JP2007328048A - Toner separation device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner separation device capable of more efficiently separating toner from a developer including toner and carrier, and an image forming apparatus equipped with the separating unit. <P>SOLUTION: The toner separation device is equipped with electrode plates for reducing adsorptive power between toner and carrier in a surplus developer due to electrostatic charge before delivery of the surplus developer to a first cyclone unit 9. The electrostatically adsorbed toner and carrier, and toner particles can be swirled in the cyclone in a state of individually separated particles. Consequently, the toner separated from the carrier can be efficiently recovered and effectively reused. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a toner separating apparatus used in an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a multifunction machine of these, and an image forming apparatus provided with the toner separating apparatus. In particular, the present invention relates to an image forming apparatus including a developing device that develops a latent image formed on an image carrier in an electrophotographic system using a mixed developer of toner and carrier, and a toner separating device included in the device.

  2. Description of the Related Art Conventionally, dry copying machines and the like that use a developing device that visualizes an electrostatic latent image on the surface of an image bearing member, that is, develops toner with a two-component developer composed of toner and carrier are known. In such a developing device, the toner is consumed by the developing operation, while the carrier is not consumed and remains in the developing device.

  Therefore, the carrier stirred together with the toner in the developing device is contaminated and deteriorated as the stirring frequency increases, such as peeling of the film on the carrier surface or sticking of the toner to the carrier surface. For this reason, the charging performance of the developer is gradually lowered to cause image quality defects such as fogging, and this is a factor for remarkably reducing the image quality. Here, “fogging” refers to a phenomenon in which, when the charging performance of a developer has deteriorated, toner charged to a reverse polarity is generated, and the toner adheres to a non-image portion on the photoreceptor during development. .

  Therefore, a new developer consisting of a mixture of carrier and toner is replenished into the developer container, and the deteriorated developer whose charging performance has been reduced is discharged from the developer container to suppress the decrease in charging performance. There is a technology called “Carrier Refresh (ACR) method”. In this technique, a new carrier is replenished into the developing container separately from the replenishment of consumed toner. As a result, the excess developer in the developer container overflows and is discharged from the developer discharge port provided on the wall surface of the developer container, and is collected in the developer recovery container. By replenishing and discharging the carrier and the deteriorated developer, the developer that is contaminated and deteriorated in the developing container is replaced with newly supplied toner and carrier. Thereby, the charging performance of the developer is maintained, and the deterioration of the image quality is suppressed.

  However, in the ACR system, fresh toner other than the deteriorated developer that should be discharged is also overflowed and discharged at the same time, and is transported to the developer recovery container and then discarded together with the deteriorated developer.

  In recent years, it is necessary to dispose a plurality of developing units in a color-compatible image forming apparatus that is in high demand. However, due to the limitation on the size of the apparatus, there is a limit to the size allowed for each developing unit. is there. Because of such space limitations, it is difficult to ensure a sufficient developer amount and a deteriorated developer recovery amount in each developing device. In this case, if the discharged developer can be separated into fresh toner and deteriorated developer, the replenished developer space and deteriorated developer recovery space can be reduced by reusing the toner. .

  By the way, generally, a technique called a “cyclone separator” is known as a technique for separating toner and foreign matter (see Patent Document 1). This technique is intended to reuse the toner by separating the transfer residual toner in the cleaner into toner and foreign matters other than the toner. In this technique, the transfer residual toner removed from the photosensitive member is conveyed by air to a collection container, the transfer residual toner being conveyed is separated into toner and an object other than the toner, and a first object that collects the object other than the toner is collected. A cyclone device is provided.

  The technology further separates the toner separated by the first cyclone device into a small particle size toner and a reusable non-small particle size toner, and collects the non-small particle size toner. Is provided. As described above, the powders having different particle diameters moving in the airflow are separated by two types of cyclone apparatuses having different setting conditions.

  However, the separation of powders having different particle diameters by the principle of the cyclone separator in the technique described in Patent Document 1 is based on the premise that the powders are not adsorbed at least while turning the inner wall of the cyclone. .

