JP2006047715A - Developing device and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus by which the direct supply of a two-component developer in an insufficiently agitated state of a replenished toner and the developer to a developer carrier is prevented and uniform images reduced in image density unevenness, such as haze unevenness, within the formed images can be obtained even if the high density images are continuously formed, and an image forming apparatus using the same. <P>SOLUTION: The developing device is equipped with the developer carrier 32, a developer housing section 33, a toner housing section 35, a developer retreating section 34, a developer separating section 38, and an agitating and rotating member 36, wherein the developer separated to the developer retreating section 34 flows into the developer housing section 33 while capturing the toner from the toner housing section 35. The developing device is equipped with a regulation section 39e for regulating the flow of the two-component developer G passing the region on the toner housing section 35 side nearer the upper side in the gravity direction than the rotation shaft of the agitating and rotating member 36in extreme proximity to the developer carrier 32 from the toner housing section 35 toward the developer carrier 32 side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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. Furthermore, since the developer amount must be set low in advance, the stress on one magnetic carrier increases, resulting in a problem that the life of the magnetic carrier is shortened, resulting in an increase in running cost. It was.

  In order to solve these problems, the present applicant previously stated in Japanese Patent Application No. 2003-185499 that the amount of magnetic carrier changes on the premise of a small and low-cost developing device that does not require a toner concentration sensor or a toner replenishment mechanism. Even if the toner density is kept stable, scumming and scattering of toner can be suppressed, and uniform toner intake enables continuous output of high-density images, and a large amount of developer is set in advance. Therefore, the present invention provides a developing device that realizes a long service life and suppresses running costs, and an image forming apparatus using the developing device.

  As shown in FIG. 13, the developing device 100 according to Japanese Patent Application No. 2003-185499 includes a magnetic field generating unit 102 inside and a developer that conveys and carries a two-component developer containing toner and a magnetic carrier. A carrier 101, a developer accommodating portion 103 that accommodates a two-component developer adjacent to the developer bearing member 101, and a toner that communicates with the developer accommodating portion 103 via a toner replenishment path 104 and through the toner replenishment path 104. And a toner storage unit 105 that stores the two-component developer in a supplyable manner, and is provided adjacent to the developer support 101 and on the downstream side of the developer support 101 in the developer transport direction with respect to the developer support 103. A developer retracting portion 106 communicating with the developer accommodating portion 103, and provided downstream of the developer carrying member 101 in the developer conveying direction with respect to the developer accommodating portion 103 and the developer retracting portion 106. Development in which a part of the two-component developer carried and conveyed by the developer carrier 101 is blocked as an excess developer, and the excess developer is separated into the developer accommodating portion 103 or the developer retracting portion 106 according to the toner concentration. The two-component developer separated into the developer retracting unit 106 is configured to flow out to both the developer accommodating unit 103 and the toner accommodating unit 105. The developing device 100 includes a developer stirring member 110 having a configuration as represented in FIG. 14 in the developer accommodating portion 103, and the developer agitating member 110 causes the developer accommodating portion 103 to include the developer agitating member 110. The toner is agitated and charged.

  However, in the developing device configured as described above, in continuous output of a high-density image, in an image whose density has decreased or in a halftone image after high-density image output, as shown in FIG. There has been a phenomenon in which a region where toner spills along the process direction and an image density clearly higher than the surroundings (hereinafter sometimes referred to as haze) occurs suddenly. This is because, in an image forming mode such as a high-density image that consumes a large amount of toner, the balance of the developer flow in the developer container is lost, and a part of the replenished toner is sufficiently agitated and mixed with the developer in the developer container. This is considered to be because the toner reaches the developer carrying member directly.

  Accordingly, the present invention has been made in view of the above-described problems, and a two-component developer in a state where stirring between the replenished toner and the developer is insufficient is directly supplied to the developer carrier. An object of the present invention is to provide a developing device and an image forming apparatus using the same, which can obtain a uniform image with little unevenness of image density such as haze in the formed image even if the high-density image is continuously formed And

