JP4534665B2 - Developing device and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine or a printer, and in particular, uses a two-component developer including a magnetic carrier and a toner, and does not use a toner concentration detecting means. The present invention relates to a developing device that autonomously controls the image forming apparatus and an image forming apparatus using the developing device.

Japanese Patent Publication No. 5-67233 JP-A-5-119625 Japanese Patent Laid-Open No. 9-22178 JP 2000-352877 A JP-A-9-197833

  In general, as a developing device used in an image forming apparatus such as an electrophotographic system, an electrostatic latent image formed on an image carrier such as a photosensitive drum is visualized with a developer. Yes. As a developing system used in this type of developing device, a one-component developing system that uses only toner that is colorant particles as a developer, and a carrier that is magnetic particles and toner that is colored particles are mixed and stirred as a developer. It is roughly divided into a two-component development system using the above.

  2. Description of the Related Art Conventionally, as a two-component developing type developing device, there are many excellent points such as image quality, cost, and stability. Therefore, there is a magnetic brush developing method in which a developer in which toner is mixed in a magnetic carrier is conveyed and developed by a magnetic field. Widely used. In this magnetic brush developing method, the toner is supported on the surface of the magnetic carrier by the electrostatic force generated by the friction between the toner and the magnetic carrier. When the toner approaches the electrostatic latent image on the image carrier, The electrostatic latent image is visualized by flying on the electrostatic latent image by an electric field formed between the electrostatic latent image carrier and the developer carrier. Further, the developer is repeatedly used while replenishing the toner consumed by the development.

  However, in such a magnetic brush developing method, if the toner concentration (mixing ratio of toner and magnetic carrier) is not controlled to be within a certain range, toner scattering and fogging occur when the toner concentration increases. On the other hand, when the toner density is reduced, density reduction, density spots, image omission, and the like occur. Therefore, it is necessary to keep the toner density constant in order to obtain a stable image.

  Therefore, in the conventional magnetic brush development method, in order to obtain a stable image, the toner density is detected using a toner density sensor, or a development patch is created to detect the toner development amount. Control is performed to keep the toner density constant by operating. For example, when the toner density is detected by the toner density sensor and it is determined that the toner density has decreased based on the detection information, the toner supply is performed by the toner supply member.

  However, in this type of magnetic brush developing method, a toner density sensor and a toner replenishing member that can be independently driven ON / OFF are indispensable, and an increase in the size and cost of the developing device cannot be avoided. In addition, there is a problem that the toner density detection system is troublesome, such as creating a density patch to be detected.

  As a prior art for solving such a problem, a developing device and a control method for maintaining a constant toner density without using a toner density sensor or a toner replenishing member have already been proposed (see, for example, Patent Documents 1 to 5). . Such a developing apparatus has a developer accommodating portion that accommodates a two-component developer, and a toner accommodating portion that communicates with the developer accommodating portion and accommodates toner, and the amount of the two-component developer on the developer carrier is reduced. The toner density is adjusted by regulating by the regulating member and autonomously controlling the toner intake of the two-component developer by changing the toner density of the two-component developer on the developer carrier.

  In addition, the autonomous control method generates a developer moving layer carried and transported by the developer carrier and a developer circulation layer in which the developer circulates in the developer container, and communicates with the developer container. The toner is taken in from the toner container. That is, when toner is consumed in the development process, the volume of the developer stored in the developer storage unit decreases, and the reduced amount of toner is supplied from the toner storage unit to the developer storage unit. The developer in the developer container holds the toner concentration.

  As an example of the developing device, in Patent Document 1, a magnetic particle layer is formed on a developing sleeve, and toner is accommodated in the toner supply unit in the container so as to come into contact with the magnetic particle layer. By the movement of the magnetic particles in the magnetic particle layer, the toner supply unit takes in the toner from the outer toner layer into the magnetic particle layer, and the developer in which the toner and the magnetic particles are mixed is regulated by the regulating member. By transporting the toner to the developing unit, insufficient charging due to excessive supply of toner is prevented.

  In Patent Document 2, in a developing sleeve rotating type magnetic brush developing device having an internal magnetic pole, an insulating layer is provided on the surface of the developing sleeve, a toner supply roll is provided near the developing sleeve, and the toner supply roll and the developing sleeve are provided. By applying an alternating voltage between them, the toner concentration and toner charging are stabilized.

  Further, Patent Document 3 uses a magnetic toner as a toner constituting the developer to stabilize toner charging and prevent toner scattering.

  Further, in Patent Document 4, the toner density is configured to be equal to or less than the limit toner density at which the toner is completely covered on the surface of one carrier when the developer carrying speed is the fastest. Therefore, it is intended to prevent soiling and toner scattering.

  Further, in Patent Document 5, in the developer accommodating portion, the second upstream of the developer carrying member in the developer carrying direction relative to the first regulating member that regulates the amount of developer carried and carried by the developer carrying member. Therefore, the toner density adjustment is simplified.

  However, in each of the above prior arts, the toner concentration is controlled by the change in the volume of the developer corresponding to the change in the toner concentration and the movement of the developer. It is necessary to make the movement of Under such demands, it is necessary to reduce the amount of developer charged around the developer carrying member and to make the volume change and the like remarkable, as compared with the usual two-component development method. The circulation of the developer is poor, and there are a portion where the developer moves actively and a portion where the developer moves inactive, so that the toner is not uniformly captured. Furthermore, if the magnetic carrier comes out of the main body of the developing device due to deterioration of charging performance or magnetization characteristics and the amount of magnetic carrier in the developer containing chamber decreases, the toner amount ratio to the amount of magnetic carrier in the developer containing portion becomes large when the toner concentration is stable. Become. As a result, there has been a problem in that sufficient toner charging is not performed and background contamination and toner scattering occur.

  In addition, since the amount of developer is small, the absolute amount of toner contained in the developer is small, and even if the toner concentration is reduced, the volume fluctuation of the developer is gradual and the toner intake speed is slow. When a high-density image with high intensity is output continuously, there is a problem that a desired density cannot be maintained.