  FIGS. 10 to 12 are diagrams for explaining the state of the centrifugal separation in the cyclone in a simplified and schematic manner. These figures show a cylindrical cyclone pipe developed in the powder movement direction, and reference numeral 51 denotes the pipe. L is the developed length of the swivel portion, 52 is a small diameter powder, and 53 is a large diameter powder.

  In FIG. 10, the small-diameter powder 52 conveyed by the air at the wind speed V from the left in the drawing moves to the right in the drawing while receiving the centrifugal force Fd and the fluid viscosity resistance Fu during the turning. In the figure, the condition that the centrifugal force Fd is larger than the fluid viscosity resistance Fu and reaches the lower surface of the pipeline 51 until the small-diameter powder 52 is conveyed through the developed length L of the pipeline 51, Become. In the figure, since the centrifugal force Fd is not so large as compared with the fluid viscosity resistance Fu and does not reach the lower surface of the pipe 51 while being conveyed through the development length L, the gas and the small-diameter powder 52 are separated. Not.

  In FIG. 11, the large-diameter powder 53 has a difference between the centrifugal force Fd and the fluid viscosity resistance Fu larger than that shown in FIG. And the large-diameter powder 53 are separated. The force of the centrifugal force Fd and the fluid viscosity resistance Fu can be expressed by parameters such as the density of the fluid and powder, the velocity of the fluid, the radius of curvature of the pipe, the viscosity of the fluid, and the particle diameter. If the parameters other than the particle size are the same, the separation condition depends on the particle size, and the larger the particle size, the higher the separation performance.

  Therefore, in FIG. 11, when the small diameter powder 52 and the large diameter powder 53 are independently conveyed in the pipe 51, the small diameter powder 52 and the large diameter powder 53 are separated under this condition. Is possible.

Japanese Patent Laid-Open No. 11-24519

  However, in the case where the powders being conveyed are adsorbed in FIG. 11, the desired separation performance cannot be expected from the principle of cyclone separation. That is, as shown in FIG. 12, when the small-diameter powder 52 is electrostatically adsorbed to the large-diameter powder 53 and is conveyed by the air flow at the wind speed V from the left direction in the figure, the apparent particle diameter is large. Become. Therefore, the difference between the centrifugal force Fd and the fluid viscosity resistance Fu becomes larger than that in the case of FIG. 11, and reaches the lower surface of the pipe line 51 while the developed length L is conveyed. As a result, although the gas and the large-diameter powder 53 or the gas and the small-diameter powder 52 are separated from each other, a phenomenon occurs in which the above-described powders 52 and 53 are not separated from each other or the separation performance is significantly reduced. .

  Therefore, even when the toner and the carrier discharged by the ACR method are separated, it is a precondition that the respective particles are made independent in the cyclone apparatus or upstream thereof. However, since toner and carrier discharged from the developing container are generally adsorbed mostly, according to the prior art as described above, normal separation based on the cyclone separation principle is difficult.

  Accordingly, the present invention has been made in view of the above-described situation, and a toner separation device capable of more efficiently separating toner from a developer having toner and a carrier, and image formation including the separation device. An object is to provide an apparatus.

  The present invention relates to a toner separation device that separates toner from a developer including toner and a carrier, a cyclone separation unit that separates the toner and the carrier in the developer, and delivery of the developer to the cyclone separation unit. In the first aspect, the apparatus includes an electrostatic attraction force reducing unit that reduces the electrostatic attraction force between the toner and the carrier by applying an electric charge to the developer.

  According to the present invention, the electrostatic attraction force reducing means reduces the attraction force due to charging of the toner and the carrier in the developer prior to the delivery of the developer to the cyclone separation means. This makes it possible to rotate the cyclone in a state where the electrostatically adsorbed toner and carrier, and the toner are separated into individual particle states. Accordingly, the separation performance between the toner and the carrier and between the toners can be dramatically improved, and the toner separated from the carrier can be efficiently collected.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

<First Embodiment>
This embodiment shows an example of an image forming apparatus provided with a toner separating apparatus, and FIG. 1 is a schematic configuration diagram of the image forming apparatus provided with the toner separating apparatus in this embodiment. In the present embodiment, as the image forming apparatus, a copying machine U using a transfer type electrophotographic process and a laser scanning exposure method is exemplified.

