JP2008015169A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of forming an image of uniform density, free from occurrence of oblique density speckles and belt-like density reduction in the formed image, and to provide a process cartridge and an image forming apparatus. <P>SOLUTION: The developing device includes: a magnetic particle carrier equipped with a magnetic field generating means and a hollow cylindrical body; a first stirring/conveying member for conveying the magnetic particles in one direction parallel to the axis of the hollow cylindrical body while stirring the magnetic particles, and then, supplying the magnetic particles to the outer surface of the magnetic particle carrier; and a second stirring/conveying member for resupplying the magnetic particles lying on the downstream side in the conveying direction of the first stirring/conveying member to the upstream side. Regarding the magnetic particle conveying capacity of the first stirring/conveying member, the capacity on the upstream side in the magnetic particle conveying direction is lower than that on the downstream side in the magnetic particle conveying direction, and regarding the magnetic particle conveying capacity of the second stirring/conveying member, the capacity on the upstream side in the magnetic particle conveying direction is lower than that on the downstream side in the magnetic particle conveying direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing device, an image forming apparatus, and a process cartridge used for a copying machine, a facsimile, a printer, and the like. Specifically, the magnetic particles carried on the magnetic particle carrier are conveyed to a developing area where the image carrier and the magnetic particle carrier are opposed to each other with a gap, and the electrostatic latent image on the image carrier is developed to produce a toner image. The present invention relates to a developing device. The present invention also relates to a process cartridge and an image forming apparatus using such a developing device.

  As shown in FIG. 7A, in a developing device used in a copying machine, a facsimile machine, a printer, etc., magnetic particles are conveyed to a developing area facing the image carrier and formed on the surface of the image carrier 2. A magnetic particle carrier 1 that develops the electrostatic latent image thus formed to form a toner image is provided (Japanese Patent Laid-Open No. 11-338233 (Patent Document 1), etc.).

  The magnetic particle carrier 1 includes a developing sleeve 1a formed in a hollow cylindrical shape, and a magnetic field that is accommodated in the developing sleeve 1a and that forms a magnetic field so as to cause spikes of magnetic particles on the surface of the developing sleeve. And a magnet roller 1b as a generating means. The magnetic particle carrier 1 spikes on the developing sleeve 1a so that the magnetic carrier constituting the magnetic particle 7 follows the lines of magnetic force generated by the magnet roller 1b when the magnetic particles 7 rise. The toner constituting the magnetic particles 7 adheres (adsorbs) together with the magnetic carrier.

  Thereafter, the amount of the magnetic particles 7 adsorbed on the developing sleeve 1a is made uniform by the magnetic particle regulating member 5, and then the image carrier 2 and the magnetic particle carrier 1 are opposed to each other with an interval. It is conveyed to a developing area formed between the carrier (latent image carrier) 2 and the magnetic particles 7 develop the electrostatic latent image formed on the image carrier 2 to form a toner image. Form.

  On the other hand, the magnetic particles 7 remaining on the surface of the magnetic particle carrier 1 are detached at the magnetic particle separation position shown in FIG. 7A and returned to the magnetic particle storage tank 3a again. Thus, the magnetic particles 7 adsorbed on the magnetic particle carrier 1 are circulated and conveyed.

  Such a developing device A includes magnetic particle storage tanks 3a and 3b for storing magnetic particles 7, screw-shaped stirring and conveying members 4a and 4b for stirring the magnetic particles 7 in the developer storage tank, and magnetic particle support And a magnetic particle regulating member 5 that makes the amount of the magnetic particles 7 pumped up by the body 1 uniform.

  The developing device B shown in FIG. 7B is different in shape from that in FIG. 7A, but the members and the operation thereof are the same.

  FIG. 7A shows a form in which the magnetic particle regulating member 5 is provided on the upper side or the lateral side of the developing roller, and the agent of the magnetic particles 7 is separated into the developing device below the magnetic particle carrier 1. 7 (b), on the contrary, the magnetic particle regulating member 5 is provided below the magnetic particle carrier 1, and the agent of the magnetic particles 7 is separated into the developing device above the magnetic particle carrier 1. These are used separately depending on the layout of the photosensitive drum and other units.

  These two developing devices shown in FIGS. 7A and 7B each include a pair of magnetic particle storage tanks and a stirring and conveying member.

  Here, the function of the stirring and conveying member will be described with reference to FIG.