  Furthermore, since the developer amount must be set small in advance, the stress applied to one magnetic carrier is increased, and the life of the magnetic carrier is shortened. That is, the running cost is increased and the response is slow, so that there is a problem that the density of the high-density image cannot be secured.

  In order to solve such a problem, the present applicant has already proposed the following developing device.

  A developing apparatus according to Japanese Patent Application No. 2003-185499 includes a developer carrying body that has a magnetic field generating means therein and carries a two-component developer containing toner and a magnetic carrier, and the developer carrying body. Adjacently, a developer accommodating portion that accommodates the two-component developer, a toner accommodating portion that is provided in communication with the developer carrying member via the developer accommodating portion, and that accommodates toner so as to be supplied thereto, and a developer carrying member A developer retracting portion provided adjacent to and downstream of the developer carrying direction of the developer carrying member and communicating with the developer containing portion; and the developer of the developer carrying member with respect to the developer containing portion and the developer retracting portion A part of the two-component developer that is provided on the downstream side in the transport direction and carried by the developer carrier is damped as an excess developer, and this excess developer is stored in the developer accommodating portion or the developer retracting portion according to the toner concentration. Separating developer The two-component developer separated into the developer retracting portion according to the toner concentration flows into the developer accommodating portion while taking in the toner replenished from the toner accommodating portion, and autonomously maintains the toner concentration. It is what I did.

  However, in the case of the developing device according to the above-mentioned Japanese Patent Application No. 2003-185499, as schematically shown in FIG. 12, the image is formed with the developing device tilted in the axial direction of the developer carrier. Compared with the developer distribution (a) in the horizontal state, the developer G gradually deviates downward in the inclination direction due to gravity (b), and the upper developer G runs short (c), causing the developer G to move in the axial direction. There is a problem that uneven distribution occurs, which causes image defects such as uneven image density in the axial direction in the formed image.

  Therefore, the present invention has been made in view of the above problems, and even when the developing device is tilted, the uneven distribution of the developer in the axial direction is suppressed, thereby suppressing the uneven image density in the axial direction, and the high quality. It is an object of the present invention to provide a developing device capable of obtaining an image and an image forming apparatus using the developing device.

  In order to achieve the above object, a developing device according to the present invention includes a developer carrying member having a magnetic field generating means therein, carrying a two-component developer containing toner and a magnetic carrier, and a developer carrying member. A developer accommodating portion that accommodates a two-component developer adjacent to the toner accommodating portion, a toner accommodating portion that communicates with the developer accommodating portion via a toner replenishment path, and that can supply toner through the toner replenishment path, and a developer A developer retracting portion provided adjacent to the accommodating portion and communicating with the developer accommodating portion; and a developer provided downstream of the developer carrying member in the developer conveying direction with respect to the developer accommodating portion and the developer retracting portion. A developer separating unit that blocks part of the two-component developer carried and transported by the carrier as an excess developer, and separates the excess developer in the developer accommodating portion or the developer retracting portion according to the toner density; , According to the toner concentration in the developer container In the developing device in which the two-component developer separated into the developer retracting portion flows into the developer accommodating portion while taking in the toner replenished from the toner accommodating portion, the developer carrying member is provided in a region where the magnetic force of the developer carrier is reached, A developer uneven distribution suppressing means for suppressing the uneven distribution of the two-component developer in the axial direction is provided.

  Here, the axial direction refers to a direction along the axial direction of the developer carrier.

  The developing device of the present invention configured as described above includes a developer carrying member, a developer accommodating portion, a toner accommodating portion, a developer retracting portion, and a developer separating means, and the toner in the developer accommodating portion. In the developing device in which the two-component developer separated into the developer retracting portion flows into the developer accommodating portion while taking in the toner replenished from the toner accommodating portion according to the density, the developer carrying member has a magnetic force region. Provided with a developer uneven distribution suppressing means for suppressing the uneven distribution of the two-component developer in the axial direction, so that even when the developing device is inclined, the uneven distribution of the developer in the axial direction is suppressed. It is possible to provide a developing device that can suppress uneven image density and obtain a high-quality image.

  Here, the developer uneven distribution suppressing means may be constituted by a magnetic force control member that changes a magnetic field formed between the developer carrying member and the developer in accordance with an inclination in the axial direction.

  In this case, since the developer uneven distribution suppressing means is constituted by a magnetic force control member that changes the magnetic field formed between the developer carrying member and the axial tilt, the magnetic field below the tilt becomes stronger. By controlling the magnetic force control member as described above, the magnetic restraint force on the developer in the lower inclined region is strengthened, and by restraining the developer, the outflow to the developer retracting portion due to the tilt in the axial direction is suppressed, It is possible to prevent the developer on the opposite side (upper) from being extremely reduced.

  The magnetic force control member may be a member in which a substance having magnetism and fluidity (hereinafter referred to as a magnetic fluid) is enclosed so as to be freely movable in the axial direction.

  In this case, since the magnetic force control member is a member in which the magnetic fluid can be freely moved in the axial direction, the magnetic fluid in the inside is inclined downward according to the inclination in the axial direction. Thus, a magnetic force control member that can change the magnetic field formed with the developer carrier in accordance with the inclination in the axial direction (increase the magnetic force in the region below the inclination) is easily realized. be able to.

  Further, a partition member for partitioning the developer accommodating portion and the developer retracting portion may be further provided, and the magnetic force control member may be disposed between the developer carrier and the partition member.

  In this case, a partition member that partitions the developer accommodating portion and the developer retracting portion is further provided, and the magnetic force control member is disposed between the developer carrying member and the partition member, so that it corresponds to the inclination in the axial direction. Therefore, it is possible to effectively suppress the developer that tends to bias downward.

  The developer retracting portion further includes a damming member provided on the downstream side in the transport direction of the two-component developer by the developer carrier, and the magnetic force control member is disposed in the vicinity of the damming member. May be.

