 pole 120 so as to face the surface of the developing sleeve 110 via a predetermined gap. The trimmer member 123 regulates the developer 101 supplied to the surfaces of the first and second developing rolls 105 and 106 at the same time, including the developer 101 supplied to the first developing roll 105. It is configured.

  Further, the developer 101 supplied to the surface of the second developing roll 106 is supplied to the facing portion 124 where the first developing roll 105 and the second developing roll 106 face each other close to each other. A separating member 125 that separates the developing roll 105 and the second developing roll 106 is disposed. The separation member 125 is disposed so as to face the surfaces of the first developing roll 105 and the second developing roll 106 with a predetermined gap therebetween.

  Further, as shown in FIG. 1, a two-component developer 101 composed of a carrier and a toner housed in the developing device main body 104 is conveyed to the inside of the developing device main body 104 while stirring, A developer supply auger 126 as a developer supply means for supplying the developing roll 106 is disposed on the back side of the second developing roll 106 so as to be rotatable along the arrow direction. Further, on the back side of the developer supply auger 126, the developer 101 is agitated and conveyed through the partition wall 127 while circulating the developer 101 between the developer supply auger 126 and the toner in the developer 101. A developer agitating / conveying auger 128 that is triboelectrically charged is disposed so as to be rotatable along the arrow direction. At both ends along the longitudinal direction of the partition wall 127, there are provided passages (not shown) for circulating and transporting the developer 101 between the developer supply auger 126 and the developer stirring and transporting auger 128. . Further, the developer agitating / conveying auger 128 is configured such that a new developer 101 containing at least toner is supplied to the inside of the developing device main body 104 at the upstream end along the developer conveying direction. . In this embodiment, a new two-component developer 101 composed of a carrier and toner is predetermined by a developer supply means (not shown) at the upstream end of the developer agitating / conveying auger 128 along the developer conveying direction. It is supplied at the specified timing.

Further, as shown in FIG. 1, a guide chute as a guide member for guiding the developer 101 peeled from the surface of the first developing roll 105 to the developer supply auger 126 is provided inside the developing device main body 104. 130 is arranged. The guide chute 130 is a non-magnetic metal plate such as aluminum or stainless steel, a synthetic resin material, or a composite material of a non-magnetic metal plate and a synthetic resin material. It is formed in a magnetic flat plate shape. In this embodiment, the entire surface including the surface in contact with the developer 101 is formed as a nonmagnetic flat plate having a thickness of about 1.5 mm, for example. The guide chute 130 has a tip 131 disposed close to the surface corresponding to the peeled magnetic pole of the first developing roll 105, and an intermediate portion 132 formed in a flat plate shape continuously to the tip 131. It arrange | positions in the state inclined only by the predetermined angle (for example, about 45 degrees-50 degrees) with respect to the direction. The guide chute 130 has its rear end portion 133 is relatively bent short so as to be positioned substantially vertically toward the developer supply auger 126 above the developer supply auger 126. Note that the rear end portion 133 of the guide chute 130 may be simply disposed above the developer supply auger 126 without being bent toward the developer supply auger 125.

  Further, as shown in FIG. 1, the developing device main body 104 includes a developer agitating / conveying auger 127 in which a developer agitating / conveying passage 130 is disposed on the side wall of the developing device main body 104. A toner concentration sensor 134 for detecting the toner concentration of the agent 101 is disposed.

  In the developing device 17, as shown in FIG. 1, the developer 101 accommodated in the developing device main body 104 is transported while being stirred between the developer supply auger 126 and the developer stirring and transporting auger 128. In the meantime, the toner in the developer 101 is negatively charged by frictional charging and supplied to the surface of the second developing roll 106 by the developer supply auger 126.

