JP2012063549A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device that suppresses an image defect including density unevenness by ensuring proper amount of developer to be discharged even with developer having high aggregation degree.SOLUTION: A developer discharge regulation member 401 is provided at a developer discharge port 48a of a developer container 41. The developer discharge regulation member 401 is formed of a mesh-like net and has a plurality of apertures that divide the discharge port 48a in a direction of gravitational force. The interval of the plurality of apertures in the direction of gravitational force is regulated so that the surface level of developer in use is between an upper edge 50b and a lower edge 50a of the developer discharge port 48a even with developer having high aggregation degree.

Description

  The present invention uses a developing device for making a visible image by attaching a developer to a latent image formed on an image carrier, and an electrophotographic method or an electrostatic recording method provided with the developing device. The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer, a facsimile, and a composite machine of these.

  2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic method generally charges the surface of a drum-shaped photoconductor, which is an image carrier, uniformly by a charger, and the charged photoconductor is converted into image information by an exposure device. In response to the exposure, an electrostatic latent image is formed on the photoreceptor. The electrostatic latent image formed on the photosensitive member is visualized as a toner image by a toner as a developer using a developing device. The visualized image is transferred to a recording material by a transfer device. Thereafter, the toner image transferred onto the recording material is melted and fixed onto the recording material with heat and pressure by a fixing device.

  As such a developing apparatus, there is one that uses a two-component developer including non-magnetic toner particles (toner) as a developer and magnetic carrier particles (carrier). In particular, in color image forming apparatuses, it is not necessary to include a magnetic substance in the toner, so that it is widely used for reasons such as good color. In the developing device using the two-component developer, the toner and the carrier are conveyed in the developing container while being agitated, and the developer is carried on the developing sleeve which is a developer carrying member. The carrying amount of the developer carried on the developing sleeve is regulated by a regulating blade that is a developer regulating member. Thereafter, by applying a developing bias between the developing sleeve and the photosensitive member, only the toner is transferred to the electrostatic latent image formed on the surface of the photosensitive member, and a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive member. Is formed.

  In recent years, an apparatus has been proposed in which deterioration of charging performance can be suppressed by supplying developer to the developing apparatus (see, for example, Patent Document 1). This apparatus has a replenishing device for replenishing a new developer into the developing container of the developing device. Then, the developer in the developing container that has become excessive due to replenishment of new developer by the replenishing device overflows and is discharged from the developer discharge port provided on the wall surface of the developing container (ACR configuration). Further, the discharged developer is recovered by a recovery device.

  In an apparatus having such an ACR configuration, replenishment of new developer and discharge of developer are sequentially repeated, whereby the deteriorated developer in the developer container is replaced with newly supplied toner and carrier. It has come to go. As a result, the developing characteristics of the developer in the developing container are maintained constant, and the charging characteristics of the developer can be maintained to suppress a reduction in copy image quality. As a result, the serviceman or the like can extend the developer replacement frequency or eliminate the replacement.

  Further, as a developing device having such an ACR configuration, there is also known a structure in which a shutter is provided at a developer discharge port so that newly supplied developer is not discharged (see Patent Document 2). Also known is a structure in which a comb-like member for preventing the developer from scattering is provided at the developer outlet (see Patent Document 3).

JP 59-1000047 A Japanese Patent Laid-Open No. 11-231624 JP 2000-112238 A

  However, in the case of the developing device having the ACR configuration as described above, the developer discharge characteristics change due to the change in the degree of aggregation of the developer. For example, when an output product with a low image ratio is output continuously, the toner charge amount increases, and at the same time, the additive added to the toner is released or embedded, thereby causing the degree of aggregation of the developer. Becomes higher. When the degree of aggregation of the developer becomes high, that is, when the developer becomes difficult to move, the bulk density of the developer changes and the surface of the developer becomes apparently high. Further, since a developer having a high degree of aggregation is discharged as an aggregate, the amount discharged is increased as compared with a developer having a low degree of aggregation.

  Furthermore, a developer with a high degree of aggregation may not stop the discharge of the developer from the developer discharge port even if the weight of the developer is small, and the amount of developer in the developer container may be reduced more than expected. . When the amount of developer in the developing container is smaller than expected, there may be image defects such as density unevenness in the longitudinal direction of the developing sleeve, or screw pitch unevenness in which the density unevenness occurs at the screw pitch.

  Patent Documents 2 and 3 describe a structure in which a shutter is provided at the discharge port and a structure in which a comb-like member is provided. In either case, the change corresponds to a change in the degree of aggregation of the developer. It is not a configuration. Further, in the case of the structure described in Patent Document 2, a configuration for opening and closing the shutter is necessary, which complicates the configuration and increases the cost.

  In view of such circumstances, the present invention has been devised in order to suppress image defects such as density unevenness by making the amount of developer discharged appropriate even when the degree of aggregation of the developer increases.

  The present invention relates to a developer container that contains a two-component developer containing toner and a carrier, a developer carrier that carries and conveys the developer in the developer container, and supplies the developer to the development area of the image carrier. A developer conveying member that conveys the developer while stirring in the developer container, the developer container having a developer supply port for supplying the developer into the developer container, and the developer container A developer discharge port provided at a predetermined height from the bottom in the gravitational direction of the developer for discharging the developer from the developer container, and supplying developer from the developer supply port in a used state. In the developing device that repeatedly discharges the developer from the developer discharge port, a developer discharge regulating member that is provided at the developer discharge port and has a plurality of openings that divide the developer discharge port in the direction of gravity. And having an interval in the gravity direction of the plurality of openings, Even when the cohesion degree of the image agent is higher than the initial state, the developer surface is set so as to be positioned between the upper edge and the lower edge in the gravity direction of the developer discharge port in the use state. The developing device is characterized.