  In this case, the developer evacuation unit further includes a damming member provided on the downstream side in the transport direction of the two-component developer by the developer carrier, and the magnetic force control member is disposed in the vicinity of the damming member. Therefore, the developer that tends to overflow into the developer retracting portion (on the partition member) can be effectively suppressed.

  Here, the developer uneven distribution suppressing means may be constituted by a developer holding member formed of a magnetic body that holds the developer in the vicinity thereof.

  In this case, since the developer uneven distribution suppressing means is constituted by a developer holding member formed of a magnetic body that holds the developer in the vicinity thereof, the developer holding member holds the developer in the vicinity thereof. Thus, uneven distribution of the developer due to the inclination in the axial direction can be suppressed.

  Further, the developer holding member may be a rod-shaped member arranged to extend in the axial direction so as to face the developer carrying member.

  In this case, since the developer holding member is a rod-like member arranged so as to extend in the axial direction, the developer holding member that suppresses the uneven distribution of the developer in the axial direction is realized with a simple configuration at low cost. be able to.

  The developer holding member may be a plurality of rod-shaped members that face the developer carrier and extend in a substantially gravitational direction and are spaced apart in the axial direction.

  In this case, since the developer holding member is a plurality of rod-shaped members that face the developer carrying member and extend in the direction of gravity and are arranged at intervals in the axial direction, The effective facing area with the developer carrier can be made larger than that of the rod-shaped member arranged so as to extend, and developer holding with a stronger developer holding power can be realized.

  Further, the developer holding member may be a lattice-like member arranged so as to face the developer carrying member and extend substantially in the direction of gravity and the axial direction.

  In this case, since the developer holding member is a lattice-like member arranged so as to face the developer carrying member and extend substantially in the gravitational direction and the axial direction, the developer holding member is effective. The opposing area can be maximized, and even when the toner in the developer accommodating portion is consumed and insufficient due to image formation, the toner from the toner accommodating portion easily passes through the mesh of the lattice-like member. In addition, since the toner can be replenished and the developer can also pass between the meshes, even when a large pressure is applied to the axial end by packing or the like, it is possible to disperse the end pressure. .

  Furthermore, the opening of the lattice member may have an opening of 710 μm or more.

  In this case, if the opening of the lattice member is 710 μm or more (based on JIS Z8801-1), a suitable lattice member capable of maintaining the allowable reflection density can be provided.

  Further, the developer holding member may be opposed to at least one of the plurality of magnetic poles constituting the magnetic field generating means.

  In this case, since the developer holding member is opposed to at least one of the plurality of magnetic poles constituting the magnetic field generating means, the developer holding member formed of a magnetic material, and the developer holding member Can stably form a magnetic field for holding the developer.

  In the above, the toner may be a spherical toner manufactured by a polymerization method, and the weight average diameter of the toner may be 4 to 12 μm.

  In this case, when a spherical toner or the like manufactured by the polymerization method is used, there is little variation in toner concentration, there is little change in the particle size over time due to selective development, etc., and there is little change in developer fluidity. Thus, stable image formation is possible.

  The present invention is not limited to the above-described developing device, and an image forming apparatus that visualizes an electrostatic latent image on an image carrier using these developing devices is also an object.

  According to the present invention, even when the developing device is inclined, the uneven distribution of the developer in the axial direction is suppressed, thereby preventing the uneven image density in the axial direction and forming a good image over a long period of time. It is possible to provide a developing device that can perform the above and an image forming apparatus using the same.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
<Embodiment 1>

  First, a schematic configuration of an image forming apparatus including a developing device according to the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention.

  In FIG. 1, reference numeral 21 denotes an electrostatic latent image carrier made of an organic photoreceptor that rotates in the direction of the arrow. The electrostatic latent image carrier 21 is charged by a charging device 22 such as a scorotron, An electrostatic latent image is written by the exposure device 23 having an LED array. This electrostatic latent image is formed as a potential image based on a contrast with a high potential portion not exposed to light because the surface potential of the electrostatic latent image carrier 21 exposed to light is lowered. Further, the developing device 24 accommodates a two-component developer composed of toner and carrier as colored particles in a developing housing 31, and supports the two-component developer on a developer carrier 32, and this developer carrier 32. By applying a developing bias from the bias power source 25 to the toner, the developer carrier 32 is held at an intermediate potential between the high potential portion and the low potential portion of the electrostatic latent image, and the image portion of the electrostatic latent image is charged. The toner is developed with toner. Further, the transfer device 26 is constituted by, for example, a transfer roll disposed in contact with the electrostatic latent image carrier 21, and applies a transfer bias in a direction in which the toner image on the electrostatic latent image carrier 21 is attracted by the bias power source 27. By being applied, the toner image on the electrostatic latent image carrier 21 is transferred to the recording material 28. The toner remaining on the electrostatic latent image carrier 21 is removed by, for example, a doctor blade type cleaning device 29.

  Further, in the present embodiment, the recording material 28 to which the toner image on the electrostatic latent image carrier 21 is transferred is conveyed to the fixing device 50, and the toner image is fixed to the recording material 28 by the fixing device 50. The The fixing device 50 has, for example, a heat roll method, and includes a heating roll 51 and a pressure roll 52. By passing the recording material 28 between the heating roll 51 and the pressure roll 52, the toner image is recorded. 28 is fixed.

  Next, the configuration of the developing device according to the present embodiment will be described with reference to FIG. FIG. 2 is a configuration diagram showing an outline of the developing device according to the present embodiment.

  In FIG. 2, the developing device 24 has a developing housing 31 that opens toward the electrostatic latent image carrier 21, and a developer carrier 32 is disposed facing the opening of the developing housing 31. 31, a developer accommodating portion 33 that accommodates the two-component developer G in a portion adjacent to the developer bearing member 32, and a developer that is adjacent to the developer bearing member 32 and is located with respect to the developer accommodating portion 33. A developer retracting portion 34 provided on the downstream side of the carrier 32 in the developer transport direction, and a two-component communicating with the developer carrier 32 via the developer accommodating portion 33 and flowing out of the toner T and the developer retracting portion 34. A toner storage unit 35 that stores the developer G is formed.

