JP2010002517A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device which, when using recycle toner, the charging characteristics of which have been deteriorated, stably maintains the charging characteristics of all the toner in the developing device. <P>SOLUTION: The developing tank 12 storing developer is partitioned by a partition member 25 into a first developer agitating area 23 and a second developer agitating area 24 so that developer may be movable. Within the developing tank 12, a second agitating conveyance member 28 agitates and conveys developer in a feeding direction whereas a first agitating conveyance member 29 agitates and conveys developer in a returning direction. A developer circulation flow from the feeding direction to the returning direction is formed in the first and the second developer agitating areas 23 and 24 partitioned by the partition member 25. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developing device and an image forming apparatus.

  In an image forming apparatus that forms an image using an electrophotographic system, a toner that is a component of a developer is supplied from a developing device to develop an electrostatic latent image formed on the surface of a photoreceptor. Thus, a toner image that is a visible image is formed, and the toner image is further transferred onto a recording paper that is a recording medium, and the toner image transferred onto the recording paper is fixed to form a robust recording image.

  At this time, the toner remaining on the photoconductor without being transferred in the transfer step is usually collected by a cleaning device such as a blade, collected in a container, and then discarded. In recent years, in response to social demands surrounding environmental problems, in order to reduce waste and reduce costs, a method of returning the collected toner to the developing process again, that is, so-called toner recycling, has been taken.

  However, the problem with this method is a problem of image contamination due to paper dust contained in the recycled toner. As one solution to such a problem, for example, Patent Document 1 discloses an image forming apparatus in which a mesh member having a predetermined opening is provided in a developer flow path in a developing device. .

  According to Patent Document 1, paper powder of a certain size or more contained in the recycled toner cannot always pass through the mesh member and always stays on the front side of the developing device. Is pulverized until it can pass through the mesh member with long-term agitation. At this time, a rubbing member for rubbing the mesh member is provided, and the paper powder in the recycled toner is positively pressed against the mesh member to reduce the size, and at the same time, the mesh member is prevented from being clogged. The paper dust that can pass through the mesh member is easily charged to the same polarity as the toner by the carrier, and is not noticeable even if it adheres to the white part of the image. Can be prevented.

  In addition, in the case of recycled toner, the charging characteristics of the toner may deteriorate due to temperature and pressure stress from the peripheral members during the movement from the first development step to the development tank and back again. In some cases, the toner adheres to form a lump. When developed with such recycled toner, defects such as image smearing and density unevenness occur. As one solution to such a problem, for example, Patent Document 2 discloses that a developer is circulated between the first and second agitation transport units while being mixed and agitated, and the developer is supplied to the first agitation transport unit. In the developing device for supplying the developing sleeve to the developing sleeve, the first and second extending portions are extended outward in the axial direction from the developing sleeve so as to be continuous with the first and second agitating and conveying portions. The first and second extending portions are caused to convey the developer in the opposite direction to the first agitating and conveying portion in the extending portion and in the second extending portion in the opposite direction to the second agitating and conveying portion. A developing device configured to circulate the developer in the section is disclosed.

  According to Patent Document 2, the developer conveyed in the first extension portion and the second extension portion is joined with the developer conveyed in the first and second agitation conveyance portions. Therefore, it is possible to crush the lump formed by the toners adhering to each other.

JP 2001-22181 A JP 2002-6631 A

  In the image forming apparatus disclosed in Patent Document 1, the rubbing member actively presses the paper powder in the recycled toner against the mesh member to reduce the size, and at the same time prevents the mesh member from being clogged. Since the surface is rubbed, the developer is subjected to an external stress and is subject to stress, and the developer may deteriorate. In addition, as described above, the recycle toner may be subjected to temperature or pressure stress from the peripheral member during the movement of being returned to the developing tank and returning, and the charging characteristics of the toner may deteriorate. No. 1 cannot be considered to prevent such deterioration of the charging characteristics of the toner.

  Further, in the developing device disclosed in Patent Document 2, as described above, the lump formed by adhesion of the toners is crushed, but the charging characteristics deteriorate, and recycled toner containing paper dust and foreign matters is removed. Reusing as a developer is not considered a consideration.

  Accordingly, an object of the present invention is to provide a developing device capable of stably maintaining the charging characteristics of the entire toner in the developing device when the recycled toner having deteriorated charging characteristics is reused. An image forming apparatus including the apparatus is provided.

The present invention relates to a developing device that develops an electrostatic latent image formed on a photoreceptor using a developer containing toner and a carrier.
A developer carrying member that is rotatably provided facing the photoconductor and supplies toner to an electrostatic latent image on the photoconductor;
A housing-like developer accommodating portion for accommodating a developer, having a length substantially equal to the axial length of the developer carrying member, for receiving replenishment of new toner which is unused toner A new toner replenishing port is formed, and a first developer agitation area part for supplying the developer to the developer carrying member, and a used toner collected and collected so as to be connected to the first developer agitation area part A developer accommodating portion comprising a second developer stirring region portion in which a collected toner replenishing port for receiving replenishment of certain collected toner is formed;
The developer carrier is rotatably supported by the developer container, and has a length exceeding the axial length of the developer carrier, and one end is the longitudinal end of the second developer agitation region A first agitating and conveying member that is provided so as to reach the vicinity of the unit and that agitates and conveys the developer in the first developer agitating region toward the second developer agitating region;
Opposite to the developer carrier via the first agitating and conveying member, the developer container is rotatably supported by the developer container, and has a length exceeding the length in the axial direction of the developer carrier and one end thereof is the second. A second agitating and conveying member that is provided so as to reach the vicinity of the end in the longitudinal direction of the developer agitating region, and agitates and conveys the developer in the second developer agitating region toward the first developer agitating region And comprising
The connecting portion where the first developer stirring region portion and the second developer stirring region portion are connected to each other includes a blocking region portion that prevents the developer from being conveyed and a passage region portion through which the developer passes. The developing device is formed to have a predetermined area ratio with respect to the surface.

According to the present invention, in the first developer stirring region portion, a flat plate-like first stirring intermediate wall member extending in the axial direction of the developer carrier is provided between the first stirring transport member and the second stirring transport member. Provided,
A flat second stirring intermediate wall member extending in the axial direction of the developer carrying member is provided in the second developer stirring region portion between the first stirring transport member and the second stirring transport member. And

  Further, the present invention is characterized in that a mesh foreign matter removing member having a mesh-like mesh opening is formed in at least a part of at least one of the blocking region portion and the second stirring intermediate wall member. To do.

  In the present invention, at least one surface of the blocking region portion and the second stirring intermediate wall member protrudes from the surface toward the inward side of the second developer stirring region portion. A plurality of protruding or hook-shaped protruding foreign matter removing members are formed.

  Further, the present invention is characterized in that a plurality of protruding or hook-shaped protruding foreign matter removing members protruding toward the inward side are formed on at least a part of the inner wall surface of the second developer stirring region. .

The present invention also conveys a portion of the first developer agitation region that is located upstream of the developer carrier in the developer conveyance direction and downstream of the new toner supply port in the developer conveyance direction. Detecting means for detecting the toner concentration of the developer to be produced;
A toner hopper for storing new toner and supplying the new toner toward the new toner supply port;
Control means for controlling the toner hopper based on the detection result of the detection means to supply new toner.

  According to the present invention, the mesh foreign matter removing member is formed in a flat plate shape having a predetermined thickness, and only an end corresponding to one side is fixed to the inner wall surface of the developer containing portion, and the other end The part is a free end.