  A first conveying member (screw in this example) 4a provided in one magnetic particle storage tank 3a is provided so as to face the cylindrical magnetic particle carrier 1 while stirring the magnetic particles 7 by rotation. While stirring in one direction (right to left in the figure) parallel to the axis of the hollow cylinder, the magnetic particles 7 are supplied to the outer surface of the magnetic particle carrier 1. After the magnetic particles 7 reaching the left end in the figure move from one magnetic particle storage tank 3a to the other magnetic particle storage tank 3b, the second stirring / conveying member (screw) provided in the other magnetic particle storage tank 3b. ) 4b rotates in the opposite direction to the first agitation transport member 4a, so that it is transported by the first agitation transport member 4a downstream in the transport direction by the first agitation transport member 4a (in the drawing) The leftmost magnetic particles 7 are conveyed while being stirred upstream (right side in the figure) in the conveying direction by the first agitating / conveying member 4a and moved from the other magnetic particle accommodating tank 3b to one magnetic particle accommodating tank 3a. Then, the magnetic particles 7 are always supplied near the surface of the magnetic particle carrier 1 because they are supplied (circulated and supplied) again to the first stirring and conveying member 4a.

  Here, among the magnetic particles 7 adsorbed on the magnetic particle carrier 1, new magnetic particles 7 corresponding to the magnetic particles transferred to the image carrier 2 are the other magnetic particle storage tank 3b or a magnetic particle (not shown). Since the supply unit supplies the second stirring and conveying member 4b to the second stirring and conveying member 4b from the lower left end in the figure, the same amount of magnetic particles 7 are always supplied by the first and second stirring and conveying members 4b. Agitated and transported.

  By such a mechanism, a uniform amount of magnetic particles 7 should be supplied to the surface of the cylindrical magnetic particle carrier, and as a result, a uniform density image should be developed.

  In reality, however, the image has oblique density spots at one end as shown in FIG. 7B and a strip-shaped density drop at the other end.

  As a result of detailed studies on the above problems, the present inventors have found that in the operating magnetic particle storage tank, the magnetic particles 7 present inside the one magnetic particle storage tank 3a and the other magnetic particle storage tank 3b. As shown in a model in FIG. 8 (c), the amount of is less on the right side in the drawing, that is, on the upstream side in the conveyance direction of the magnetic particles 7 than on the downstream side, and on the downstream end. In the other magnetic particle storage tank 3b, the left side in the figure, that is, the upstream side in the conveyance direction of the magnetic particles 7 is smaller than the downstream side, and at the downstream end. It has been found that there is a tendency that a state in which the amount of magnetic particles 7 is increased due to retention tends to be formed.

  In this case, in the vicinity of the upstream end in the conveyance direction of the magnetic particles 7 by the stirring and conveying member 4a, the height of the aggregate composed of the magnetic particles 7 is reduced, so that the magnetic force from the magnetic particle carrier 1 to the magnetic particles 7 is increased. Is weak, the magnetic particle 7 is poorly adsorbed to the magnetic particle carrier 1, and oblique density spots as shown in the vicinity of the right end of FIG. 7B are generated, or the image density is lowered. On the contrary, in the vicinity of the downstream end of the stirring and conveying member 4a in the direction of conveyance of the magnetic particles 7, the height of the aggregate composed of the magnetic particles 7 is increased, and the magnetic particle detachment in the magnetic particle carrier 1 is performed. Since the magnetic particles 7 are close to the position, the phenomenon that the magnetic particles 7 are prevented from being detached from the magnetic particle carrier 1 or the magnetic particles 7 once separated are easily adsorbed to the magnetic particle carrier 1 as a result. Magnetic particles 7 with low concentration are magnetic Go to the child carrier 1, to be developed, it was found that the strip-like density reduction as shown in the vicinity of the left end in FIG. 7 (b) results in image density becomes thin, or omission white occurs.

Such a poor balance of the axis method of the magnetic particle carrier 1 of the magnetic particles 7 is basically transferred in the delivery of the magnetic particles 7 between one stirring and conveying member 4a and the other stirring and conveying member 4b. This occurs because the magnetic particles 7 are likely to stay on the delivery side, and the delivered magnetic particles 7 are immediately conveyed downstream on the delivery side. That is, the amount of the magnetic particles 7 is reduced at the upstream end of each stirring and conveying member. Such a phenomenon is likely to occur with the recent increase in speed, and the probability of occurrence due to long-term use has increased along with a request for a longer life.
JP 11-338233 A

  The present invention has been made in order to solve the above-described problems, and it is possible to form an image having a uniform density without causing oblique density spots and band-shaped density reduction in the formed image. It is an object to provide a developing device, a process cartridge, and an image forming apparatus.