  According to the present invention, by regulating the intervals in the gravitational direction of the plurality of openings of the developer discharge regulating member, even if the degree of aggregation of the developer is higher than the initial state, the developer surface of the developer is discharged in the usage state. It is located between the upper edge and the lower edge in the gravity direction of the outlet. For this reason, even when the degree of aggregation of the developer increases, the amount of developer discharged can be made appropriate to suppress image defects such as density unevenness.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. 1 is a schematic cross-sectional view of a developing device according to a first embodiment. The figure which cut | disconnected a part and was seen from the upper direction of FIG. FIG. 3 is a schematic diagram illustrating a configuration of a developer discharge unit. The schematic diagram for demonstrating the aggregation degree of a developing agent. FIG. 3 is an enlarged view showing a first example of a developer regulating member according to the first embodiment. The enlarged view which similarly shows the 2nd example. (A) is a figure which shows the relationship between the idling time of a conveyance screw, and a repose angle, (B) is a figure which shows the relationship between the number of image formation, and a repose angle, respectively. Schematic for demonstrating the measuring method of a repose angle. FIG. 3 is a schematic diagram of toner and carrier in a developer. (A) is a developer discharge characteristic when the angle of repose is small, and (B) is a graph showing the developer discharge characteristic when the angle of repose is large. FIG. 5 is a schematic sectional view of a developing device according to a second embodiment of the present invention. FIG. 10 is a schematic diagram illustrating a configuration of a developer discharge unit according to a third embodiment of the present invention. FIG. 10 is a schematic diagram illustrating two examples of a developer regulating member according to a fourth embodiment of the present invention.

<First Embodiment>
A first embodiment of the present invention will be described with reference to FIGS.

[Image forming apparatus]
First, the overall configuration and operation of the image forming apparatus of this embodiment will be described with reference to FIG. The image forming apparatus 100 forms an image according to image information from a document reading apparatus connected to the image forming apparatus main body (apparatus main body) or a host device such as a personal computer connected to the apparatus main body so as to be communicable. In the case of this embodiment, four-color full-color images of yellow (Y), magenta (M), cyan (C), and black (Bk) are recorded on a recording material (recording paper, plastic sheet, cloth, etc.) using an electrophotographic system. ) Can be formed.

  For this purpose, the image forming apparatus 100 has a quadruple tandem configuration, and forms first, second, third, and fourth images that respectively form yellow, magenta, cyan, and black images as a plurality of image forming units. Image forming units (image forming stations) PY, PM, PC, and PBk. Then, while the intermediate transfer belt 51 provided in the transfer device 5 as a transfer unit moves in the direction of the arrow shown in the figure and passes through each image forming unit, images of each color are superimposed on the intermediate transfer belt 51 in each image forming unit. . A recorded image is obtained by transferring the multiple toner images superimposed on the intermediate transfer belt 51 onto a recording material. In this embodiment, a two-component developer containing a nonmagnetic toner and a magnetic carrier is used as the developer.

  The configuration of each image forming station is substantially the same except that the development colors are different. Therefore, in the following, in order to indicate that the element belongs to any one of the image forming stations unless particularly distinguished. The subscripts Y, M, C, and K given to the reference numerals are omitted, and a general description will be given.

  The image forming station P includes a drum-shaped photosensitive member (photosensitive drum) 1 as an image carrier. Around the outer periphery of the photoreceptor 1, there are a charger 2 as a charging means, an exposure device 3 as an exposure means (for example, a laser exposure optical system), a developing device 4 as a developing means, a transfer device 5, and a cleaning device 7 as a cleaning means. A static elimination device 8 is provided as a static elimination means.

  The transfer device 5 has an intermediate transfer belt 51 as an intermediate transfer member. The intermediate transfer belt 51 is wound around a plurality of rollers and rotates (circulates) in the direction of the arrow shown in the drawing. A primary transfer member 52 is disposed at a position facing each photoconductor 1 via the intermediate transfer belt 51. A secondary transfer member 53 is provided at a position facing one of the rollers around which the intermediate transfer belt 51 is wound.

  At the time of image formation, first, the surface of the rotating photoreceptor 1 is uniformly charged by the charger 2. Next, an electrostatic latent image is formed on the photosensitive member 1 by scanning and exposing the surface of the charged photosensitive member 1 according to an image information signal by the exposure device 3. The electrostatic latent image formed on the photosensitive member 1 is visualized as a toner image with the toner of the developer using the developing device 4. At this time, the replenisher is supplied from the hopper 20 to the developing device 4 through a replenishment path (not shown) according to the consumed toner amount. The toner image formed on the photoreceptor 1 is intermediated by the action of the primary transfer bias applied to the primary transfer member 52 in the primary transfer portion (primary transfer nip) where the intermediate transfer belt 51 and the photoreceptor 1 abut. Transfer (primary transfer) is performed on the transfer belt 51. For example, when a four-color full-color image is formed, a toner image is transferred from each photoreceptor 1 onto the intermediate transfer belt 51 sequentially from the first image forming unit PY, and the four-color toner image is formed on the intermediate transfer belt 51. A superimposed toner image is formed.