  In the invention, it is preferable that the mesh foreign matter removing member is arranged so that the punching direction of the mesh opening portion is the same direction toward the developer conveying direction.

  In the invention, it is preferable that the mesh foreign matter removing member is a member made of stainless steel or a member whose surface is plated with a tin cobalt alloy or gold.

According to the present invention, the new toner has a shape factor SF-1 of 100 to 160 and a shape factor SF-2 of 100 to 150.
The present invention also provides an image forming apparatus comprising the developing device.

  According to the present invention, the connecting portion where the first developer stirring region portion and the second developer stirring region portion are connected to each other includes a blocking region portion that prevents the developer from passing, and a passage region through which the developer passes. The portion is formed to have a predetermined area ratio with respect to the connecting surface. As a result, the blocking region portion separates the first developer stirring region portion and the second developer stirring region portion, but since the passage region portion is formed, the developer accommodated in the developer accommodating portion is It can move in both directions between the first developer agitation region and the second developer agitation region through the passage region.

  The second agitating and conveying member agitates and conveys the developer in the second developer agitating region portion toward the first developer agitating region portion. That is, the second agitating and conveying member agitates and conveys the developer in the direction from one end of the second developer agitating region to the connecting portion, and the developer that has hit the blocking region is second agitated. The developer is agitated and conveyed along the blocking area in the region to the first agitating and conveying member side, and the developer that has passed through the passing region is agitated and conveyed in the direction toward the developer carrying member in the first developer agitating region. The developer conveying direction by the second agitating / conveying member is called a feeding direction for convenience.

  The first agitating and conveying member agitates and conveys the developer in the first developer agitating region toward the second developer agitating region. That is, the first agitating and conveying member agitates and conveys the developer in the direction from one end of the first developer agitating region to the connected portion, and the developer that has hit the blocking region is the first developer agitating. The developer is agitated and transported along the blocking region portion in the region portion toward the second agitating / conveying member, and the developer passing through the passing region portion is further agitated and conveyed in the second developer agitating region portion. The developer transport direction by the first agitation transport member is referred to as a return direction for convenience.

  As described above, in the developer accommodating portion, the second agitating and conveying member agitates and conveys the developer in the feeding direction, and the first agitating and conveying member agitates and conveys the developer in the returning direction. In each of the first developer agitation region portion and the second developer agitation region portion thus formed, a developer circulation flow is formed that continues from the feed direction to the return direction.

  Since a circulation flow of the developer is formed in the first developer agitation area, supply is performed when new toner is supplied into the developer storage part from the new toner supply port formed in the first developer agitation area. The resulting new toner is thoroughly agitated on the circulating flow. Therefore, the developer can be supplied to the developer carrying member with a uniform toner concentration.

  In addition, since the circulation flow of the developer is formed in the second developer stirring area, when the collected toner is supplied into the developer accommodating section from the collected toner supply port formed in the second developer stirring area. The supplied recovered toner is sufficiently stirred on the circulating flow of the second developer stirring area. Further, the collected toner passes through the gap portion of the partition wall member and is sufficiently agitated along the circulation flow in the first developer agitating region. For this reason, the collected toner is sufficiently brought into contact with the carrier in the developer to be charged, and the developer can be supplied to the developer carrying member in a state where the charging characteristics of the toner are uniform.

  According to the invention, in the first developer stirring region, a flat plate-shaped first stirring intermediate wall extending in the axial direction of the developer carrier between the first stirring transport member and the second stirring transport member. A member is provided. A flat second stirring intermediate wall member extending in the axial direction of the developer carrier is provided in the second developer stirring region portion between the first stirring transport member and the second stirring transport member. Thereby, it is possible to efficiently generate a circulation flow in each of the first developer stirring region portion and the second developer stirring region portion.

  According to the invention, the mesh foreign matter removing member having the mesh opening is formed in at least one of the blocking region portion and the second stirring intermediate wall member. The collected toner may contain paper dust or foreign matter, but the mesh foreign matter removing member can capture paper dust or foreign matter having a size larger than a predetermined size without passing through the mesh opening.

  According to the invention, at least one surface of the blocking region portion and the second stirring intermediate wall member has a plurality of convex shapes protruding from the surface toward the inner side of the second developer stirring region portion. Alternatively, a hook-shaped protruding foreign material removing member is formed. The protruding foreign matter removing member can catch paper dust and foreign matter in the developer that is stirred and conveyed so as to be caught.

  According to the invention, a plurality of protruding or hook-shaped protruding foreign matter removing members that protrude inward are formed on at least a part of the inner wall surface of the second developer stirring region. As a result, the ability to capture paper dust and foreign matter in the second developer stirring region can be improved.

  According to the invention, the detection means is located upstream of the developer carrying member in the developer transport direction in the first developer stirring region, and downstream of the new toner supply port in the developer transport direction. The toner density of the developer conveyed through the position is detected. The control unit controls the toner hopper based on the detection result of the detection unit to supply new toner from the new toner supply port. As a result, the developer whose toner density is adjusted with high accuracy can be supplied to the developer carrying member.

  According to the invention, the mesh foreign matter removing member is formed in a flat plate shape having a predetermined thickness, and only the end corresponding to one side is fixed to the inner wall surface of the developer containing portion, and the other end The part is the free end. As a result, the mesh foreign matter removing member is displaced by the pressing force accompanying the stirring and conveyance of the developer when the developer passes through the mesh opening. Since the pressing force accompanying the developer agitation and conveyance is not constant but varies, the magnitude of displacement of the mesh foreign matter removing member also varies. Therefore, when the developer passes through the mesh opening, the mesh foreign matter removing member vibrates with the magnitude of the displacement fluctuating, thereby preventing the mesh opening from being clogged with the agglomerated toner. In addition, it is possible to prevent the developer from deteriorating without applying an excessive load to the developer colliding with the mesh foreign matter removing member.

  Further, according to the present invention, the mesh foreign matter removing member is disposed such that the punching direction of the mesh opening is the same direction toward the developer transport direction. Accordingly, it is possible to prevent the developer from being deteriorated at a sharp portion (burr) formed when the mesh opening of the mesh foreign matter removing member is manufactured by punching. In addition, it is possible to prevent the developer from being obstructed by the protrusion of the burr at the mesh opening, and to prevent the burr from falling off.

  According to the present invention, the mesh foreign matter removing member is a member made of stainless steel or a member whose surface is plated with a tin cobalt alloy or gold. The mesh foreign matter removing member configured as described above has excellent moisture resistance, prevents rust from being generated, and can prevent the developer from being adversely affected.

  According to the present invention, the new toner has a shape factor SF-1 of 100 to 160 and a shape factor SF-2 of 100 to 150. By using the new toner whose shape factor is adjusted as described above as the toner component of the developer, it can be developed as a toner image capable of forming a high-quality image.

  According to the invention, the image forming apparatus is realized by including the developing device.

  FIG. 1 is a diagram showing a configuration of a developing device 10 according to the first embodiment of the present invention. FIG. 1A is a top view showing the internal structure of the developing tank 12 in the developing device 10. FIG. 1B is a cross-sectional view of the internal structure of the second developer stirring region 24 in the developing device 10 as viewed from the end on the second developer stirring region 24 side. FIG. 2 is a cross-sectional view showing the configuration of the image forming unit 1 of the image forming apparatus 100 according to the embodiment of the present invention.