The developing device of the present invention has been conceived to solve the above problems based on the above knowledge. A magnetic particle carrier comprising: a magnetic field generating means; and a hollow cylindrical body containing the magnetic field generating means and adsorbing magnetic particles on the outer surface by the magnetic field generating means. The magnetic particle carrier is provided so as to face the magnetic particle carrier, and while stirring the magnetic particles, the magnetic particles are conveyed in one direction parallel to the axis of the hollow cylindrical body to supply the magnetic particles to the outer surface of the magnetic particle carrier. 1 stir-conveying member and second stirrer for supplying again the magnetic particles on the downstream side in the conveying direction conveyed by the first agitating-conveying member to the upstream side in the conveying direction by the first agitating / conveying member In a developing device provided with a conveying member,
(A) In the first stirring and conveying member, the magnetic particle conveying ability of the upstream portion in the magnetic particle conveying direction is smaller than the magnetic particle conveying ability of the downstream portion in the magnetic particle conveying direction, and
(B) In the second stirring and conveying member, the magnetic particle conveying ability in the upstream portion in the magnetic particle conveying direction is smaller than the magnetic particle conveying ability in the downstream portion in the magnetic particle conveying direction. It is a developing device.

  The developing device according to the present invention is the developing device according to claim 1, wherein the first stirring and conveying member and the second stirring and conveying member are both screw-shaped. The thickness of the screw blade on the upstream side in the magnetic particle conveying direction of these stirring and conveying members is thicker than the thickness of the downstream screw blade.

  According to a third aspect of the present invention, there is provided the developing device according to the second aspect, wherein the screw blades of the first agitating and conveying member and the second agitating and conveying member are both on the outer peripheral side. The thickness is constant, and the thickness on the screw shaft side is thicker on the upstream side than the downstream side in the magnetic particle transport direction of the stirring transport member.

  According to a fourth aspect of the present invention, there is provided the developing device according to the second aspect, wherein the screw blades of the first agitating and conveying member and the second agitating and conveying member are both on the screw shaft side. And the thickness of the outer peripheral side is thicker on the upstream side than the downstream side of the stirring and conveying member in the magnetic particle conveying direction.

  According to a fifth aspect of the present invention, a process cartridge includes the developing device according to any one of the first to fourth aspects.

  According to a sixth aspect of the present invention, there is provided an image forming apparatus comprising the developing device according to any one of the first to fourth aspects.

  According to the developing device of the present invention, with the above-described configuration, the magnetic particle carrying ability of the upstream part in the magnetic particle carrying direction of the stirring and carrying member of the two stirring and carrying members is the same as that of the downstream part in the magnetic particle carrying direction. Since it is smaller than the particle transfer capacity, even if it is operated for a long time, the magnetic particles near the transfer start point do not decrease, and the magnetic particle carrier with uniform magnetic particles over the entire axial direction Therefore, it is possible to stably form an image having a uniform density without occurrence of oblique density spots or band-shaped density reduction.

  Further, according to the developing device according to claim 2, since the effect of the invention according to claim 1 can be realized with a simple configuration of the agitating / conveying member and the manufacturing cost does not increase, an inexpensive developing device equivalent to the conventional technology can be achieved. An apparatus can be provided.

  According to the developing device according to claim 3 and claim 4, since the screw of the stirring and conveying member is provided with an inclination, it can be easily manufactured by resin injection molding and has a complicated mold structure. Therefore, the developing device can be made more inexpensive.

  Further, according to the process cartridge of the fifth aspect, since the developing device according to any one of the first to fourth aspects is used, it is small in size and excellent in granularity, and image spots can be observed over a long period of time. It is possible to obtain a process cartridge capable of obtaining an excellent image without any problem.

  Further, according to the image forming apparatus of the sixth aspect, since the developing device according to any one of the first to fourth aspects is used, the image forming apparatus is small in size, excellent in granularity, and has a long-term image. An excellent image without spots can be obtained.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following examples.

  An example of the present invention will be described with reference to FIG.

