JP5622076B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a developing device, a process cartridge, and an image forming apparatus that use a developer composed of toner and a carrier.

  In recent years, in image forming apparatuses, it has become the mainstream to employ a two-component developing type developing device comprising a toner and a carrier. Many developing devices of this type are configured by arranging two screws arranged horizontally. Of these two screws, the first screw located closer to the photosensitive drum supplies the developer to the developer carrying member (developing sleeve) and collects the developer after passing through the developing unit. Used for. The second conveying screw is used for mixing and stirring the developer collected from the developing sleeve and the newly supplied developer.

  On the other hand, in recent years, in an image forming apparatus using an electrophotographic system such as a copying machine or a printer, there has been an increasing demand for downsizing the apparatus main body in order to achieve space saving. However, since a plurality of developing devices are used, the size of the developing device is larger than that of a monochrome device. However, it is desired to reduce the size as much as possible.

  For this reason, a developing device has been proposed in which two conveying screws, which are circulation means for agitating and conveying the developer and circulating in the developing container, are arranged vertically (Patent Document 1 and Patent Document 2). Such a developing device includes a developing container containing a developer, and has a developing sleeve which is a developer carrying member at an opening facing the photosensitive drum of the developing container. A developing transport chamber and a stirring transport chamber partitioned by a partition are formed vertically on the opposite side of the opening in the developing container, and a circulation means is provided in the developing transport chamber and the stirring transport chamber. First and second conveying screws are respectively installed. The first transport screw transports the developer in the developing transport chamber, and the second transport screw enters the stirring transport chamber from the toner supply port into the stirring transport chamber and the toner supplied to the upstream side of the second transport screw. The existing developer is conveyed while stirring, and the toner concentration of the developer is made uniform.

  In the vertical agitation type developing device as described above, the development conveyance chamber and the agitation conveyance chamber are arranged vertically above and below, so that the space occupied in the horizontal direction can be small. In a color image forming apparatus such as a tandem system that is mounted in parallel in the direction, advantages such as contributing to downsizing of the apparatus can be obtained.

  The flow of the developer in such a vertical stirring type developing device will be described. Replenishment toner accompanying toner consumption is supplied into the device from a toner supply port provided in a part of the stirring conveyance chamber. The replenished toner is agitated and mixed by the second conveying screw together with the existing developer in the agitating and conveying chamber, and the toner density of the developer is made uniform. The developer having a uniform toner concentration is dropped and moved from the feeding section downstream in the developer transport direction of the stirring transport chamber to the development transport chamber, and is fixedly disposed inside while being transported by the first transport screw. It is pumped over the entire length of the developing sleeve by the magnetic pole of the magnetic roll. The amount of the developer that has been pumped up is regulated by the developer regulating member, and the developer that finally adheres to the developing sleeve and does not reach the developing area is stirred and conveyed from the delivery section downstream in the developer conveying direction of the developer conveying chamber. Returned to the room. Further, the developer that adheres to the developing sleeve and reaches the developing region but does not move to the image carrier is left from the developing sleeve by the agent separating magnetic pole and is returned to the upper agitating and conveying chamber.

  By the way, in the thing of the said patent document 1, since the developer control member (doctor blade) which controls the quantity of the developer carry | supported by the developer carrying body exists in the upper direction of a developing sleeve, a one-way circulation of a developer is carried out. Conveyance is configured to be conveyed from a supply screw disposed above to a developing sleeve and then to a collection screw disposed below. For this reason, in the developing device having such a configuration, the forward development is performed when the transfer unit of the image forming apparatus is disposed below, and the reverse development is performed when the transfer unit is disposed above. May be a restriction.

  For this reason, there is one in which a one-way circulating conveyance of the developer is performed in the case where the doctor blade is disposed below the developing sleeve (Patent Document 3). In this case, the supply screw is arranged below and the recovery screw is arranged above, and the developer conveyed from below is separated from the sleeve at the upper part of the two-stage roller, thereby allowing the one-way circulation upward conveyance. We have proposed a development system that can reduce stress on the developer. Thus, in this type of developing device, it is preferable to arrange the developer regulating member (doctor blade) below the developing sleeve.

  By the way, in such a developing device, the agitating and conveying chamber is provided with the delivery from the developing and conveying chamber on the upstream side, the return from the developer sleeve from the almost entire length, and the replenishment of toner corresponding to the amount of consumption. is there. When supplying toner into the developer, it is necessary to perform mixing and dispersion with sufficient stirring until the toner reaches the developing sleeve. However, since the specific gravity of the toner is lighter than that of the developer in the stirring / conveying chamber where the toner and developer gather, there is a risk that a so-called “upslip” phenomenon occurs in which newly supplied toner floats and moves above the developer. There is. If such “upslip” occurs, the toner density becomes non-uniform, which may cause background stains and toner scattering. Furthermore, if the newly replenished toner is transported without being dispersed to a certain extent in the stirring and transporting chamber, the stirring becomes insufficient and the toner is sent to the developing transport chamber with poor stirring. Caused dirt and toner scattering.

  In view of such circumstances, the present invention intends to provide a developing device, a process cartridge, and an image forming apparatus capable of preventing scumming and toner scattering and obtaining good image quality (high-precision image quality). It is.