  On the other hand, a recording material accommodated in a cassette 9 as a recording material accommodating portion is conveyed by a recording material conveying member such as a pickup roller, a conveying roller, and a registration roller. The recording material is conveyed in synchronization with the toner image on the intermediate transfer belt 51 at a secondary transfer portion (nip portion) where the intermediate transfer belt 51 and the secondary transfer member 53 abut. The multiple toner images on the intermediate transfer belt 51 are transferred onto the recording material by the action of the secondary transfer bias applied to the secondary transfer member 53 in the secondary transfer portion.

  Thereafter, the recording material separated from the intermediate transfer belt 51 is conveyed to the fixing device 6. The toner image transferred onto the recording material is melted and mixed by being heated and pressurized by the fixing device 6 and is fixed onto the recording material. Thereafter, the recording material is discharged out of the apparatus.

  Deposits such as toner remaining on the photoreceptor 1 after the primary transfer step are collected by the cleaning device 7. Further, the electrostatic latent image remaining on the photosensitive member 1 is erased by the static eliminator 8. Thereby, the photoreceptor 1 is prepared for the next image forming process. Further, deposits such as toner remaining on the intermediate transfer belt 51 after the secondary transfer step are removed by the intermediate transfer body cleaner 54.

  Note that the image forming apparatus 100 can also form a single-color or multi-color image using an image forming unit for a desired single color or some of four colors, such as a black single-color image. .

[Two-component developer]
Next, the two-component developer used in this embodiment will be described. The toner includes colored resin particles containing a binder resin, a colorant, and other additives as necessary, and colored particles to which an external additive such as colloidal silica fine powder is externally added. Yes. The toner is a negatively chargeable polyester resin, and the volume average particle diameter d is 4.0 μm or more and 10.0 μm or less (4.0 μm ≦ d ≦ 10.0 μm). Preferably, the thickness is 5.0 μm or more and 8.0 μm or less (5.0 μm ≦ d ≦ 8.0 μm). In this embodiment, d is set to 7.0 μm.

As the carrier, for example, surface-oxidized or non-oxidized iron, nickel, cobalt, manganese, chromium, rare earth and other metals, alloys thereof, oxide ferrite, etc. are preferably usable. The method for producing magnetic particles is not particularly limited. The carrier has a volume average particle diameter D of 10.0 μm or more and 60.0 μm or less (10.0 μm ≦ D ≦ 60.0 μm). Preferably, 20.0 to 60.0 μm (20.0 μm ≦ D ≦ 60.0 μm), more preferably 30.0 to 50.0 μm (30.0 μm ≦ D ≦ 50.0 μm). The resistivity is 10 ⁷ Ωcm or more, preferably 10 ⁸ Ωcm or more. In this embodiment, a carrier having a volume average particle diameter D of 40 μm, a resistivity of 5 × 10 ⁸ Ωcm, and a magnetization amount of 260 emu / cc (260 × 10 ³ A / m) is used.

  For the toner, the volume average particle size was measured by the following apparatus and method. As a measuring device, a Coulter counter TA-II type (manufactured by Coulter), an interface for outputting number average distribution and volume average distribution (manufactured by Nikka) and a CX-I personal computer (manufactured by Canon) were used. A 1% NaCl aqueous solution prepared using primary sodium chloride was used as the electric field aqueous solution.

  The measuring method is as follows. That is, 0.1 ml of a surfactant, preferably alkyl benzene sulfonate, is added as a dispersant to 100 to 150 ml of the electric field aqueous solution, and 0.5 to 50 mg of a measurement sample is added. The aqueous solution of the electric field in which the sample is suspended is dispersed for about 1 to 3 minutes with an ultrasonic disperser, and the particle size distribution of 2 to 40 μm particles is measured using the above Coulter Counter TA-II with a 100 μm aperture as the aperture. To obtain a volume average distribution. From the volume average distribution thus obtained, a volume average particle size was obtained.

  Moreover, the resistivity of the magnetic carrier was measured as follows. That is, using a sandwich type cell having a measurement electrode area of 4 cm and an interelectrode spacing of 0.4 cm, an applied voltage E (V / cm) between both electrodes is applied to one electrode under a pressure of 1 kg. Measured by a method of obtaining the carrier resistivity from the current flowing in the circuit. Further, the volume average particle size of the magnetic carrier was measured by dividing the range of particle size of 0.5 to 350 μm into 32 logarithms on a volume basis using a laser diffraction particle size distribution measuring device HEROS (manufactured by JEOL). And the number of particles in each channel was measured. From the measurement results, the median diameter of 50% volume was defined as the volume average particle diameter.

  The magnetic properties of the magnetic carrier were measured using an oscillating magnetic field automatic magnetic recording apparatus BHV-30 manufactured by Riken Denshi Co., Ltd. The magnetic properties of the carrier powder were 795.7 kA / m and 79.58 kA / m external magnetic fields, respectively, and the magnetization strength of the magnetic carrier was determined. The sample for measuring the magnetic carrier is prepared in a state packed in a cylindrical plastic container so as to be sufficiently dense. In this state, the magnetization moment is measured, and the actual weight of the sample filled as described above is measured to determine the magnetization strength (emu / g). Further, the true specific gravity of the magnetic carrier particles is obtained by, for example, a dry automatic densitometer Accupic 1330 (manufactured by Shimadzu Corporation), and the true specific gravity is multiplied by the magnetization intensity obtained as described above. The intensity of magnetization per unit volume can be obtained.