  FIG. 1 includes a magnetic field generation unit 1b and a hollow cylindrical body 1a that contains the magnetic field generation unit 1b and that adsorbs magnetic particles on the outer surface by the magnetic field generation unit 1b, and is provided so as to face each other. A magnetic particle carrier 1 for transporting magnetic particles adsorbed on the image carrier, and a magnetic particle carrier 1, which is provided so as to face the magnetic particle carrier 1, and in one direction parallel to the axis of the hollow cylinder 1 a while stirring the magnetic particles A first agitating and conveying member 4a that conveys and supplies magnetic particles to the outer surface of the magnetic particle carrier 1, and a magnetic particle conveying direction by the first agitating and conveying member 4a conveyed by the first agitating and conveying member 4a , A developing device provided with a second agitating / conveying member 4b that supplies the magnetic particles on the downstream side again to the upstream side in the conveying direction by the first agitating / conveying member 4a, the first agitating / conveying member 4a, and the second agitating member The conveying member 4b The thickness of the screw blades on the upstream side in the magnetic particle conveying direction of the stirring and conveying members 4a and 4b is thicker than the thickness of the downstream screw blades. The magnetic particle conveying ability (per unit time) of the upstream portion in the magnetic particle conveying direction in the one agitating and conveying member 4a is the magnetic particle conveying ability (per unit time) of the downstream portion in the magnetic particle conveying direction. And (b) the second agitating and conveying member 4b has a magnetic particle conveying capacity (per unit time) in the upstream part in the magnetic particle conveying direction of the downstream part in the magnetic particle conveying direction. It is smaller than the magnetic particle carrying capacity per unit time (per unit time).

  With such a configuration, in the magnetic particle transfer portion from the stirring and conveying member 4b to the stirring and conveying member 4a, the magnetic particles can be prevented from being reduced in the stirring and conveying member 4a even after long-time operation. In both cases, the distribution of the presence of the magnetic particles in the transport direction in both of them is constant, so that no poor adsorption of the magnetic particles to the magnetic particle carrier 1 occurs, and a good image can be stably obtained. Can do.

  On the other hand, in the agitating / conveying member 4b, since the screw blades in the upstream portion in the magnetic particle conveying direction by the agitating / conveying member 4b are thicker than the screw blades in the other portions, the upstream as shown in FIG. The state where the magnetic particles on the side are partially reduced can be prevented, and the distribution of the presence of the magnetic particles in the magnetic particle conveyance direction can be made constant. In the entire magnetic particle conveying region performed by the agitating / conveying member 4a and the agitating / conveying member 4b, the height of the aggregate of the magnetic particles is constant, thereby eliminating the partial image defect that has conventionally occurred. To do.

  In the example shown in FIG. 1, the magnetic particle transport per unit time in the axial direction of the screw is made by making the thickness of the screw blades on the upstream side of the stirring transport members 4a and 4b thicker than the thickness of the screw on the downstream side. Optimized ability. However, in the present invention, the thickness of the upstream screw blade only needs to be relatively greater than the thickness of the downstream screw blade, so that as shown in FIG. The screw blade thickness on the downstream side may be made thinner than the blade thickness. In this case, of course, the aggregate of magnetic particles in the entire magnetic particle conveyance region performed by the agitation conveyance member 4a and the agitation conveyance member 4b. By making the height of the image constant, it is possible to obtain the effect of the present invention that a partial image defect that has conventionally occurred is eliminated.

  The first stirring and conveying member 4a and the second stirring and conveying member 4b are both screw-shaped, and the thickness of the upstream screw blade in the magnetic particle conveying direction of these stirring and conveying members is the thickness of the downstream screw blade. An example in which the thickness is larger than the above will be described with reference to FIGS. 3 (a) and 3 (b). FIG. 3A is a model diagram of a part of the screw, and FIG. 3B is a model cross-sectional view taken along a straight line KK in FIG.

  In this example, a screw having a thickness T2 of the screw blade on the shaft side is thicker than a thickness T1 of the screw blade on the outer diameter side, and the thickness T1 is kept constant in the conveying direction of the agitating and conveying member. For example, T2 on the upstream side in the transport direction may be partially thicker than other locations, or T2 on the downstream side may be partially thinner than other locations.

  By such an adjustment, the magnetic particle conveying capacity in the axial direction of the stirring and conveying member is adjusted, and the magnetic particle conveying capacity per unit time of the upstream portion of the stirring and conveying member in the magnetic particle conveying direction is set to the The magnetic particle carrying capacity is small compared to the magnetic particle carrying capacity per unit time, and even when operated for a long time, there is no decrease in the magnetic particles in the vicinity of the starting point of conveyance, and the magnetic particles are evenly carried over the entire axial direction. Since it can be supplied to the body, it is possible to stably form an image having a uniform density without occurrence of oblique density spots or band-shaped density reduction.

