JP2012037738A - Developing device, process cartridge and image forming device - Google Patents

Abstract

A developing device capable of reducing the occurrence of uneven image density by suppressing the occurrence of a developer accompanying phenomenon and an image forming apparatus using the same.
In a developing device having a path including a developer carrying member, a first transport path having a first agitation transport member, and a second transport path having a second agitation transport member, a second transport path is provided. A plate-like member 16 is arranged at a position where the developer is lifted from 11 to the first conveyance path so as to be parallel to the advancing direction of the developer conveyed by the second stirring and conveying member 7. The developer is lifted from the transport path to the first transport path, the developer lifting and transporting ability by the plate-like member 16 is higher than the developer transporting ability by the second stirring and transporting member 7, and the development by the first stirring and transporting member is performed. The developer transport capability upstream of the developer transport direction was made higher than the developer lifting and transport capability of the plate-like member 16.
[Selection] Figure 7

Description

  The present invention relates to a developing device of an electrophotographic image forming apparatus that is applied to a copying machine, a facsimile, a printer, and the like and forms an image using toner.

  An electrostatic latent image is formed on the image carrier, the electrostatic latent image is developed with toner to form a toner image on the image carrier, and an electric field is applied by bringing a transfer paper into contact with the toner image. Image forming apparatuses such as a copying machine, a printer, a facsimile, and a complex machine such as these which transfer a toner image onto a transfer paper, and heat and pressurize the transfer paper to fix the toner image and then eject the toner image. Are known.

  As a developer used in the above-described image forming apparatus, a two-component developer in which a magnetic or nonmagnetic toner and a carrier formed of a magnetic material are mixed is known. In this two-component developer, the toner charged by the triboelectric charging action between the toner and the carrier generated during stirring and mixing is electrostatically attracted to the electrostatic latent image on the image carrier. Is done. As a developing device using this two-component developer, a developer carrier that forms a developer spike on its peripheral surface by magnetic force and supplies the developer toward an electrostatic latent image on the image carrier; A first developer agitating and conveying member that supplies a developer that is agitated and mixed with the developer carrying member, and a second developer agitating member that agitates and mixes the developer and the replenishment toner and conveys the developer to the first developer agitating and conveying member. In the image forming apparatus equipped with the developing device, the electrostatic latent image on the image carrier is developed with toner supplied from the developing device to form a toner image. The developer that has consumed the toner is again collected by the developing device.

  An example of the developing device described above is shown in FIG. This developing device is a system in which developer agitating and conveying members 2 and 3 are juxtaposed in the horizontal direction, and the developer agitating and conveying members 2 and 3 are circulated while being agitated and conveyed by the developer agitating and conveying members 2. The developer is supplied to and collected from the developing roller 1, and the developer and the replenishing toner are mixed and stirred by the developer stirring and conveying member 3. In this developing device, the developer stirring and conveying member 2 that supplies the developer to the developing roller 1 and the developer stirring and conveying member 3 that collects the developer after development from the developing roller 1 are the same. Although the developer can be made almost uniform in the developer conveyance direction, the developer whose toner density is reduced due to development is also collected in the same conveyance path, so that the developer is conveyed downstream in the conveyance path. As the toner is supplied to the developing roller 1 a plurality of times, the toner density of the developer gradually decreases, and density unevenness occurs.

  Therefore, as shown in FIG. 13, for example, a developing device disclosed in “Patent Document 1” has been proposed. In the developing device 4, the developer that is carried on the developing roller 8 and conveyed to the developing area A but is not used for development in the developing area A is left on the developing roller 8 by the second developer agitating and conveying member 7. After the toner is collected and appropriately replenished so that the toner density in the developing device becomes uniform, the replenished toner and the developer are agitated and mixed by the second developer agitating / conveying member 7, and the agitated and mixed development is performed. The agent is transferred to the first developer stirring and conveying member 6. Accordingly, since only the developer sufficiently stirred by the second developer stirring / conveying member 7 is always delivered to the first developer stirring / conveying member 6, a developer having a uniform toner density is always supplied to the developing roller 8. As a result, a uniform image without density unevenness can be obtained.