A developer carrier that is disposed opposite to an image carrier that carries an electrostatic latent image and encloses a magnetic field generating means, and is disposed to face the lower side of the developer carrier and is carried by the developer carrier. A developer regulating member that regulates the amount of the developed developer, wherein the developer has a carrier and toner, and is disposed substantially opposite to the developer carrying member so as to extend the developer in the longitudinal direction. A first conveying member that is supplied to the developer carrying member while being conveyed, and a developer that is disposed above the first conveying member and that has separated from the developer carrying member, and collects the developer carrying member A second conveying member that conveys the developer in a direction opposite to the first conveying member while stirring along the rotation axis direction; a downstream portion in the conveying direction of the second conveying member; and an upstream portion in the conveying direction of the first conveying member. Connecting the developer conveyed by the second conveying member to the first conveying member And infeed Komu Ri, the delivery section of the delivery unit for connecting the upstream side of the conveyance direction downstream section and the second conveying member of the first conveying member, a toner according to toner consumption in the developer second conveying member A toner replenishing port for supplying the toner to the upstream side of the first conveying member, and the developer regulated by the developer regulating member having a uniform toner density conveyed to the downstream side of the first conveying member via the toner replenishing port. the toner asked downward side in the delivery side of the second conveying member is supplied to the upstream side of the second conveying member Te, but to pass from above of that.

  According to the developing device of the present invention, the developer can be supplied to the developer carrying member by the first conveying member, and the first conveying member is along a direction opposite to the conveying direction of the first conveying member. The developer can be fed by the second transport member that transports the developer. Further, the toner in the developer is sequentially replenished from the toner replenishing port according to the toner consumption. Then, the toner supplied from the toner supply port is transferred from above to the developer by the second conveying member. That is, the developer separated from the developing carrier in the process of transporting the toner-rich developer by replenishment can be covered by the transport member and stirred and transported by the transport member. In this case, the specific gravity of the toner is smaller (lighter) than that of the developer that is a mixture of the toner and the carrier. For this reason, a developer having a large specific gravity is supplied from above the toner having a small specific gravity.

  The rotation direction of the first transport member is set in the same direction as the rotation direction of the developer carrier, and the rotation direction of the second transport member is set in a direction opposite to the rotation direction of the developer carrier. A toner replenishment unit is provided upstream of the transfer unit in the developer transport direction, and the transfer unit includes a first replenishment unit disposed below the straight line connecting the shaft center of the first transport member and the shaft center of the second transport member. A wall portion that shields the first conveying member side and the second conveying member side is provided, and an opening that communicates the first conveying member side with the second conveying member side is formed at least above the straight line. preferable.

  By setting the rotation direction of the second conveying member to be opposite to the rotation direction of the developer carrier, the developer can be brought to the opposite side of the developer carrier. By setting the rotation direction of the first conveying member to the same direction as the rotation direction of the developer carrier, the developer can be supplied to the second conveying member from above, and the replenishment toner can be mixed from above. Stirring can be performed effectively. Moreover, by providing the wall part which shields the 1st conveyance member side and the 2nd conveyance member side, the fall to the 1st conveyance member from a 2nd conveyance member can be prevented.

  The feeding portion is provided with a wall portion that shields the first conveying member side and the second conveying member side below a straight line connecting the axial center of the first conveying member and the axial center of the second conveying member. It is preferable that an opening for communicating the first transport member side and the second transport member side is formed at least above the straight line. With this configuration, when the developer moves from the second conveying member to the first conveying member, the developer moves over the wall while being stirred along the rotation direction of the second conveying member and moves to the first conveying member. Will do.

  The toner has a shape factor SF-1 in the range of 100 to 180, and a shape factor SF-2 in the range of 100 to 180.

  One image forming apparatus of the present invention comprises the developing device described above.

  The process cartridge includes at least one of the developing device described above, an image carrier, a charging unit, and a cleaning unit, and is detachably installed on the main body of the image forming apparatus.

  Another image forming apparatus of the present invention includes the process cartridge.

  In the present invention, developer is delivered from above to the toner replenished from the toner replenishing port. For this reason, it is possible to prevent the toner from slipping due to the difference in specific gravity between the toner and the developer, and to effectively disperse the toner without lowering the developer conveying ability. As a result, it is possible to suppress the occurrence of soiling and toner scattering.

  The rotation direction of the second conveying member is set in the direction opposite to the rotation direction of the developer carrying member, and the rotation direction of the first conveying member is set in the same direction as the rotation direction of the developer carrying member. Generation and promotion of toner dispersion can be prevented by the effect of moving toward the side opposite to the developer carrying member on the member transfer portion side and the mixing and stirring effect of the developer from above on the replenishing toner.

  In addition, by providing a wall portion that shields the first conveying member side and the second conveying member side in the delivery unit, it is possible to prevent the second conveying member from falling onto the first conveying member, and to delay toner supply. Can be prevented. If there is no such wall portion in the transfer section, the replenishment toner slides above the overflow agent from the first transport member, the toner is difficult to disperse, and the rotation direction of each transport member is opposite to that described above. Then, it becomes difficult to mix and stir.