  In the present embodiment, the two-component developer G is a developer composed of toner T and a magnetic carrier, and the toner T uses, for example, a non-magnetic toner, as long as the charging characteristics are different from those of the magnetic carrier. Magnetic toner may be used.

  Further, in the present embodiment, the developer carrier 32 includes a rotatable rotating sleeve 321 and a magnetic pole roll 322 fixedly disposed inside the rotating sleeve 321. The magnetic pole roll 322 has, for example, a conveying magnetic pole (S3 in this example) aligned with the right side of the horizontal plane passing through the roll body center O, and the conveying magnetic pole (S3) with respect to the rotation direction (counterclockwise) of the rotating sleeve 321. ) From the transport magnetic pole (S3) to the upstream side at a predetermined interval, while the transport magnetic pole (N1 in this example) and the developing magnetic pole (S1 in this example) are disposed downstream from the transport magnetic pole (S1). In this example, N3), a carrier magnetic pole (S2 in this example), and a carrier magnetic pole (N2 in this example) are arranged. In the present embodiment, the developing magnetic pole (S1) faces the electrostatic latent image carrier 21, and the pickup magnetic pole (N3) captures the two-component developer G in the developer containing portion 33. It has become. Of course, the magnetic pole pattern is not limited to this, and the arrangement and number of magnetic poles may be appropriately selected. On the other hand, the rotating sleeve 321 rotates counterclockwise, and faces the electrostatic latent image carrier 21 in the developing portion where the developing magnetic pole (S1) of the magnetic pole roll 322 is disposed.

  Further, in the present embodiment, the developer accommodating portion 33 has a space for accommodating the two-component developer G, and the developer accommodating portion 33 is located near (or in contact with) the developer carrying member 32. The developer stirring member 36 is rotatably arranged (counterclockwise). Further, the bottom shape of the developer container 33 has a curved shape along the developer carrier 32 and the developer agitating member 36, and a predetermined interval is provided between the developer carrier 32 and the developer agitating member 36. The developer transport path is secured.

  In the present embodiment, the developer stirring member 36 is composed of, for example, a magnetic or non-magnetic roll. In order to improve the stirring property in the axial direction of the developer carrier 32, a spiral auger or roll circle is used. A blender having blades on the circumference may be used, or a plurality of blenders may be provided.

  Further, in the present embodiment, the toner storage unit 35 includes a toner stirring member 351 that can stir and convey the toner T stored and the two-component developer G flowing out from the developer retracting unit 34. The toner agitating member 351 is, for example, an elastic film attached to a rotating body, and sweeps out the toner T and the two-component developer G flowing out from the developer retracting portion 34 along the bottom wall surface of the toner containing portion 35. It is.

  The bottom shape of the toner storage portion 35 has a curved shape along the movement rotation locus of the toner stirring member 351, and a partition wall portion 31 w is provided between the developer storage portion 33 and the toner storage portion 35. In addition, the developer accommodating portion 33 and the toner accommodating portion 35 communicate with each other via a toner supply path 37 formed on the side surface of the partition wall portion 31w.

  In the present embodiment, the transport magnetic pole (N1), the development magnetic pole (S1), and the transport magnetic pole (N1) in the developer carrying member 32 are located downstream from the transport magnetic pole (N1) in the developer transport direction (counterclockwise direction side). Between them, a damming portion 41 is disposed so as to face the developer carrier 32. The damming portion 41 has the same width as the developer carrier 32, one end is supported by the development housing 31, and the tip is close to the developer carrier 32 with a gap of several tens to several hundreds of μm. I am letting. In the present embodiment, the developer separating means is configured by the damming portion 41 and the transport magnetic pole (N1) arranged on the upstream side of the damming portion 41 in the rotation direction.

  In the present embodiment, the damming portion 41 also serves as a layer thickness regulating function that regulates the layer thickness of the two-component developer G carried and conveyed by the developer carrier 32. What is the layer thickness regulating function? You may make another. In this case, for example, a mode in which a layer thickness regulating member is provided between the damming portion 41 and the developing magnetic pole (S1) can be mentioned.

  Further, in the present embodiment, the developer accommodating portion 33 and the developer retracting portion 34 are separated by a partition member 39.

  For example, as shown in an enlarged view in FIG. 3, the partition member 39 has a base plate 39a formed with a width approximately the same as that of the developer carrier 32. The base plate 39a has an upper side on the developer carrier 32 side. Thus, it is inclined and arranged obliquely downward so that the opposite side is downward. The length of the inclined portion of the base plate 39a is set such that the developer flowing on the inclined portion flows into the developer accommodating portion 33, and a part of the developer flowing on the inclined portion is part of the developer accommodating portion. The excess amount flows out to the toner storage unit 35. However, the length of the inclined portion may be set to such a value that all the developer flowing on the partition member flows into the toner containing portion 35. The tip 39b of the base plate 39a located on the developer carrier 32 side is located immediately above the transport magnetic pole (N1) in the developer carrier 32 or upstream from the transport magnetic pole (N1) in the developer transport direction ( The surface of the developer carrier 32 is opposed to the surface of the developer carrier 32 at a position of several hundred μm to several mm. In the present embodiment, in order to supply a large amount of the two-component developer G to the above-described damming portion 41, the gap between the upper end portion 39b of the partition member 39 and the developer carrying member 32 is separated from the damming portion 41 and the developing member. It is set wider than the gap with the agent carrier 32.

  On the other hand, the lower end portion 39c opposite to the tip end portion 39b is shaped to form the upper wall surface of the toner supply path 37 described above. The inclination angle of the base plate 39a may be arbitrarily set.

  Further, in the developing device according to the present invention, the uneven distribution of the developer in the axial direction is suppressed in a region to which the magnetic force by the magnetic pole roll 322 that is a magnetic field generating means inside the developer carrier 32 is applied (in the vicinity of the partition member 39). Developer uneven distribution suppressing means 45 is disposed.