  However, although the above-described technique has an advantage that the toner density of the developer supplied to the developing roller 8 is uniform, the distribution of the amount of the developer 14 in the developing device is biased as shown in FIG. There is a problem that. The developer 14 supplied from the first developer agitating / conveying member 6 to the developing roller 8 is transferred to the second developer agitating / conveying member 7 without returning to the first developer agitating / conveying member 6. The amount of the developer 14 transported by the agitation transport member 6 gradually decreases from the upstream side to the downstream side in the transport direction, and the developer amount in the supply developer chamber 10 is biased. In FIG. 14, reference numeral 15 denotes a lifting portion that lifts the developer 14 upward from the recovery stirring developer chamber 11 to the supply developer chamber 10 via the communication port. The developer 14 is against gravity. Since it is a part to be conveyed, the developer 14 tends to accumulate in the vicinity thereof.

  If the developer 14 accumulates in the vicinity of the downstream end of the recovery stirring developer chamber 11 in the developer conveyance direction, a malfunction phenomenon occurs in which the developer is accompanied. The developer rotation phenomenon means that the developer on the developing roller 8 that has once passed through the developing area A does not leave the surface of the developing roller 8 at a position where the developing roller 8 and the recovery stirring developer chamber 11 face each other. This is a phenomenon that the ink is conveyed again to the development area A. Once the developer has passed through the development area A, the toner density has decreased, and if such toner is transported to the development area A many times and a phenomenon accompanied by the developer occurs, the amount of toner required in the development area A is reduced. The image density cannot be ensured and the image density is lowered, resulting in image quality problems such as uneven image density.

  Note that the developer dragging phenomenon described above occurs due to a large amount of developer in the vicinity of the downstream end in the developer transport direction in the collected developer developer chamber 11. Therefore, it does not occur unless the developer amount in the vicinity of the downstream end in the developer transport direction in the recovery stirring developer chamber 11 is small (if the height of the developer in the recovery stirring developer chamber 11 is low). Further, since the toner replenished upstream of the second developer agitating / conveying member 7 is lighter in weight than the developer, the toner is conveyed without being taken into the developer when the agitation and mixing are insufficient. As a result, the replenished toner is not sufficiently charged, and there is a problem that background stains occur in which toner with a low charge amount adheres to the background portion (white portion) of the image.

  Further, for example, “Patent Document 2” discloses a developing device shown in FIG. This developing device uses the stirring member shown in FIG. 15 to disperse the replenishment toner in the developer, but in the same manner as described above, the developer retention is reduced at the developer lifting portion. The effect of reducing the occurrence of the accompanying phenomenon cannot be obtained.

  The present invention solves the above-mentioned problems and develops the developer by transporting the developer to the developer chamber for supply without staying in the vicinity of the downstream end in the developer transport direction in the developer chamber for collecting agitation. It is an object of the present invention to provide a developing device capable of reducing the occurrence of image density unevenness by suppressing the occurrence of an agent accompanying phenomenon and an image forming apparatus using the same.

  According to a first aspect of the present invention, there is provided a developer carrying member that carries a two-component developer composed of toner and a magnetic carrier and visualizes an electrostatic latent image on the latent image carrying member with the toner, and the developer. A first conveyance path having a first agitating / conveying member that is arranged in parallel with the carrier and conveys the developer and supplies the developer to the developer carrier, and the development is disposed below the first conveyance path. And a second conveying path having a second agitating and conveying member that conveys the developer and collects the developer from the developer carrier, and the developer circulates between the first conveying path and the second conveying path. In the developing device having a path to perform, a plate-like shape arranged so as to be parallel to the traveling direction of the developer conveyed by the second agitating and conveying member at a position where the developer is lifted from the second conveying path to the first conveying path. The plate-like member is centered on the second stirring and conveying member. The developer is lifted from the second conveyance path to the first conveyance path, and the developer conveyance capacity by the plate member is higher than the developer conveyance capacity by the second agitation conveyance member, and The developer conveying capability upstream of the developer conveying direction by the first agitating and conveying member is higher than the developer lifting and conveying capability by the plate-like member.

  According to a second aspect of the present invention, in the developing device according to the first aspect, the first agitation is performed in order to increase the developer conveying ability of the first agitating and conveying member as compared with the developer conveying ability of the plate-like member. The number of rotations of the conveying member is set.

  According to a third aspect of the present invention, in the developing device according to the first aspect, the first agitating / conveying member has a screw shape, and the developer conveying ability of the first agitating / conveying member is increased by the plate-like member. The screw pitch of the 1st stirring conveyance member is set so that it may improve compared with a conveyance capability, It is characterized by the above-mentioned.