  In order to achieve the above object, the developing device of the present invention accommodates a two-component developer that carries and conveys a two-component developer including toner and carrier by magnetic force, and a two-component developer adjacent to the developer carrier. A developer accommodating portion, a toner accommodating portion that is provided in communication with the developer carrier via the developer accommodating portion, and that accommodates toner so as to be supplied thereto, and is adjacent to the developer accommodating portion and communicates with the developer accommodating portion. And 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 container and the developer retractor and is carried and transported by the developer carrier. As a surplus developer, developer separating means for separating the surplus developer into the developer accommodating portion or developer retracting portion according to the toner concentration, and a developer carrying unit provided in the developer accommodating portion for stirring the developer At least the stirring rotating member to be transported to the body In the developing device in which one or more developer separated into the developer retracting portion flows into the developer accommodating portion while taking in the toner from the toner accommodating portion, from the rotating shaft of the stirring rotation member closest to the developer carrying member And a restricting portion for restricting the flow of the two-component developer passing through the region on the toner containing portion side from the toner containing portion side toward the developer carrying member side.

  The developing device according to the present invention configured as described above includes a developer carrier, a developer container, a toner container, a developer retracting unit, a developer separating unit, and a stirring rotation member. In the developing device in which the developer separated in the developer retracting portion flows into the developer accommodating portion while taking in the toner from the toner accommodating portion, above the rotation axis of the agitation rotating member closest to the developer carrying member in the gravity direction. In addition, since there is provided a restricting portion that restricts the flow of the two-component developer passing through the toner containing portion side region from the toner containing portion side toward the developer carrying member side, stirring of the replenished toner and the developer is not required. The two-component developer in a sufficient state is regulated to be supplied directly to the developer carrier via the upper part of the direction of gravity than the rotation axis of the stirring rotating member, thereby continuously forming high-density images and the like. Even with image density unevenness No, it is possible to provide a developing device capable of obtaining a uniform image.

  Further, the apparatus further includes a partition member that separates the developer accommodating portion and the developer retracting portion, and the restricting portion is provided at a lower end of the partition member, and a tip of the restricting portion is in a gravitational direction with respect to a rotation shaft of the stirring rotating member. It may be formed so as to be opposed to the outer peripheral surface of the agitation rotating member on the upper side and in the region on the toner containing portion side.

  In this case, it further includes a partition member that separates the developer accommodating portion and the developer retracting portion, and the restricting portion is provided at the lower end of the partition member, the tip of which is above the rotational axis of the agitation rotating member in the gravity direction. And the two-component development in a state where the agitation between the replenished toner and the developer is insufficient because it is formed so as to oppose the outer peripheral surface of the agitation rotating member in the region on the toner container side. It is possible to effectively realize a restricting portion that prevents the agent from being directly supplied to the developer carrying member via the upper part of the rotation direction of the stirring rotating member via the upper part in the gravity direction.

  The outer peripheral surface of the stirring rotary member means the outer peripheral surface in the case of a cylindrical rotary member, and when a member such as a blade is attached to the peripheral surface of the rotary shaft, the outer peripheral surface thereof. The track surface drawn by the outer peripheral part shall be said.

  Furthermore, the rotation direction of the stirring rotation member closest to the developer carrier may be opposite to the rotation direction of the developer carrier.

  In this case, since the rotation direction of the stirring rotation member closest to the developer carrying member is opposite to the rotation direction of the developer carrying member, the two components are in a state where stirring of the replenished toner and the developer is insufficient. The developer is guided along the rotating direction of the stirring rotating member to promote stirring, and the flow of the two-component developer in the reverse direction is suppressed, and the two-component developer in a state where stirring is insufficient is directly developed. Supplying to the agent carrier can be more effectively suppressed.

  Here, the restricting portion may be a blade member formed such that a tip thereof is in contact with the outer peripheral surface, or may be a brush member.

  In this case, since the tip of the restricting portion is a blade member or a brush member formed so as to be in contact with a predetermined outer peripheral surface of the stirring rotation member, the replenished toner and the developer are not sufficiently stirred. It is possible to reliably prevent the two-component developer from being supplied directly to the developer carrying member via the upper part of the rotation direction of the stirring rotating member via the upper part in the gravity direction.

  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, the replenished toner and the developer are sufficiently stirred even when the high-density image is continuously formed in the developing device that autonomously takes in the toner and keeps the toner concentration of the developer constant. Therefore, it is possible to prevent the occurrence of haze or the like in the formed image. That is, it is possible to provide a developing device capable of obtaining excellent in-plane uniformity with little image density unevenness and an image forming apparatus using the developing device.

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

  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. 3 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention.

  In FIG. 3, 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 FIGS. FIG. 1 is a configuration diagram showing an outline of a developing device according to the present embodiment, and FIG. 2 is an enlarged view around a partition member for explaining a regulating portion according to the present invention.