  The developer 101 supplied to the surface of the second developing roll 106 is transported by the conveying magnetic pole formed by the third N3 pole 119 and the second S2 pole 120 as the second developing sleeve 110 rotates. After being transported in the counterclockwise direction and the layer thickness of the developer 101 is regulated by the trimmer member 123, the first developing roll 105 and the second developing roll 106 are transported to a facing portion 124 that is closely opposed to each other. The With the rotation of the second developing sleeve 110, the developer 101 transported to the facing portion 124 where the first developing roll 105 and the second developing roll 106 are close to each other faces the facing portion 124 or the vicinity thereof. The first developing roll 105 and the second developing roll 106 are separated by the separating member 125 arranged in the first position. The developer 101 separated on the first developing roll 105 side is conveyed in the clockwise direction by the conveying magnetic pole constituted by the second S2 pole 116 and the third N3 pole 112 as the developing sleeve 109 rotates. Then, it reaches the developing region 111 facing the surface of the photosensitive drum 15 and becomes a magnetic brush of the developer 101 by the third N3 pole 112 as a developing pole, and is formed on the surface of the photosensitive drum 15. The electrostatic latent image is developed. After that, the developer 101 held on the surface of the first developing roll 105 is transported magnetic poles composed of the third N3 pole 112 and the first S1 pole 113 as the first developing sleeve 109 rotates. Is peeled off from the surface of the developing sleeve 109 by a peeling magnetic pole that forms a repulsive magnetic field between the first N1 pole 114 and the second N2 pole 115. The new developer 101 is supplied by the second developing roll 106.

  On the other hand, the developer 101 separated to the second developing roll 106 side is conveyed by the conveying magnetic pole constituted by the second N2 pole 121 and the first S1 pole 117 as the second developing sleeve 110 rotates. It is conveyed in the counterclockwise direction, reaches the developing region 135 facing the surface of the photosensitive drum 15, and becomes a magnetic brush of the developer 101 by the first S1 pole 117 as a developing pole. The electrostatic latent image formed on the surface is developed. After that, the developer 101 held on the surface of the second developing roll 106 is transported magnetic poles composed of the first S1 pole 117 and the first N1 pole 118 as the second developing sleeve 110 rotates. Is peeled off from the surface of the developing sleeve 110 by a peeling magnetic pole that forms a repulsive magnetic field between the first N1 pole 118 and the third N3 pole 119. The new developer 101 is supplied by the developer supply auger 126.

  Further, as shown in FIG. 1, the developer 101 peeled off from the surface of the first developing roll 105 is guided by a guide chute 130 and dropped and supplied to the upper portion of the developer supply auger 126, thereby developing the developer supply auger. 126, the developer 101 in the developing device main body 104 is conveyed while being stirred, and is supplied to the surface of the second developing roll 106. Note that the rotation direction of the developer supply auger 126 is set to the same direction as the rotation direction of the second developing roll 106 (in the illustrated example, the clockwise direction), and therefore the peeling is performed from the surface of the second developing roll 106. The developed developer 101 is not immediately supplied to the surface of the second developing roll 106, but is conveyed to the opposite side of the second developing roll 106 by the developer supply auger 126, After being stirred with the developer 101, it is supplied to the surface of the second developing roll 106.

  Incidentally, in the developing device 17 configured as described above, as shown in FIG. 1, the first developing roll 105 and the second developing roll 106 are arranged close to each other, and the first developing roll 105 is arranged. Magnetic poles N1 pole 114, N2 pole 115 and S2 pole 120 having opposite polarities are arranged at opposing positions where the first developing roller 106 and the second developing roll 106 are opposed to each other. Therefore, in the first developing roll 105, on the upstream side of the counter magnetic pole in the rotation direction of the developing sleeve 109, a peeling magnetic pole having a polarity opposite to that of the counter magnetic pole S2 pole 116 that peels the developer from the surface of the first developing sleeve 109. N1 pole 114 and N2 pole 115 are arranged. On the other hand, in the second developing roll 106, the counter magnetic pole N 2 pole that conveys the developer 101 along the surface of the second developing sleeve 109 is upstream of the N 2 pole 121 that is the counter magnetic pole in the developing sleeve rotation direction. Thus, a carrier magnetic pole S2 pole 120 having a polarity opposite to that of the magnetic pole 121 is disposed.

  Therefore, according to the study by the present inventors, as shown in FIG. 6, the magnetic flux is guided between the peeled magnetic pole of the first developing roll 105 and the S pole that is the conveying magnetic pole of the second developing roll 106. As shown in FIG. 7, the developer 151 guided along the surface of the guide chute 130 is constrained and retained by the magnetic circuit 150 passing through the magnetic circuit 150. understood. As described above, when the developer 151 stays on the surface of the guide chute 131, the developer 101 that should be dropped and supplied above the developer supply auger 126 via the guide chute 130 is first developed. The toner image is partially dropped through the gap between the roll 105 and the guide chute 131 and is supplied to the first and second developing rollers 105 and 106 as they are. It has become clear that there is a risk of image quality degradation such as typical density degradation.