  A fourth aspect of the present invention is the developing apparatus according to any one of the first to third aspects, further comprising a plurality of the plate-like members.

  According to a fifth aspect of the present invention, in the developing device according to the fourth aspect, at least one of the plurality of plate-like members is plate-like, and the rest has a gap through which the developer can pass. .

  A sixth aspect of the present invention is a process cartridge having the developing device according to any one of the first to fifth aspects.

  A seventh aspect of the invention is an image forming apparatus having the process cartridge of the sixth aspect.

  An eighth aspect of the invention is an image forming apparatus having the developing device according to any one of the first to fifth aspects.

  According to the present invention, the developer can be satisfactorily retained without causing the developer to stay in the upstream portion in the developer transport direction of the first agitation transport member and the lifting portion that lifts the developer from the second transport path to the first transport path. It is possible to circulate, and by suppressing the occurrence of the developer accompanying phenomenon, it is possible to obtain a good image without image density unevenness.

1 is a schematic front view of an image forming apparatus employing an embodiment of the present invention. It is the schematic which shows the image creation part used for one Embodiment of this invention. 1 is a schematic side view of a developing device used in an embodiment of the present invention. It is the schematic explaining the plate-shaped member used for one Embodiment of this invention. FIG. 6 is a schematic diagram illustrating a malfunction phenomenon of a developer according to an embodiment of the present invention. It is the schematic explaining the flow of the developer in one Embodiment of this invention. It is a schematic perspective view explaining the structure of the plate-shaped member used for one Embodiment of this invention. It is a schematic perspective view explaining the bracket used for one Embodiment of this invention. It is a schematic sectional drawing explaining the bracket used for one Embodiment of this invention. It is a partial schematic sectional drawing explaining the structure of the plate-shaped member used for one Embodiment of this invention. It is a schematic side view of the developing device used for the modification of one Embodiment of this invention. It is a schematic front view of the conventional developing device. It is a schematic front view of the conventional developing device. It is a schematic side view explaining the problem of the conventional developing device. It is a schematic side view of the conventional developing device.

  FIG. 1 shows a printer 50 as an image forming apparatus to which an embodiment of the present invention can be applied, and FIG. 2 shows an image forming unit of the printer 50. As shown in FIG. 1, an intermediate transfer unit 20 having an intermediate transfer belt 28 is disposed at a substantially central position of the apparatus main body 100, and yellow, magenta, cyan, and black are opposed to the intermediate transfer belt 28. The image forming units 26Y, 26M, 26C, and 26K corresponding to the colors are arranged in parallel. Here, the four image forming units 26Y, 26M, 26C, and 26K in the printer 50 have substantially the same structure except that the color of the toner used in the image forming process is different. The alphabets (Y, M, C, K) of reference numerals for the photosensitive drum 21 as the image carrier and the primary transfer roller 29 are omitted.

  In FIG. 2, the image forming unit 26 includes a photosensitive drum 21, a charging unit 24, a developing unit 25, a cleaning unit 22 and the like disposed around the photosensitive drum 21 (FIG. 1 shows the developing unit 25). Only shown). An image forming process (charging process, exposure process, developing process, transfer process, cleaning process, charge eliminating process), which will be described later, is performed on the photosensitive drum 21, and a desired toner image is formed on the photosensitive drum 21. The photosensitive drum 21, the charging unit 24, the developing device 25, and the cleaning unit 22 described above are configured to be detachable from the apparatus main body 100, and can be individually replaced when they reach the end of their lives. ing.

  In the above-described configuration, the photosensitive drum 21, the charging unit 24, the developing device 25, and the cleaning unit 22 that constitute the image forming unit 26 are each a single unit. Of these units, the developing device 25 and at least one of the other units are included. The process cartridge may be integrated and detachable from the apparatus main body 100. Thereby, the workability at the time of performing maintenance of the image forming unit 26 is improved.