  The developing device 10 is provided in the image forming unit 1 of the image forming apparatus 100 that forms an image using an electrophotographic method, and uses a two-component developer composed of a toner and a carrier to statically fix the surface of the photoreceptor 2. An apparatus for developing an electrostatic latent image.

  Here, the toner constituting the two-component developer can be produced by a production method well known in this field, for example, a pulverization method, a suspension polymerization method, an emulsion polymerization method, a solution polymerization method, an ester extension polymerization method, or the like. The toner has a volume average particle diameter of about 6 μm. The volume average particle diameter can be measured by a Coulter counter (trade name: TA-II, manufactured by Beckman Coulter, Inc.) which is a measuring apparatus using a laser diffraction / scattering method.

  Further, toner having a toner shape factor SF-1 in the range of 100 to 160 and a toner shape factor SF-2 in the range of 100 to 150 can be used. More preferably, SF-1 is 110 to 150, and SF-2. Is 110-140. When the shape factor SF-1 is smaller than 100, the toner may be nearly spherical, and when the toner is transferred from the photoreceptor 2 to the transfer unit 5, the toner slips on the transfer unit 5 and the transferred image is disturbed. There is. When the shape factor SF-1 exceeds 160, the irregular shape of the toner becomes large, and the angular portion of the toner surface is agitated in the developing tank 12 to be separated from the toner surface to become fine powder, and the toner scatters and the carrier surface. Alternatively, it may adhere to the surface of the developing sleeve 22 and hinder sufficient frictional charging with the toner.

  When the shape factor SF-2 is smaller than 100, the toner may slip on the transfer unit 5 due to the smoothness of the toner surface, and the transferred image may be distorted. When the shape factor SF-2 exceeds 150, the unevenness of the toner surface becomes large, the toner charge amount varies, and the image density and fog may not be stable.

  Here, the shape factor SF-1 of the toner indicates the degree of roundness of the toner particles, and the shape factor SF-2 indicates the degree of unevenness of the toner particles. Such a shape factor is obtained by randomly sampling 100 toner images magnified by 500 times using an electron microscope (trade name: FE-SEM (S-800), manufactured by Hitachi, Ltd.). Information can be obtained by analyzing with an image analysis device (trade name: Luzex III, manufactured by Nireco Corporation).

  As the carrier, a ferrite resin-coated carrier having a volume average particle diameter of about 40 μm can be used, but the carrier is not limited to this, and a carrier without a ferrite resin coat, an iron powder type, or a binder type carrier can also be used. Can do.

  In the two-component developer, the charge amount of the toner when a charge is applied by the carrier is about −30 μC / g. The amount of charge of the toner is such that a mirror image that remains on the carrier is obtained by placing about 200 mg of a two-component developer on a metal mesh 500 mesh in an electrically shielded casing, and sucking the toner with air through the metal mesh. The charge can be determined by measuring with a commercially available coulomb meter.

  The image forming apparatus 100 forms an image on a recording medium such as recording paper in accordance with image information included in a print command from an external device. As the external device, an electric / electronic device that can form or acquire image information and can be connected to the image forming apparatus 100 by wire or wirelessly can be used. For example, a computer, a digital camera, a digital video camera, a television Examples include an image receiving device, a video recorder, a DVD (Digital Versatile Disc) recorder, a Blu-ray disc recorder, a Blu-ray disc player, a facsimile device, a mobile phone, and a portable information terminal device.

In addition, as wired or wireless, for example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network (virtual private network)
network), telephone line network, mobile communication network, satellite communication network, and the like.

Further, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, wireless USB (UWB), etc.
The image forming unit 1 of the image forming apparatus 100 includes a photoconductor 2, a charging unit 3, an exposure unit 4, a developing device 10, a transfer unit 5, and a cleaning unit 6.

  The photosensitive member 2 is a roller-like member having a photosensitive film on which a latent electrostatic image and a toner image are formed. As the photoreceptor 2, for example, one including a conductive substrate (not shown) and a photosensitive film (not shown) formed on the surface of the conductive substrate can be used. As the conductive substrate, a conductive substrate having a cylindrical shape, a columnar shape, a sheet shape or the like can be used, and among them, the cylindrical conductive substrate is preferable. Examples of the photosensitive film include an organic photosensitive film and an inorganic photosensitive film. As an organic photosensitive film, a laminate of a charge generation layer, which is a resin layer containing a charge generation material, and a charge transport layer, which is a resin layer containing a charge transport material, a charge generation material and a charge transport material in one resin layer And monolayers containing Examples of the inorganic photosensitive film include films containing one or more selected from zinc oxide, selenium, amorphous silicon and the like. A base film may be interposed between the conductive substrate and the photosensitive film, and a surface film (protective film) for mainly protecting the photosensitive film may be provided on the surface of the photosensitive film.

  The charging unit 3 is a roller-like member that can be rotationally driven around an axis by a driving unit (not shown) and is in contact with the photosensitive member 2. A power supply (not shown) is connected to the charging means 3 and receives a voltage applied from the power supply to charge the surface of the photoreceptor 2 to a predetermined polarity and potential. In the present embodiment, the charging unit 3 uses a charging roller that applies a charge to the surface of the photoreceptor 2 in contact with the charging unit 3, but is not limited thereto. For example, a corona charger, a brush type charger, a charger type A charger, an ion emission charger, a magnetic brush charger, or the like can be used.

  The exposure unit 4 irradiates the surface of the photoconductor 2 with signal light 4a corresponding to image information to form an electrostatic latent image corresponding to the image information. The image information is included in a print command input to the image forming apparatus 100. In the present embodiment, a laser scanning unit (not shown) (hereinafter referred to as “LSU”) is used as the exposure unit 4. The LSU includes a laser emitting unit and a laser reflecting unit. The laser emitting means emits signal light 4a corresponding to the image information. Although a semiconductor laser is used as the laser emitting means, it is not limited thereto, and an electroluminescence (EL) element, a light emitting diode (LED) element, or the like can be used. The laser reflecting means reflects the signal light 4 a emitted from the laser emitting means to reach the surface of the photoreceptor 2. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photoreceptor 2. A reflection mirror or the like can be used as the laser reflecting means.

  The developing device 10, which will be described in detail later, is the developing device of the present invention shown in FIG. 1 and supplies toner to the electrostatic latent image on the surface of the photoreceptor 2 to form a toner image. Further, as the developing device provided in the image forming unit 1 of the image forming apparatus 100, a developing device 60 which is another embodiment of the present invention described later may be used.

  The transfer means 5 is a roller-like member that is rotatably supported by a support means (not shown), is rotatably driven by a drive means (not shown), and is provided so as to be in pressure contact with the surface of the photoreceptor 2. A pressure contact portion between the transfer unit 5 and the photosensitive member 2 is a transfer nip portion. For the transfer means 5, for example, a roller-shaped member including a metal core with a diameter of 8 to 10 mm and a conductive elastic layer formed on the surface of the metal core is used. As the metal forming the metal core, stainless steel, aluminum, or the like can be used. As the conductive elastic layer, a rubber material in which a conductive material such as carbon black is blended with a rubber material such as ethylene-propylene rubber (EPDM), foamed EPDM, or foamed urethane can be used.

  A power supply (not shown) is connected to the transfer unit 5, and a transfer bias voltage is applied to the transfer unit 5 when the toner image on the surface of the photoreceptor 2 is transferred to a recording medium. The transfer bias voltage is a voltage having a polarity opposite to the charging polarity of the toner constituting the toner image. By applying the transfer bias voltage, the toner image is smoothly transferred to the recording medium. In the transfer means 5, one recording medium is fed from a paper feed tray (not shown) through a pickup roller and a registration roller (not shown) in synchronization with the toner image being conveyed to the transfer nip portion by the rotation of the photosensitive member 2. Supplied one by one. As the recording medium passes through the transfer nip portion, the toner image on the surface of the photoreceptor 2 is transferred to the recording medium. According to the transfer means 5, the toner image on the surface of the photoreceptor 2 is transferred to the recording medium.