  Hereinafter, the developer uneven distribution suppressing unit according to the present embodiment will be described with reference to FIGS.

  For example, as shown in FIG. 4, the developer uneven distribution suppressing unit 45 in the present embodiment includes a magnetic force control member 46 that changes a magnetic field formed between the developer carrying member 32 and the axial inclination. It is configured.

  Specifically, as shown in FIG. 6, the magnetic force control member 46 has a casing composition in which a magnetic fluid 46 a is enclosed so as to be freely movable in the axial direction. As shown in (a), the internal magnetic fluid 46a is uniformly distributed in the axial direction as shown in (a). However, in the state where the device is installed inclined in the axial direction, (b) As shown in FIG. 4, the magnetic fluid 46a inside is biased downward in the tilt direction due to the action of gravity, thereby strengthening the magnetic restraining force of the developer in the lower region in the tilt direction and restraining the developer in the region. Thus, the developer is prevented from overflowing onto the partition member 39 due to the inclination, and the developer on the opposite side (upwardly inclined) is prevented from being extremely reduced.

  Here, as the magnetic fluid 46a, magnetic liquid such as N-504 manufactured by Sigma High Chemical Co., or magnetic powder such as steel shot for blasting (spherical particle diameter 300 μm) can be used.

  The magnetic force control member 46 may be installed at an arbitrary location as long as the magnetic force by the magnetic pole roll 322 is within the range, but as a suitable installation location, for example, as shown in FIG. Examples include the surface of the member 39 facing the developer carrier 32 and the inside of the housing 31 in the vicinity of the damming portion 41 as shown in FIG.

  Here, when the partition member 39 is attached to the opposite surface of the developer carrier 32, the developer that tends to be biased to the lower end according to the inclination can be effectively suppressed, whereas it is attached in the vicinity of the damming portion 41. In this case, it is possible to effectively suppress the developer that tends to overflow on the partition member 39.

  Next, the operation of the developing device according to the present embodiment will be described again with reference to FIG.

  In FIG. 2, the two-component developer G in the developer container 33 is stirred by the developer stirring member 36 and captured by the pickup magnetic pole (N 3) in the developer carrier 32. Thereafter, the two-component developer G that has been captured is subjected to the developer carrier 32 (rotating sleeve 321) by the magnetic attraction force of the pickup magnetic pole (N3) and the transport magnetic pole (S3) and the frictional force between the surface of the developer carrier 32. ) In the rotation direction. When the transported two-component developer G reaches the vicinity of the damming portion 41, a spike is formed by the transport magnetic pole (N1). Further, the rising of the two-component developer G is regulated by the damming portion 41, so that the developer layer is formed on the developer carrier 32, and this developer layer is conveyed to the development area. . Further, the developer layer of the two-component developer G conveyed to the development area forms a magnetic brush by the magnetic attraction force of the developing magnetic pole (S1), and the toner T in the two-component developer G forming this magnetic brush is The electrostatic latent image on the electrostatic latent image carrier 21 is visualized by a developing electric field formed between the electrostatic latent image carrier 21 and the developer carrier 32.

  Next, the flow of the two-component developer G in the developing device 24 configured as described above will be described with reference to FIGS.

  First, in FIG. 7, a case is assumed where the toner concentration of the two-component developer G carried and conveyed by the developer carrier 32 is low. Since the two-component developer G has a small amount of toner in the developer, the magnetic carrier density per unit volume is relatively large. That is, since the magnetic attraction force received by the two-component developer G from the external magnetic field (N1 in this example) is increased, the two-component developer G having a low toner concentration is reliably conveyed to the vicinity of the damming portion 41. The two-component developer G reliably transported to the damming portion 41 pushes out the staying developer staying in the vicinity of the damming portion 41 by the damming force of the damming portion 41 and the magnetic restraining force of the conveying magnetic pole (N1). The pushed out staying developer becomes a falling developer and falls onto the partition member 39, passes through the developer retracting portion 34, and then flows into the developer accommodating portion 33 or the toner accommodating portion 35.

  At this time, when the two-component developer G having a low toner concentration is guided to the developer retracting portion 34 as described above, a space is made in the developer accommodating portion 33 accordingly. As a result, the two-component developer G in the toner supply path 37 is quickly drawn into the space by the conveying force of the developer agitating member 36 and the weight of the two-component developer G, and the two-component developer G in the vicinity of the toner supply path 37. The component developer flows. As a result, the toner replenishment path 37 receives the toner T and the two-component developer G having a high toner concentration from the toner container 35, and the toner T and the two-component developer G having a very high toner concentration are supplied to the toner replenishment path. Through 37, the toner is quickly supplied to the developer accommodating portion 33.

  On the other hand, assuming that the toner concentration of the two-component developer G carried and conveyed by the developer carrier 32 is high, the two-component developer G has a large amount of toner covering the surface of the magnetic carrier, The magnetic carrier density per unit volume is small. That is, as shown in FIG. 8, since the magnetic attraction force received by the two-component developer G from the external magnetic field (N1 in this example) is small, most of the two-component developer G having a high toner concentration is a developer carrier. It will fall in the position of the upstream side rather than the front-end | tip 39b of the partition member 39 with respect to 32 rotation directions. As a result, the two-component developer G does not reach the staying developer staying in the vicinity of the damming portion 41 and does not fall on the partition member 39. For this reason, the two-component developer G does not fall on the partition member 39 but falls at a position upstream of the tip end portion 39b of the partition member 39 with respect to the rotation direction of the developer carrier 32, and is directly developed. Return to the agent container 33. At this time, unlike the case where the toner density is low, no space is created in the developer accommodating portion 33, and the two-component developer G in the vicinity of the toner supply path 37 does not flow, and is thus blocked by the two-component developer G. Thus, the toner T and the two-component developer G having a very high toner density are not supplied from the toner container 35.