  Next, the image forming process of the photosensitive drum 21 will be described. The photosensitive drum 21 is rotationally driven in a clockwise direction in FIG. 2 by a driving unit (not shown), and the surface thereof is uniformly charged at a position facing the charging unit 24 (charging process). Thereafter, the charged surface of the photosensitive drum 21 reaches a laser irradiation position from the LED array 23, and an electrostatic latent image is formed on the surface of the photosensitive drum 21 by exposure scanning at this position (exposure process). The latent image forming portion of the photosensitive drum 21 reaches a portion facing the developing device 25, and a developer is supplied to the electrostatic latent image at this position to form a desired toner image (developing step). The toner image formed on the surface of the photosensitive drum 21 reaches a position facing the intermediate transfer belt 28 and the primary transfer roller 29, and the toner image on the photosensitive drum 21 is transferred onto the intermediate transfer belt 28 at this position. (Primary transfer step). At this time, a small amount of untransferred toner remains on the photosensitive drum 21. After the primary transfer, the surface of the photosensitive drum 21 reaches a position facing the cleaning unit 22, and untransferred toner is collected by the cleaning blade 22a at this position (cleaning step). Finally, the surface of the photosensitive drum 21 reaches a portion facing a neutralizing unit (not shown), and the residual potential is removed at this position (static elimination step). By this series of operations, the image forming process of the photosensitive drum 21 is completed.

  The above-described image forming process is performed in each of the four image forming units 26Y, 26M, 26C, and 26K. Laser light based on image information is emitted toward each photosensitive drum 1 from an exposure unit disposed below each image forming unit 26. Specifically, the photosensitive drum 21 is irradiated via a plurality of optical elements while scanning with a polygon mirror laser light emitted from the light source of the exposure unit. Thereafter, the color toner images formed on the photosensitive drums 21 through the development process are superimposed and transferred onto the intermediate transfer belt 28 to form a full-color toner image on the intermediate transfer belt 28.

  The four primary transfer rollers 29Y, 29M, 29C, and 29K sandwich the intermediate transfer belt 28 with the corresponding photosensitive drums 21Y, 21M, 21C, and 21K to form primary transfer nips. When the intermediate transfer belt 28 travels in the direction indicated by the arrow in FIG. 1 and passes through the primary transfer nip of each primary transfer roller 29, a transfer bias having a polarity opposite to the toner polarity is applied to each primary transfer roller 29. As a result, the color toner images on the photosensitive drums 21 are superimposed and transferred onto the intermediate transfer belt 28.

  The intermediate transfer belt 28 on which the full-color toner image is superimposed and transferred reaches a position facing the secondary transfer roller 30, and the intermediate transfer belt 28 is sandwiched between the secondary transfer backup roller 31 and the secondary transfer roller 30 at this position. Thus, a secondary transfer nip is formed. The full-color toner image formed on the intermediate transfer belt 28 is transferred to a transfer material P such as transfer paper conveyed to the secondary transfer nip. At this time, the transfer material P is transferred onto the intermediate transfer belt 28. Untransferred toner that could not be transferred remains. The remaining untransferred toner is removed by an intermediate transfer belt cleaning unit (not shown), the intermediate transfer belt 28 returns to the initial state, and a series of transfer processes performed on the intermediate transfer belt 28 is completed.

  The material P to be transferred conveyed to the secondary transfer nip is conveyed from a paper supply unit 32 disposed below the apparatus main body 100 via a paper supply roller 33, a registration roller pair 34, and the like. A plurality of transfer materials P are accommodated in the paper supply unit 32, and the uppermost sheet is separated and fed toward the registration roller pair 34 by the rotation of the paper supply roller 33. The separated material P to be transferred is temporarily stopped at the nip position of the registration roller pair 34, and the registration roller pair 34 is rotationally driven in time with the full-color toner image on the intermediate transfer belt 28 to perform secondary transfer. It is conveyed toward the nip and a desired full color image is transferred at the secondary transfer nip.

  The material P to which the full color image is transferred at the secondary transfer nip is conveyed to the fixing unit 35. In the fixing unit 35, the full color image is fixed on the surface of the transfer material P by heating and pressing with the fixing roller and the pressure roller. The transfer material P on which the image is fixed is discharged by a pair of discharge rollers 36 and sequentially stacked on the stack unit 37 as an output image. As described above, a series of image forming processes in the printer 50 is completed.