[Developer]
Next, the developing device 4 will be described with reference to FIGS. The developing device 4 includes a developing container 41 in which a two-component developer containing toner and a carrier as a developer is accommodated. Further, a developing sleeve 44 as a developer carrying means and a regulating blade 46 for regulating the ears of the developer carried on the developing sleeve 44 are arranged at a position facing the photoreceptor 1 of the developing container 41. .

  Further, the inside of the developing container 41 is partitioned into a developing chamber 41a and a stirring chamber 41b by a partition wall 41c extending substantially in the direction perpendicular to the paper surface, and the developer is separated into the developing chamber 41a and the stirring chamber 41b. Contained.

  In the developing chamber 41a and the stirring chamber 41b, first and second conveying screws 42 and 43 are arranged as developer conveying members, respectively. The first conveying screw 42 is disposed substantially parallel to the bottom of the developing chamber 41a along the axial direction of the developing sleeve 44, and rotates in the direction indicated by the arrow (clockwise direction) in the developing chamber 41a. The agent is conveyed while stirring in one direction along the axial direction. The reason for the clockwise rotation is that it is advantageous from the viewpoint of supplying the developer to the developing sleeve 44. The second conveying screw 43 is disposed at the bottom of the stirring chamber 41b substantially in parallel with the first conveying screw 42, and rotates in the opposite direction (counterclockwise) to the first conveying screw 42. The developer in 41b is conveyed while being stirred in the opposite direction to the first conveying screw.

  As described above, the developer is conveyed by the rotation of the first and second conveying screws 42 and 43, so that the developer passes through the openings (that is, the communicating portions) 41d and 41e at both ends of the partition wall 41c. Cycled between.

  Further, the developer container 41 is provided at a predetermined height from the bottom of the developer container 41 in the gravity direction, and a developer supply port 49 for supplying the developer into the developer container, and discharges the developer from the developer container. A developer discharge port 48a. Here, the gravitational direction is the vertical direction of FIG. In the case of this embodiment, a developer replenishing port 49 is provided in the upper part of the stirring chamber 41b, and from the hopper 20 (see FIG. 1) for replenishing the replenished developer in which the toner and the carrier are mixed, through the developer replenishing port 49. Developer is supplied into the stirring chamber 41b. On the other hand, the developer discharge port 48a is provided at a predetermined height from the bottom of the side wall 41d of the stirring chamber 41b, and discharges the developer beyond the lower edge 50a of the developer discharge port 48a. The developer discharged from the developer discharge port 48a is transported to a collection box (not shown) by the developer transport member 48b in the surplus developer storage chamber 48.

  The developing container 41 has an opening at a position corresponding to the developing region α facing the photosensitive member 1, and the developing sleeve 44 is rotatably disposed in the opening so that the developing sleeve 44 is partially exposed in the direction of the photosensitive member 1. Has been. The developing sleeve 44 and the photosensitive member 1 are close to each other. For example, the diameter of the developing sleeve 44 is 20 mm, the diameter of the photosensitive member 1 is 80 mm, and the closest region between the developing sleeve 44 and the photosensitive member 1 is a distance of about 300 μm. As a result, the developing is carried out in a state where the developer conveyed to the developing region α by the developing sleeve 44 is in contact with the photosensitive member 1.

  Such a developing sleeve 44 is made of a nonmagnetic material such as aluminum or stainless steel, and a magnet roller 45 serving as a magnetic field means is installed in a non-rotating state therein. The magnet roller 45 has a magnetic pole N3, a magnetic pole N2, a magnetic pole S2, and a magnetic pole in order from the developing pole S1 disposed facing the photoreceptor 1 in the developing area α to the developing sleeve 44 in the rotation direction (arrow direction, clockwise). N1.

  At the time of development, the developing sleeve 44 rotates (carrying and transporting) while the developer is carried on the developing sleeve 44 by the magnetic attraction force of the magnet roller 45. The developing sleeve 44 carries a two-component developer whose layer thickness is regulated by the cutting of the magnetic brush by the regulating blade 46, and conveys this to the developing area α facing the photoreceptor 1. Then, a developer is supplied to the electrostatic latent image formed on the photoreceptor 1 to develop the latent image.

  At this time, in order to improve the developing efficiency, that is, the application rate of toner to the latent image, a developing bias voltage in which a DC voltage and an AC voltage are superimposed is applied to the developing sleeve 44 from a power source. In the present embodiment, a DC voltage of −500 V, a peak-to-peak voltage Vpp of 800 V, and a frequency f of 12 kHz are used. However, the DC voltage value and the AC voltage waveform are not limited to this. In general, in the two-component magnetic brush development method, when an AC voltage is applied, the development efficiency increases and the image becomes high-quality, but conversely, fogging easily occurs. For this reason, fogging is prevented by providing a potential difference between the DC voltage applied to the developing sleeve 44 and the charged potential (that is, the white background potential) of the photosensitive member 1.

  In the developing area α, the developing sleeve 44 of the developing device 4 is moved in the forward direction and the moving direction of the photosensitive member 1, and the peripheral speed ratio is 1.75 times that of the photosensitive member. The peripheral speed ratio is set between 0.5 and 2.5 times, preferably between 1.0 and 2.0 times. The larger the moving speed ratio, the higher the development efficiency. However, if the movement speed ratio is too large, problems such as toner scattering and developer deterioration occur. Therefore, the moving speed ratio is preferably set within the above range.