In the present embodiment, the toner weight in the image area of the transfer image having an image area ratio of 100% is adjusted in the range of 0.20 to 0.40 mg / cm ² . When the toner weight is less than 0.20 mg / cm ² , a sufficient image density cannot be obtained. When the toner weight exceeds 0.40 mg / cm ² , a large amount of toner is required to be developed on the photosensitive member 2, and the amount of toner consumption increases, and the toner is transferred from the photosensitive member 2 to the transfer unit 5. The transfer efficiency may be reduced, and an extra developing toner may be required. Further, in the case of a transfer image of process black (a state in which three colors of yellow, cyan, and magenta are superimposed), the toner weight in the image area with an image area ratio of 100% is 0.60 to 1. It is adjusted in the range of ² mg / cm ² . Further, for example, six colors including light cyan (LC), light magenta (Lm), and black having the same hue as cyan and magenta and a lighter density may be used, and the toner weight is 1.2 to It is adjusted to the range of 2.4 mg / cm ² .

  The cleaning unit 6 includes a cleaning blade 6a and a toner storage tank 6b. The cleaning blade 6a extends parallel to the longitudinal direction of the photosensitive member 2 and is provided so that one end in the short direction contacts the surface of the photosensitive member 2, and remains on the surface of the photosensitive member 2 after the toner image is transferred to a recording medium. This is a plate-like member that removes toner and paper dust derived from the recording medium from the surface of the photoreceptor 2. The toner storage tank 6b is a container-like member having an internal space, and temporarily stores the toner (collected toner 52) removed by the cleaning blade 6a. The collected toner 52 collected in the toner storage tank 6b includes paper powder and foreign matter (for example, paper fiber, kaolin, talc, calcium carbonate, dust, dust, metal powder, resin powder, toner lump) and the like. .

  A toner image is transferred to the recording medium that has passed through the image forming unit 1, and a fixing unit (not shown) passes the recording medium to which the toner image has been transferred to the fixing nip portion to melt the toner that constitutes the toner image. At the same time, the toner image is fixed on the recording medium by pressing against the recording medium, and the image is printed. The recording medium on which the image is printed is discharged and stacked on a paper discharge tray provided on a vertical upper surface or a vertical side surface of the image forming apparatus 1 by a conveying unit (not shown).

  As shown in FIG. 1, the developing device 10 of the present invention includes a developing roller 11 that is a developer carrying member that carries a developer, a developing tank 12 that is a developer containing unit that contains the developer, and a developing tank 12. Among them, an agitating and conveying member 13 for agitating and conveying the developer and a toner sensor 14 for detecting the toner concentration of the developer in the developing tank 12 are included.

  In the present embodiment, the developing roller 11 is a so-called magnet roller having a magnet member 21 and including a developing sleeve 22 that is rotatably provided on the outer periphery of the magnet member 21. The magnet member 21 is made of, for example, a permanent magnet piece, and N poles and S poles are substantially alternately arranged in the circumferential direction to form a cylindrical shape as a whole. The developing sleeve 22 is a cylindrical member made of a nonmagnetic material such as aluminum, and is provided so as to be rotatable around the magnet member 21. The developing roller 11 faces the photosensitive member 2 and is arranged so that its axis is parallel to the rotational axis of the photosensitive member 2, and is supported by the frame portion of the main body of the developing device 10.

  As the developer carried on the developing roller 11, a two-component developer containing toner and carrier is used. The developing roller 11 attracts the carrier carrying the toner by the magnetic force of the magnet member 21 to form a magnetic brush in which the developer is linked in a spike shape on the surface of the developing sleeve 22. Thus, the developer is carried on the developing roller 11 in the form of a magnetic brush. A toner having a charge in the developer forming the magnetic brush is supplied from the developing roller 11 to the photoconductor 2 according to the potential difference between the developing roller 11 and the photoconductor 2 to develop the electrostatic latent image, and the toner image Form.

  The developing tank 12 is a container member made of, for example, hard synthetic resin and having an approximately rectangular parallelepiped shape in appearance. The developing tank 12 is formed to have a length exceeding the length L1 of the developing roller 11 in the axial direction. The developing tank 12 is provided in a length portion substantially corresponding to the length L1 of the developing roller 11 in the axial direction, and a first developer stirring area portion 23 to which the developer transported by stirring is supplied to the developing roller 11; The developer is connected to the first developer agitating region 23 and is provided at a position exceeding the axial length L1 of the developing roller 11, and the agitated and conveyed developer is supplied to the first developer agitating region 23. The second developer agitation region 24 in which a part of the remaining developer supplied to the developing roller 11 is collected.

  In the present embodiment, the volume of the second developer stirring region 24 is configured to be approximately 15 to 30% of the volume of the first developer stirring region 23. If it is less than 15%, although details will be described later, the collected toner 52 cannot be sufficiently stirred in the second developer stirring region 24, and the collected toner 52 is not given sufficient charge from the carrier. On the other hand, if it exceeds 30%, the developer is excessively stirred in the second developer stirring region 24, and an excessive load is applied to the developer, which deteriorates the developer.

  Further, a flat plate is provided in the developing tank 12 so as to extend in a direction perpendicular to the axis of the developing roller 11 and partitions the first developer stirring area 23 and the second developer stirring area 24. A partition wall member 25 is provided. The partition wall member 25 serves as a blocking region portion that prevents the developer from being conveyed at the connecting portion between the first developer stirring region portion 23 and the second developer stirring region portion 24. The partition wall member 25 is made of a material that does not take away charges from the toner in the developer and does not accumulate charges. For example, ABS resin (acrylonitrile-butadiene-styrene copolymer resin) or POM resin is used. (Polyacetal resin).

  The partition wall member 25 divides the first developer stirring region 23 and the second developer stirring region 24, but completely separates the first developer stirring region 23 and the second developer stirring region 24 from each other. Instead of partitioning so as to be sealed, the first gap 26 and the first gap 26 for communicating the first developer agitation region 23 and the second developer agitation region 24 at two positions on both ends of the developing tank 12 in the short direction. 2 gaps 27 are formed. The first and second gaps 26 and 27 serve as a passage region portion through which the developer passes at a connecting portion between the first developer stirring region portion 23 and the second developer stirring region portion 24. As described above, the partition wall member 25 partitions the developer tank 12 into the first developer stirring region portion 23 and the second developer stirring region portion 24, but the first and second gaps 26 and 27 are formed. A part of the developer stored in the developing tank 12 can move from the first developer stirring region 23 to the second developer stirring region 24, and conversely, the second development. The developer stirring area 24 can be moved to the first developer stirring area 23.

  In the present embodiment, the area of the partition wall member 25 is 45 to 55% of the area of the connecting surface where the first developer stirring region portion 23 and the second developer stirring region portion 24 are connected. Is set to be That is, the remaining portions corresponding to 45 to 55% of the area of the connecting surface are the first gap 26 and the second gap where the first developer stirring area 23 and the second developer stirring area 24 are communicated. The gap area ratio of the gap 27 is obtained. Here, in the present embodiment, the gap areas of the first gap 26 and the second gap 27 are set to be the same. When the area ratio of the partition wall member 25 is less than 45%, the developer circulation flow is not formed in the first developer stirring region portion 23 and the second developer stirring region portion 24 as will be described in detail later. Further, when the area ratio of the partition wall member 25 exceeds 55%, the movement of the developer between the first developer stirring region portion 23 and the second developer stirring region portion 24 is not smoothly performed.