  Next, the developing device 25 which is a characteristic part of the present invention will be described. In this developing device 25, members equivalent to those of the developing device 4 shown in FIG. 13 and FIG. The developing device 25 includes a developing roller 8 that is a developer carrying member disposed opposite to the photosensitive drum 21, and a doctor blade 41 that is a developer regulating member that is disposed so that an end thereof is opposed to the upper surface of the developing roller 8. The first developer agitating and conveying member 6 as the first agitating and conveying member disposed in the supply developer chamber 10 as the first conveying path, and the recovered agitating developer chamber 11 as the second conveying path. A second developer agitating half-storage member 7 as a second agitating / conveying member disposed, a casing 42 for accommodating these members, and the like are provided. In the developer chambers 10 and 11, a two-component developer 14 composed of a carrier and toner is accommodated. Further, in the developer chambers 10 and 11, a toner concentration sensor (not shown) for detecting the toner concentration in the developer. Is provided.

  In the developing device 25, the second developer is provided at the portion of the lifting portion 15 illustrated in FIG. 14, that is, at the portion where the developer 14 is transferred from the second developer agitating and conveying member 7 to the first developer agitating and conveying member 6. The developer 14 is conveyed while being lifted from the second developer agitating / conveying member 7 to the first developer agitating / conveying member 6 rather than the developer conveying ability (maximum amount of developer that can be conveyed per unit time) of the agitating / conveying member 7. It is characterized by a high capability, that is, a high conveying capability of the developer 14. In order to achieve this, as shown in FIG. 3, a plate-like member 16 is arranged on the lifting portion 15 so as to be parallel to the traveling direction of the developer 14 conveyed by the second developer agitating and conveying member 7. Yes. The plate-like member 16 composed of a stirring paddle or the like is connected to a driving source different from the developing roller 8, the first developer stirring and conveying member 6, and the second developer stirring and conveying member 7, and is driven separately from these. Is done. As shown in FIG. 4, the plate-like member 16 is rotationally driven so as to scrape off the developer 14 around the screw-like blade 7 a of the second developer agitating / conveying member 7 around the second developer agitating / conveying member 7. Then, the developer 14 is transported from the recovered stirring developer chamber 11 to the supply developer chamber 10 so as to jump up.

  When the developer 14 is transported by the plate-like member 16 described above, if the developer-carrying capacity of the developer 14 by the plate-like member 16 is higher than the developer transport ability of the second developer stirring and transporting member 7, FIG. As described above, the developer 14 can be supplied from the recovery stirring developer chamber 11 into the supply developer chamber 10 without the developer 14 remaining in the lifting portion 15. Here, the developer chamber 10 for supply and the developer chamber 11 for recovery agitation are connected by a communication port. If the developer 14 does not remain in the lifting portion 15, the developer 14 falls from the developer chamber 10 for supply. However, the developer 14 dropped from the supply developer chamber 10 is splashed up again by the plate-like member 16, and does not return to the recovered stirring developer chamber 11. Therefore, no trouble occurs because the toner is conveyed into the developer chamber 10 for supply.

  In the above-described configuration, the rotational speed of the second developer agitating / conveying member 7 is higher than the ability of the second developer agitating / conveying member 7 to convey the developer 14 in order to increase the lifting and conveying ability of the developer 14 in the lifting portion 15. What is necessary is just to enlarge the rotation speed of the plate-shaped member 16 rather than. As a specific example, the diameter of the developing roller 8 is 10 mm, the screw pitch of the first developer stirring and conveying member 6 is 30 mm, the screw pitch of the second developer stirring and conveying member 7 is 28 mm, and the rotation speed of the developing roller 8 is 520 rpm. When the rotation speed of each of the transport members 6 and 7 is 1000 rpm, the developer 14 is accumulated in the lifting portion 15 and a phenomenon of developer rotation occurs. At this time, the transport speed of the developer 14 by the second developer stirring transport member 7 is 15 cm / s. Therefore, since the second developer agitating and conveying member 7 conveys the developer 14 to the lifting portion 15 at a conveying speed of 15 cm / s, the plate-like member 16 is used for collecting and agitating at a conveying speed of 15 cm / s or more. If the developer 14 is transported from the developer chamber 11 to the supply developer chamber 10, the developer 14 does not stay in the lifting portion 15, and the plate-like member 16 is driven to rotate at 1500 rpm to 15 cm / s. The developer 14 can be transported from the recovery stirring developer chamber 11 to the supply developer chamber 10 at the above transport speed.