  The copying machine U has a document placing table 21 on the upper surface, and an exposure optical system 22 below the document placing table 21. When a document is placed and set on the document table 21 with the image surface facing downward, and a copy button (not shown) is pressed, the exposure optical system 22 causes the document image placed on the document table 21 to face downward. The photoelectric reading process.

  A rotating drum type electrophotographic photosensitive member D (hereinafter also simply referred to as “photosensitive member”) as an image carrier is disposed in the center of the inside of the copying machine U. On the outer periphery of the photoreceptor D, a charger 24 that charges the surface thereof to a predetermined potential, and a developing device 1 that develops an electrostatic latent image formed on the surface of the photoreceptor D to form a toner image. Are arranged. Further on the outer periphery of the photoconductor D, a transfer charger 26 that transfers a toner image on the surface of the photoconductor D onto a recording paper (sheet material), and a cleaning device 27 that removes and collects residual toner on the surface of the photoconductor D. Are arranged. Further, a laser scanner 25 as an exposure device is arranged on the left side of the developing device 1 in FIG.

  A timing roller pair 28, a transport roller pair 29, a transport roller pair 30, first and second paper feed cassettes 31A and 31B, and paper feed rollers 32A and 32B are provided on the paper input side with respect to the photoreceptor D. It is arranged. The timing roller pair 28 supplies recording paper to the photoconductor D at a predetermined timing. On the other hand, a fixing device 33 for fixing the toner image transferred onto the paper to the recording paper is disposed on the paper output side with respect to the photoreceptor D.

  First, the surface of the photoconductor D that is rotationally driven is uniformly charged by the charger 24, and then scanned and exposed with a laser beam 25a from a laser scanner 25 as an exposure device, so that the surface of the photoconductor D is statically exposed. An electrostatic latent image is formed. The latent image is developed by the developing device 1 to form a toner image on the surface of the photoreceptor D. The laser scanner 25 outputs a laser beam 25a modulated in accordance with a time-series electric digital pixel signal of an original image photoelectrically read by the exposure optical system 22 and electrostatically corresponding to the original image on the photosensitive member D surface. A latent image is written and formed.

  On the other hand, one sheet of recording paper P is separated and fed from the first paper feed cassette 31A (or second paper feed cassette 31B) by the paper feed roller 32A (or paper feed roller 32B). Then, the recording paper P is introduced into the transfer portion between the photosensitive member D and the transfer charger 26 at a predetermined timing via the conveyance roller pairs 30 and 29 and the timing roller pair 28. Then, the toner image on the photoconductor D is sequentially transferred onto the recording paper P by the transfer bias applied to the transfer charger 26. The recording paper P to which the toner image has been transferred is sent to the fixing device 33, where the toner image is fixed by pressurization and heating to form a permanent image, and is discharged onto the paper discharge tray 34 in that state.

  The toner remaining on the photoreceptor D after the transfer of the toner image to the recording paper P is removed by the cleaning device 27 to prepare for the next image forming process.

  Next, the developing device and the toner separation device will be described with reference to FIG. FIG. 2 is an enlarged schematic view showing the developing device shown in FIG. 1 and a toner separating device provided adjacent to the developing device.

[Developer]
The developing device 1 in FIG. 2 adopts the ACR method described above. The mixing ratio of the non-magnetic toner and magnetic carrier of the two-component developer accommodated in the developing device 1 is, for example, about 1: 9 by weight. The particle size of the toner is about 5 [μm], the specific gravity is about 1.2, the particle size of the carrier is about 20-30 [μm], and the specific gravity is about 1.4-1.6. The weight ratio should be appropriately adjusted according to the charge amount of the toner, the particle diameter of the carrier, the configuration of the copying machine U, and the like, and does not necessarily follow this numerical value.

  The developing device 1 is rotatably provided with a developing sleeve 5 as a developer carrying member disposed in a developing region portion facing the photoconductor D. The developing sleeve 5 rotates in the direction of arrow A in FIG. 2 during the developing operation, holds the two-component developer T in the developing device 1, and develops the electrostatic latent image formed on the photoreceptor D. A predetermined developing bias is applied to the developing sleeve 5. The developer after developing the electrostatic latent image is collected in the developing device 1 as the developing sleeve 5 rotates.

