JP4820581B2 - Developing device, image forming apparatus, and process cartridge - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a fax machine, and a printer, and a developing device and a process cartridge employed in the image forming apparatus.

  Conventionally, in a developing device that visualizes an electrostatic latent image using a two-component developer composed of a toner and a carrier, the mixed state of the toner and the carrier in the developer affects the image. It is desired to perform stirring and mixing well. As the developer agitating and conveying member, a spiral blade member provided with a spiral blade on the outer periphery of the rotating shaft is often used. This spiral blade member has good developer agitation in the lateral direction, but is not configured to play an active role in fine dispersion of the replenishment toner. Therefore, a member in which a member for improving fine dispersion of the replenishing toner is provided on the spiral blade member has been proposed.

  As an example of this, the applicant of the present invention in Patent Document 1, the rotating shaft, the spiral blade member formed around the rotating shaft, and both ends or the vicinity of both ends are fixed to the spiral blade member, and at least the rotating shaft In contrast, a developing device using a developer stirring and conveying member composed of a linear member provided to have an angle other than 0 degrees is proposed. In this developing device, the linear member enters and exits the developer as the developer agitating / conveying member rotates about the axis, thereby taking in the toner in the direction of the rotation axis of the developer agitating / conveying member. And extruding in a direction away from the axis. In addition, since the linear member is other than 0 degree with respect to the rotation axis, the entire linear member is buried in the developer at once, and the drive torque of the developer agitating / conveying member does not come out at once. Can be made difficult to occur. Thus, the developer can be sheared efficiently and at high speed without increasing the torque so much, and the dispersibility and agitation of the replenishment toner to the developer can be improved.

JP 2004-258237 A

  In the case of using the spiral blade member as described above, in order to suppress the influence of the processing accuracy and fluctuation of the spiral blade, as shown in FIG. 10, the developer storage case 49, the spiral blade member 43, and A gap is provided between them. The spiral blade member 43 transports the developer within the rotation radius range, but does not transport the developer in the gap between the developer storage case 49 and the spiral blade member 43. Therefore, in the developer accommodating case 49, a speed difference relating to movement can be made between the developer within the rotation radius range and the developer in the gap. In the portion having such a speed difference, the developer is well mixed and good stirring is performed. However, as described above, the developer in the gap is not transported to the spiral blade member 43 and moves due to the mixing of the above-mentioned developers, and therefore the moving speed is slow and the developer tends to stay. If the developer stays in the gap, the effective developer circulating in the developer containing case is reduced, and the life of the developer is shortened. The amount of the developer staying in the gap is not less than the total amount of the developer stored in the developer storage case, although it depends on the size of the developer storage case. In particular, in a small apparatus having a small developer accommodating case, the ratio to the amount of developer accommodated in the entire developer accommodating case becomes large. For this reason, in order to obtain a predetermined developer life, an extra amount of developer must be added in advance.

  Further, in order to suppress the decrease in the developer life due to the developer retention, as shown in FIG. 11, the gap between the developer storage case 49 and the spiral blade member 43 where the developer stays is almost eliminated. It can also be considered. However, when there is almost no gap, the developer within the rotation radius of the spiral blade member 43 only moves in parallel, and it becomes difficult to generate a speed difference related to the movement of the developer. Will drop significantly. For this reason, the developer in the developer storage case 49 and the replenished toner are not mixed and are carried as they are to the development region, and an abnormal image in which the toner adheres to the non-image portion is generated. Further, depending on the processing accuracy and shake of the spiral blade member, the developer comes in contact with the developer containing case 49, causing uneven rotation, and an abnormal image with uneven density such as pitch unevenness and banding is likely to occur.

  The present invention has been made in view of the above background, and can develop all the developer in the developer storage case with good stirring and circulation so that all the developer in the developer storage case can be effectively utilized. The present invention provides an image forming apparatus and a process cartridge including the apparatus, the developing device, and the like.