  Next, the stirring and conveying member 13 that stirs and conveys the developer in the developing tank 12 will be described. The agitation transport member 13 includes a first agitation transport member 29 and a second agitation transport member 28. The first stirring / conveying member 29 faces the developing roller 11 and is rotatably supported by the developing tank 12, and the second stirring / conveying member 28 faces the developing roller 11 via the first stirring / conveying member 29. 12 is rotatably supported.

  The second agitating and conveying member 28 is provided so as to be rotatable from the second developer agitating region 24 to the first developer agitating region 23 in parallel to the longitudinal direction of the developing tank 12, so that the second developer agitating member 28 is rotated. The developer in the region 24 is stirred and conveyed toward the first developer stirring region 23, and the developer is stirred and conveyed in the direction toward the developing roller 11.

  FIG. 3 is a view showing the shape of the second stirring / conveying member 28. The second agitating and conveying member 28 is a so-called screw member in which screw blades are formed at predetermined pitch intervals in the shaft portion, and agitates and conveys the developer in the developing tank 12 by rotating. In the second stirring and conveying member 28 that is such a screw member, the developer is conveyed while being inclined to the left or right in the conveying direction, depending on the winding direction and the rotating direction of the screw blades. For example, when the developer is transported with an upper right slope, more developer is transported while being in contact with the right wall surface in the developer tank 12.

  FIG. 4 is a graph showing the relationship between the conveyance speed and the conveyance amount due to the difference in the pitch interval P of the screw blades 28a in the second agitation conveyance member 28. In FIG. 4, the horizontal axis represents the conveyance speed (m / min) at which the developer is conveyed, and the vertical axis represents the conveyance amount (g / min) per unit time of the developer to be conveyed.

  The conveyance speed can be adjusted by controlling the rotation speed of the second agitation conveyance member 28, but the conveyance amount also increases or decreases in proportion to the conveyance speed. That is, the developer conveyance amount can be adjusted by controlling the rotation speed of the second agitation conveyance member 28. Further, as the pitch interval P of the screw blades 28a is reduced to 25 mm, 20 mm, and 15 mm, a large conveyance amount can be obtained at a small conveyance speed. That is, the developer transport amount can be adjusted by adjusting the pitch interval P of the screw blades 28a. Further, in the second agitation transport member 28 that is a screw member, the transport amount of the developer can also be adjusted by adjusting the inclination and outer diameter of the screw blade 28a, the shaft thickness, and the like. Although the developer conveyance efficiency by the second agitating / conveying member 28 varies depending on the type and fluidity of the developer, the pitch interval P and the inclination of the screw blades 28a described above may be appropriately selected and set.

  The second agitating / conveying member 28 causes the developer to extend from the vicinity of one end 39 in the longitudinal direction of the developing tank 12 and far from the developing roller 11 in the extending direction exceeding the length L1 of the developing roller 11. And agitating and conveying in the direction of the arrow 31 toward the direction, and the developer hitting the partition wall member 25 is agitated and conveyed in the direction of the arrow 32 along the partition wall member 25 in the second developer agitating region 24. The developer that has passed through the one gap 26 is further agitated and conveyed in the direction of the arrow 35 toward the developing roller 11 in the first developer agitating region 23. The developer conveying direction from the vicinity of one end 39 of the developing tank 12 toward the developing roller 11 is referred to as a feeding direction for convenience.

  Further, the developing tank 12 is provided between the developing roller 11 and the second stirring / conveying member 28, that is, closer to the developing roller 11 than the second stirring / conveying member 28, in parallel with the longitudinal direction of the developing tank 12. A first agitation transport member 29 that agitates and conveys the developer in a direction away from the developing roller 11 from the developer agitation region 23 to the second developer agitation region 24 is rotatably provided. The first agitation transport member 29 is also a so-called screw member, similarly to the second agitation transport member 28, and agitates and transports the developer in the developing tank 12 by rotating.

  By setting the developer conveying capability of the first agitating / conveying member 29 to be the same as that of the second agitating / conveying member 28, components such as screw blades, shafts, and bearings are shared by the two agitating / conveying members 28 and 29. The cost can be reduced. On the other hand, by making the conveying capabilities of the two agitating and conveying members 28 and 29 different from each other, it is possible to optimize the developer having different fluidity on the developing tank side.

  The first agitating and conveying member 29 moves the developer conveyed by the second agitating and conveying member 28 to the vicinity of the other end 40 in the longitudinal direction of the developing tank 12 in the direction of the arrow 37 along the developing roller 11 toward the partition wall member 25. While being conveyed, the developer hitting the partition wall member 25 is conveyed along the partition wall member 25 in the direction of the arrow 38 toward the second agitating / conveying member 28 in the first developer agitating region 23, The developer that has passed through the gap 27 is further conveyed in the direction of the arrow 33 toward the vicinity of the one end 39 in the second developer stirring region 24. The developer transport direction from the vicinity of the other end 40 of the developing tank 12 toward the vicinity of the one end 39 along the developing roller 11 is referred to as a return direction for convenience.

  In the developing device 10, a first stirring intermediate wall member 41 is provided between the second stirring and conveying member 28 and the first stirring and conveying member 29 in the first developer stirring region portion 23. The first stirring intermediate wall member 41 is a flat plate member made of, for example, a synthetic resin, and is provided so as to extend in the longitudinal direction of the developing tank 12 and rise from the bottom of the developing tank 12. However, since the first stirring intermediate wall member 41 is formed to have a length shorter than the length in the longitudinal direction of the first developer stirring region portion 23, the other portions in the first developer stirring region portion 23 In the vicinity of the end portion 40, the developer flows in the direction of the arrow 36 from the second agitating / conveying member 28 to the first agitating / conveying member 29, and in the vicinity of the partition wall member 25, the first agitating / conveying member 29 A developer flow is formed in the direction of the arrow 38 toward the member 28.

  Therefore, in the first developer stirring region 23, the first and second stirring and conveying members 28, 29, the partition wall member 25, and the first stirring intermediate wall member 41 are connected in the return direction from the feeding direction. A developer circulation flow, that is, a developer circulation flow indicated by arrows 35, 36, 37, and 38 in FIG. 1, is formed.

  In the second developer agitation region 24, a second agitation intermediate wall member 42 is provided between the second agitation conveyance member 28 and the first agitation conveyance member 29. The second stirring intermediate wall member 42 is a flat plate member made of synthetic resin, for example, and is provided so as to extend in the longitudinal direction of the developing tank 12 and to rise from the bottom of the developing tank 12. However, since the second stirring intermediate wall member 42 is formed so as to have a length shorter than the length in the longitudinal direction of the second developer stirring region 24, a partition is formed in the second developer stirring region 24. In the vicinity of the wall member 25, the developer flows in the direction of the arrow 32 from the second agitating / conveying member 28 to the first agitating / conveying member 29, and in the vicinity of the one end 39, the first agitating / conveying member 29 to the second agitating / conveying member A developer flow in the direction of arrow 34 toward 28 is formed.