  In FIG. 1, 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. 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 conveyance magnetic pole (S3 in this example) aligned with the right side of the horizontal plane passing through the center of the roll body, and the conveyance magnetic pole (S3) with respect to the rotation direction (counterclockwise) of the rotating sleeve 321. The transport magnetic pole (N1 in this example) and the developing magnetic pole (S1 in this example) are disposed from the transport magnetic pole (S3 in this example) at intervals of 30 ° from the downstream to the pickup magnetic pole (main In the example, N3), a transport magnetic pole (S2 in this example), and a transport 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. However, the arrangement pattern of the magnetic poles is not limited to this, and the arrangement and number of the 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.

  In the present embodiment, the developer accommodating portion 33 has a space for accommodating the two-component developer G, and in a predetermined direction (clockwise in the present embodiment) for agitating the accommodated developer. ) Is provided with one developer stirring member 36 which is a stirring rotating member that rotates. 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.

  Here, in the present embodiment, the developer stirring member 36 is a magnetic roll made of a magnetic material. However, in order to improve the stirrability, the developer stirring member 36 has a blender or paddle shape provided with blades on the circumference of the roll. May be. A plurality of augers may be provided, such as a two-auger as in a normal two-component developer system.

  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 containing portion 35 has a curved shape along the movement rotation locus of the toner agitating member 351, and the connecting portion between the developer containing portion 33 and the toner containing portion 35 has a toner shape. A supply path 37 is provided.

  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 38 is configured by the damming portion 41 and the transport magnetic pole (N1) arranged on the upstream side in the rotational direction from the damming portion 41.

  Further, in the present embodiment, the damming portion 41 also serves as a layer thickness regulating function for regulating 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.

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

  As shown in an enlarged view in FIG. 2, the partition member 39 has, for example, a base plate 39a formed with a width approximately the same as that of the developer carrier 32. The base plate 39a is formed on the developer carrier 32 side. 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 toner supply path 37, and a part of the developer flowing on the inclined portion passes through the toner supply path 37. As a result, the surplus flows out to the developer container 33 to the toner container 35. However, the length of the inclined portion may be set so that all the developer flowing on the inclined plate flows into the toner containing portion 35. The upper end portion 39b of the base plate 39a located on the developer carrier 32 side is directly above the conveyance magnetic pole (N1) in the developer carrier 32 or upstream from the conveyance magnetic pole (N1) in the developer conveyance 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 upper end portion 39b is shaped to form the upper wall surface of the toner replenishment path 37 described above, and the end portion 39e on the developer stirring member 36 side is the tip end thereof. Is formed so as to face the outer peripheral surface of the developer stirring member 36 with a predetermined gap (gap) therebetween. Specifically, an area that is above the rotation axis O of the developer agitating member 36 in the gravity direction and that corresponds to the toner container 35 side (corresponding to the arc angle R, the upper right in the figure with respect to the rotation axis O). (Region) is formed so as to face the outer peripheral surface of the developer stirring member 36. In this manner, in the region corresponding to the arc angle R, the end 39e of the partition member 39 is opposed to the outer peripheral surface of the developer stirring member 36, thereby flowing into the developer containing portion 33 via the toner supply path 37. A restricting portion is formed that restricts the two-component developer G from passing through the upper region of the developer stirring member 36 and being supplied directly to the developer carrier 32 without sufficient stirring.

  For the facing region, when the restricting portion 39e is opposed to the outer peripheral surface of the developer agitating member 36 beyond the arc angle R, the flow rate of the toner replenishment path 37 is restricted (on the lower right side in the figure relative to the rotation axis O). The flow of the two-component developer G sufficiently stirred and mixed toward the developer carrier 32 through the lower side of the developer agitating member 36 is regulated (when viewed from the rotation axis O). Therefore, it is preferable to make them face each other on the outer peripheral surface in the area corresponding to the arc angle R.

  Further, when a plurality of developer agitating members 36 are provided, the restricting portion 39e defines an area corresponding to the arc angle R of the developer agitating member closest to the developer carrying member 32 on the toner accommodating portion 35 side. As long as it is formed so as to prevent the flow of the two-component developer that passes from the toner toward the developer carrier 32 side.

  Here, the gap between the restricting portion 39e and the outer peripheral surface of the developer stirring member 36 is preferably 2.5 mm or less.