In order to achieve the above object, the invention of claim 1 is a developer storage case for storing a developer composed of toner and magnetic particles, and the developer in the developer storage case is stirred and conveyed by rotating. A developer agitating / conveying member that circulates while developing, and a developer agitating / conveying aid that conveys and stirs the developer in the gap between the rotation radius of the developer agitating / conveying member and the developer storage case as members, Ri consists nonmagnetic particles mixed into the developer circulation area in the developer accommodating case, density comprises approximately equal stirred particles the apparent density of the developer, the rotational radius of the developer stirring and conveying member The diameter of the stirring particles is larger than the gap between the developer storage case and the developer storage case .
The invention of claim 2 is the developing device according to claim 1, it is characterized in that it has facilities hydrophobic treatment on the surface of the stirring particles.
The invention of claim 3 is the developing device according to claim 1 or 2, it is characterized in that the stirring particles are ceramic particles.
According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier that carries a latent image; and a developing device that develops the latent image formed on the image carrier. , 2 or is characterized in that using the developing device 3.
According to a fifth aspect of the present invention, there is provided a process cartridge which integrally supports a developing device and at least one means selected from an image carrier, a charging device, and a cleaning device, and is detachable from an image forming apparatus main body. in claim 1 as the developing unit, 2 or is characterized in that using the developing device 3.

In the first to fifth aspects of the present invention, the developer in the gap between the rotation radius of the developer agitating and conveying member and the developer storage case is conveyed and agitated by the developer agitating and conveying auxiliary member. Therefore, the developer in the gap can also move without stagnation, and the entire developer in the developer storage case circulates.

According to the first to fifth aspects, there is an excellent effect that all the developer in the developer accommodating case can be effectively utilized by stirring and circulating all the developer in the developer accommodating case. .
In particular, according to the invention of claim 1, since the density of the stirring particles is substantially equal to the apparent density of the developer composed of toner and magnetic particles, the stirring particles are well mixed with the developer and are not biased. Since the developer in the gap is pushed out, the agitation of the developer in the entire developer containing portion is improved. Further, since the diameter of the stirring particles is larger than the rotation radius of the developer stirring and conveying member and the gap between the developer storage case, the stirring particles moved by the developer stirring and conveying member efficiently remove the developer in the gap. It can be moved while being pushed out. By moving in this way, the developer in the gap can be stirred and circulated more efficiently, and as a result, the entire developer in the developer storage case can be circulated more efficiently and used.
According to the second aspect of the invention, since the surface of the stirring particles is subjected to a hydrophobic treatment, it is possible to prevent the toner from being fixed on the surface of the stirring particles.
According to the invention of claim 3 , since the stirring particles are ceramic particles, even if mixed with toner or magnetic particles, they do not deform or react, so that they do not affect the charging of the developer and are relatively inexpensive and stable. Available. Furthermore, since the ceramic particles can be separated from the developer by a simple sizing process such as a coarse sieve, they can be regenerated and reused.

  An embodiment in which the present invention is applied to an electrophotographic printer (hereinafter simply referred to as “printer”) as an image forming apparatus will be described below. FIG. 1 is a schematic configuration diagram of the printer of this embodiment. The printer includes a charging device 2, an optical writing device 3, a developing device 4, a transfer device 5, a drum cleaning device 6, and a charge eliminating device 7 around a drum-shaped photoconductor 1 that is an image carrier. Further, a fixing unit 8 is provided on the left side of the transfer device 5 in the figure.

  A photosensitive member 1 that is rotated in the clockwise direction in the drawing by a driving means (not shown) has an organic photosensitive layer formed on the surface of a raw tube made of aluminum or the like. Is uniformly charged. Then, the potential of the exposure unit is attenuated by the scanning of the laser light L emitted from the optical writing device 3 that constructs the optical scanning information based on image information sent from a personal computer (not shown) or the like. As a result, an electrostatic latent image having a lower potential than the background portion around the exposed portion is carried. The electrostatic latent image contains toner and a magnetic carrier carried on the developing sleeve 41 of the developing device 4 when passing through the developing position that is opposite to the developing device 4 as the photosensitive member 1 rotates. Is rubbed against the developing developer. Then, for example, negative polarity toner contained in the developer is electrostatically adhered to be developed into a toner image.