  Therefore, in the developing device 17 according to this embodiment, as shown in FIG. 1, between the peeling magnetic pole of the first developing roll 105 and the S pole that is the conveying magnetic pole of the second developing roll 106, FIG. As shown, the magnetic circuit suppressing member 140 made of a magnetic material that suppresses the magnetic circuit from being formed by the magnetic flux passing through the guide chute 130 is provided.

  As the magnetic circuit suppressing member 140, for example, a relatively thin plate member made of a magnetic material such as magnetic stainless steel such as SUS430 or SUS631, iron, or nickel is used. Although the thickness of the magnetic circuit suppressing member 140 depends on the magnetic permeability, when the relative magnetic permeability of the magnetic circuit suppressing member 140 is 100, for example, the thickness is set to about 0.1 to 0.5 mm. However, if the magnetic circuit suppressing member 140 is too thick, the end portion of the magnetic circuit suppressing member 140 may be magnetized. About 1 to 0.3 mm is desirable.

  As shown in FIG. 1, the magnetic circuit suppressing member 140 is provided on the back surface side of the guide chute 131 by means such as adhesion over substantially the entire surface thereof. More specifically, as shown in FIG. 8, the magnetic circuit suppressing member 140 is an intermediate portion inclined from the tip 131 of the guide chute 130 except for the predetermined length d at the tip of the guide chute 130. It is provided over the entire length. As the magnetic circuit suppressing member 140, for example, a plate made of magnetic stainless steel (SUS430) having a thickness of 0.2 mm is used. Since the magnetic circuit suppressing member 140 is disposed relatively close to the peeling magnetic pole of the first developing roll 105, the magnetic circuit suppressing member 140 is described above when the magnetic circuit suppressing member 140 is too thick. As described above, the tip of the magnetic circuit suppressing member 140 facing the peeled magnetic pole of the first developing roll 105 is magnetized and may cause the developer 101 to be adsorbed. According to the study by the present inventors, when the magnetic circuit suppressing member 140 has a magnetic permeability of 100, a sufficient effect can be obtained by using a plate made of magnetic stainless steel having a thickness of about 0.2 mm. understood.

  In this embodiment, as shown in FIGS. 1 and 8, the magnetic circuit suppressing member 141 is also arranged on the back surface side of the trimmer member 123. As the magnetic circuit suppressing member 141 disposed on the back side of the trimmer member 123, for example, a plate material made of magnetic stainless steel having a thickness of about 0.5 mm is used.

  In the above configuration, in the image forming apparatus to which the developing device according to this embodiment is applied, the developer peeled from one developer holding body among the plurality of developer holding bodies is conveyed as follows. It is possible to suppress the formation of a magnetic circuit between the developer holding member and the other developer holding member through the guide member that guides to the portion.

  That is, in the image forming apparatus to which the developing device according to this embodiment is applied, as shown in FIG. 2, cyan (C), magenta (M), high chroma cyan (HC), high chroma magenta (HM), yellow (Y ), In each of the black (K) image forming portions 13C, 13M, 13HC, 13HM, 13Y, and 13K, the surface of the photosensitive drum 15 is charged by the scorotron 16, and then the image exposure device 14 performs an image according to the image data. Exposure is performed, and an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 15. The electrostatic latent image formed on the surface of the photosensitive drum 15 is developed with the corresponding color toner by the developing device 17 as shown in FIG. 1, and a toner image is formed on the surface of the photosensitive drum 15. Is done.

  Cyan (C), magenta (M), high chroma cyan (HC), high chroma magenta (HM), yellow (Y), black (K) image forming units 13C, 13M, 13HC, 13HM, 13Y, 13K photoconductors The toner images of the respective colors formed on the drum 15 are subjected to multiple primary transfer onto the intermediate transfer belt 25 and then subjected to secondary transfer collectively from the intermediate transfer belt 25 onto the recording paper 34 at the secondary transfer position 50. Is done.