  Further, the restricting portion 39e may be formed integrally with the partition member 39 as a part thereof, or a blade member or a brush member made of an elastic member such as rubber or a film member may be formed on the lower end portion 39c of the partition member 39. It may be attached to form the restricting portion 39e.

  Note that the rotation directions of the developer carrier 32 and the developer agitating member 36 are opposite to each other (for example, when the developer carrier 32 rotates counterclockwise, the developer agitating member 36 is clockwise. Rotation). In this way, by being configured to rotate in opposite directions, the flow of the two-component developer G supplied via the toner replenishment path 37 is smoothly guided in the rotation direction of the developer stirring member 36 and stirred. And the flow of the two-component developer G in the reverse direction can be reliably regulated.

  Further, when the rotation directions of the developer carrier 32 and the developer agitating member 36 are opposite to each other, for example, the tip of the blade member or the brush member constituting the restricting portion 39e is set to the arc angle. You may comprise so that the outer peripheral surface of the developer stirring member 36 corresponding to R may be contacted. In this way, the flow of the two-component developer G in the direction opposite to the rotation direction of the developer agitating member 36 is reliably blocked by configuring the outer peripheral surface of the developer agitating member 36 and the restricting portion 39e to contact each other. be able to. That is, in this case, all of the toner and developer supplied from the toner replenishment path 37 pass below the rotation axis of the developer agitating member 36 in the direction of gravity, which is sufficient with the developer in the developer accommodating portion 33. The developer reaches the developer carrier 32 after being stirred and mixed.

  Next, the operation of the developing device according to the present embodiment will be described below.

  In FIG. 1, the two-component developer G in the developer container 33 is stirred by the developer stirring member 36 and is captured by the pickup magnetic pole (N3) 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 behavior of the two-component developer G in the vicinity of the damming portion 41 will be described with reference to FIGS.

  First, in FIG. 4, it is assumed that the toner density 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 near 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 stirring member 36 and the weight of the two-component developer G, and the two-component developer in the vicinity of the toner supply path 37. Developer flows. As a result, the toner replenishment path 37 receives the toner T and the two-component developer G having a high toner density from the toner storage unit 35, and the toner T and the two-component developer G having a very high dark toner density are used as the developer. It is promptly supplied to the housing part 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. 5, 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 the developer carrier 32. It will fall in the position of the upstream rather than the front-end | tip of the partition member 39 with respect to the rotation direction. 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 concentration 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, so that it is blocked by the two-component developer G. In other words, 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.

  By the way, in a developing device that autonomously controls the developer concentration based on such a toner replenishment mechanism, when a high-density image or the like that consumes a large amount of toner is continuously output, a haze or the like is included in the formed image as described above. The phenomenon that the image non-uniformity is generated has occurred.

  This phenomenon will be described with reference to FIGS. 6 to 8 with respect to the generation mechanism found as a result of intensive studies by the present inventors.

  First, when a high-density image or the like that consumes a large amount of toner is continuously output, the developer agitation member 36 does not sufficiently supply the developer onto the developer carrier 32 with respect to the toner consumption. There is a difference between the developer toner density on the upper side and the developer toner density in the developer container 33. As a result, the timing at which the developer starts to flow onto the partition member 39 is delayed from the timing at which the developer should originally flow out onto the partition member 39. That is, as understood from the measurement result of the toner density shown in FIG. 6, when continuously outputting a high density image or the like, the toner density at which the developer starts to flow into the developer retracting portion 34 on the partition member 39. However, the original saturation starts when the developer starts to flow onto the partition member 39 during normal image output (when the image is output when the developer on the developer carrier 32 is sufficiently replaceable with respect to toner consumption). The density is lower than the toner density (ON / OFF toner density). For this reason, during continuous output of a high-density image or the like, the conveyance force with respect to the developer becomes large, and as can be understood from the measurement result of the developer amount on the partition member 39 in FIG. Accordingly, a large space for the developer and the toner to enter into the developer accommodating portion 33 is formed, and excessive developer or toner is supplied from the toner accommodating portion 35. found.

  Under such circumstances, it is difficult for all of the new developer and toner to be replenished to be sufficiently agitated and mixed with the developer in the developer accommodating portion 33, and some of them are directly developed. As shown in FIG. 8, the developer carrier 32 is reached, and the region on the toner container 35 side that is above the rotation axis of the developer stirring member 36 and is on the toner container 35 side is developed from the toner container 35 side. It has been found that a flow of developer passing toward the carrier 32 is generated, and as a result, image density unevenness such as a haze is generated in the formed image.