  A transfer position where the photoconductor 1 and the transfer device 5 face each other is formed downstream of the developing position in the rotation direction of the photoconductor. When the toner image developed on the photosensitive member 1 enters this transfer position as the photosensitive member 1 rotates, it is transferred to a sheet-like transfer paper P that is conveyed in time by a sheet feeding unit (not shown). Superimposed. Then, it is electrostatically transferred onto the recording medium P under the influence of a transfer electric field formed between the exposed portion of the photoreceptor 1 and the transfer device 5. The transfer paper P electrostatically attached to the photoconductor 1 during this transfer is separated from the photoconductor by the action of paper weight, rigidity, paper and members for separating and conveying (not shown), and the like. . The recording material P on which the toner image is electrostatically transferred in this way is sent from the transfer position to the fixing unit 8. The fixing unit 8 forms a fixing nip by contact between a heating roller 8a having a heat source (not shown) inside and a pressing roller 8b pressed against the heating roller 8a. These rollers are rotationally driven so as to move the respective surfaces in the same direction at the mutual contact portions. The recording material P sent to the fixing means 8 having such a configuration is sandwiched in the fixing nip and conveyed in the roller surface moving direction. At this time, the toner image is fixed by the influence of nip pressure and heating. The fixing transfer paper P is discharged out of the apparatus via a paper discharge means (not shown). On the other hand, when the surface of the photoconductor 1 that has passed the transfer position passes through a position facing the drum cleaning device 6 as it rotates, residual toner is cleaned. Then, after the residual charge is removed by the static eliminator 7, it is uniformly charged by the charging means and returns to the initial state.

  In FIG. 1, the charging device 2 is a system in which a bias member such as a charging roller to which a charging bias is applied is brought into contact with the photosensitive member 1, but a non-contact system such as a charging charger is used. Also good. Moreover, although the example which provided the optical writing device 3 which forms an electrostatic latent image by irradiation of a laser beam was shown, what performs optical writing by the LED light from an LED array may be used. Further, an electrostatic latent image may be formed by ion ejection or the like instead of optical writing. Further, as the transfer device 5, a roller contact type in which a transfer roller to which a transfer bias is applied is brought into contact with the photosensitive member 1 is shown, but a belt contact type in which a belt is brought into contact or a non-contact type such as a transfer charger. May be used. Further, the drum cleaning device 6 has a scraping method using a cleaning blade, but an electrostatic recovery method that contacts a brush or a roller to which a cleaning bias is applied may be used. Further, although an example in which the drum-shaped photoconductor 1 is provided as the latent image carrier has been described, a belt-shaped photoconductor may be used.

  Further, although an example of a printer in which the photoconductor 1 and its peripheral devices are individually provided has been described, a process cartridge in which the photoconductor 1 and its peripheral devices are housed in a common casing as one unit may be used. . For example, the photosensitive member 1, the charging device 2, the developing device 4, and the drum cleaning device 6 are configured as one process cartridge so as to be detachable from the printer main body.

  FIG. 2 is an enlarged configuration diagram showing a main configuration of the developing device 4. The developing device 4 includes a developing unit and a developer accommodating unit in a casing 49. The developing portion is provided with a developing sleeve 41 that exposes a part of the peripheral surface from the opening of the casing 49, a doctor blade 42, and the like. The cylindrical developing sleeve 41 is made of a nonmagnetic material such as aluminum, brass, stainless steel, or conductive resin, and its surface is roughened to a 10-point average roughness Rz of about 10 to 20 [μm] by sandblasting or the like. It has been. By such roughening, the friction resistance with the developer is increased and a predetermined agent pumping ability is exhibited. Instead of roughening by sandblasting or the like, a surface having a plurality of grooves with a depth of several tens to several hundreds [mm] may be used. A magnet roller (not shown) is fixed inside the developing sleeve 41 that is rotationally driven by a driving means (not shown) so as not to rotate around the sleeve. This magnet roller has a plurality of magnetic poles divided in the circumferential direction. Due to the influence of these magnetic poles, a plurality of magnetic fields extending in the normal direction are formed around the developing sleeve 41.