  However, if the plate-like member 16 is provided to make the developer lifting and conveying capability of the plate-like member 16 higher than the developer conveying capability of the second developer stirring and conveying member 7, the first development indicated by reference numeral 17 in FIG. The developer 14 stays in the upstream portion of the developer stirring / conveying member 6 in the developer transport direction, and the developer 14 is hardly transported from the recovery stirring developer chamber 11 to the supplying developer chamber 10, and has a plate shape. Even if the member 16 is disposed, the developer 14 stays in the lifting portion 15, and the phenomenon that the developer is accompanied occurs. For this reason, on the upstream side of the first developer stirring and conveying member 6 in the developer conveying direction, it is necessary to convey a larger amount of developer 14 than the amount of developer lifted and conveyed by the plate-like member 16.

  As a means for improving the conveying ability of the developer 14 on the upstream side in the developer conveying direction of the first developer agitating / conveying member 6, first, the rotation speed of the first developer agitating / conveying member 6 is increased. As a specific example, the diameter of the developing roller 8 is 10 mm, the screw pitch of the first developer agitating and conveying member 6 is 30 mm, the screw pitch of the second developer agitating and conveying member 7 is 28 mm, the rotation speed of the developing roller 8 is 520 rpm, and each conveying When the rotational speed of the members 6 and 7 is 1000 rpm and the rotational speed of the plate-like member 16 is 1500 rpm, the developer 14 stays in the upstream portion 17, and the developer 14 is not lifted up and the phenomenon of the developer accompanying is generated. When the rotation speed of the first developer agitating / conveying member 6 was set to 1000 rpm or more, for example, 1500 rpm, the developer 14 could be transported without causing the developer 14 to stay in the upstream portion 17.

  Another means is to increase the screw pitch of the first developer stirring and conveying member 6. A large screw pitch means that the spacing between adjacent screw blades is large as the screw blades and shafts approach more parallel. If the pitch of the screw is large, the distance that the developer 14 is transported in the axial direction during one rotation of the screw becomes long, so that the transport capability increases. As a specific example, by setting the screw pitch of the first developer agitating and conveying member 6 to 40 mm, when the conveying members 6 and 7 have a rotation speed of 1000 rpm and the plate-like member 16 has a rotation speed of 1500 rpm, as shown in FIG. In addition, the developer 14 could be transported without causing the developer 14 to stay in the upstream portion 17.

  With the above-described configuration, the developer is lifted in the developer conveying direction upstream portion 15 of the first developer agitating / conveying member 6 and the lifting portion 15 for lifting the developer 14 from the collected developer chamber 11 to the supplying developer chamber 10. The developer 14 can be circulated satisfactorily without stagnation of the toner 14, and a good image free from unevenness in image density can be obtained by suppressing the occurrence of the developer accompanying phenomenon.

  FIG. 7 shows a specific configuration of the plate-like member 16 described above. The plate-like member 16 is provided integrally with the bracket 44 shown in FIGS. 8 and 9, and the bracket 44 has a cylindrical body portion 44a having a hole 44b and a transmission shaft 44c bent in a crank shape. Is integrated. As shown in FIG. 10, the bracket 44 is rotatably supported on the outer periphery of the body portion 44a with respect to the casing 42 by a bearing 45, and the second developer agitating and conveying member 7 is supported by a bearing 46 fitted in the hole portion 44b. The shaft is rotatably supported. The transmission shaft 44 c is connected to a drive source 47 such as a motor, and the rotation center of the portion connected to the drive source 47 is configured to coincide with the rotation center of the second developer agitating and conveying member 7. With this configuration, when the drive source 47 is actuated, the rotational force is transmitted to the transmission shaft 44c, and the bracket 44, which is rotatably supported by the bearing 42 by the bearing 45, rotates, whereby the plate member 16 is second developed. The agent stirring and conveying member 7 is rotated. At this time, a gap indicated by a symbol G in FIG. 7 is provided between the plate-like member 16 and the blade 7a, and interference between the plate-like member 16 and the second developer agitating and conveying member 7 is prevented. .

  FIG. 11 shows a modification of the above-described embodiment. In this example, a plurality of plate-like members 16 and 18 are provided. When the number of rotations of the plate member is the same between the case where a plurality of plate members are provided and the case where a single plate member is provided, the case where a plurality of plate members are provided is more positive for the supply developer chamber 10. Thus, the developer 14 can be conveyed. Also, when trying to obtain the same developer conveyance amount when a plurality of plate-like members are provided and when a single plate-like member is provided, a desired conveyance amount can be obtained at a lower rotational speed when a plurality of plate-like members are provided. And the scattering of the developer 14 can be prevented by setting the rotational speed to a low value. As a specific example, when two plate members 16 are used, even when the number of rotations of the plate members 16 is reduced from 1500 rpm when 1000 plates are used to 1000 rpm, a conveyance amount equivalent to that when one plate member 16 is used can be obtained.