  Accordingly, in the second developer stirring region 24, the first and second stirring and conveying members 28 and 29, the partition wall member 25, and the second stirring intermediate wall member 42 are connected in the return direction from the feeding direction. A developer circulation flow, that is, a developer circulation flow indicated by arrows 31, 32, 33, and 34 in FIG. 1, is formed.

  Further, the developing device 10 includes a toner sensor 14 that detects the toner concentration of the developer in the developing tank 12. As the toner sensor 14, a magnetic permeability sensor is used, and a toner concentration that is a mixing ratio of the carrier and the toner is detected.

  A non-magnetic material is used for the toner of the two-component developer, and a magnetic material such as iron powder or ferrite is used for the carrier. By detecting the magnetic permeability of the magnetic material in the developer, the mixing ratio of the magnetic material and the non-magnetic material in the developer, that is, the change in the relative concentration of the magnetic material, and the magnetic permeability of the developer are determined. By detecting, it is possible to detect the concentration of the carrier that is a magnetic material in the developer, and conversely, the concentration of the toner that is a non-magnetic material in the developer.

  The toner sensor 14 faces the second agitating and conveying member 28 in the first developer agitating region 23 upstream of the developing roller 11 in the agitating and conveying direction of the developer, that is, near the other end 40 of the developing tank 12. The toner density is detected by being mounted on the wall material of the first developer stirring area 23. By providing the toner sensor 14 as described above, the toner sensor 14 can measure the toner concentration of the developer before being supplied to the developing roller 11, that is, before being used for development. The developing device 10 controls the replenishment amount and replenishment timing of the new toner 50 and the recovered toner 52 based on the detection result of the toner concentration by the toner sensor 14, and the toner concentration of the developer before being used for development. Is set to an appropriate toner density.

  In the developing device 10 of the present invention, the control unit operates a toner hopper (not shown) in accordance with the toner density detection output value from the toner sensor 14 to replenish the developing tank 12 with new toner 50 as new toner. . The toner hopper is a container member made of, for example, hard synthetic resin. The toner hopper accommodates new toner 50 in its internal space, and drives the new toner replenishing roller 49 in response to an operation command from the control unit. Then, new toner 50 is supplied.

  The new toner replenishing roller 49 is disposed above the second agitating and conveying member 28 in the first developer agitating region 23 and serves as an opening for replenishing the new toner 50 from the toner hopper into the developing tank 12. The toner supply port 49a is provided so that its outer periphery can rotate while sliding. The new toner replenishing roller 49 is provided with a cylindrical porous elastic member such as foamed urethane around a core metal, and the toner held by the porous elastic member of the new toner replenishing roller 49 in the toner hopper. However, the new toner replenishing port 49a and the new toner replenishing roller 49 are rubbed off from the new toner replenishing roller 49 and replenished to the developing tank 12.

  The position of the new toner supply port 49a, which is an opening through which the new toner 50 is supplied to the developing tank 12, is above the second stirring and conveying member 28 in the first developer stirring region 23 and in the vicinity of the partition wall member 25. The second agitating and conveying member 28 corresponds to the most upstream side in the conveying direction for conveying the developer from the one end 39 side of the developing tank 12 toward the developing roller 11 in the first developer agitating region 23. . That is, the position of the new toner replenishing port 49a is the first developer stirring region 23 when viewed in the stirring transport path formed in the developing tank 12 by the second stirring transport member 28 and the first stirring transport member 29. It is the farthest position from the site where the developer is supplied to the developing roller 11. Therefore, a sufficient stirring time can be ensured between the time when the new toner 50 is supplied from the new toner supply port 49a and the time when the new toner 50 is supplied to the developing roller 11, and the development stored in the developing tank 12 is maintained. Since the agent and the replenished new toner 50 are sufficiently agitated, it can be supplied to the developing roller 11 as a developer having a uniform toner concentration.

  Further, the collected toner 52 collected in the toner storage tank 6b of the cleaning unit 6 included in the image forming apparatus 100 is conveyed to the vicinity of the second developer stirring area 24 by a conveyance path (not shown), and a collected toner supply roller. The toner is dropped by 51 and supplied into the developing tank 12 from the collected toner supply port 51a.

  The position of the recovered toner replenishing port 51a, which is an opening through which the recovered toner 52 is supplied to the developing tank 12, is above the first agitating and conveying member 29 in the second developer agitating region 24 and in the vicinity of the partition wall member 25. In the second developer agitation region 24, a portion corresponding to the most upstream side in the conveyance direction in which the first agitation conveyance member 29 conveys the developer from the other end 40 side to the one end 39 side of the developing tank 12. It is. That is, the position of the recovered toner replenishing port 51a is the second developer stirring region 24 when viewed in the stirring transport path formed in the developing tank 12 by the second stirring transport member 28 and the first stirring transport member 29. It is the farthest position from the site where the developer is supplied to the developing roller 11. Therefore, a sufficient stirring time can be ensured between the time when the collected toner 52 is supplied from the collected toner replenishing port 51 a and the time when the collected toner 52 is supplied to the developing roller 11, and the development stored in the developing tank 12. After the developer and the supplied recovered toner 52 having deteriorated charging performance are sufficiently stirred in the second developer stirring region 24, they are further transported to the first developer stirring region 23 and stirred. Therefore, the recovered toner 52 is sufficiently brought into contact with the carrier in the developer to be charged, and can be supplied to the developing roller 11 as a developer having uniform charging performance.

  FIG. 5 is a graph showing the relationship between the elapsed time after supply, the toner charge amount, and the toner concentration when the collected toner is supplied into the developing tank. FIG. 5A shows a change in the charge amount of the toner supplied to the developing roller and the toner sensor when the developing device of the present invention in which the developing tank has the first and second developer stirring area portions is used. The change in toner density is shown. FIG. 5B shows a change in the charge amount of the toner supplied to the developing roller and a change in the toner concentration detected by the toner sensor when a developing device having one developer stirring area in the developing tank is used. Indicates. As shown in FIG. 5, when the developing device of the present invention in which the developing tank has the first and second developer stirring area portions is used, even if the collected toner is supplied into the developing tank, the toner charge amount with the elapsed time It can also be seen that the change width of the toner density is small. On the other hand, in the case of using a developing device with one developer stirring area in the developing tank, after the collected toner is supplied into the developing tank, the toner charge amount and the toner concentration are increased with the lapse of time. It can be seen that the range of change is large.

  From the above results, in the developing device 10, in the second developer stirring region 24 in the developing tank 12, a developer circulation flow for recovering the deterioration of the collected toner 52 is formed, and the first developer stirring is performed. In the region 23, a developer circulation flow having a relatively high ratio of the new toner 50 is formed, and the first partition wall member 25 that communicates the second developer stirring region 24 and the first developer stirring region 23 is formed. Since both circulating flows are mixed at an optimal ratio through the first and second gaps 26 and 27, the stirring efficiency of the entire developing tank 12 is improved, the toner concentration becomes uniform, and the charging performance of the recovered toner 52 is deteriorated. The developer having recovered can be supplied to the developing roller 11.

  As a result, even if the image forming apparatus on which the developing device 10 is mounted is a high-speed machine, the first and second stirring and conveying members 28 and 29 are replenished at a low speed without increasing the rotational speed. The new toner 50 and the collected toner 52 and the developer stored in the developing tank 12 can be sufficiently agitated and made uniform and supplied to the developing roller 11, reducing the load on the developer and developing. The life of the agent can be extended.