  The developer accommodating portion of the developing device 4 is provided with two conveying screws 43 and 44 as developer agitating and conveying members, a toner concentration sensor (hereinafter referred to as T sensor) (not shown), and the like. A developer 47 containing toner and a magnetic carrier is accommodated in the developer accommodating portion. The developer 47 has a large number of toners attached to the surface of the magnetic carrier. Then, friction charging is performed while being agitated and conveyed by the two conveying screws 43 and 44. The developer 47 that is agitated and conveyed to the conveyance screw 43 on the left side in the drawing contacts the surface of the developing sleeve 41 in the axial direction thereof. Then, under the influence of the magnetic field extending from the developing sleeve 41, it is carried on the surface of the sleeve and pumped up from the developer accommodating portion. Then, it is conveyed along with the sleeve surface.

  The doctor blade 42 is fixed to the casing 49 so as to maintain a predetermined gap between the tip thereof and the surface of the developing sleeve 41. This gap is called a doctor gap, and is set to about 0.3 to 0.7 [mm] in the developing device 4 of the printer. When the developer 47 pumped up from the developer accommodating portion passes through the doctor gap along with the sleeve surface, the layer thickness is regulated and the developer 47 is in an amount suitable for development. Specifically, the amount is about 20 to 100 [mg / cm 2]. Then, along with the rotation of the sleeve surface, it is conveyed to a developing position that is a position facing a photoconductor (not shown). The preferred normal direction magnetic flux density at the exit of the development region on the surface of the development sleeve on the development main pole is 60 mT or more. In order to improve the pumping property and the black solid image following property, the number of magnets (magnetic poles) may be further increased. The carrier of the developer 47 rises in a chain shape on the developing sleeve so as to follow the normal line of magnetic force emitted from the magnet roller, and the charged toner adheres to the carrier that has risen in the chain shape. A magnetic brush is constructed. The magnetic brush is transferred in the same direction as the developing sleeve (clockwise as viewed in the figure) by the rotation of the developing sleeve. During development, an oscillating bias voltage in which an AC voltage is superimposed on a DC voltage is applied to the developing sleeve as a developing bias by a power source. In an alternating electric field, the toner and carrier of developer 47 vibrate vigorously, and the toner flies off the electrostatic sleeve to the developing sleeve and carrier and flies to the photosensitive drum, and adheres corresponding to the latent image on the photosensitive drum. To do. As a result of this adhesion, the electrostatic latent image is developed into a toner image. The developer 47 that has consumed toner by development moves along with the sleeve surface into the casing, and is separated from the sleeve surface under the influence of a repulsive magnetic field (not shown) and returns to the developer containing portion. The volume average particle diameter of the magnetic carrier is larger than the average volume particle diameter of the toner, and the magnetization is 30 to 1000 emu / cm 3 (in a 1 kOe magnetic field). As a result, an effect of suppressing carrier adhesion to the photosensitive member 1 at the time of development and prevention of excessive contact pressure when the tip of the magnetic brush consisting of the developer 47 is in contact with the photosensitive member 1 can produce a high-quality image without a feeling of roughness. Obtainable.

  In this printer, the development gap, which is the distance between the photosensitive member 1 and the development sleeve 41 at the development position, is set to 0.3 [mm]. The development gap is preferably set to about 10 times (0.55 mm) or less when the particle size of the magnetic carrier of the developer 47 is 50 [μm]. If the development gap is wider than this, it is difficult to obtain a desired image density under the condition of applying a DC development bias voltage.