  Conversely, by changing the thickness T1 while fixing the thickness T2, the magnetic particle carrying capacity per unit time of the upstream portion in the magnetic particle carrying direction of the stirring and carrying member is changed to the unit time of the downstream portion in the direction. The same effect can be obtained by making it smaller than the hitting magnetic particle carrying ability.

  Hereinafter, an embodiment of an image forming apparatus to which the present invention is applied will be described with reference to the drawings. In the following embodiment, an electrophotographic printer capable of forming a full-color image is illustrated.

  The printer α shown in FIG. 4 corresponds to four color image forming apparatuses 10Y (yellow), 10C (cyan), 10M (magenta), and 10K (black) as process cartridges formed on the apparatus main body α side. It is detachably attached to an image forming station (not shown), and includes an optical unit 20, an intermediate transfer body unit 30, a paper feeding unit 40, a fixing unit 50, and the like as exposure means capable of irradiating laser light.

  The image forming apparatuses 10Y, 10C, 10M, and 10K have the same structure, and the photosensitive drums 12Y, 12C, 12M, and 12K as latent image carriers are charged, and the photosensitive drums are charged as process means that act on the photosensitive drums. Charging devices 13Y, 13C, 13M, and 13K, and cleaning devices 15Y, 15C, 15M, and 15K that remove magnetic particles remaining on the photosensitive drum are integrally configured, and formed on each photosensitive drum. The developing devices 14Y, 14C, 14M, and 14K for developing the latent images are connected.

  The intermediate transfer body unit 30 includes a transfer belt 31 as an intermediate transfer body, a plurality of (here, three) rollers 32, 33, and 34 that rotatably support the transfer belt 31, and toner formed on each photosensitive drum 12. A primary transfer roller 35 for transferring the image to the transfer belt 31 and a secondary transfer roller 36 for transferring the toner image transferred onto the transfer belt 31 to the recording paper P are provided.

  The paper feed unit 40 includes a paper feed roller 43 and a registration roller 44 that convey the recording paper P from the paper feed cassette 41 or the manual paper feed tray 42 to the secondary transfer region. The fixing unit 50 includes a fixing roller 51 and a pressure roller 52, and has a known configuration in which fixing is performed by applying heat and pressure to the toner image on the recording paper P.

  In such a configuration, first, in the first color yellow image forming device 10Y, the photosensitive drum 12Y is uniformly charged by the charging device 12Y, and then the latent image is developed by the laser light emitted from the optical unit 20. 14 is developed to form a toner image.

  The toner image formed on the photosensitive drum 12 is transferred onto the transfer belt 31 by the action of the primary transfer roller 35. The photosensitive drum 12Y after the primary transfer is cleaned by the cleaning device 15Y to prepare for the next image formation. The residual toner collected by the cleaning device 15Y is stored in a waste toner collection bottle 16 installed in the take-out direction of the image forming device 10Y (the rotation axis direction of the photosensitive drum). The waste toner collection bottle 16 is detachable from the image forming apparatus main body α so that it can be replaced when the storage amount is full. A similar image forming process is performed in each of the image forming apparatuses 10C, 10M, and 10K for C, M, and K to form toner images of the respective colors, which are sequentially transferred to the previously formed toner images.

  On the other hand, the toner image formed on the transfer belt 31 by the action of the secondary transfer roller 36 is transferred to the recording paper P conveyed from the paper feed cassette 41 or the manual paper feed tray 42 to the secondary transfer region. . The recording paper P to which the toner image has been transferred is conveyed to the fixing unit 50, where the toner image is fixed at the nip portion between the fixing roller 51 and the pressure roller 52 of the fixing unit 50, and the discharge roller 55 discharges the upper part of the apparatus. The paper is discharged to the paper tray 56.

  At the upper part of the image forming apparatus main body α, toner bolts Y1, C1, M1, and K1 respectively storing toner to be supplied to a toner replenishing port 145, which will be described later, are detachable from the image forming apparatus main body α separately from each image forming apparatus. It is attached to.

  Next, the configuration of the image forming device and the developing device will be described. Each device configuration is the same except that the color of the supplied toner as the magnetic particles is different, so an example of the image forming device 10Y will be described below with reference to FIG.

  The charging device 13Y provided in the image forming device 10Y includes a charging roller 131 and a cleaning roller 132 that cleans the surface of the charging roller 131. The cleaning device 15Y includes a cleaning brush 151 and a cleaning blade 152 that are in contact with the surface of the photosensitive drum, and a toner recovery coil 153 that transports the toner scraped off by the cleaning brush 151 and the cleaning blade 152 toward the waste toner recovery bottle 16. It has.