  In the case where the feeding unit is provided with a wall portion that shields the first conveying member side and the second conveying member side, the wall portion is moved over to the first conveying member while being stirred along the rotation direction of the second conveying member. As a result, the dispersibility of the toner in the feeding portion can be improved. If there is no such wall portion in the feeding portion, the developer immediately moves from the second conveying member side to the first conveying member side in the feeding portion, and the stirring effect in the second conveying member is generated. Absent.

  When the shape factor SF-1 is in the range of 100 to 180 and the shape factor SF-2 is in the range of 100 to 180, the toner has a nearly spherical shape, so that the toners are in contact with each other or between the toner and the photoreceptor. Becomes point contact and the adsorptive power becomes weak, so that the toner fluidity becomes high, and the toner replenishment property and the toner density uniformity by stirring become high. Further, since the attracting force with the photoreceptor is weakened, the transfer rate is improved and a high-quality image can be obtained.

  Since the developing device is used in the process cartridge and the image forming apparatus of the present invention, the replenishment toner has good dispersibility, the developer can be sufficiently agitated, and the occurrence of soiling and toner scattering can be suppressed. . For this reason, a high quality image can be formed.

1 is an overall simplified view of an image forming apparatus of the present invention. FIG. 2 is an enlarged cross-sectional view of a main part of the image forming apparatus. FIG. 3 is an enlarged simplified view of a main part of the image forming apparatus for explaining a rotation direction of a conveying member. It is a simplified diagram showing the flow of the developer. FIG. 6 is a perspective view of the process cartridge on the delivery unit side. It is sectional drawing of a delivery part. FIG. 6 is a perspective view of the process cartridge on the feeding portion side. It is sectional drawing of a sending-in part. FIG. 6 is a diagram schematically showing a toner shape for explaining a shape factor SF-1. FIG. 6 is a diagram schematically illustrating a toner shape for explaining a shape factor SF-2. It is a cross-sectional perspective view of the delivery part of a process cartridge. It is a cross-sectional perspective view of the delivery part which shows the 1st modification of a process cartridge. The dispersion member used for the delivery part shown in the said FIG. 12 is shown, (a) is a front view, (b) is a side view. It is a cross-sectional perspective view of the delivery part which shows the 2nd modification of a process cartridge. The dispersion member used for the delivery part shown in the said FIG. 14 is shown, (a) is a front view, (b) is a side view. It is a cross-sectional perspective view of the delivery part which shows the 3rd modification of a process cartridge. The dispersion member used for the delivery part shown in the said FIG. 16 is shown, (a) is a front view, (b) is a side view.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention according to embodiments shown in the drawings will be described.

  FIG. 1 is a schematic configuration diagram illustrating a printer as an image forming apparatus, and FIG. 2 is a schematic cross-sectional view of an image forming unit provided in the image forming apparatus.

  As shown in FIG. 1, the image forming apparatus main body 20 includes image forming units 6Y and 6M corresponding to the respective colors (yellow, magenta, cyan, black) so as to face the intermediate transfer belt 8 provided in the intermediate transfer unit 10. , 6C, 6Bk are juxtaposed. The image forming units 6Y, 6M, 6C, and 6Bk have substantially the same structure except that the color of the toner used in the image forming process is different.

  As shown in FIG. 2, the image forming unit 6 includes a photosensitive drum 1 as an image carrier, a charging unit (charging means) 2 disposed around the photosensitive drum 1, and a developing device 3 as a developing unit. The cleaning unit (cleaning means) 4 and the like. In FIG. 2, alphabets (Y, M, C, Bk) of symbols representing color identification are omitted. 1 shows only the developing device 3 and the photosensitive drum 1 among the components shown in FIG.

  The photosensitive drum 1, the charging unit 2, the developing device 3, and the cleaning unit 4 constituting the image forming unit 6 are configured as a process unit that can be integrally attached to and detached from the image forming apparatus main body 20. With such a configuration, the workability of the maintenance work of the image forming unit 6 is improved. Further, the photosensitive drum 1, the charging unit 2, the developing device 3, and the cleaning unit 4 may be configured to be detachable from the image forming apparatus main body 20 independently. In this case, when each reaches the end of its life, it can be replaced with a new one.

  In FIG. 1, four primary transfer rollers 9Y, 9M, 9C, and 9Bk as primary transfer units are disposed at positions facing the four photosensitive drums 1Y, 1M, 1C, and 1Bk via the intermediate transfer belt 8. ing. Each of the primary transfer rollers 9Y, 9M, 9C, 9Bk forms a primary transfer nip by sandwiching the intermediate transfer belt 8 with the photosensitive drums 1Y, 1M, 1C, 1Bk.

  A secondary transfer roller 7 as a secondary transfer unit is disposed on the outer peripheral surface side of the intermediate transfer belt 8. A secondary transfer backup roller 17 is disposed at a position facing the secondary transfer roller 7, and the intermediate transfer belt 8 is sandwiched between the secondary transfer backup roller 17 and the secondary transfer roller 7 to perform secondary transfer. A nip is formed.