  In the developer accommodating portion, a partition wall 45 is provided between the two transport screws 43 and 44. The partition wall 45 divides the inside of the developer accommodating portion into two. Of the two conveying screws 43 and 44, the one arranged on the left side in the figure supplies the developer 47 to the developing sleeve 41 while conveying the developer 47, for example, from the back side to the front side in the figure in accordance with the rotational drive. To do. The developer 47 conveyed to the front end in the figure passes through an opening (not shown) provided in the partition wall 45 and is transferred to the conveyance screw 44 on the right side in the figure. Then, after taking in the replenishment toner falling from the replenishing port 46 while being conveyed from the front side to the back side in the figure, it passes through the other opening (not shown) provided in the partition wall 45 in the figure. It is returned to the left conveying screw 43. In this way, the developer 47 is circulated and conveyed in the developer accommodating portion. As described above, when a plurality of transport screws 43 and 44 are used, the developer transport directions of at least the pair of transport screws 43 and 44 are arranged in the opposite directions. In addition, a gap of 1 to 0.5 mm is provided between the casing 49 and the rotation radius of the transport screws 43 and 44 in order to suppress the processing accuracy of the transport screws 43 and 44 and the influence of vibration.

  Next, features of the present invention will be described. In the printer of this embodiment, the stirring particles 48 are mixed in the developer 47 of the developer container as a developer stirring / conveying auxiliary member. As the stirring particles, nonmagnetic metal particles such as copper and tin, silica, alumina, zirconia, titania, ceramic particles such as silicon carbide and silicon nitride, resin particles such as nylon, and the like can be used. The movement of the developer 47 in the casing 49 when such stirring particles 48 are mixed will be described. At the rotation radius of the transport screws 43 and 44, the developer 47 is transported and moved to the transport screws 43 and 44 and circulates in the casing 49. A part of the mixed stirring particles 48 enters the rotation radius of the transport screws 43 and 44, is transported to the transport screws 43 and 44, and moves together with the developer 47. Further, the other part of the mixed stirring particles 48 is in a state of being applied to the end portions (outermost sides) of the blades of the conveying screws 43 and 44. The stirring particles 48 in such a state are transported by the transport screws 43 and 44 and are moved while forcibly pushing out the developer in the gap between the transport screws 43 and 44 and the casing 49. The developer 47 pushed out in this manner is conveyed while being agitated with the developer 47 within the rotation radius of the conveying screws 43 and 44 and circulates in the casing 49, so that all the developer 47 in the developer container is circulated. Can be used. This has the same effect as increasing the content of the developer as compared with the conventional developing device.

  Further, the mixing of the stirring particles 48 makes it easy for the developer in the developer container and the supplied toner to be mixed when the toner is supplied. Therefore, the toner can be charged even when the toner is replenished, and a stable high-quality image can be obtained. Further, since the charging of the toner is stabilized, DC development at a low potential can be stably performed.

  The ratio of the stirring particles 48 to be mixed is preferably 3 to 20 wt% with respect to the developer 47. If it is less than 3 wt%, the effect of stirring is small, and if it is 20 wt% or more, the mixed particles 48 are likely to come into contact with each other, and the proportion of effective developer is reduced. More preferably, 5-10 wt% is good.

  Next, the behavior of the stirring particles 48 at the upstream portion of the doctor blade 42 of the developing device 4 will be described. As shown in FIG. 3, the developer 47 including a magnetic carrier is carried on the sleeve surface under the influence of a magnetic field extending from the developing sleeve 41, and is pumped up from the developer accommodating portion. At this time, since the stirring particles 48 are non-magnetic, they are transported by the transport screw 43 without being affected by the magnetic field. If there is a foreign object immediately before the doctor blade 42, an abnormal image such as white streaks is generated. However, since the stirring particles 48 do not reach the position immediately before the doctor blade 42 as described above, no abnormal image is generated.

  FIG. 4 schematically shows the relationship between the diameter d of the mixed stirring particles 48 and the gap g between the conveying screw 43 and the casing 49. The diameter d of the stirring particles 48 is made larger than the gap g between the conveying screws 43 and 44 and the casing 49. By setting the size of the stirring particles 48 in this way, the stirring particles 48 moved by the transport screw 43 can move the developer in the gap g between the transport screw 43 and the casing 49 while more efficiently pushing out the developer. Can do. As a result, the developer in the gap g between the conveying screw 43 and the casing 49 can be more efficiently stirred and circulated, and as a result, the entire developer in the developer container can be more efficiently circulated and used. Become.