  When a plurality of plate-like members 16 and 18 are provided, a configuration is provided in which at least one (plate-like member 16) is left plate-like, and the remaining plate-like member 18 is provided with a plurality of gap portions 18a through which the developer 14 can pass. It is good. Here, the reason why at least one sheet is plate-shaped is that it is difficult to obtain a developer conveying capability higher than the conveying capability of the second developer stirring and conveying member 7 if all plate-like members are provided with gaps. This is because the developer 14 stays in the lifting portion 15 and the developer accompanying phenomenon occurs.

  Since the gap 18 a is formed in the plate-like member 18, when the developer 14 is moved, a part of the developer 14 can be passed through the gap 18 a. In the case where there is no gap as in the plate-like member 16, the developer 14 is only pushed and moved, but the provision of the gap 18 a facilitates mixing of the developers 14, Dispersibility can be increased. As a result, by improving the contact frequency between the toner and the carrier in the lifting portion 15 and facilitating the friction between the toner and the carrier when passing through the gap portion 18a, the frictional charging can be performed satisfactorily. Therefore, the replenished toner can be sufficiently dispersed in the developer 14 and charged, and the occurrence of background stains can be reduced.

  In the above embodiment, an example in which a color printer is used as the image forming apparatus has been described. However, the image forming apparatus to which the present invention can be applied is not limited to this, and other devices such as a copying machine, a plotter, a facsimile machine, and a multifunction machine thereof. The present invention can also be applied to other image forming apparatuses.

6 1st stirring conveyance member (1st developer stirring conveyance member)
7 Second agitating and conveying member (second developer agitating and conveying member)
8 Developer carrier (developing roller)
10 First transport path (supply developer chamber)
11 Second transport path (recovery stirring developer chamber)
14 Two-component developer (Developer)
16, 18 Plate-like member 18a Gap 21 Latent image carrier (photosensitive drum)
25 Developing device 50 Image forming device (printer)

Japanese Patent Laid-Open No. 11-272062 Japanese Patent Publication No. 5-82944

Claims (8)

A developer carrier that carries a two-component developer composed of toner and a magnetic carrier and visualizes the electrostatic latent image on the latent image carrier with the toner, and the developer carrier that is provided side by side with the developer carrier. A first conveying path having a first agitating and conveying member that conveys the developer and supplies the developer to the developer carrier, and is disposed below the first conveying path to convey the developer and the developer. A developing device having a second conveyance path having a second agitation conveyance member for recovering the developer from the carrier, and having a path through which the developer circulates between the first conveyance path and the second conveyance path;
A plate-like member disposed so as to be parallel to the traveling direction of the developer conveyed by the second agitating and conveying member at a position where the developer is lifted from the second conveying path to the first conveying path; The member is driven to rotate around the second agitating and conveying member to lift the developer from the second conveying path to the first conveying path, and the developer by the plate-like member is more than the developer conveying ability by the second agitating and conveying member. And a developer conveying capability upstream of the developer conveying direction by the first agitating and conveying member is higher than a developer conveying and conveying capability by the plate-like member. The developing device according to claim 1,
A developing device, wherein the number of rotations of the first agitating / conveying member is set so as to increase the developer conveying ability of the first agitating / conveying member as compared with the developer conveying ability of the plate-like member. The developing device according to claim 1,
The first agitating / conveying member has a screw shape, and the screw pitch of the first agitating / conveying member is set so as to increase the developer conveying ability of the first agitating / conveying member compared to the developer conveying ability of the plate-like member. A developing device. The developing device according to any one of claims 1 to 3,
A developing device comprising a plurality of the plate-like members. The developing device according to claim 4.
2. A developing device according to claim 1, wherein at least one of the plurality of plate-like members is plate-like, and the remainder has a gap through which the developer can pass.   6. A process cartridge comprising the developing device according to claim 1.   An image forming apparatus comprising the process cartridge according to claim 6.   An image forming apparatus comprising the developing device according to claim 1.

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