Further, the regulation blade 46 which is a spike cutting member is made of a non-magnetic member formed of plate-like aluminum or the like extending along the longitudinal axis of the developing sleeve 44, and the developing sleeve is rotated in the rotational direction of the photosensitive member 1. Arranged upstream. Then, both the toner of the developer and the carrier pass between the tip of the regulating blade 46 and the developing sleeve 44 and are sent to the developing area. It should be noted that by adjusting the gap (gap) between the regulating blade 46 and the surface of the developing sleeve 44, the amount of spike of the developer magnetic brush carried on the developing sleeve 44 is regulated, and the development conveyed to the developing region α. The dosage is adjusted. For example, the regulating blade 46 regulates the developer coating amount per unit area on the developing sleeve 44 to 30 mg / cm ² . The gap between the regulating blade 46 and the developing sleeve 44 is set to 200 to 1000 μm, preferably 300 to 700 μm. In this embodiment, it is set to 500 μm.

[Developer discharge regulating member]
Here, the discharge of the developer from the developer discharge port 48a will be described in detail. FIG. 4 is a schematic diagram of the developer discharge port 48a when the developer container 41 is viewed from the stirring chamber 41b side, and the developer discharge regulating member 401 that covers the developer discharge port 48a. In the developing device 4, the developer is conveyed by the rotation of the first and second conveying screws 42 and 43, so that the developer passes through the openings (that is, the communicating portions) 41 d and 41 e at both ends of the partition wall 41 c and the developing chamber 41 a and the stirring chamber 41 b. It is circulated between. Further, the developing device 4 in the present embodiment employs an ACR configuration in which developer replenishment and developer discharge are sequentially repeated in order to maintain the charging characteristics of the developer. That is, the developing device 4 has a configuration in which the developer supply from the developer supply port 49 and the developer discharge from the developer discharge port 48a are repeated in the use state.

  As described above, the discharge amount from the developer discharge port 48a changes due to the change in the degree of aggregation of the developer. As a result, the amount of developer in the developing container 41 is not stable, and density unevenness and screw pitch unevenness in the longitudinal direction of the developing sleeve may occur. For example, when an output product with a low image ratio is output continuously, the toner charge amount increases, and at the same time, the additive added to the toner is released or embedded, thereby causing the degree of aggregation of the developer. Changes. At this time, as shown in FIG. 5, even with the same amount of developer, the bulk density of the developer changes depending on the degree of aggregation. That is, as shown in FIG. 5 (A), when the developer aggregation degree is low, the bulk density h becomes small, and as shown in FIG. 5 (B), when the developer aggregation degree is high. The bulk density H is increased. When the bulk density of the developer is increased, the developer surface is apparently increased and is unnecessarily discharged from the developer discharge port 48a.

  Further, since a developer having a high degree of aggregation is discharged as an aggregate, the amount discharged is increased as compared with a developer having a low degree of aggregation. For this reason, the amount of discharge from the developer discharge port 48a changes due to a change in the degree of aggregation of the developer, causing density unevenness in the longitudinal direction of the developing sleeve, or screw pitch unevenness in which this density unevenness occurs at the screw pitch. In some cases, such as image defects may occur.

  Therefore, in the present embodiment, the developer discharge regulating member 401 is provided at the developer discharge port 48a and has a plurality of openings that divide the developer discharge port 48a in the direction of gravity. In the case of the present embodiment, such a developer discharge regulating member 401 is constituted by a mesh-like net, and the developer discharge port 48a is covered by this net. Such a developer discharge regulating member 401 employs a mesh under the following conditions. That is, even if the intervals in the gravity direction of the plurality of openings are higher than the initial state, the developer surface is in the state of use where the developer surface is the upper edge 50b and the lower edge 50a in the gravity direction of the developer discharge port 48a. It is set to be between.

  Such a developer discharge regulating member 401 is configured, for example, as shown in FIG. 6 or FIG. In the case of the structure shown in FIG. 6, it is knitted into a mesh shape having an inner diameter of 300 μm, for example, with a stainless steel wire (W). Such a mesh can be substituted with, for example, a commercially available and widely used one, and can be reduced in cost because it is inexpensive. In the case of the configuration shown in FIG. 7, for example, a molded plate (M) is formed by resin molding, etching, pressing, or the like into a mesh shape having an inner diameter of 300 μm. In such a configuration, since the mesh shape is accurate, highly accurate and accurate developer discharge is performed, and highly stable image formation can be achieved.

  Next, an example of the developer discharge characteristic when the mesh that is the developer discharge regulating member 401 is provided in the developer discharge port 48a will be described. In order to fulfill the function as a developer discharge port provided with the developer discharge regulating member 401 in this embodiment, a mesh is required so that the developer discharge characteristics do not change due to the change in the degree of aggregation. That is, when the aggregation degree is low, the developer is discharged regardless of the presence or absence of the developer discharge regulating member, and it is required that the developer discharge decreases as the aggregation degree increases. However, there is no effect if it is discharged even when the degree of aggregation is low or when it is discharged even when the degree of aggregation is high. That is, it becomes meaningless in the situation where the mesh opening interval is smaller than the toner or smaller than the carrier and the developer is hardly discharged or the mesh opening interval is too wide to obtain the mesh effect.

  In addition, as described above, since the bulk density changes depending on the degree of aggregation of the developer and the developer surface of the developer changes, the gap between the openings in the mesh corresponds to the direction in which the agent surface changes as the mesh opening interval. However, this affects the discharge characteristics of the developer. Therefore, in the present embodiment, the distance between the openings of the mesh in the direction of gravity is appropriately regulated.