  Further, the density of the stirring particles 48 to be mixed is preferably substantially equal to the apparent density of the developer 47. If the stirring particles 48 having a specific gravity similar to the apparent density of the developer 47 are used, they are well mixed with the developer without sinking below the developer containing portion or flowing upward. Therefore, the stirring particles 48 can push out the developer in the gap g without being biased, thereby improving the stirring ability of the entire developer in the developer accommodating portion.

  In addition, ceramic particles are particularly suitable as the stirring particles 48 to be mixed. The ceramic particles 48 do not deform or react even when mixed with toner or a carrier, and thus are hardly affected by the charging of the developer 47, and can be stably obtained at a relatively low cost. Furthermore, since the ceramic particles can be separated from the developer 47 by a simple ball-spinning process such as a coarse sieve, they can be regenerated and reused.

  Further, the toner can be prevented from being fixed on the surface of the stirring particles 48 by subjecting the surface of the stirring particles 48 to a hydrophobic treatment. Hydrophobization can be obtained by subjecting dimethyldichlorosilane, hexamethylenedisilazane, polymethylsiloxane (silicone oil) or the like to a surface treatment by a dry method.

  FIG. 5 shows a graph in which the influence of the presence or absence of mixing of the stirring particles 48 on the stirring property of the developer 47 is examined. Specifically, the gap g between the conveying screws 43 and 44 of the developing device 4 and the casing 49 is 1 mm, and 5 wt% of ceramic (silica) having a particle diameter d of 3 mm as the stirring particles 48 is mixed. Moreover, the outer diameter of the conveying screws 43 and 44 is 16 mm, and a 35 μm ferrite carrier is used as a developer. Under such conditions, the stirrability is characterized by the deviation of the 5-point toner concentration of the developer 47 when the toner is supplied to the developer with a toner concentration of 5 wt% in the developer container so that the toner concentration becomes 7 wt%. Shown as value. As shown in FIG. 5, by mixing the stirring particles 48, the toner concentration deviation can be reduced by mixing the stirring particles 48 even in the same stirring time. This indicates that the stirring property of the developer 47 in the developer container is improved by mixing the stirring particles 48. In addition, when the stirring particles 48 were mixed, the developer life was extended as compared with the case where the stirring particles 48 were not mixed. This indicates that when the stirring particles 48 are mixed, the effective developer circulating in the developer accommodating portion increases, and the developer in the developer accommodating portion can be effectively used.

  Further, as shown in FIG. 6, by making the connection interval L between the blades of the conveying screw 43 wider than the diameter d of the stirring particles 48, the stirring particles 48 do not stagnate in the screw and are the same as the developer. Can be moved. Therefore, the agitation can be improved without affecting the driving.

  Next, a modified example of the conveying screw as the developer stirring and conveying member will be shown. FIG. 7 shows a developer stirring / conveying member 80 disclosed in Japanese Patent Laid-Open No. 10-63081, which includes a spiral blade and a mesh-like screen member 82 provided between the blades. By rotating the developer agitating and conveying member 80, the developer is conveyed and passed through the mesh-like screen member 82 a plurality of times, and the developer is agitated. As a result, it is configured such that appropriate charging is performed by friction between the toner and the carrier.

FIG. 8 is a schematic configuration diagram of a developer stirring and conveying member disclosed in Japanese Patent Application Laid-Open No. 2000-19823. This developer agitating and conveying member is provided with a spiral blade member 56 as a conveying portion and a plurality of protruding members 57 as agitating portions around a rotating shaft 55. Furthermore, the maximum projection area X of the projection member when projected from the direction perpendicular to the projecting direction of the projection member is
Formula 1 (P × D) / 200 ≦ X ≦ (P × D) / 7
Formula 2 0.015 [D × (F + f)] ≦ X ≦ 0.2 [D × (F + f)]
It is set to become a relationship. In the formula, P is the pitch distance [mm] of the spiral blade member of the transport unit, D is the diameter [mm] of the rotational locus of the tip of the spiral blade member of the transport unit, and X is the maximum projected area [mm 2] of the protruding member. ], F is the width dimension [mm] in the rotation axis direction at the base part of the transport part, and f is the width dimension [mm] at the tip part of the transport part 45B.