  A lower part of the image forming apparatus main body 20 is provided with a paper feed tray 11 that stores paper P as a recording medium, a paper feed roller 12 that carries the paper P out of the paper feed tray 11, and the like. On the other hand, a pair of paper discharge rollers 13 for discharging paper and a paper discharge tray 14 for stocking the discharged paper are disposed on the upper part of the image forming apparatus main body 20.

  Further, a conveyance path R for guiding paper from the lower paper feed tray 11 to the upper paper discharge tray 14 is formed in the image forming apparatus main body 20. In the conveyance path R, a pair of registration rollers 15 are disposed on the way from the paper feed roller 12 to the secondary transfer roller 7. In addition, a fixing device 16 for fixing an image on the paper is provided on the way from the secondary transfer roller 7 to the paper discharge roller 13. The fixing device 16 includes a heating roller 16a having a heating source therein, and a pressure roller 16b that pressurizes the heating roller 16a. A fixing nip is formed at a pressure contact portion where the heating roller 16a and the pressure roller 16b are in pressure contact with each other.

  Next, the basic operation of the image forming apparatus will be described with reference to FIGS. When the image forming operation is started, the photosensitive drum 1 of the image forming unit 6 shown in FIG. 2 is rotationally driven clockwise by a driving device (not shown), and the surface of the photosensitive drum 1 is predetermined by the charging unit 2. Uniformly charged to polarity. The charged surface of the photosensitive drum 1 is irradiated with a laser beam L from an exposure device (not shown) to form an electrostatic latent image on the surface of the photosensitive drum 1. At this time, the image information exposed on the photosensitive drum 1 is single-color image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. By supplying toner to the electrostatic latent image formed on the photosensitive drum 1 in this way by the developing device 3, the electrostatic latent image is visualized as a toner image (developer image).

  The image forming operation is performed in each of the four image forming units 6Y, 6M, 6C, and 6Bk shown in FIG. Thereafter, the toner images formed on the photosensitive drums 1Y, 1M, 1C, and 1Bk reach the primary transfer nips where the photosensitive drums 1Y, 1M, 1C, and 1Bk and the intermediate transfer belt 8 face each other. At the position of the primary transfer nip, the toner images are sequentially superimposed and transferred onto the intermediate transfer belt 8 running in the direction of the arrow in the figure. More specifically, the toner images on the photosensitive drums 1Y, 1M, 1C, and 1Bk are transferred to the primary transfer rollers 9Y, 9M, 9C, and 9Bk by applying a transfer bias having a polarity opposite to the charging polarity of the toner. When the nip is reached, the toner image is electrostatically transferred onto the intermediate transfer belt 8. Thus, the intermediate transfer belt 8 carries a full-color toner image (color image) on its surface.

  On the other hand, toner that could not be transferred to the intermediate transfer belt 8 remains on the surface of each photosensitive drum 1Y, 1M, 1C, 1Bk, but residual toner on each photosensitive drum 1Y, 1M, 1C, 1Bk remains. These are removed by the cleaning blade 4a provided in the cleaning unit 4 shown in FIG. Further, the residual potential on each of the photoconductive drums 1Y, 1M, 1C, and 1Bk is removed by a static eliminator (not shown) to prepare for the next image formation.

  Thereafter, the color image transferred onto the intermediate transfer belt 8 reaches a secondary transfer nip where the intermediate transfer belt 8 and the secondary transfer roller 7 face each other, and the sheet conveyed at this position is transferred onto the intermediate transfer belt 8. The color image is transferred. At this time, a transfer bias having a polarity opposite to the toner charging polarity is applied to the secondary transfer roller 7, whereby the color image on the intermediate transfer belt 8 is electrostatically transferred onto the sheet.

  The sheet conveyed to the position of the secondary transfer nip is conveyed from the sheet feeding tray 11. Specifically, the paper P accommodated in the paper feed tray 11 is sent out to the transport path R by rotating the paper feed roller 12. The paper P sent out to the transport path R is temporarily stopped by the registration roller 15. Then, the rotation of the registration roller 15 is resumed in synchronization with the toner image on the intermediate transfer belt 8, and the sheet is conveyed to the secondary transfer nip. In this way, a desired color image is transferred to the paper. Further, the surface of the intermediate transfer belt 8 after the color image is transferred is cleaned by a cleaning device (not shown) to remove residual toner.

  Thereafter, the sheet on which the color image is transferred at the position of the secondary transfer nip is conveyed to the fixing device 16. Then, the paper is heated and pressed by the heating roller 16a and the pressure roller 16b to fix the color image. Thereafter, the sheet on which the image is fixed is discharged to a discharge tray 14 by a discharge roller 13.

  The above description is an image forming operation when a full-color image is formed on a sheet. A single color image can be formed using any one of the four image forming units 6Y, 6M, 6C, and 6Bk. Two or three image forming units can be used to form a two-color or three-color image.

  As shown in FIG. 3, the developing device 3 is a developing device in which a fixed amount of a developer in which a toner (5.8 μm) mainly composed of a polyester resin and a carrier (35 μm) that is a magnetic fine particle are uniformly mixed to 7 wt% is filled. A case 25 and a developer carrier 49 that is rotatably supported by the developing case 25 and is disposed opposite to and in close proximity to the image carrier 1 (see FIGS. 1 and 2) through an opening formed in the developing case. A developing sleeve 51 that rotates counterclockwise, and a magnetic roll 55 that is fixed in the sleeve 51 and has five magnetic poles P1 to P5. It has.