  The developing device 14Y carries a toner of two-component magnetic particles and rotates it counterclockwise in FIG. 6 to a developing region facing the photosensitive drum 12Y to convey the developing sleeve (outer surface) as a magnetic particle carrier. A hollow cylindrical body that adsorbs magnetic particles to the developing sleeve 141 and the developing sleeve 141 as a magnetic particle regulating portion that controls the layer thickness of the toner carried on the surface of the developing sleeve 141. A doctor blade 146 as a regulating member formed between the surface of the toner and the magnetic particles stored in the developing device 14Y and the replenishing toner supplied from the toner replenishing port 145 while stirring the axial direction of the photosensitive drum 12Y Two transport screws that guide to the developing sleeve 141 while reciprocally transporting them to the axis of the hollow cylindrical body while stirring the magnetic particles A first agitating and conveying member that conveys the magnetic particles to the outer surface of the magnetic particle carrier by conveying in one direction, and conveying by the first agitating and conveying member conveyed by the first agitating and conveying member. Second agitating / conveying members 142, 143 for supplying magnetic particles on the downstream side in the direction to the upstream side in the conveying direction by the first agitating / conveying member), and a developing casing 144 for accommodating and supporting these members. ing. The doctor blade 146 is supported so as to be sandwiched between the developing casings 144.

  Inside the developing sleeve 141, a plurality of magnets (not shown) are arranged as magnetic field generating means.

  A receiving member 147 supported by the developing casing 144 is provided upstream of the doctor blade 146 in the moving direction of the developing sleeve 141. The developing sleeve 141, the doctor blade 146, and the receiving member 147 are extended in the axial direction of the photosensitive drum. The receiving member 147 has a substantially right triangle shape, and protrudes from the developing casing toward the space 148 where the toner is pumped up and stays by the conveying screw 143 inside the developing casing 144. Specifically, the top of the right triangle protrudes so as to be located toward the surface of the developing sleeve 141 and is adjacent to the doctor blade 146. The receiving member 147 is provided with a toner receiving surface 147 a that moves from the space portion 148 toward the doctor blade 146. The top of the receiving member 147 is substantially the same as or somewhat lower than the tip of the doctor blade 146.

  According to the developing device 14Y having such a configuration, the receiving member 147 is provided around the layer thickness regulating portion of the doctor blade 146 in the space portion 148 where the toner stays and flows toward the doctor blade 146. Other than that, it is concealed by the receiving member 147. As a result, the toner pressure applied to the doctor gap S is reduced, and the displacement of the doctor gap S is suppressed, so that the variation in the toner supplied to the photosensitive drum 12Y is extremely reduced.

  Although the receiving member 147 is provided on the back side of the doctor blade 146, if a gap is formed between the back side of the doctor blade 146 and the receiving member 147, toner may accumulate between the two, and the doctor gap S can be narrowed. For this reason, a gap S1 is provided in advance between the back side of the doctor blade 146 and the receiving member 147, and a plate-like elastic member 150 serving as a seal member is inserted into the gap S1 to insert the gap S1. It is possible to prevent toner accumulation and agent dropping with respect to the gap.

  Also, in this embodiment, each toner bottle is detachable from the image forming apparatus main body α separately from each image forming apparatus, so that each toner bottle and each image forming apparatus can be exchanged individually, which is unnecessary. Therefore, the user's expense at the time of parts replacement can be reduced. Further, since the number of times of opening / closing and taking in / out of other parts of the apparatus is reduced, it is possible to prevent toner scattering and improve maintainability.

  A toner having a sphericity of 0.93 or more can also be used as the toner used in this embodiment. In other words, it is known to reduce the toner particle size in order to improve the image quality of the image, but in the case of reducing the particle size, the conventional pulverized toner has a particle size distribution that is broad. There is a characteristic that it is difficult. Therefore, it is possible to achieve high image quality by increasing the circularity of the toner by a polymerization method or the like and by making the particle size distribution sharp. However, when the circularity of the toner is increased, the toner approaches a spherical shape, so that cleaning with the cleaning device 15Y becomes very difficult. However, in this embodiment, since the receiving member 147 is provided, the photosensitive drum due to the displacement of the doctor gap S is provided. Since there is no variation in the amount of toner supplied to 12Y, the cleaning performance can be maintained even when spherical toner obtained by polymerization or the like is used.