  A part or all of the toner images of cyan (C), magenta (M), high chroma cyan (HC), high chroma magenta (HM), yellow (Y), and black (K) are secondarily transferred together. As shown in FIG. 2, the recording sheet 34 is heated and pressurized by a fixing device 37 to fix an unfixed toner image, and then conveyed to a cooling unit 41 by a sheet conveying device 40 to be cooled and curled. The paper is discharged onto a discharge tray 43 provided outside the image forming apparatus main body 1 with the curl corrected by the correction unit 42.

  At that time, in the developing device 17, as shown in FIG. 1, the developer 101 accommodated in the developing device main body 104 is conveyed while being agitated by the developer supply auger 126 and the developer agitating / conveying auger 128. In the meantime, the toner in the developer 10 is negatively charged by frictional charging with the carrier or the like, and is supplied to the second developing roll 106 by the developer supply auger 126. The developer 101 supplied to the second developing roll 106 is conveyed along the counterclockwise direction as the developing sleeve 110 of the second developing roll 106 rotates, and the developer 101 is fed by the trimmer member 123. In a state in which the layer thickness is regulated, the second developing roll 106 and the first developing roll 105 are conveyed to a facing portion 124 that is in close proximity and facing. The developer 101 is separated into the first developing roll 106 and the second developing roll 105 by the separating member 125. The developer 101 separated on the first developing roll 106 side is transported along the clockwise direction as the developing sleeve 109 of the first developing roll 105 rotates, and the developing 101 faces the surface of the photosensitive drum 15. After moving to the region 111 and used for developing the electrostatic latent image on the surface of the photosensitive drum 15, it is transported along the clockwise direction as the developing sleeve 109 rotates, and the developing sleeve 109 is peeled off by the peeling magnetic pole. And a new developer 101 is supplied at a portion 124 facing the second developing roll 106.

  On the other hand, the developer 101 separated on the second developing roll 106 side is conveyed along the counterclockwise direction as the developing sleeve 110 of the second developing roll 105 rotates, and the developer 101 is separated from the surface of the photosensitive drum 15. After moving to the opposite developing area 135 and being used for developing the electrostatic latent image on the surface of the photosensitive drum 15, it is conveyed along the counterclockwise direction as the developing sleeve 109 rotates, and the peeled magnetic pole Is peeled off from the surface of the developing sleeve 109, and a new developer 101 is supplied by the developer supply auger 126.

  At this time, in the developing device 17, as shown in FIG. 1, the first and second developing rolls 105 of the facing portion 124 where the first developing roll 105 and the second developing roll 106 face each other close to each other, On the upstream side in the rotational direction of 106, there are an N1 pole 114 and an N2 pole 115 as separation magnetic poles on the first developing roll 105, and a second S2 pole 120 as a conveying magnetic pole of the second developing roll 106. Magnetized. Therefore, in the developing device 17, the magnetic flux formed between the separation magnetic poles N1 pole 114 and N2 pole 115 of the first developing roll 105 and the S2 pole 120 that is the transport magnetic pole of the second developing roll 106 is shown in FIG. As shown, there is a possibility that the magnetic circuit 150 passing through the surface of the guide chute 130 is constructed.

  However, in the developing device 17 according to this embodiment, as shown in FIG. 1, an S pole that is a separation magnetic pole of the first developing roll 105 and a conveying magnetic pole of the second developing roll 106 is provided on the back surface side of the guide chute 130. A magnetic circuit suppressing member 140 made of a magnetic material that suppresses the formation of a magnetic circuit that passes through the guide chute is disposed. Therefore, in the developing device 17, as shown in FIG. 1, between the separation magnetic poles N1 pole 114 and N2 pole 115 of the first developing roll 105 and the S2 pole 120 which is the transport magnetic pole of the second developing roll 106, As shown in FIG. 9, the magnetic flux passing through the magnetic circuit suppressing member 140 disposed on the back surface side of the guide chute 130 is formed, and the magnetic circuit 150 passing through the surface of the guide chute 130 is not formed at all, or the magnetic circuit 150 is The formation can be suppressed.

Therefore, the developer 101 separated from the surface of the first developing roll 105 by the separation magnetic poles N1 pole 114 and N2 pole 115 is not restrained by the surface of the guide chute 130 as shown in FIG. In a state where the surface of 130 is slid by gravity, it is dropped and supplied to the upper portion of the developer supply auger 126, and is conveyed while being agitated with the developer in the developing device main body 104 by the developer supply auger 126. It is supplied to the surface of the developing roll 106.