  FIG. 3 shows the positions where the magnetic forces of the five magnetic poles P1 to P5 are peaked. A doctor blade 52 as a developer restricting member supported by the developing case 25 is disposed close to the lower side of the developing roller 50, and the amount of developer on the developing roller 50 is restricted by the doctor blade 52. The developing device 3 is provided with a developing transport chamber 61 obliquely below the developing roller 50 and an agitating transport chamber 62 that is substantially horizontal and above (develops upward) the developing transport chamber. A first conveying screw (first conveying member) 53 as a developer conveying member is provided in the developing conveying chamber 61, and a second conveying screw (second conveying member) 54 as a developer conveying member is provided in the agitating and conveying chamber, respectively. Has been placed.

  The first conveying member 53 and the second conveying member 54 have their axes parallel to the axis of the developing roller 50, and the first conveying member 53 is adjacent to the entire length of the developing roller 50 in the axial direction. The length of one transport member 53 in the axial direction is set to be equal to or slightly longer than the length of the developing roller 50. Similarly, the second conveying member 54 that is adjacent to the entire length of the developing roller 50 in the axial direction may have the same length as the first conveying member 53, but in this embodiment, the length of the second conveying member 54 is the first conveying member. It is set longer than the member 53.

  Further, the first transport member 53 disposed below and the second transport member 54 disposed obliquely upward adjacent to the first transport member 53 are straight lines m connecting the respective axis centers (rotation axes) O1 and O2. However, for example, it is set so as to be inclined at about 30 ° to 50 ° with respect to the horizontal plane. The rotation direction of the first conveying member 53 is the direction of the arrow A1, which is the same direction as the rotation direction of the developing roller 50 (the direction of the arrow A). The rotation direction of the second conveyance member 54 rotates in the direction of arrow B opposite to the rotation direction of the developing roller 50 and the first conveyance member 53. The first and second conveying members 53 and 54 convey the developer while stirring by rotating at 600 to 800 rpm, and perform uniform mixing of toner and carrier and charging.

  FIG. 4 is a development explanatory view showing the flow of the developer in the developing device according to the present invention. In FIG. 4, a toner concentration sensor (not shown) is provided in the developing device, and when the sensor detects an insufficient toner concentration, it is provided on the upstream side (left end in the figure) of the agitating and conveying chamber 62 in the developer conveying direction. An amount of toner corresponding to the amount consumed from the toner supply port 30 serving as a toner supply unit is supplied.

  The agitating / conveying chamber 62 is provided with a transfer portion 31 through which the developing / conveying chamber 61 and the agitating / conveying chamber 62 communicate with each other after the toner replenishing port 30, and a developer regulating member is provided in the developing and conveying chamber 61. Developer G or the like scraped off is sent to a doctor blade 52. A collecting guide (separating member) formed in the developing case 25 is a developer G that is carried by the developing roller 50 and reaches the developing region but is not used for development in the agitating and conveying chamber 62 that has passed the delivery unit 31. It returns as shown by an arrow g1 (see FIG. 3) via 57. That is, the developer separating force from the developing roller 50 is obtained by applying the repulsive force by arranging the P3 and P4 poles of the magnetic roll (mag roller) 55 included therein to apply the repulsive force, and applying the centrifugal force by the rotation of the developing roller 50. Separated in the g1 direction. The returning developer G extends over almost the entire length of the developing roller, and these developers are conveyed to the right in the drawing by the rotation of the second conveying screw. The collection guide 57 has its tip disposed slightly downstream from the separation point at which the developer is separated from the developing roller 50, collects the separated developer, and takes it into the second conveying member (collection screw) 54. Yes.

  By being conveyed while being agitated by the second conveying member 54, the developer G in the agitating / conveying chamber 62 in which the toner density becomes uniform is fed into the developing / conveying chamber 61 from a feeding portion 33 provided on the downstream side in the conveying direction. It is. Since the agitating / conveying chamber 62 is located above the developing / conveying chamber 61 in the feeding portion 33, the feeding is performed by dropping its own weight. The positions of the transfer portion 31 and the feeding portion 33 are provided at positions that respectively exceed the left end and the right end of the developing roller 50. In the transfer section 31 and the feeding section 33, it is preferable that the screw of each of the transport members 53 and 54 is provided with a paddle or a reversely wound screw so as to have a transport capability in a direction perpendicular to the transport direction.

  As described above, the developing device 3 supplies the developer to the developing roller 50 as indicated by an arrow g (see FIG. 3) while stirring and transporting by the first transport member 53, and collects all by the second transport member 54. Taking the formula. For this reason, as shown in FIG. 4, the developer accumulation state in the developing and conveying chamber 61 and the agitating and conveying chamber 62 becomes oblique (the amount of developer in the supply screw decreases in the downstream direction). When the developer transport amount capability obtained from the diameter, pitch and rotation speed of the first transport member 53 is Wm, and the developer transport amount on the developing roller 50 is Ws, the developer when the relationship between them is Wm> Ws. Are uniformly conveyed onto the developing roller 50. If this condition is not satisfied, the developer becomes insufficient on the downstream side of the first conveying member 53, and it becomes impossible to supply the developer G to the developing roller 50.