  As described above, the toner replenishment mechanism according to the present embodiment uses the change in magnetic attraction force in addition to the change in fluidity and bulk of the two-component developer G according to the toner concentration. The toner is supplied to the low two-component developer G, and the toner is not supplied to the two-component developer G having a high toner concentration.

  When the toner density is low, the two-component developer G is temporarily guided to the developer retracting portion 34, thereby emphasizing the bulk change and fluidity of the two-component developer G in the developer containing portion 33. As a result, the two-component developer G in the developer accommodating portion 33 can quickly take in the toner T in the toner accommodating portion 35 and the two-component developer having a very high toner concentration. It can cope with continuous output of images. Further, due to the mechanism described above, the saturated toner concentration on the developer carrier 32 depends on the magnetic attractive force acting on the two-component developer and does not depend on the volume of the two-component developer. Even if the amount of the magnetic carrier in the apparatus is decreased, the saturated toner concentration is maintained at a stable value. When the toner and the two-component developer having a very high toner density are supplied from the toner storage unit 35, the two-component developer G passes through the developer retracting unit 34, so that the two-component development in the developer storage unit 33 is performed. The circulation of the agent G becomes very active, and the toner and the two-component developer having a very high concentration are uniformly taken in. Further, the bulk change and fluidity of the two-component developer G are emphasized, and the magnetic carrier may flow out from the developer accommodating portion 33 and the developer retracting portion 34 to the toner accommodating portion 35. Since the amount of the developer to be charged can be increased, the stress on the developer can be reduced, and the lifetime of the developer can be extended and the running cost can be reduced.

Further, in the developing device according to the present embodiment, the developer is unevenly distributed so that the magnetic field formed between the developer carrier 32 and the developer carrier 32 is changed in accordance with the inclination in the axial direction. Since the restraining means 45 is provided, even when the developing device is installed at an inclination, the magnetic restraining force on the developer in the region below the inclination is strengthened, and the developer is restrained, so that the partition member 39 is inclined by the axial inclination. In addition, it is possible to prevent the developer on the opposite side (upwardly inclined) from being extremely reduced. As a result, a developing device that suppresses uneven distribution of the developer in the axial direction and suppresses uneven density in the axial direction of the formed image even when the image is formed in an inclined state, and can obtain a high-quality image. It becomes possible to provide.
<Embodiment 2>

  Next, a second embodiment of the developing device according to the present invention will be described with reference to FIG. FIG. 9 is a diagram schematically showing a developing device according to the second embodiment.

  In the developing device according to the present embodiment, the developer uneven distribution suppressing unit is configured by a developer holding member formed of a magnetic material that holds a nearby developer. That is, in the previous embodiment, the magnetic fluid is moved according to the inclination in the axial direction, and the magnetic restraint force of the developer under the inclination is increased, thereby suppressing the uneven distribution of the developer in the axial direction. In the present embodiment, the developer holding member extending in the axial direction suppresses the movement of the developer due to the inclination in the entire axial direction. In addition, the same code | symbol is attached | subjected to the member which has the same function as previous embodiment, and the description is abbreviate | omitted. An image forming apparatus to which the developing device according to the present embodiment can be applied is also the same as that of the previous embodiment, and a description thereof will be omitted.

  As schematically shown in FIG. 9, the developing device 24 according to the present embodiment has a peripheral development in a region where the magnetic force of the developer carrier 32 between the developer carrier 32 and the partition member 39 is reached. A developer holding member 47 formed of a magnetic material that holds the developer and serving as developer uneven distribution suppressing means is provided.

  As the developer holding member 47, a member having an appropriate size and shape can be arranged in a region where the magnetic force of the developer carrier 32 is exerted.

  For example, the developer holding member 47a shown in FIG. 9A extends in the space between the developer carrying body 32 and the partition member 39 so as to face the developer carrying body 32 and extend in the axial direction. It is an example of the rod-shaped member arrange | positioned. By using such a rod-like member 47a extending in the axial direction, the developer holding member 47 can be realized simply and inexpensively.

  Further, the developer holding member 47b shown in FIG. 9B extends in a substantially gravitational direction in the space between the developer carrier 32 and the partition member 39 so as to face the developer carrier 32. And it is an example of the several rod-shaped member arrange | positioned in the axial direction at intervals. Specifically, the developer holding member 47b is arranged in the axial direction so that a plurality of rod-like members are opposed to the developer carrier 32 between the tip 39b of the partition member 39 and the top 31t of the partition wall 31w. Is suspended at a predetermined interval. By using such a developer holding member, the effective opposing area with the developer carrier 32 can be further increased.

  Further, the developer holding member 47c shown in FIG. 9C is provided in a space between the developer carrying body 32 and the partition member 39 so as to face the developer carrying body 32 and extend in a substantially gravity direction and an axial direction. It is an example of the lattice-like (mesh-like) member arrange | positioned so that it may extend. Specifically, the developer holding member 47c is obtained by suspending a lattice (mesh) member between the tip 39b of the partition member 39 and the top 31t of the partition wall 31w. By using such a developer holding member 47c, the effective facing area with respect to the developer carrying member 32 can be further increased, and the toner in the developer containing portion 33 is consumed due to image formation and is insufficient. However, since the toner supplied from the toner storage unit 35 passes between the meshes, the developer can pass between the meshes without interfering with the necessary toner replenishment. Even when a large pressure is applied to the portion, such end pressure can be dispersed.

  Using the developing device according to the present embodiment having such a developer holding member 47 and a developing device having a conventional configuration not having the developer holding member 47, each developing device is arranged in the axial direction of the developer carrier 32. FIG. 10 shows the result of measuring the degree of density reduction when the image forming process is performed with an inclination of 30 mm. FIG. 10 is a diagram showing the relationship between the reflection density difference between the axially inclined end portions (the upper end portion and the lower end portion) and the number of printed sheets.

  As shown in FIG. 10, in the case of a developing device having a conventional configuration, when image formation is performed while being inclined in the axial direction, the difference in reflection density at the end in the axial direction increases by about 0. 8, which is much higher than the allowable density difference of 0.4 or less.