  Therefore, in the developing device 24 according to the present embodiment, as described above, for example, the lower end of the partition member 39 is provided with the restricting portion 39e formed so as to face the developer stirring member 36 in a predetermined region. This restricts the flow of toner and developer that are replenished from the toner replenishment path 37 and passes above the rotation axis O of the developer agitating member 36 in the direction of gravity. Even when the developer is replenished into the developer accommodating portion 33, the two-component developer with insufficient stirring is prevented from reaching the developer carrier 32 directly, thereby causing fogging at the time of high density image formation. It is possible to obtain a high-quality image without image density unevenness.

  Next, the result of verifying and evaluating the effect of the restricting portion 39e using the developing device according to the present invention will be shown as an example.

In this example, by using the developing device (see FIG. 1) according to the above-described embodiment, the gap between the restricting portion 39e and the agitating blender 36 is changed to visually evaluate the presence or absence of moire spots and the reflection densitometer. The concentration was measured by X-rite 404. In addition, the gap with the developer stirring member 36 in the case of a conventional developing device (see FIG. 13) in which the partition member 39 is not provided with the restricting portion 39e was 5 mm. The setting conditions of the developing device 24 in the present embodiment are as follows.
Two-component developer G: A ferrite carrier having a volume average particle size of 50 μm is used as the magnetic carrier, and a polyester toner having a volume average particle size of 9.0 μm containing 20% by weight of magnetic powder is used as the toner T. used. The initial two-component developer charge amount was 100 g, and the toner amount charged into the toner storage unit 35 was 50 g.
Developer carrier 32: A φ16 mm magnetized roll having 6 poles on the surface was used, and the peripheral speed was set to 340 mm / s (rotated counterclockwise). The magnetizing pattern used was a pattern as shown in FIG.
Agitating blender 36: φ10 mm, pitch 10 mm, and peripheral speed set to 255 mm / s.
Development nip parameter: -460V for charging potential (Vh), -100V for latent image potential (Vl), -400V for developing bias (Vdev), electrostatic latent image carrier 21 and developer carrier 32 The gap (DRS) was set to 300 μm, and the developer amount (MOS) on the developer carrier 32 was set to 35 mg / cm ² .

  Under the above-mentioned conditions, the initial toner density was set to 12%, and a cycle of outputting 10 sheets of 100% image density chart and then outputting 1 sheet of 20% image density was continuously executed 5 times. FIG. 10 shows the measurement results of the gap between the partition member 39 and the developer stirring member 36 and the number of halftone images in which the haze is generated.

  As shown in FIG. 10, when the gap is 4 mm or more, it is understood that a haze is generated in the halftone image.

  Next, FIG. 11 shows the result of performing the same verification with the rotation direction of the agitating blender 36 being the same direction (counterclockwise direction) as the rotation direction of the developer carrier 32.

  In this case, as understood from FIG. 11, when the gap becomes 2.5 mm or more, it can be seen that a haze is generated in the halftone image.

  Accordingly, it can be understood that the gap interval can be increased by reversing the rotation directions of the developer carrier 32 and the developer stirring member 36. In other words, it can be understood that reversing the directions of rotation of the developer carrier 32 and the developer agitating member 36 has a higher effect of suppressing generation of haze.

  Next, the density of the 10th image density 100% chart after 5 cycles was measured with a reflection densitometer X-rite 404. The measurement results are shown in FIG. In addition, as a judgment criterion of the quality of a measurement result, it is required that the density is 1.35 or more.

  As shown in FIG. 12, when the rotation direction of the stirring blender 36 is the opposite direction (clockwise rotation) to the rotation direction of the developer carrier 32, the density of 1.35 or more is maintained in all the gaps. Is understood.

  On the other hand, when the rotation direction of the stirring blender 36 is the same as the rotation direction of the developer carrier 32 (counterclockwise rotation), the density of 1.35 or more cannot be maintained unless the gap is 1.0 mm or more. It is understood.

  As described above, according to the developing device of the present invention, the gap between the regulating portion 39e provided in a predetermined region with respect to the developer stirring member 36 is set to a predetermined value or less, so It was confirmed that the occurrence was suppressed. Furthermore, it has been confirmed that the occurrence of fog is more effectively suppressed by setting the rotation direction of the developer carrier 32 and the rotation direction of the developer stirring member 36 to be opposite to each other.