  Here, the degree of aggregation of the developer can be measured by the angle of repose. An appropriate range of the repose angle of the developer in the present embodiment is 25 to 50 °, preferably 30 to 45 °. If the angle of repose of the two-component developer is less than 25 °, the problem of scattering and hollowing out during multiple transfers due to high fluidity, and maintaining transferability during high-speed printing (when many printings are performed) are maintained. Can not be satisfied enough. When the angle of repose is larger than 50 °, the scattering at the initial stage of printing and the level of hollowing out are good, but at high speed and durability, developability deteriorates and the load on the conveying screw increases, leading to screw lock. Therefore, in the present embodiment, the angle of repose when not used as a two-component developer is 25 °, and the angle of repose when the developing device 4 of the present embodiment is idled at 50 ° C. and 15% relative humidity for 24 hours. Is used with an angle of 50 °.

FIG. 8A shows the transition of the angle of repose when idling at a temperature of 50 ° C. and a relative humidity of 15%. From this figure, it can be confirmed that the repose angle converges to about 50 ° in about 10 hours of idling. FIG. 8B shows the transition of the angle of repose when the image forming apparatus according to the present embodiment changes the image ratio (Duty) and forms 100 × 10 ³ images. As shown in the figure, the angle of repose increases when the image ratio is low. From the above, it can be seen that an angle of repose of 50 ° is the lowest fluidity of this developer.

  FIG. 9 is a schematic explanatory diagram for explaining an example of a method for measuring an angle of repose. The angle of repose Φ of the toner in this embodiment was measured using the following method. First, the measuring device is a powder tester PT-N type (Hosokawa Micron Corporation). Moreover, the measuring method is based on the measurement of the angle of repose in the instruction manual attached to the powder tester PT-N type (the opening of the sieve 301 is 710 μm, the vibration time is 180 s, and the amplitude is 2 mm or less). The developer is dropped from the funnel 303 onto the disk 302, and the angle formed by the generatrix of the developer 500 deposited conically on the disk 302 and the surface of the disk 302 is determined as the repose angle.

  However, after the sample was allowed to stand overnight at 23 ° C. and a relative humidity of 60% (hereinafter referred to as 60% RH), the angle of repose was measured with a measuring device in an environment of 23 ° C. and 60% RH. The value obtained by repeating the measurement once and taking the arithmetic average is defined as Φ.

  Table 1 shows whether or not the developer passes when the repose angle of the developer is 25 ° and 50 ° when the distance x in the gravity direction of the opening of the developer discharge regulating member 401 is changed. The circles in Table 1 indicate the case where the developer almost passes through the developer discharge regulating member, the triangle indicates the case where a part of the developer passes, and the case where the cross hardly passes.

  Here, as shown in FIG. 10, it is assumed that the toner t and the carrier c are true spheres, and that the toner t is ideally present for one layer with respect to the carrier c. When the diameter (volume average particle diameter) of the toner t is d and the diameter (volume average particle diameter) of the carrier c is D, the diameter of one aggregate of the developer is (d × 2 + D).

From Table 1, when the degree of aggregation is low, the developer is discharged regardless of the presence or absence of the developer discharge regulating member, and the situation where the developer discharge decreases as the degree of aggregation increases is as follows.
1.5 × (d × 2 + D) ≦ x ≦ 50 × (d × 2 + D)

  Here, when the angle of repose is small, that is, when the flowability of the developer is high, the developer is less aggregated. In such a situation, there is a high possibility that the toner and carrier in the developer exist alone, and the toner and carrier can pass even if the interval between the openings of the developer regulating member is narrow. On the other hand, when the angle of repose is large, that is, when the flowability of the developer is low, the developer is often aggregated. In such a situation, the toner and carrier reach the developer discharge port 48a while a plurality of toners and carriers are present, so that the toner and the carrier may not be discharged unless a certain amount of space is secured.

  For this reason, as a condition for stably using the developing device 4, the developer discharge regulating member 401 is provided in the developer discharge port 48 a, and even when the developer aggregation degree is higher than the initial state, The developer surface is positioned between the upper and lower edges of the developer discharge port 48a in the direction of gravity. Specifically, even when the developer is supplied to the developing device 4 from the developer supply port 49 above the upper edge of the developer discharge port 48a under the condition that the angle of repose is maximized, Make sure the conditions are met. That is, the developer discharge regulating member is set so that the developer surface height when the developing device 4 is driven and becomes stable is between the upper edge 50b and the lower edge 50a of the developer discharge port 48a. 401 may be set, that is, the distance between the openings of the developer discharge regulating member 401 in the gravity direction may be regulated.

  The reason for regulating the opening interval of the developer discharge regulating member 401 in this way is as follows. That is, when the developer is in the stable state, the developer surface height is higher than the upper edge 50b of the developer discharge port 48a, which means that the developer is not properly discharged from the developer discharge port 49a. It means that. Accordingly, when the developer is replenished in order to form an image in such a state, the amount of developer in the developing container continues to increase, and the load on the conveying screw increases, leading to screw locking. On the other hand, when the developer is in a stable state, the developer surface height is in the vicinity of the lower edge 50a of the developer discharge port 48a or lower than the lower edge 50a. Means. Therefore, despite the provision of the developer discharge restricting member 401, the developer in the developing container continues to decrease, causing uneven density in the longitudinal direction of the developing sleeve, and uneven screw pitch in which this uneven density occurs at the screw pitch. Image defects may occur.