  This is because, when image formation is performed with the developing device inclined in the axial direction, the developer in the developing device is biased downward in the inclination direction due to gravity, and the image forming process is continued as it is. This is probably because the amount of the developer is insufficient, and the image density corresponding to this region is lowered.

  On the other hand, when the developing device according to the present embodiment is used, any of the developer holding members 47a, 47b, and 47c has a reflection density difference that is an allowable value regardless of an increase in the number of printed sheets. It is understood that 0.4 or less is satisfied.

  Further, it can be seen that the reflection density difference between the axial ends is such that the developer holding member 47c <the developer holding member 47b <the developer holding member 47a. That is, it can be seen that the larger the effective area of the developer holding member 47 facing the developer carrier 32, the greater the effect of reducing the density difference between the axial ends.

  When the lattice-shaped (mesh-shaped) member 47c that has the greatest effect of reducing the difference in reflection density between the end portions in the axial direction is used, if the mesh opening is small, the toner container 35 is transferred to the developer container 33. There was a problem that the amount of toner to be replenished was insufficient.

  Therefore, the number of prints when the mesh opening of the grid member 47c is changed to determine a suitable grid member 47c that can suppress the uneven distribution of the developer in the axial direction without hindering toner supply. The reflection density according to was measured. The measurement results are shown in FIG. FIG. 11 is a diagram showing the relationship between the average value of the results of measurement of the reflection density of the black portion of the image and the number of prints in each case where the mesh openings of the grid-like member 47c are changed.

  As can be seen from FIG. 11, when the mesh size (conforming to JIS Z8801-1) is 500 μm or less, the reflection density of 1.0, which is an allowable value, falls below the allowable value as the number of printed sheets increases. . In addition, when the mesh size is 1000 μm or more, it can be seen that even if the number of printed sheets increases, the allowable value exceeds 1.0. Therefore, when the critical value which does not fall below the allowable value of 1.0 or more is obtained by the interpolation method even when the number of printed sheets increases, it is found to be 710 μm. Therefore, when the lattice member 47c is used, it is understood that if the mesh opening is set to 710 μm or more, the allowable reflection density of 1.0 or more is satisfied regardless of the increase in the number of printed sheets. The

  Further, when such a grid-like member 47c is used, the developer holding force is larger than that of the other developer holding members 47a and 47b, and the toner in the developer containing portion 33 is consumed by image formation. Even if the toner is insufficient, the toner from the toner storage unit 35 can pass between the meshes and replenish the toner to the developer storage unit 33. Further, since the developer in the developer accommodating portion 32 can also pass between the meshes, even when a large pressure is applied to the end portion in the axial direction due to packing or the like, the end portion pressure can be dispersed. Become.

  The developer holding members 47a, 47b, and 47c as described above and at least one magnetic pole (for example, S3 in the present embodiment) of the magnetic pole roll 322 that constitutes the magnetic field generating means of the developer carrier 32. It is preferable that they are facing each other. Thus, by arranging the developer holding member 47 so as to face at least one magnetic pole, a magnetic field for holding the developer can be stably formed.

  Examples of the toner suitable for the developing device of the present invention include spherical toners produced by emulsion polymerization or suspension polymerization (particularly those having a weight average diameter in the range of 4 to 12 μm).

  In the present invention, it is preferable to keep the toner concentration in the developer in a more stable state, and according to such a polymerization method, a chemical synthesis process is performed, so that a spherical toner can be easily manufactured. At the same time, since the surface coverage is high in the case of spherical toner, a difference in density is unlikely to occur, thereby stabilizing the toner concentration in the developer and enabling stable image formation over a long period of time. The toner suitable for the present invention may be one obtained by classifying a toner produced by a pulverization method, but one produced by a polymerization method such as the above emulsion polymerization method or suspension polymerization method may be classified or treated. Less time is required for post-treatment such as spheroidization treatment, which is more preferable.

1 is an explanatory diagram showing an embodiment of an image forming apparatus including a developing device to which the present invention is applied. It is explanatory drawing which shows the outline | summary of the image development apparatus concerning this invention. It is an enlarged view of the partition member periphery which concerns on this invention. 6 is a diagram illustrating an example of an installation location of a magnetic force control member of the developing device according to Embodiment 1. FIG. It is a figure which shows another example of the installation location of the magnetic force control member of the developing device which concerns on Embodiment 1. FIG. It is a figure explaining the outline | summary of the magnetic force control member which concerns on Embodiment 1. FIG. FIG. 4 is an explanatory diagram showing a flow of a two-component developer and toner at a low toner concentration. FIG. 4 is an explanatory diagram illustrating a flow of a two-component developer and toner at a high toner concentration. 6 is a diagram illustrating an example of a developer holding member of a developing device according to Embodiment 2. FIG. It is a figure which shows the result of having measured the image density difference between the inclination edge parts using the developing apparatus which concerns on Embodiment 2, and the developing apparatus of a conventional structure. It is a figure which shows the result of having measured the reflection density at the time of changing the opening of the lattice-shaped holding member which concerns on Embodiment 2. FIG. It is a figure which shows typically distribution of a developer at the time of making the developing device of the conventional structure incline to an axial direction.