  In this developing device, a developer regulating member (doctor blade 52) is provided at the lower part of the two vertical axes of a second conveying member (collection screw) 54 and a first conveying member (supply screw) 53 as conveying means. It is a method. For this reason, in the system in which the transfer member (intermediate transfer belt 8) is provided in the upper part, the developer unidirectional circulation that does not return the developer used for development to the supply path is realized. In addition, a developing system (with development) in which the developing roller 50 rotates in the forward direction with respect to the photosensitive drum 1 can be established.

  By the way, the delivery part 31 is formed in the casing 65 as shown in FIG. 5 and FIG. The casing 65 includes an inclined wall 65a parallel to the straight line m, an opposing wall 65b facing (facing) the inclined wall 65a, and curved walls 65c and 65d that connect ends of the inclined wall 65a and the opposing wall 65b. Is provided.

  The opposing wall 65b is composed of a pair of arc portions 66 and 67 that are continuous with the curved walls 65c and 65d. Further, the ends of the arc portions 66 and 67 on the side opposite to the curved wall are connected, and this connecting portion constitutes a wall portion 68 disposed between the first transport member 53 side and the second transport member 54 side. To do. In this case, the wall portion 68 is disposed at a position below the straight line m. An opening 69 that connects the first transport member 53 side and the second transport member 54 side is formed above the wall 68.

  For this reason, in the transfer portion corresponding portion of the developing conveyance chamber 61, as shown in FIG. 6, the developer G is agitated from above as indicated by the arrow C by the rotation of the first conveying member 53 in the arrow A1 direction. It is delivered through the opening 69 at the delivery part corresponding part of the transfer chamber 62. Further, in the transfer portion corresponding portion of the agitating / conveying chamber 62, the toner supplied from the replenishing port 30 has moved in the arrow B direction from the lower end portion because the second conveying member 54 rotates in the arrow B direction. It is in a state. In other words, the developer carrier 49 can be moved to the opposite side.

  Accordingly, the developer is delivered from above to the toner replenished from the toner replenishing port 30. In this way, since the specific gravity of the toner is lighter than that of the developer G when it is delivered, the light developer is covered with the heavy developer G. For this reason, in the agitation transport chamber 62, it is possible to suppress the phenomenon of upslip that causes the replenished toner to move on the developer. In other words, it is possible to prevent the toner from slipping up due to the difference in specific gravity between the toner and the developer G, and to effectively disperse the toner without lowering the developer conveying ability. As a result, it is possible to suppress the occurrence of soiling and toner scattering.

  By setting the rotation direction of the second conveyance member 54 to be opposite to the rotation direction of the developer carrier 49 and setting the rotation direction of the first conveyance member 53 to be the same direction as the rotation direction of the developer carrier 49. The toner is dispersed due to the effect of moving toward the opposite side of the developer carrier 49 on the delivery portion 31 side of the second conveying member 54 and the mixing and stirring effect of the developer from above on the replenishing toner. Can prevent promotion. In addition, the transfer unit 31 is provided with a wall portion 68 that shields the first conveyance member side 53 and the second conveyance member 54 side, thereby preventing the second conveyance member 54 from falling onto the first conveyance member 53. And delay in toner supply can be prevented.

  The feeding portion 33 is formed by a casing 70 as shown in FIGS. The casing 70 includes an inclined wall 70a parallel to the straight line m, an opposing wall 70b facing (facing) the inclined wall 70a, and curved walls 70c and 70d connecting ends of the inclined wall 70a and the opposing wall 70b. Is provided. The inner surface of the facing wall 70b is configured by a block piece 73 having an arc surface 71 continuous with the inner surface of the curved wall 70c and an arc surface 72 continuous with the inner surface of the curved wall 70d.

  For this reason, the wall part 75 arrange | positioned between the 1st conveyance member 53 side and the 2nd conveyance member 54 side is formed in the junction part of the circular arc surface 71 and the circular arc surface 72. FIG. In this case, the wall portion 75 is disposed at a position below the straight line m. An opening 76 that connects the first transport member 53 side and the second transport member 54 side is formed above the wall 75.

  In the feeding portion corresponding portion of the agitation transport chamber 62, the second transport member 54 rotates in the direction of arrow B, so that the developer is fed into the development transport chamber 61 from above as shown in FIG. That is, the second conveying member 54 rotates counterclockwise in FIG. 8 and conveys the developer while being shifted to the side opposite to the developing roller 50. However, since the wall portion 75 is provided in the feeding portion 33, even if the developer arrives at the feeding portion 33, the feeding portion 33 does not move to the first conveying member 53 side as it is. At this time, it is fed as indicated by an arrow D over the wall 75 along the rotational direction of the second transport member 54 while keeping the offset. For this reason, a dispersion effect can be exhibited in the feeding portion 33.