It is explanatory drawing which shows the outline | summary of the image development apparatus concerning this invention. FIG. 3 is an enlarged view of a partition member and its peripheral portion of the developing device according to the present invention. 1 is an explanatory diagram showing an embodiment of an image forming apparatus including a developing device to which the present invention is applied. FIG. 6 is an explanatory diagram when a two-component developer having a low toner concentration is carried and conveyed in the embodiment. 6 is an explanatory diagram when a two-component developer having a high toner concentration is carried and conveyed in the embodiment. FIG. FIG. 7 is a diagram illustrating a toner concentration of a developer on a developer carrier before image output and at the start of inflow on a partition member. FIG. 6 is a diagram comparing developer flow rates on a partition member according to image density during continuous output. It is a figure which shows the developer flow at the time of a haze group generation | occurrence | production. It is a figure which shows the magnetization pattern of the developer carrier used for the Example. In an Example, it is a figure which shows the result of having verified the relationship between a haze and a gap in case a rotation of a developing agent carrier and a stirring member is a reverse direction. In an Example, it is a figure which shows the result of having verified the relationship between a haze and a gap in case a rotation of a developing agent carrier and a stirring member is the same direction. In an Example, it is a figure which shows the result of having measured the image density of the image density 100% chart. It is a schematic block diagram which shows the outline | summary of the conventional image development apparatus. It is a figure which shows an example of a developer stirring member. It is explanatory drawing which shows generation | occurrence | production of the haze in the developing apparatus of a conventional structure.

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, 32: developer carrier, 33: developer accommodating portion, 34: developer retracting portion, 35: toner accommodating portion, 36: stirring rotating member, 37: toner replenishment path, 38: developer separating means, 39: Partition member, 39a: Base plate, 39b: Upper end portion, 39c: Lower end portion, 39e: Restricting portion, 41: Damping portion, 50: Fixing device, 51: Heating roll, 52: Pressure roll, 100: Developing device, 101: Developer carrier, 102: Magnetic field generation means, 103: Developer storage section, 104: Toner supply path, 105: Toner storage section, 106: Developer retracting section, 107: Developer separation means, 11 : Developer stirring member, 321: rotating sleeve, 322: pole roll, 351: toner stirring member, G: two-component developer, O: rotating shaft, R: arc angle, T: Toner

Claims (6)

Developing through a developer carrier, a developer carrier that carries and transports a two-component developer including toner and carrier by magnetic force, a developer container that contains the two-component developer adjacent to the developer carrier, and a developer container A toner accommodating portion that is provided in communication with the developer carrier and accommodates toner so as to be supplied thereto, a developer retracting portion that is adjacent to the developer accommodating portion and communicates with the developer accommodating portion, a developer accommodating portion, and a developer retracting portion Part of the two-component developer that is provided downstream of the developer carrying member with respect to the developer conveying direction and is carried and carried by the developer carrying member as an excess developer, and accommodates the developer according to the toner concentration A developer separating means for separating the surplus developer in the section or developer retracting section, and at least one stirring rotating member provided in the developer accommodating section for stirring the developer and transporting it to the developer carrying member. Developer separated in the agent retracting part In the developing device flowing into the developer accommodating portion while taking the toner from the toner accommodating portion,
Regulates the flow of the two-component developer passing through the region on the toner container side from the toner container side toward the developer carrier side above the rotation axis of the stirring rotating member closest to the developer carrier. A developing device comprising a restricting portion that performs the above operation.   A partition member that separates the developer accommodating portion and the developer retracting portion; and the restricting portion is provided at a lower end of the partition member, the tip of which is above the rotational axis of the agitation rotating member in the gravity direction. 2. The developing device according to claim 1, wherein the developing device is formed so as to face an outer peripheral surface of the agitation rotating member in a region on the toner accommodating portion side.   3. The developing device according to claim 1, wherein the rotation direction of the stirring rotation member closest to the developer carrying member is opposite to the rotation direction of the developer carrying member.   The developing device according to claim 3, wherein the restricting portion is a blade member formed such that a tip thereof is in contact with the outer peripheral surface.   The developing device according to claim 3, wherein the restricting portion is a brush member formed such that a tip thereof is in contact with the outer peripheral surface.   An image forming apparatus comprising the developing device according to claim 1.

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