Explanation of symbols

  21: electrostatic latent image carrier, 22: charging device, 23: exposure device, 24: developing device, 25: bias power source, 26: transfer device, 27: bias power source, 28: recording material, 29: cleaning device, 31 : Development housing, 31w: Partition part, 31t: Top part, 32: Developer carrier, 33: Developer storage part, 34: Developer retracting part, 35: Toner storage part, 36: Developer stirring member, 37: Toner Replenishment path, 39: Partition member, 39a: Base plate, 39b: Upper end portion, 39c: Lower end portion, 41: Damping portion, 45: Developer uneven distribution suppressing means, 46: Magnetic force control member, 46a: Magnetic fluid, 47a, 47b, 47c: developer holding member, 50: fixing device, 51: heating roll, 52: pressure roll, 321: rotating sleeve, 322: magnetic pole roll, 351: toner stirring member, G: two-component development , T: toner

Claims (9)

A developer carrying member having a magnetic field generating means therein, carrying a two-component developer containing toner and a magnetic carrier, and a developer containing portion containing the two-component developer adjacent to the developer carrying member A toner container that communicates with the developer container via a toner replenishment path, and that accommodates the toner through the toner replenishment path so that toner can be supplied, and is provided adjacent to the developer container and communicates with the developer container. A part of the two-component developer that is provided on the downstream side in the developer transport direction of the developer carrier relative to the developer retractor, the developer container, and the developer retractor, and carried and transported by the developer carrier. A developer separating means for separating the excess developer in the developer accommodating portion or the developer retracting portion according to the toner concentration, and retaining the developer according to the toner concentration in the developer accommodating portion; The two-component developer separated into In the developing device flowing into the developer accommodating portion while taking a toner supplied from the accommodating portion,
A partition member that partitions the developer accommodating portion and the developer retracting portion;
A developer uneven distribution suppressing means provided in a region where the magnetic force of the developer carrying member is provided, and suppressing the uneven distribution of the two-component developer in the axial direction ;
With
The developer uneven distribution suppressing means is disposed between the developer carrying member and the partition member, and changes the magnetic field formed between the developer carrying member and the developer carrying member according to the inclination in the axial direction. A developing device characterized in that a magnetic fluid is enclosed in the inside so as to be freely movable in the axial direction . A developer carrying member having a magnetic field generating means therein, carrying a two-component developer containing toner and a magnetic carrier, and a developer containing portion containing the two-component developer adjacent to the developer carrying member A toner container that communicates with the developer container via a toner replenishment path, and that accommodates the toner through the toner replenishment path so that toner can be supplied, and is provided adjacent to the developer container and communicates with the developer container. A part of the two-component developer that is provided on the downstream side in the developer transport direction of the developer carrier relative to the developer retractor, the developer container, and the developer retractor, and carried and transported by the developer carrier. A developer separating means for separating the excess developer in the developer accommodating portion or the developer retracting portion according to the toner concentration, and retaining the developer according to the toner concentration in the developer accommodating portion; The two-component developer separated into In the developing device flowing into the developer accommodating portion while taking a toner supplied from the accommodating portion,
A dampening member provided on the downstream side in the transport direction of the two-component developer by the developer carrying member of the developer retracting section, and clogs excess developer;
A developer uneven distribution suppressing means provided in a region where the magnetic force of the developer carrying member is provided, and suppressing the uneven distribution of the two-component developer in the axial direction;
With
The developer uneven distribution suppressing means is disposed in the vicinity of the damming member, and a magnetic fluid is axially disposed therein so that a magnetic field formed between the developer carrying member and the developer carrier is changed according to an inclination in the axial direction. A developing device characterized by being a member enclosed so as to be freely movable . A developer carrying member having a magnetic field generating means therein, carrying a two-component developer containing toner and a magnetic carrier, and a developer containing portion containing the two-component developer adjacent to the developer carrying member A toner container that communicates with the developer container via a toner replenishment path, and that accommodates the toner through the toner replenishment path so that toner can be supplied, and is provided adjacent to the developer container and communicates with the developer container. A part of the two-component developer that is provided on the downstream side in the developer transport direction of the developer carrier relative to the developer retractor, the developer container, and the developer retractor, and carried and transported by the developer carrier. A developer separating means for separating the excess developer in the developer accommodating portion or the developer retracting portion according to the toner concentration, and retaining the developer according to the toner concentration in the developer accommodating portion; The two-component developer separated into In the developing device flowing into the developer accommodating portion while taking a toner supplied from the accommodating portion,
A partition member that partitions the developer accommodating portion and the developer retracting portion;
A developer uneven distribution suppressing means provided in a region where the magnetic force of the developer carrying member is provided, and suppressing the uneven distribution of the two-component developer in the axial direction;
With
The developer uneven distribution suppressing means is formed of a magnetic body that holds the developer in the vicinity thereof, and extends in a substantially gravitational direction between the developer carrying body and the partition member so as to face the developer carrying body. And a plurality of rod-shaped members arranged at intervals in the axial direction . A developer carrying member having a magnetic field generating means therein, carrying a two-component developer containing toner and a magnetic carrier, and a developer containing portion containing the two-component developer adjacent to the developer carrying member A toner container that communicates with the developer container via a toner replenishment path, and that accommodates the toner through the toner replenishment path so that toner can be supplied, and is provided adjacent to the developer container and communicates with the developer container. A part of the two-component developer that is provided on the downstream side in the developer transport direction of the developer carrier relative to the developer retractor, the developer container, and the developer retractor, and carried and transported by the developer carrier. A developer separating means for separating the excess developer in the developer accommodating portion or the developer retracting portion according to the toner concentration, and retaining the developer according to the toner concentration in the developer accommodating portion; The two-component developer separated into In the developing device flowing into the developer accommodating portion while taking a toner supplied from the accommodating portion,
A partition member that partitions the developer accommodating portion and the developer retracting portion;
A developer uneven distribution suppressing means provided in a region where the magnetic force of the developer carrying member is provided, and suppressing the uneven distribution of the two-component developer in the axial direction;
With
The developer uneven distribution suppressing means is formed of a magnetic body that holds the developer in the vicinity thereof, and is located between the developer carrying body and the partition member so as to face the developer carrying body in a substantially gravitational direction and an axial direction. A developing device, wherein the developing device is a grid-like member arranged so as to extend over the entire area . The developing device according to claim 4 , wherein the opening of the lattice member has an opening of 710 μm or more. The toner developing device according to any one of claims 1, characterized in that a spherical toner 5. The developing device according to claim 6 , wherein the spherical toner is a toner manufactured by a polymerization method. The developing device according to claim 6 , wherein a weight average diameter of the toner is 4 to 12 μm. An image forming apparatus comprising: a developing device according to any one of claims 1 to 8.

Images