  FIG. 6 is a diagram illustrating a configuration of the developing device 60 according to the second embodiment of the present invention. FIG. 6A is a top view showing the internal structure of the developing tank 12 in the developing device 60. FIG. 6B is a cross-sectional view of the internal structure of the second developer stirring region 24 in the developing device 60 as viewed from the end on the second developer stirring region 24 side. The developing device 60 according to the second embodiment is similar to the developing device 10 according to the first embodiment, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.

  A characteristic configuration of the developing device 60 according to the second embodiment is that a mesh-like foreign matter removing member 25 a is provided in a part of the partition wall member 25. The foreign matter removing member 25a is a flat plate-like member. Since the foreign matter removing member 25a is a member that comes into contact with the developer, the material constituting the foreign matter removing member 25a does not take charge from the toner in the developer and does not accumulate charge. It is preferable to select from materials. Furthermore, considering that the foreign matter removing member 25a is configured to vibrate as the developer is conveyed as described later, it is preferable to select the material from a relatively low density material. Specifically, the foreign matter removing member 25a is a flat plate member made of SUS (stainless steel), or a member whose surface is tin-cobalt alloy or gold plated. The foreign matter removing member 25a made of such a material is further excellent in moisture resistance, is prevented from generating rust, and does not adversely affect the developer.

  A part of the developer supplied with the recovered toner 52 in the second developer stirring region 24 passes through the first gap 26 by the second stirring and conveying member 28 and is first developed from the second developer stirring region 24. Although transported to the agent stirring area 23, the remaining part collides with the partition wall member 25.

  The foreign matter removing member 25a is provided on the side of the partition wall member 25 where the second stirring / conveying member 28 is disposed. In other words, the foreign matter removing member 25a is transported in the second developer stirring region 24 when viewed from the transport path of the collected toner 52 supplied into the second developer stirring region 24 from the recovered toner replenishment port 51a. It is provided on the most downstream side in the direction. Further, the foreign matter removing member 25a is arranged so that the punching direction of the mesh opening is the same direction toward the developer transport direction. Thereby, it is possible to prevent the developer from being deteriorated at a sharp portion (burr) formed when the mesh opening of the foreign matter removing member 25a is manufactured by punching. Further, it is possible to prevent the passage of the developer from being hindered by the protrusion of the burr at the mesh opening, and it is possible to prevent the burr from falling off.

  Here, the deterioration of the developer is a state in which peeling of the coating layer on the carrier surface, fixing of the toner to the carrier surface (spent), or the like has occurred. Such a carrier cannot impart a normal charge to the toner, which causes a reduction in image quality.

  When the developer passes through the mesh opening of the foreign matter removing member 25a, paper dust or foreign matter having a size larger than a predetermined size derived from the collected toner 52 contained in the developer is captured. Further, even when there is aggregated toner in which toner particles adhere to each other in the developer, the aggregated toner is crushed when passing through the mesh opening of the foreign matter removing member 25a, and more There is also an effect of facilitating mixing. Paper dust and foreign matter captured without being able to pass through the mesh opening of the foreign matter removing member 25a are stirred by the first and second stirring and conveying members 28 and 29 in the second developer stirring region 24, and the mesh opening. Until it can pass through. Paper dust and foreign matter that can pass through the mesh opening are easily charged to the same polarity as the toner by the carrier, and are not noticeable even if they adhere to the white part of the image, preventing the occurrence of background stains. it can.

  The opening diameter of the mesh opening of the foreign matter removing member 25a is set so that the toner and carrier constituting the developer can pass through the mesh opening, and paper dust and foreign matters having a predetermined size or larger can be captured. The In this embodiment, the opening diameter of the mesh opening can pass toner having a volume average particle diameter of about 6 μm and a carrier having a volume average particle diameter of about 40 μm, and can capture paper dust and foreign matters having a volume average particle diameter of about 80 μm or more. Is set to be Specifically, the opening diameter of the mesh opening is set to about 2 to 3 times the maximum primary particle diameter of a carrier having a particle size distribution.

  Further, the area of the foreign matter removing member 25 a formed on a part of the partition wall member 25 is set to be 20% or more with respect to the area of the partition wall member 25. If it is less than 20%, sufficient capturing ability of paper dust and foreign matters by the foreign matter removing member 25a cannot be obtained.

  Further, in the foreign matter removing member 25a formed on a part of the partition wall member 25 on the side where the second agitating / conveying member 28 is disposed, the formation position with respect to the surface of the partition wall member 25 is the screw of the second agitating / conveying member 28. It is preferable to set in consideration of the winding direction and rotation direction of the blades 28a. Specifically, as described above, in the second agitating and conveying member 28, the developer is agitated and conveyed while being inclined to the left or right depending on the winding direction and the rotating direction of the screw blade 28a. By disposing the foreign material removing member 25a on the higher side in the inclination direction where the developer is inclined and conveyed, paper dust and foreign materials can be efficiently captured.

  Further, the flat foreign substance removing member 25a is configured such that only one end corresponding to one side is fixed to the wall surface of the developing tank 12, and the other end is a free end, and has a predetermined thickness. As a result, the foreign matter removing member 25a is displaced by the pressing force accompanying the stirring and conveyance of the developer when the developer passes through the mesh opening. Since the pressing force accompanying the developer agitation and conveyance is not constant but varies, the displacement of the foreign matter removing member 25a also varies. Accordingly, the foreign matter removing member 25a can vibrate with the magnitude of displacement fluctuating when the developer passes through the mesh opening, thereby preventing the mesh opening from being clogged with the aggregated toner. At the same time, the developer can be prevented from being deteriorated without applying an excessive load to the developer.

  The thickness of the foreign matter removing member 25a is such that the first and second agitating / conveying members 28 and 29 convey the developer with respect to the developer so as to vibrate due to the displacement by the pressing force by the agitated and conveyed developer (the developer is agitated and conveyed). (Conveying speed and conveying amount) is set. In the present embodiment, the conveying ability of the first and second agitating and conveying members 28 and 29 with respect to the developer is such that the conveying speed is 6.2 m / min and the conveying amount is 1700 g / min. The thickness of 25a is set to 0.08 to 0.1 mm.

  Further, the remaining developer that has not passed through the mesh opening of the foreign matter removing member 25a is stirred and conveyed and circulated in the second developer stirring region 24 along the partition wall member 25 to be further stirred. It will be.

  7 and 8 are diagrams showing another example of the foreign matter removing member formed on the partition wall member 25. FIG. FIG. 7A is a cross-sectional view of the partition wall member 25 on which the foreign matter removing member 25b is formed as viewed from the end on the second developer stirring region 24 side. FIG. 7B is a plan view of the foreign matter removing member 25c. FIG. 8A is a side view of the foreign matter removing member 25d formed on the partition wall member 25. FIG. FIG. 8B is a side view of the foreign matter removing member 25 e formed on the partition wall member 25.

  As the foreign matter removing member formed on the partition wall member 25, as shown in FIG. 7A, the entire surface of the partition wall member 25 on the side where the second stirring and conveying member 28 is disposed (second stirring and conveying member 28). A flat and mesh-like foreign matter removing member 25b may be formed in a portion corresponding to (except for a portion in contact with). Moreover, as shown in FIG.7 (b), it is good also as the foreign material removal member 25c so that the whole surface of the partition wall member 25 may become mesh shape. As described above, when the foreign matter removing members 25b and 25c having a mesh surface are formed on the connecting portion between the first developer stirring region portion 23 and the second developer stirring region portion 24, the mesh portion is It becomes a blocking area part that blocks the conveyance of the developer, and the mesh opening part becomes a passing area part through which the developer passes.