  Therefore, according to the developing device 17, the developer 101 to be supplied to the upper side of the developer supply auger 126 via the guide chute 131 partially passes through the gap between the first developing roll 105 and the guide chute 130. The toner image drops and is supplied to the first and second developing rolls 105 and 106 as they are, and the toner image developed on the photosensitive drum 15 has a reduced image quality such as a partial density decrease, and a development history. It is possible to effectively prevent or suppress the occurrence of development ghost and the like appearing in the toner image.

Experimental Example The inventors made a prototype of a developing device 17 as shown in FIG. 1 and performed a first magnetic field analysis using a two-dimensional vector potential method under the same conditions as the arrangement of each member of the developing device 17. And the magnetic field generated by the magnetic flux formed around the second developing rolls 105 and 106, the guide chute 130, and the trimmer member 123, and the gap between the first developing roll 105, the guide chute 130, and the second developing roll 106 is obtained. An experiment was conducted in which the distribution of the magnetic flux formed and the situation in which the developer 101 was restrained on the surface of the guide chute 131 of the experimentally developed developing device 17 were compared.

  As a magnetic field analysis method, as shown in FIG. 10, the shapes of the first and second developing rolls 105 and 106, the guide chute 130, and the trimmer member 123 of the prototyped developing device 17 are input as two-dimensional parameters. In addition, the magnetic circuit suppressing member 140 is disposed on the back surface of the guide chute 130 and the magnetic circuit suppressing member 141 is disposed on the back surface of the trimmer member 123.

  FIG. 11 shows the calculation with the relative permeability of the magnetic circuit suppressing member 140 and the magnetic circuit suppressing member 141 as 50. 6 shows the magnetic field analysis results when the magnetic circuit suppressing member is not provided, and FIG. 9 shows the magnetic field analysis results when the relative permeability of the magnetic circuit suppressing member 140 and the magnetic circuit suppressing member 141 is calculated as 100, respectively. .

  Further, FIG. 12 shows a case where the magnetic circuit suppressing member is not provided (FIG. 6), a case where the relative permeability of the magnetic circuit suppressing member 140 and the magnetic circuit suppressing member 141 is calculated as 50 (FIG. 11), and a magnetic circuit suppressing member. The direction perpendicular to the surface of the guide chute 130 (Y direction) and the tip side along the surface of the guide chute 130 when the relative permeability of the member 140 and the magnetic circuit suppressing member 141 is calculated as 100 (FIG. 9). FIG. 6 is a graph showing values obtained by actually measuring the distribution of the magnetic flux density in the horizontal direction (Z direction) toward the center in the experimental developing device 17 and values obtained by magnetic field analysis.

  As is apparent from FIG. 12, when the relative permeability of the magnetic circuit suppressing member 140 and the magnetic circuit suppressing member 141 is calculated as 100 (FIG. 9), the actual measurement is performed as shown in FIG. It can be seen that the obtained value and the value obtained by the magnetic field analysis are substantially the same.

  13 to 18 show magnetic flux density distributions in the direction perpendicular to the surface of the guide chute 130 (Y direction) and in the horizontal direction toward the tip side along the surface of the guide chute 130 (Z direction). Shows the result of actual measurement by changing the thickness of the magnetic circuit suppressing member 140 and the state where the developer staying on the surface of the guide chute 130 is actually observed and photographed. .

  As is apparent from FIGS. 13 to 18, if the thickness of the magnetic circuit suppressing member 140 is 0.1 mm or 0.2 mm, the amount of developer staying on the surface of the guide chute 130 can be greatly reduced. Can be seen and desirable. In addition, when the thickness of the magnetic circuit suppressing member 140 is 0.3 mm, the amount of developer staying on the surface of the guide chute 130 can be reduced to almost no amount. It can be seen that a slightly stagnant developer appears.

  Note that the inventors conducted an experiment to observe the amount of the developer staying on the surface of the guide chute 130 by changing the toner concentration in the developer to 4% and 12%. Obtained.

Embodiment 2
FIG. 19 shows a second embodiment of the present invention. The same reference numerals are given to the same parts as those in the first embodiment. In the second embodiment, the first developing roll is used. In order to further improve the stirring ability of the peeled developer, an auxiliary stirring member for assisting the developer stirring is arranged at the end of the developer chute direction along the surface of the guide chute 130. It is.