  Next, toner that is preferably used in a printer will be described. In order to reproduce minute dots of 600 [dpi] or more, the volume average particle diameter of the toner is preferably 3 to 8 [μm]. The ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) is preferably in the range of 1.00 to 1.40. The closer (Dv / Dn) is to 1.00, the sharper the particle size distribution. With such a toner having a small particle size and a narrow particle size distribution, the toner charge amount distribution is uniform, a high-quality image with little background fogging can be obtained, and the electrostatic transfer method has a high transfer rate. can do.

The toner shape factor SF-1 is preferably in the range of 100 to 180, and the shape factor SF-2 is preferably in the range of 100 to 180. FIG. 9 is a diagram schematically showing the shape of the toner in order to explain the shape factor SF-1. FIG. 10 is a diagram schematically showing the shape of the toner in order to explain the shape factor SF-2. The shape factor SF-1 indicates the ratio of the roundness of the toner shape, and is expressed by the following formula 1. This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.

  When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.

The shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is expressed by the following formula 2. A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner on the two-dimensional plane by the figure area AREA and multiplying by 100π / 4.

  When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.

  Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), and introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) for analysis. And calculated.

  When the shape of the toner is close to a spherical shape, the contact state between the toner and the toner or the toner and the photoconductor becomes a point contact, so that the adsorbing force between the toners becomes weak and the fluidity increases, and the toner and the photoconductor The attraction force becomes weaker and the transfer rate becomes higher. If either of the shape factors SF-1 and SF-2 exceeds 180, the transfer rate is lowered, which is not preferable.

  As the toner, when the shape factor SF-1 is in the range of 100 to 180 and the shape factor SF-2 is in the range of 100 to 180, the toner shape is nearly spherical, so that the contact state between the toners or between the toner and the photoconductor Becomes point contact and the adsorptive power becomes weak, so that the toner fluidity becomes high, and the toner replenishment property and the toner density uniformity by stirring become high. Further, since the attracting force with the photoreceptor is weakened, the transfer rate is improved and a high-quality image can be obtained.

  FIG. 12 shows a first modification. As shown in FIG. 11, the dispersion member 80 is disposed in the range H in the casing 65 of the transfer section 31. The dispersion member 80 is made of a plate material having a thickness of 0.2 to 0.8 mm made of a resin such as polyethylene terephthalate (PET).

  That is, as shown in FIGS. 13A and 13B, the dispersion member 80 includes a first wall 81 attached to the inner surface of the inclined wall 65 a of the casing 65 and a first wall 81 that is bent at a right angle with respect to the first wall 81. It consists of two walls 82 and a third wall 83 that bends at a predetermined angle with respect to the second wall 82. A plurality of through holes 84 are provided on the second wall 82 on the first wall 81 side. The through holes 84 in this case are arranged in a three-row zigzag pattern as shown in FIG.

  The dispersion member 80 has a first wall 81 attached to the inner surface of the inclined wall 65a of the casing 65, and a third wall 83 attached to the inner surface of the arc portion 66 of the opposing wall 65b. It arrange | positions so that the opening part 69 between the 2nd conveyance member 54 side may be plugged up. In this case, the plurality of through holes 84 are arranged so as to be positioned above the straight line m. For example, a double-sided tape can be used for joining the dispersing member 80 to the inner surface of the casing 65. Here, the double-sided tape refers to a tape having adhesiveness on each of the front and back surfaces. Moreover, you may use an adhesive agent without using a double-sided tape.

  If such a dispersing member 80 is provided, when the developer is transferred from the first conveying member 53 side to the second conveying member 54 side, the dispersing member 80 is passed through the through holes 84 arranged in a staggered manner. Done. For this reason, the developer is dispersed when passing through the through hole 84. Further, since the plurality of through holes 84 are arranged so as to be positioned above the straight line m, it is possible to prevent the developer from dropping from the second conveying member 54 side to the first conveying member 53 side.

  FIG. 14 shows a second modification. In this case, as shown in FIGS. 15 (a) and 15 (b), an eave 85 is provided in the through hole 84. FIG. In other words, the second wall 82 is provided with a semicircular slit, and the remaining portion in the slit is raised by a predetermined angle. In this case, the through-hole 84 is also preferably arranged so as to be positioned above the straight line m.

  In the state in which the dispersion member 80 is mounted, the eaves 85 are in a state of projecting horizontally from the first transport member 53 side to the second transport member 54 side. For this reason, it can be delivered from the first conveying member 53 to the second conveying member 54 through the through-hole 84, and the developer can be dispersed during the delivery. Further, the developer shaken off from the second conveying member 54 side is struck against the eaves 85, the return is prevented, and the dispersion effect can be enhanced.

  Next, FIG. 16 shows a third modification. In this case, a dispersion member 86 is arranged in the feeding portion 33. The dispersion member 86 in this case is also bent at a right angle with respect to the first wall 87 attached to the inner surface of the inclined wall 65a of the casing 65 and the first wall 87, as shown in FIGS. It consists of a second wall 88 and a third wall 89 that bends at a predetermined angle with respect to the second wall 88. A plurality of through holes 90 are provided on the second wall 88 on the first wall 87 side. The through-hole 90 in this case is formed of a rectangular hole extending in the width direction of the dispersion member 86 as shown in FIG. A plurality of through holes 90 (five in the illustrated example) are arranged at a predetermined pitch in the vertical direction perpendicular to the width direction of the dispersion member 86. In this case, it is preferable to arrange the through hole 84 so as to be positioned above the straight line m.