  Each of the mesh-like foreign matter removing members 25b and 25c is configured such that only one end is fixed to the wall surface of the developing tank 12 and the other end is a free end, similar to the foreign matter removing member 25a described above. Capturing paper dust and foreign matters larger than a predetermined size that cannot pass through the mesh opening.

  Further, as shown in FIG. 8A, a plurality of convex foreign matter removing members 25 d that protrude from the surface of the partition wall member 25 toward the inner side of the second developer stirring region 24 may be used. Further, as shown in FIG. 8B, a plurality of hook-shaped foreign matter removing members 25e protruding from the surface of the partition wall member 25 toward the inner side of the second developer stirring region 24 may be used. The foreign matter removing members 25d and 25e formed so as to protrude from the surface of the partition wall member 25 both catch paper dust and foreign matter in the developer that is stirred and conveyed along the surface of the partition wall member 25. To capture.

  In addition to the partition wall member 25, a part or all of the second stirring intermediate wall member 42 is meshed in order to improve paper powder and foreign matter capturing ability in the second developer stirring region 24. Good. Moreover, you may provide the convex-shaped or hook-shaped foreign material removal member which protrudes from the surface of the 2nd stirring intermediate wall member 42. FIG. In addition, a convex or hook-shaped foreign matter removing member that protrudes inward may be provided on the inner wall surface of the second developer stirring region 24.

  As described above, in the developing devices 10 and 60, the developing roller 11 is supplied with the developer whose stirring efficiency of the entire developing tank 12 is improved, the toner density becomes uniform, and the charging performance of the recovered toner 52 is restored. The electrostatic latent image can be developed by supplying it to the photoconductor 2 via. Therefore, the image forming apparatus 100 including the developing devices 10 and 60 can form a high-quality image with a uniform image density, excellent dot reproducibility, and prevention of fogging over a long period of time.

  Here, the image density can be measured using a portable spectral colorimetry densitometer (trade name: X-Rite 939, manufactured by X-Rite). The dot reproducibility can be easily evaluated by printing isolated dots of 1 dot printing-3 not printing, and measuring the density of the area including the isolated dots with a portable spectrophotometric densitometer. The fog can be evaluated by measuring the density of a portion without printing and the density of paper that has not passed through the printing process with a portable spectrocolorimetric densitometer and measuring the difference.

  Note that the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope disclosed in the claims, and obtained by appropriately combining technical means disclosed in different embodiments. Such embodiments are also included in the technical scope of the present invention.

1 is a diagram illustrating a configuration of a developing device 10 according to a first embodiment of the present invention. 1 is a cross-sectional view illustrating a configuration of an image forming unit 1 of an image forming apparatus 100 according to an embodiment of the present invention. It is a figure which shows the shape of the 2nd stirring conveyance member. 4 is a graph showing a relationship between a conveyance speed and a conveyance amount according to a difference in pitch interval P of screw blades 28a in a second agitation conveyance member 28. 6 is a graph showing a relationship between a post-supply elapsed time, a toner charge amount, and a toner concentration when the collected toner is supplied into the developing tank. It is a figure which shows the structure of the developing device 60 which is 2nd Embodiment of this invention. It is a figure which shows the other example of the foreign material removal member formed in the partition wall member. It is a figure which shows the other example of the foreign material removal member formed in the partition wall member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming unit 2 Photoconductor 10,60 Developing device 11 Developing roller 12 Developing tank 14 Toner sensor 23 First developer stirring area 24 Second developer stirring area 25 Partition wall members 25a, 25b, 25c, 25d, 25e Foreign matter removing member 28 Second agitating and conveying member 29 First agitating and conveying member 41 First agitating intermediate wall member 42 Second agitating intermediate wall member 49 New toner supply roller 49a New toner supply port 51 Collected toner supply roller 51a Collected toner supply port

Claims (11)

In a developing device for developing an electrostatic latent image formed on a photoreceptor using a developer containing toner and a carrier,
A developer carrying member that is rotatably provided facing the photoconductor and supplies toner to an electrostatic latent image on the photoconductor;
A housing-like developer accommodating portion for accommodating a developer, having a length substantially equal to the axial length of the developer carrying member, for receiving replenishment of new toner which is unused toner A new toner replenishing port is formed, and a first developer agitation area part for supplying the developer to the developer carrying member, and a used toner collected and collected so as to be connected to the first developer agitation area part A developer accommodating portion comprising a second developer stirring region portion in which a collected toner replenishing port for receiving replenishment of certain collected toner is formed;
The developer carrier is rotatably supported by the developer container, and has a length exceeding the axial length of the developer carrier, and one end is the longitudinal end of the second developer agitation region A first agitating and conveying member that is provided so as to reach the vicinity of the unit and that agitates and conveys the developer in the first developer agitating region toward the second developer agitating region;
Opposite to the developer carrier via the first agitating and conveying member, the developer container is rotatably supported by the developer container, and has a length exceeding the length in the axial direction of the developer carrier and one end thereof is the second. A second agitating and conveying member that is provided so as to reach the vicinity of the end in the longitudinal direction of the developer agitating region, and agitates and conveys the developer in the second developer agitating region toward the first developer agitating region And comprising
The connecting portion where the first developer stirring region portion and the second developer stirring region portion are connected to each other includes a blocking region portion that prevents the developer from being conveyed and a passage region portion through which the developer passes. A developing device, wherein the developing device is formed to have a predetermined area ratio with respect to a surface. In the first developer stirring region portion, a flat plate-like first stirring intermediate wall member extending in the axial direction of the developer carrier is provided between the first stirring transport member and the second stirring transport member.
A flat second stirring intermediate wall member extending in the axial direction of the developer carrying member is provided in the second developer stirring region portion between the first stirring transport member and the second stirring transport member. The developing device according to claim 1.   The mesh foreign matter removing member having a mesh-like mesh opening is formed in at least a part of at least one of the blocking region portion and the second stirring intermediate wall member. The developing device described.   At least one surface of at least one of the blocking region portion and the second stirring intermediate wall member has a plurality of convex shapes protruding from the surface toward the inward side of the second developer stirring region portion, or The developing device according to claim 2, wherein a hook-shaped protruding foreign matter removing member is formed.   5. A plurality of protruding or hook-shaped protruding foreign matter removing members that protrude inward are formed on at least a part of the inner wall surface of the second developer stirring region. The developing device according to any one of the above. In the first developer agitation region, a portion of the developer that is transported is located upstream of the developer carrier in the developer transport direction and downstream of the new toner supply port in the developer transport direction. Detecting means for detecting toner density;
A toner hopper for storing new toner and supplying the new toner toward the new toner supply port;
6. The developing device according to claim 1, further comprising a control unit configured to control the toner hopper based on a detection result of the detection unit to supply new toner.   The mesh foreign matter removing member is formed in a flat plate shape having a predetermined thickness, and only an end corresponding to one side is fixed to the inner wall surface of the developer containing portion, and the other end is a free end. The developing device according to claim 3, wherein the developing device is provided.   The developing device according to claim 3, wherein the mesh foreign matter removing member is arranged such that a punching direction of the mesh opening portion is the same in a developer transport direction.   The developing device according to claim 3, wherein the mesh foreign matter removing member is a member made of stainless steel, or a member whose surface is plated with a tin cobalt alloy or gold.   The developing device according to claim 1, wherein the new toner has a shape factor SF-1 of 100 to 160 and a shape factor SF-2 of 100 to 150.   An image forming apparatus comprising the developing device according to claim 1.

Images