  FIGS. 9A and 9B are schematic configuration diagrams of a developer stirring and conveying member disclosed in Japanese Patent Application Laid-Open No. 2004-191882. The developer stirring and conveying member includes a spiral blade member 56 formed around the rotation shaft and a plurality of linear members 58 fixed to the spiral blade member 56 at a predetermined angle with respect to the axial direction of the rotation shaft. Is used. As the developer agitating / conveying member rotates about the shaft, the linear member enters and exits the developer, so that the toner is taken in the rotating shaft direction of the developer agitating and separating from the shaft. Squeeze out in the opposite direction. Thus, the developer can be sheared efficiently and at high speed without increasing the torque so much, and the dispersibility and agitation of the replenishment toner to the developer can be improved.

  7, 8, 9 (a) and 9 (b), the developer stirring / conveying member rotates a spiral blade member provided with various members for improving the stirring ability. Is. Even in the case of using such a spiral blade member, a gap is provided between the casing and the spiral blade member. As described above, since the developer tends to stay in the gap, the effective developer circulating in the developer storage case is reduced, and the life of the developer is shortened. Therefore, even in those using these developer stirring and conveying members, it is effective to mix the stirring particles as described above as a developer stirring and conveying auxiliary member. The entire developer is circulated. This has the same effect as increasing the content of the developer as compared with the conventional developing device.

  Further, the present applicant has proposed in Japanese Patent Application Laid-Open No. 2004-205535 that a stirring member is provided separately on the outer peripheral portion of the spiral blade member. In this developing device, the stirring member at the outer peripheral portion can efficiently shear the developer at high speed, and can make the replenishment toner excellent in dispersibility and stirring in the developer. In addition, by using a separate stirring member, the speed of each of the spiral blades and the stirring member on the outer peripheral portion can be changed, or the speed of either one of the members can be changed. As a result, control corresponding to fluctuations in the rising charge amount of the toner becomes possible, and the margin for preventing background contamination and toner scattering can be increased. Similarly, in this developing device, the developer stays in the gap between the casing and the stirring member on the outer peripheral portion, and the effective developer circulating in the developer containing case is reduced, thereby shortening the life of the developer. Resulting in. Therefore, also in this developing device, it is effective to mix the stirring particles as described above as the developer stirring and conveying auxiliary member, and the developer in the gap between the casing and the stirring member on the outer peripheral portion is conveyed and stirred. The entire developer in the casing is circulated.

As described above, according to the present embodiment, the developer agitating / conveying auxiliary member conveys and stirs the developer in the gap between the rotation radius of the developer agitating / conveying member and the casing 49 as the developer accommodating case. As a result, the entire developer in the casing is circulated. This has the same effect as increasing the content of the developer as compared with the conventional developing device.
Further, as the developer agitation and conveyance auxiliary member, the agitation particles 48 made of non-magnetic particles are mixed in the developer 47 in the developer accommodating portion. A part of the mixed stirring particles 48 is applied to the end portions (outermost sides) of the blades of the transport screws 43 and 44, transported to the transport screws 43 and 44, and moved while forcibly pushing out the developer in the gap. . In this way, the developer in the gap is pushed out and moved by the stirring particles 48, and is stirred and transported with the developer within the rotation radius of the transport screws 43 and 44, thereby circulating in the casing 49. Therefore, all of the developer 47 in the developer accommodating portion can be circulated and used.
Further, the diameter d of the stirring particles 48 is made larger than the gap g between the transport screws 43 and 44 and the casing 49. Thereby, the stirring particles 48 moved by the conveying screw 43 can be moved more efficiently while pushing out the developer in the gap g between the conveying screw 43 and the casing 49. For this reason, the whole developer in the casing 49 can be circulated more efficiently.
Further, the density of the stirring particles 48 to be mixed is approximately equal to the apparent density of the developer 47. As a result, the developer particles in the gap g are pushed out without the stirring particles 48 being well mixed and biased with the developer 47, so that the developer stirring ability of the entire developer containing portion is improved.
In addition, ceramic particles are suitable as the stirring particles 48 to be mixed. Since the ceramic particles 48 are not deformed or reacted even when mixed with toner or carrier, the ceramic particles 48 hardly affect the charging of the developer, and can be stably obtained at a relatively low cost. Furthermore, since the ceramic particles can be separated from the developer by a simple sizing process such as a coarse sieve, they can be regenerated and reused.
Further, the toner can be prevented from being fixed on the surface of the stirring particles 48 by subjecting the surface of the stirring particles 48 to a hydrophobic treatment.
Further, the connection interval L between the blades of the conveying screws 43 and 44 is set wider than the diameter d of the stirring particles 48. As a result, the stirring particles 48 can move in the same manner as the developer without stagnation in the conveying screws 43 and 44, and the stirring performance can be improved without affecting the driving.
Further, the developing device 4, the photosensitive member 1, the charging device 2, the drum cleaning device 6, and the like are configured to be detachable from the printer body as one process cartridge. By using such a process cartridge, it is possible to obtain a process cartridge that improves the maintainability and obtains a predetermined developer life.