  Next, the results of examining the relationship between the developer capacity in the developer container and the developer discharge amount (developer discharge characteristics) will be described with reference to FIG. Here, “when black is solid” in FIG. 11 indicates a case where printing is performed with an image ratio of 100% duty, and “when white is solid” indicates a case where printing is performed with 0% duty. Further, in FIG. 11, the discharge when the gap x in the gravity direction of the opening of the developer discharge regulating member 401 is 1.5 × (d × 2 + D) to 50 × (d × 2 + D) from the result of Table 1. Show the characteristics. 11A shows the discharge characteristics when the angle of repose is small, that is, when the angle of repose is 25 °, and FIG. 11B shows the discharge characteristics when the angle of repose is large, that is, when the angle of repose is 50 °. In the figure, the horizontal axis represents the developer weight, and the vertical axis represents the developer discharge amount per unit time.

  As is clear from FIG. 11, when the amount of developer is large, the amount of developer discharged increases, and when the amount of developer is small, the amount of developer discharged decreases. In addition, the discharge characteristics differ depending on the angle of repose. When the angle of repose is large, the discharge amount of the developer may not stop decreasing particularly when the image ratio is low.

  Further, when the angle of repose of the developer is small, as shown in FIG. 11A, if the gap x in the gravity direction of the opening of the developer discharge regulating member 401 is 2 × (d × 2 + D) or more, It turns out that it shows the same emission characteristic. It was also confirmed that the maximum capacity of the developer at this time was smaller than the capacity of the agent for starting screw lock. On the other hand, when the angle of repose of the developer is large, as shown in FIG. 11 (B), when the distance x in the gravity direction of the opening is from 2 × (d × 2 + D) to 40 × (d × 2 + D), the developer It has been found that the surface is in a stable state between the upper edge 50b and the lower edge 50a of the developer discharge port 48a. On the other hand, when the interval x is 1.5 × (d × 2 + D), the discharge amount decreases, and the developer continues to increase, causing screw lock. Further, when 50 × (d × 2 + D), the discharge amount is large and the lowering cannot be stopped, resulting in uneven density in the longitudinal direction of the developing sleeve and unevenness in screw pitch.

Therefore, in this embodiment, even if the degree of aggregation of the developer is higher than the initial state, the developer surface in the use state is between the upper edge 50b and the lower edge 50a in the gravity direction of the developer discharge port. The distance x in the gravitational direction of the opening of the developer discharge regulating member 401 located at is as follows.
2 × (d × 2 + D) ≦ x ≦ 40 × (d × 2 + D)

  That is, within this range, when the degree of aggregation is low, the developer is appropriately discharged regardless of the presence or absence of the developer discharge regulating member 401. On the other hand, even when the developer discharge becomes less as the degree of aggregation increases, there is no occurrence of density unevenness or screw pitch unevenness in the longitudinal direction of the developing sleeve, and screw locking does not occur.

In this embodiment, as described above, since d = 7 μm and D = 40 μm, the applicable range of the distance x in the gravity direction of the opening of the developer discharge regulating member 401 is
108 μm ≦ x ≦ 2160 μm
It becomes.

  As described above, according to the present embodiment, even when a change in the degree of aggregation of the developer occurs, image defects such as density unevenness in the longitudinal direction of the developing sleeve and screw pitch unevenness can be obtained without discharging the developer more than expected. We were able to provide a developing device that can be controlled.

  Note that the material of the photosensitive drum, the developer, and the configuration of the image forming apparatus used in the image forming apparatus of the present embodiment are not limited to these, and the present invention can be applied to various developers and image forming apparatuses. Needless to say. Specifically, the color and number of toners, the order in which each color toner is developed, the number of developer carrying members, the material of the developer discharge regulating member, and the like are not limited to the present embodiment. Further, regarding the configuration of the developing device, in this embodiment, the developing chamber 41a and the agitating chamber 41b are horizontally arranged, but the developing device in which the developing chamber 41a and the agitating chamber 41b are vertically arranged, or other forms. The present invention can also be applied to this developing device. Further, the developer level when the developing device 4 is driven and stabilized when the angle of repose is the largest is such that the developer surface height is between the upper edge 50b and the lower edge 50a of the developer discharge port 48a. Needless to say, if the interval of the developer discharge regulating member 401 is set, the present invention is applied.

<Second Embodiment>
A second embodiment of the present invention will be described with reference to FIG. Note that the basic configuration of the image forming apparatus of the present embodiment is the same as that of the first embodiment described above, and therefore the description of the entire image forming apparatus is omitted.

  In the case of the present embodiment, the developing device 4 includes a vibrating member 50 that is a vibrating unit that vibrates the developer discharge regulating member 401. The vibration member 50 includes a motor, and vibrates by rotating the motor. Further, the vibration member 50 is disposed so as to contact the developing container 41, and transmits the vibration to the developer discharge regulating member 401 via the developing container 41. In the present embodiment, the vibration member 50 is vibrated during non-image formation. For example, the image forming apparatus is vibrated when the power is turned on, when returning from the sleep state, or between sheets during continuous printing. In addition, as a vibration means for vibrating the developer discharge regulating member 401, other methods such as connecting the regulating member 401 to an external motor and applying vibration by the external motor may be used.