  A replenishing device 6 as a toner collecting / replenishing unit is disposed above the developing device 1. The replenishing device 6 sequentially replenishes the developing device 1 with a high-density two-component developer for replenishment. Replenishment of new developer from the replenishing device 6 into the developing device 1 is performed at the following timing. In other words, a decrease in toner density due to toner consumption of the two-component developer T in the developing device 1 is detected by a detecting means (not shown). When it is determined that the toner density is lower than the reference density based on the detection, a two-component developer (toner + carrier) having a higher toner density is supplied from the replenishing device 6 into the developing device 1.

  Exclusion of excess developer in the developing device 1 due to the developer replenishment described above is an overflow from the developer discharge port (developer recovery port) 7 provided at the rear end (left end in FIG. 2) of the developing device 1. Made.

[Toner Separator]
The toner separation device of the present embodiment includes an excess developer transport line 8a, a first cyclone unit 9, an excess developer transport line 8b, a second cyclone unit 11, a replenishing device 6, a duct 12, a fan 13, and a filter. 14 is provided.

  The surplus developer (discharged developer) discharged from the developer discharge port 7 of the developing device 1 passes through the surplus developer transport line 8 a communicating with the developer discharge port 7, and the leading end portion of this transport line 8 a ( It is sent to a first cyclone unit 9 which is a cyclone separating means arranged at the upper end). The surplus developer discharged from the developer discharge port 7, that is, the toner and carrier powder, is conveyed by air in the surplus developer transport line 8a as an air-fuel mixture.

  As shown in FIG. 2, the surplus developer transport pipe 8 a extends downward from a portion communicating with the developer discharge port 7, then bends and extends linearly upward, and communicates with the cyclone outer cylinder 18. Yes. A deteriorated developer storage unit 10 as a waste carrier recovery unit is disposed adjacent to the replenishing device 6 at an upper portion of the developing device 1, and a lower end portion of the cyclone outer cylinder 18 is disposed in the deteriorated developer storage unit 10. It communicates with the upper part. One end portion of the surplus developer conveyance pipe line 8b communicates with the upper part of the cyclone outer cylinder 18, and the other end part of the surplus developer conveyance pipe line 8b communicates with the upper part of the replenishing device 6. It communicates with the second cyclone unit 11 as the cyclone separating means. One end of a duct 12 communicates with the upper part of the second cyclone unit 11, and a fan 13 and a filter 14 are provided at the other end of the duct 12.

  FIG. 3 is a cross-sectional view showing in detail the main part of the surplus developer transport conduit 8a in this embodiment, and FIG. 4 is a top view of the outer cylinder 15 in FIG. 3 cut along the arrow BB. FIG.

  As shown in FIG. 3, the surplus developer conveying pipe 8a has an outer cylinder 15. The outer cylinder 15 is formed in a square cylinder section using a resin material having high hermeticity and insulating properties. Has been. One end of a relay pipe 17 (see also FIG. 2) communicates with the inlet of the first cyclone unit 9, and the other end of the relay pipe 17 is connected to an excess developer transport pipe 8 a (that is, It is connected and communicated with the upper end of the outer cylinder 15).

  As shown in FIGS. 3 and 4, electrode plates 16 a and 16 b as first and second electrodes made of a conductive metal member are provided on the inner wall of the outer cylinder 15 in the transport direction of excess developer ( Oppositely arranged in parallel with the vertical direction in FIG. An AC bias is applied to the electrode plate 16a by an AC power source (AC voltage applying means) 60, and the electrode plate 16b is grounded. As a result, an alternating electric field (see arrow E in FIG. 4) is generated between the electrode plates 16a and 16b.

  That is, the electrode plates 16a and 16b are arranged so as to face the delivery path of the surplus developer discharged from the developing device 1 to the cyclone unit 9, and are held at different potentials to generate an electric field between them. An electroadhesive force reduction means is comprised. These electrode plates 16a and 16b reduce electrostatic attraction between the toner t in the developer and the carrier c due to charging prior to the delivery of the surplus developer to the first cyclone unit 9. Thus, the electrostatic attraction force reducing means in the present embodiment is realized by a simple configuration in which the electrode plates 16a and 16b are opposed to each other.