1 is a schematic diagram of a printer according to an embodiment of the present invention. 1 is a configuration diagram of a developing device employed in a printer according to an embodiment of the present invention. Explanatory drawing of the behavior of the developer and the stirring particles in the upstream part of the doctor blade of the developing device. Explanatory drawing of the relationship between the diameter of a stirring particle and the clearance gap between a conveyance screw and a casing. The graph which shows the influence which it has on the stirring property of a developer, when stirring particle | grains are mixed. Explanatory drawing of the relationship between the blade connection space | interval of a conveyance screw, and the diameter of stirring particle | grains. Schematic of an example of the developer stirring conveyance member of a prior art. Schematic of an example of the developer stirring conveyance member of a prior art. (A) Schematic of an example of the developer stirring conveyance member of a prior art. (B) Sectional drawing of an example of the developing agent stirring conveyance member of a prior art. Explanatory drawing of a motion of a developer when there exists a clearance gap between a screw and a casing. Explanatory drawing of a motion of a developer when there is no gap | interval between a screw and a casing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging device 3 Optical writing device 4 Developing device 5 Transfer device 6 Drum cleaning device 7 Static elimination device 8 Fixing means 41 Developing sleeve 42 Doctor blade 43, 44 Conveying screw 43a Rotating shaft 43b Blade 45 Partition wall 46 Supply port 47 Developer 48 Stirrer particle 49 Casing 55 Rotating shaft 56 Spiral blade member 57 Projection member 58 Linear member 80 Developer stirring and conveying member 81 Spiral blade body 82 Mesh screen member

Claims (5)

A developing device comprising: a developer housing case that houses a developer composed of toner and magnetic particles; and a developer stirring and transporting member that rotates and circulates the developer in the developer housing case while stirring and transporting the developer. In
As a developer stirring / transporting auxiliary member that transports and stirs the developer in the gap between the rotation radius of the developer stirring / conveying member and the developer storing case, the developer stirring / conveying member is mixed into the developer circulation region in the developer storing case. It is composed of non-magnetic particles and has stirring particles whose density is approximately equal to the apparent density of the developer ,
The developing device according to claim 1, wherein the diameter of the stirring particles is larger than a gap between a rotation radius of the developer stirring and conveying member and the developer storage case . The developing device according to claim 1 .
Developing apparatus is characterized in that it has facilities hydrophobic treatment on the surface of the stirring particles. The developing device according to claim 1 or 2, a developing device, wherein the stirring particles are ceramic particles. In an image forming apparatus comprising: an image carrier that carries a latent image; and a developing device that develops the latent image formed on the image carrier.
Claim 1 as the developing unit, 2 or the image forming apparatus characterized by using the developing device 3. In a process cartridge that integrally supports a developing device and at least one means selected from an image carrier, a charging device, and a cleaning device, and is detachable from an image forming apparatus main body,
Process mosquitoes characterized in that claim 1, 2 or is using the developing apparatus 3 as the developing unit - cartridge.

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