  That is, in the second embodiment, as shown in FIG. 19, a paddle 160 as an auxiliary stirring member for assisting the stirring of the developer is rotatably disposed on the back side of the guide chute 130 inside the developing device main body 104. Has been. As shown in FIG. 20, the paddle 160 includes four stirring members, and the developer 101 guided along the surface of the guide chute 130 by being driven to rotate in the counterclockwise direction in the figure. Is forcibly conveyed to the developer supply auger 126 while being stirred by four stirring members.

  Thus, as shown in FIG. 19, by providing the paddle 160 as an auxiliary stirring member, the developer 101 guided along the surface of the guide chute 130 is forcibly conveyed to the developer supply auger 126. It is possible to further suppress the developer from staying on the surface of the guide chute 130.

  Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.

Embodiment 3
FIG. 21 shows a third embodiment of the present invention. The same reference numerals are given to the same parts as those in the first embodiment, and this third embodiment relates to the present embodiment. The developing device is not a tandem full-color image forming apparatus, but is applied to a single-color image forming apparatus having only one image carrier.

  That is, in the third embodiment, as shown in FIG. 21, only one photosensitive drum 15 as an image holding member is disposed in the image forming apparatus main body 1 so as to be rotatable along the arrow direction. Around the photosensitive drum 15, a charging roll 16 as primary charging means, an image exposure device 13, and a developing device 17 according to the embodiment of the present invention are arranged.

  The electrostatic latent image formed on the surface of the photosensitive drum 15 is developed with, for example, black (K) toner by the first and second developing rolls 105 and 106 of the developing device 17, and then the paper feeding tray 44. Are transferred by a transfer roll 26 onto a recording sheet 34 as a recording medium supplied one by one by a sheet feeding roll 46a, a retard roll 46b, and a feed roll 46c. The recording paper 34 can also be fed from a manual feed tray 44 a disposed on the side surface of the image forming apparatus main body 1.

  The recording paper 34 onto which the toner image has been transferred from the photosensitive drum 15 is fixed by heat and pressure by the heating roll 38 and the pressure roll 39 of the fixing device 37, and then the upper portion of the image forming apparatus main body 1 by the discharge roll 54a. The paper is discharged onto a paper discharge tray 43 provided in the printer.

  Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.

  15: photosensitive drum, 105: first developing roll, 106: second developing roll, 126: developer transport auger, 130: guide chute, 140: magnetic circuit suppressing member.

Claims (5)

A plurality of developer holders having a magnetic roll disposed vertically opposite the image carrier and having a plurality of magnetic poles magnetized therein;
A conveying member that is arranged adjacent to one developer holding body among the plurality of developer holding bodies and conveys the developer held by the plurality of developer holding bodies via the one developer holding body. When,
A separating member that is disposed between the plurality of developer holders and separates the developer conveyed by the conveying member into the plurality of developer holders;
Of the plurality of developer holders, at least a surface in contact with the developer that guides the developer peeled from the developer holder disposed relatively above to the transport member is made of a non-magnetic material. A guide member;
Development that is arranged along the axial direction of the developer holder other than the separation member on the opposite side of the surface of the guide member that contacts the developer, and that is adjacent to the developer holder that is disposed relatively upward. A developing device comprising: a magnetic circuit suppressing member made of a magnetic material that suppresses formation of a magnetic circuit passing through the guide member between the agent holding member and the agent holding member.   The magnetic roll of the developer holding body and the magnetic roll of the adjacent developer holding body that are disposed relatively above have magnetic poles of opposite polarities magnetized at positions facing each other. The developing device according to claim 1.   The developing device according to claim 1, wherein the magnetic circuit suppressing member is set to a thickness of 0.1 to 0.3 mm.   The developer holder disposed relatively above rotates so that a surface facing the image holder moves in a direction opposite to the moving direction of the image holder, and the relatively below 4. The developer holding member arranged so as to rotate such that a surface facing the image holding member moves in the same direction as the moving direction of the image holding member. 5. The developing device described. An image carrier for holding an electrostatic latent image;
Developing means for developing the electrostatic latent image held on the image carrier with toner;
Transfer means for transferring the toner image developed on the image holding member to a recording medium directly or via an intermediate transfer member,
An image forming apparatus using the developing device according to claim 1 as the developing unit.