  The toner t and the carrier c overflowing from the developer discharge port 7 and conveyed by air as an air-fuel mixture from the lower part of FIG. 3 are agitated in the developing device 1 so that the toner t is negative and the carrier c is positive. Charged to each other and electrostatically adsorbed to each other. The charge amount in the combined state of the electrostatically adsorbed toner t and the carrier c is about 30 [μC / g], and it is known from the experimental results that the toner is mainly charged to the negative polarity. The charge amount may be positive depending on environmental conditions and the like. In any case, the charge amount is within a range of about ± 50 [μC / g].

  In the present embodiment, the AC bias value of the electrode plate 16a is set to 8 [kvpp], and the interval between the electrode plates 16a and 16b is set to 30 [mm], which is sufficient to eliminate the charge amount between both electrodes. A strong electric field (see arrow E in FIG. 4) is generated. Discharge occurs due to the formation of this alternating electric field, and positive and negative charges are generated. Then, by applying the generated charges to the toner and the carrier, an action of canceling out the charges already possessed by both of them occurs, and the electrostatic adsorption force of the both decreases.

  The electrostatically adsorbed toner t and carrier c are neutralized when transported between the two electrode plates 16a and 16b, and the attraction force disappears (or the attraction force is greatly reduced). As a result, most of the excess developer is returned to the individual independent particle state, then passes through the relay pipe 17 and flows into the first cyclone unit 9.

  FIG. 5 is a cross-sectional view showing in detail the main part of the first cyclone unit 9 in the present embodiment, and FIG. 6 is a cross-sectional view of the cyclone outer cylinder 18 and the cyclone inner cylinder 19 in FIG. FIG.

  The first cyclone unit 9 includes a cyclone outer cylinder 18 that communicates with the surplus developer transport pipe 8a, a cyclone that has one end communicating with the upper portion of the cyclone outer cylinder 18 and the other end communicating with the second cyclone unit 11. And an inner cylinder 19. The cyclone outer cylinder 18 is made of a resin material having high hermeticity and conductivity, and has a substantially conical shape (that is, a substantially truncated cone shape) in which a head facing downward in the figure is cut. The cyclone inner cylinder 19 is formed in a cylindrical shape made of a resin material having high hermeticity and conductivity.

  An AC bias is applied to the cyclone inner cylinder 19, and an electric field (see arrow E in FIGS. 5 and 6) between the cyclone inner cylinder 19 and the cyclone outer cylinder 18 that is grounded (grounded). Has occurred. The cyclone outer cylinder 18 and the cyclone inner cylinder 19 constitute second electrostatic attraction force reducing means for generating an electric field between them held at different potentials.

  In the present embodiment, the AC bias value of the cyclone inner cylinder 19 is set to 8 [kvpp], and the interval between the cyclone inner cylinder 19 and the cyclone outer cylinder 18 is set to 30 [mm], so that it is conveyed between both cylinders. A sufficient electric field is generated to neutralize the toner and carrier.

  In this state, the toner and the carrier that have not been neutralized during conveyance of the surplus developer conveyance pipeline 8a are neutralized while being conveyed through the cyclone inflow portion (upper side in FIG. 5) of the first cyclone unit 9. The adsorption power is lost. Thereby, the excess developer is returned to the individual independent particle state. In some cases, the toner adheres to the surface of the deteriorated carrier due to factors other than the power. However, depending on the conditions, the ratio is a little less than 20% of the whole, and it has been found from past studies that most of them are electrostatically adsorbed.

  Next, the mixture of the toner, the carrier, and the air, which has been returned to the independent particle state having different particle diameters and specific gravity due to the charge eliminating effect, swirls along the inner wall of the cyclone outer cylinder 18. At this time, the carrier 20 having a larger particle size and specific gravity than the toner collides with the inner wall of the cyclone outer cylinder 18 by centrifugal force, and then settles by its own weight. The settled carrier 20 is accumulated inside a deteriorated developer storage section 10 (see FIG. 2) provided below the first cyclone unit 9. Here, the cyclone separation conditions of the first cyclone unit 9 are set so that particles having a particle size of approximately 10 [μm] or less cannot be separated.