  Further, according to the developing device of the present embodiment, the magnetic particles (magnetic carrier) constituting the developer have an average particle diameter of 20 μm or more and 50 μm or less. By using magnetic particles having a particle size in such a range, the granularity of the image is improved and a high-quality image can be obtained. In addition, the magnetic particles have a resin coating film on the magnetic core, and the resin coating film is charged with a resin component obtained by crosslinking a thermoplastic resin such as acrylic and a melamine resin. It contains an agent. By using this magnetic particle, it is possible to obtain a good balance between the effect of absorbing impact and suppressing scraping and holding large particles with a strong adhesive force, and the effect of preventing impact on the coating film and cleaning spent materials. it can. Accordingly, it is possible to prevent the magnetic particles from having a long life, that is, film scraping and spent.

  Further, according to the developing device of the present embodiment, the toner of the magnetic particles is prepared by dispersing a toner composition including at least a prepolymer, a colorant, and a release agent in an aqueous medium in the presence of resin fine particles. A polymerized toner obtained by polyaddition reaction of the toner composition is used. By using such a toner, there is no pulverization step, resource can be reduced, particle size distribution and charge distribution can be sharpened, and shape control that changes the circularity can be easily performed. Obtainable.

  Further, according to the developing device of the present embodiment, the magnetic particle transport capability per unit time of the upstream portion of the first stirring transport member in the magnetic particle transport direction is the same as that of the downstream portion of the magnetic particle transport direction. The magnetic particle carrying capacity per unit time is small compared to the magnetic particle carrying capacity per unit time, and the second agitating and conveying member of the upstream part in the magnetic particle carrying direction is downstream in the magnetic particle carrying direction. Since it is smaller than the magnetic particle transfer capacity per unit time of the side part, even if it is operated for a long time, the magnetic particles near the transfer start point do not decrease, and the magnetic properties of the magnetic particles are uniform over the entire axial direction. Since supply to the particle carrier is possible, it is possible to stably form an image having a uniform density without occurrence of oblique density spots and band-shaped density reduction.

  In addition, since the image forming apparatus of the present embodiment includes such a developing device, the magnetic particles near the conveyance start point do not decrease even when the operation is performed for a long time. Since uniform supply to the magnetic particle carrier is possible, it is possible to stably form an image having a uniform density without occurrence of oblique density spots and band-shaped density reduction.

  Four types of screw type agitating / conveying members (1) to (4) are produced two by two, and incorporated into the developing device of the printer shown in FIG. 4 as the first and second agitating / conveying members, respectively, and actually used. saw.

At this time, in the screw type stirring and conveying member (1) according to the conventional technique, the thickness T1 ₁ on the circumferential side of the upstream screw blade in the magnetic particle conveying direction, the thickness T2 ₁ on the axial side of the screw blade on the upstream side, circumferential side thickness T1 2 of the screw blades of the same _downstream, and were all thickness T2 _2-axis side of the screw blades of the downstream 1 mm.

Further, in the screw type agitating and conveying member (2) (Example 1) according to the present invention, the thickness T1 ₁ on the circumferential side of the upstream screw blade in the magnetic particle conveying direction, and the thickness on the axial side of the upstream screw blade. T2 ₁ , circumferential thickness T1 ₂ of the downstream screw blade, and axial thickness T2 ₂ of the downstream screw blade are 1.5 mm, 1.5 mm, 1 mm, and It was 1 mm.

Alternatively, in the screw type stirring and conveying member (3) according to the present invention (Example 2), the thickness T1 ₁ on the circumferential side of the upstream screw blade in the magnetic particle conveying direction and the thickness on the axial side of the upstream screw blade in the same direction. T2 ₁ , circumferential thickness T1 ₂ of the downstream screw blade, and axial thickness T2 ₂ of the downstream screw blade are 1.5 mm, 2 mm, 1.5 mm, and It was 1.8 mm.

Further, in the screw type agitating and conveying member (4) according to the present invention (Example 3), the thickness T1 ₁ on the circumferential side of the upstream screw blade in the magnetic particle conveying direction and the thickness on the axial side of the upstream screw blade are shown. T2 ₁ , circumferential thickness T1 ₂ of the downstream screw blade, and axial thickness T2 ₂ of the downstream screw blade are 1.8 mm, 2 mm, 1.5 mm, and It was 2 mm.

  The outer diameters (outer diameters) of the stirring and conveying members (1) to (4) are all 16 mm, the shaft diameters of the stirring and conveying members are all 7 mm, and the pitch of the screw blades of the stirring and conveying members is 20 mm. .