  According to the present embodiment, even when there is a developer aggregated more than expected in the developer container 41 or when foreign matter larger than the carrier enters and the developer discharge regulating member 401 is clogged. The clogging can be prevented by the vibration of the vibration member 50. That is, even if the developer discharge regulating member 401 is clogged, the clogging can be eliminated by vibrating the developer discharge regulating member 401 by the vibrating member 50 during non-image formation. As a result, it is possible to prevent the load of the conveying screw from being increased or screw-locked due to the increase in the developer more than expected due to clogging. Further, even when a change in the degree of aggregation of the developer occurs, image defects such as density unevenness in the longitudinal direction of the developing sleeve and screw pitch unevenness can be suppressed without discharging more developer than expected. Other configurations and operations are the same as those in the first embodiment.

<Third Embodiment>
A third embodiment of the present invention will be described with reference to FIG. In the present embodiment, the developer discharge restricting portion 401a is composed of a plurality of wires arranged in a direction (horizontal direction) intersecting the gravitational direction. And the space | interval of the gravity direction of a some wire is controlled similarly to the space | interval of the gravity direction of the some opening described in the above-mentioned 1st Embodiment.

  According to this embodiment, unlike the above-described embodiments, there is no restriction member in the gravity direction (vertical direction) of the developer discharge restriction member, and the horizontal width of the opening can be widened. For this reason, even when there is a developer aggregated more than expected in the developing container 41 due to a temperature rise or when a foreign substance larger than the carrier enters, it can be easily discharged from the developer discharge port 48a. . As a result, clogging of the developer discharge regulating member can be suppressed. Further, in the case of the present embodiment, clogging can be suppressed without providing the vibrating means as in the second embodiment described above, so that the developer configuration is complicated, the cost is reduced, and the cost is reduced compared to the second embodiment. Space can be realized. Other configurations and operations are the same as those in the first embodiment or the second embodiment described above.

<Fourth Embodiment>
A fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, the intervals in the gravitational direction of the plurality of openings of the developer discharge regulating members 401 and 401a are increased toward the upper side in the gravitational direction. Here, (A) of FIG. 14 shows what is constituted by a wire as in the third embodiment, and (B) shows what is formed in a mesh shape as in the first embodiment. The intervals in the gravity direction of the openings are within the range described in the first embodiment, that is, 2 × (d × 2 + D) ≦ x ≦ 40 × (d × 2 + D), and upward in the gravity direction. It is getting wider as you go.

  According to this embodiment, even when there is a developer that has aggregated more than expected in the developer container due to a temperature rise or the like, or when a foreign material larger than the carrier enters, The sheet can be discharged at a wide interval, and clogging of the developer discharge regulating member can be suppressed. This is the same as the first embodiment or the third embodiment described above.

  The present invention is not limited to the configuration of each of the above-described embodiments, and can have various configurations. Moreover, it is also possible to carry out by appropriately combining the embodiments.

DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 1 ... Photoconductor (image carrier), 4 ... Developing device, 41 ... Developing container, 41a ... Developing chamber, 41b ... Stirring chamber, 41c ... partition walls, 41d, 41e ... delivery section, 42 ... first conveying screw (developer conveying member), 43 ... second conveying screw (developer conveying member), 44 ... Developer sleeve (developer carrier), 48a ... developer discharge port, 49 ... developer supply port, 50a ... lower edge, 50b ... upper edge, 401, 401a ... developer discharge Regulatory member

Claims (8)

A developer container containing a two-component developer containing toner and carrier;
A developer carrier for carrying and transporting the developer in the developer container and supplying the developer to the development region of the image carrier;
A developer conveying member that conveys the developer while stirring in the developer container;
The developer container is provided at a predetermined height from a developer replenishing port for replenishing the developer into the developer container and a bottom portion in the gravitational direction of the developer container, and for discharging the developer from the developer container. Developer outlet
In a developing device that repeats supply of developer from the developer supply port and discharge of developer from the developer discharge port in a use state,
A developer discharge regulating member provided at the developer discharge port and having a plurality of openings that divide the developer discharge port in the direction of gravity;
Even if the developer cohesion degree is higher than the initial state, the developer surface of the plurality of openings in the gravitational direction is more than the initial state between the upper edge and the lower edge in the gravity direction of the developer discharge port. Set to be in between,
A developing device. The interval x in the gravitational direction of the plurality of openings is defined as follows when the volume average particle diameter of the carrier is D and the volume average particle diameter of the toner is d.
2 × (d × 2 + D) ≦ x ≦ 40 × (d × 2 + D)
The developing device according to claim 1, wherein: The intervals in the gravitational direction of the plurality of openings become wider toward the upper side in the gravitational direction.
The developing device according to claim 1, wherein The developer discharge regulating member is constituted by a mesh-like net,
An interval in the gravitational direction of the mesh is an interval in the gravitational direction of the plurality of openings.
The developing device according to any one of claims 1 to 3, wherein the developing device is characterized in that: The developer discharge regulating member is composed of a plurality of wires arranged in a direction intersecting the direction of gravity,
The intervals in the gravity direction of the plurality of wires are intervals in the gravity direction of the plurality of openings.
The developing device according to any one of claims 1 to 3, wherein the developing device is characterized in that: The angle of repose of the two-component developer is 25 to 50 °,
The developing device according to claim 1, wherein the developing device is any one of the above. Having vibration means for vibrating the developer discharge regulating member;
The developing device according to any one of claims 1 to 6, wherein the developing device is characterized in that: In an image forming apparatus comprising: an image carrier; and a developing device that develops an electrostatic latent image formed on the image carrier.
The developing device is the developing device according to any one of claims 1 to 7,
An image forming apparatus.

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