  By the way, the dispersion member 86 is made of a metal plate such as a thin phosphor bronze plate having a thickness of about 0.1 mm to 0.3 mm, for example. Moreover, when using such a copper plate (metal plate), the through-hole 90 can be formed by an etching process or the like.

  Thus, by using a copper plate having a small thickness for the dispersion member 86, the developer collides with the dispersion member 86, thereby generating vibrations and exhibiting the dispersion effect.

In addition, this invention is not limited to the above-mentioned Example, Of course, a various change can be added in the range which does not deviate from the summary of this invention. Examples of the image forming apparatus according to the present invention include an electrophotographic copying machine, a laser beam printer, and a facsimile machine.
As an inclination angle of the straight line m connecting the axis center of the first conveyance member 53 and the axis center of the second conveyance member 54 with respect to the horizontal plane, the first conveyance member 53 side to the second conveyance member 54 side as indicated by an arrow C in FIG. Various changes can be made within a range in which the developer can be moved and the replenished toner on the second conveying member 54 side does not move to the first conveying member side.

  The dispersion member 80 is not limited to resin, and may be made of metal. Further, the number, size, shape, and the like of the through holes 84 in the dispersion member 80 can be variously changed as long as the developer can be moved from the first conveying member 53 side to the second conveying member 54 side. The dispersion member 86 shown in FIG. 17 may be used on the delivery part 31 side, or the dispersion member 80 shown in FIGS. 13 and 15 may be used on the feeding part 33 side. In addition, when using a resin plate for the dispersion members 80 and 86, it is not restricted to PET, and when using a metal plate, it is not restricted to phosphor bronze. In other words, any material can be used as long as it can function as the dispersing members 80 and 86 and can be attached to the developing device.

DESCRIPTION OF SYMBOLS 1 Image carrier 2 Charging means (charging part)
4 Cleaning means (cleaning part)
30 Toner replenishment port 31 Delivery section 33 Feed section 53 First transport member 54 Second transport member 68 Wall section 75 Wall section

JP-A-5-333691 Japanese Patent Laid-Open No. 11-174810 Japanese Patent No. 3950735

Claims (7)

A developer carrier that is disposed opposite to an image carrier that carries an electrostatic latent image and encloses a magnetic field generating means, and is disposed to face the lower side of the developer carrier and is carried by the developer carrier. A developer regulating member that regulates the amount of the developed developer, the developer having a carrier and a toner,
A first conveying member that is disposed substantially opposite the developer carrier and that supplies the developer to the developer carrier while conveying the developer in the longitudinal direction;
The developer disposed above the first conveying member, recovering the developer separated from the developer carrying member, and collecting the developer while stirring along the rotation axis direction of the developer carrying member. A second conveying member that conveys in the opposite direction;
A feeding section that connects the downstream portion in the transport direction of the second transport member and the upstream portion in the transport direction of the first transport member, and sends the developer transported by the second transport member to the first transport member;
A delivery part for connecting the downstream part in the transport direction of the first transport member and the upstream side in the transport direction of the second transport member;
A toner replenishing port for supplying toner to the upstream side of the delivery portion of the second conveying member according to toner consumption in the developer ,
The developer regulated by the developer regulating member having a uniform toner density conveyed to the downstream side of the first conveying member is supplied to the upstream side of the second conveying member through the toner replenishing port, and is supplied to the second conveying member. in the transfer portion side of the toner to be attracted to the lower side, the developing device characterized by passing from the top of it.   The rotation direction of the first transport member is set in the same direction as the rotation direction of the developer carrier, and the rotation direction of the second transport member is set in a direction opposite to the rotation direction of the developer carrier. A toner replenishment unit is provided upstream of the transfer unit in the developer transport direction, and the transfer unit includes a first replenishment unit disposed below the straight line connecting the shaft center of the first transport member and the shaft center of the second transport member. A wall portion that shields the first conveying member side and the second conveying member side is provided, and an opening that communicates the first conveying member side and the second conveying member side is formed at least above the straight line. The developing device according to claim 1.   The feeding portion is provided with a wall portion that shields the first conveying member side and the second conveying member side below a straight line connecting the axial center of the first conveying member and the axial center of the second conveying member. 3. The developing device according to claim 1, wherein an opening that communicates the first conveying member side and the second conveying member side is formed at least above the straight line. 4.   4. The toner according to claim 1, wherein the toner has a shape factor SF-1 in the range of 100 to 180 and a shape factor SF-2 in the range of 100 to 180. 5. Development device.   An image forming apparatus comprising the developing device according to claim 1.   The image forming apparatus includes at least one of the developing device according to any one of claims 1 to 4 and an image carrier, a charging unit, and a cleaning unit, and is detachable from the image forming apparatus main body. A process cartridge that is installed.   An image forming apparatus comprising the process cartridge according to claim 6.

Images