  For a long time, image formation was repeatedly performed under the same conditions in the image forming apparatuses each incorporating such screw type stirring and conveying members (1) to (4). At this time, the distribution balance of the magnetic particles in the magnetic particle storage tank was visually observed, and “×” indicates that the magnetic particles are significantly collapsed, “△” indicates that they are collapsed, and “○” indicates that they are slightly collapsed. Each case where there was almost no collapse was evaluated as “◎”.

  In addition, the final obtained image was visually evaluated with respect to the oblique density spots and the belt-like density. When the spots and the density-reduced images were at a level having a practical problem, “x”, “△” indicates that there are spots and a decrease in density, but there is no problem in practical use, “O” indicates that there is almost no spots and a decrease in density, and there is no problem, and there is no decrease in density. Each case was evaluated as “◎”.

  As shown in Table 1, when the developing device according to the present invention is used, the balance of magnetic particle distribution in the magnetic particle storage tank is good, and slant-like density spots and strip-like density reductions are reduced. I can understand that it is a problem-free level.

  In the developing device of the present invention, the process cartridge of the present invention, and the developing device in the image forming apparatus of the present invention, slanting density spots and strip-shaped density reduction can be reduced, and it can be set to a level that does not cause a problem in practice. Therefore, it can be widely used in the field of electrophotography which has been conventionally used.

It is a model diagram showing an example of a developing device of the present invention. It is a model figure which shows the other example of the image development apparatus of this invention. It is a model figure for demonstrating the screw blade shape of a screw-shaped stirring conveyance member. (A) It is a side view. (B) It is sectional drawing in KK of (a). It is a model explanatory drawing of the printer provided with the developing device of the present invention. It is a partial expansion model explanatory drawing of the brewery apparatus 10Y of the printer of FIG. (A) It is model sectional drawing of an example of the developing device of the electrophotographic system based on a prior art. (B) It is model sectional drawing of the other example of the developing device of the electrophotographic system based on a prior art. (A) It is a model figure explaining the function of a stirring conveyance member. (B) It is a figure which shows the slant-like density spot and strip | belt-shaped density fall which were produced with the conventional image development apparatus. (C) It is a model figure which shows the uneven distribution of the magnetic particle which has arisen with the conventional image development apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic particle carrier 1a Developing sleeve 1b Magnet roller 2 Image carrier (latent image carrier)
3a, 3b Magnetic particle storage tank 4a, 4b Agitating and conveying member 5 Magnetic particle regulating member 7 Magnetic particle

Claims (6)

A magnetic particle carrier comprising: a magnetic field generating means; and a hollow cylindrical body containing the magnetic field generating means and adsorbing magnetic particles on the outer surface by the magnetic field generating means, so as to face the magnetic particle carrier A first agitating and conveying member that is provided on the outer surface of the magnetic particle carrier to convey the magnetic particles in one direction parallel to the axis of the hollow cylindrical body while stirring the magnetic particles; and In a developing device including a second agitating and conveying member that is supplied by the first agitating and conveying member and supplies the magnetic particles on the downstream side in the conveying direction to the upstream side in the conveying direction by the first agitating and conveying member.
(A) In the first stirring and conveying member, the magnetic particle conveying ability of the upstream portion in the magnetic particle conveying direction is smaller than the magnetic particle conveying ability of the downstream portion in the magnetic particle conveying direction, and
(B) In the second stirring and conveying member, the magnetic particle conveying ability in the upstream portion in the magnetic particle conveying direction is smaller than the magnetic particle conveying ability in the downstream portion in the magnetic particle conveying direction. Development device.   The first agitation transport member and the second agitation transport member are both screw-shaped, and the thickness of the upstream screw blade in the magnetic particle transport direction of these agitation transport members is equal to that of the downstream screw blade. The developing device according to claim 1, wherein the developing device is thicker than the thickness.   The screw blades of the first agitating and conveying member and the second agitating and conveying member both have a constant outer peripheral thickness, and the screw shaft side thickness is downstream of the agitating and conveying member in the magnetic particle conveying direction. The developing device according to claim 2, wherein the upstream side is thicker than the side.   The screw blades of the first agitating and conveying member and the second agitating and conveying member both have a constant thickness on the screw shaft side, and the outer peripheral side thickness is downstream of the agitating and conveying member in the magnetic particle conveying direction. The developing device according to claim 2, wherein the upstream side is thicker than the side.   A process cartridge comprising the developing device according to any one of claims 1 to 4.   An image forming apparatus comprising the developing device according to claim 1.

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