  FIG. 7 is a simplified theoretical diagram of the particle separation limit cyclone radius for each inflow air velocity. As shown in the figure, the air velocity Vf flowing into the cyclone is set to 5 [m / sec] and the cyclone radius rm is set to 10 [cm], so that particles of 10 [μm] or more are deteriorated developer storage portions. 10 is accumulated. However, particles less than 10 [μm] are not accumulated in the deteriorated developer reservoir 10.

  The mixture of toner and air below 10 [μm] passes through the surplus developer transport line 8b communicating with the upper part of the first cyclone unit 9, and is connected to the tip of the surplus developer transport line 8b (communication). ) Is sent to the second cyclone unit 11.

  The mixture of air and toner sent to the second cyclone unit 11 swirls along the inner wall of the cyclone unit 11. As a result, the reusable toner 3 having a particle size collides with the inner wall by centrifugal force and then settles by its own weight. The settled toner 3 is collected in a high-density two-component developer supply device 6 provided below the second cyclone unit 11 and reused as fresh toner.

  The cyclone separation conditions of the second cyclone unit 11 are set so that particles having a particle size of approximately 5 [μm] or less cannot be separated. In the present embodiment, the air velocity Vf flowing into the cyclone is 5 [m / sec] and the cyclone radius rm is 2.5 [cm], so that particles of about 5 [μm] have a high-density two-component developer. Is collected in the replenishing device 6. However, extremely small-diameter toner that is inappropriate as a developer of less than 5 [μm] is not collected in the replenishing device 6.

  The mixture of toner and air below 5 [μm] is exhausted by a fan 13 connected to the tip of the duct 12 via a duct 12 (see FIG. 2) communicating with the upper part of the second cyclone unit 11. Is done. When the air-fuel mixture passes through the filter 14, the small diameter toner is trapped by the filter 14, and the air excluding the small diameter toner is discharged to the outside of the copying machine U.

  As described above, the second cyclone unit 11 takes in the air-fuel mixture obtained by mixing the toner separated by the first cyclone unit 9 and separates the toner having a predetermined specific particle diameter from the toner. Then, the replenishing device 6 collects the toner having a specific particle size separated by the second cyclone unit 11 and replenishes the developing device 1 as fresh toner.

  According to the above configuration, the developer discharged from the developing device 1 through the developer discharge port 7 can be passed through the electric field between the electrode plates 16a and 16b prior to delivery to the first cyclone unit 9. . This eliminates (or reduces) the adsorption force due to the charging between the toner and the carrier in the developer, and in the state where the electrostatically adsorbed toner and carrier and toners are separated into individual particle states. Can be swiveled.

  For this reason, the separation performance between the toner and the carrier and the toner is dramatically improved, the toner separated from the carrier is efficiently collected, the maximum amount of reusable toner is acquired, and the toner is effectively reused as a fresh toner. be able to. As a result, the toner consumption efficiency is improved and the unit price per image forming sheet can be suppressed. In addition, since the toner separated by the toner separation device is dropped into the replenishing device 6 or trapped by the filter 14 due to the difference in particle size, only the carrier 20 is attached to the deteriorated developer storage section 10 provided in the copying machine U. It only has to be stored. For this reason, it is possible to reduce the size of the container for collecting the waste developer and realize the space-saving copying machine U.

  Further, since the second cyclone unit 11 and the replenishing device 6 are provided, it is possible to effectively distribute the toner, which has been neutralized into individual particles, into a reusable particle size toner and a non-reusable toner. Thus, reusable toner can be efficiently supplied via the supply device 6.

<Second Embodiment>
In the present embodiment, only the configuration of the electrostatic attraction force reducing unit in the toner separating apparatus is different from that of the first embodiment, and the other configurations are the same. Therefore, only the configuration of the electrostatic attraction force reducing unit will be described here. To do.

[Toner Separator]
As described above, the surplus developer discharged from the developer discharge port 7 passes through the surplus developer transport conduit 8a communicating with the developer discharge port 7, and is disposed at the tip of the surplus developer transport conduit 8a. To the first cyclone unit 9 (see FIG. 2). The surplus developer discharged from the developer discharge port 7, that is, the powder of toner and carrier, is air-conveyed as an air-fuel mixture in the surplus developer transport line 8a.

  FIG. 8 is a cross-sectional view showing in detail the main part of the surplus developer transport conduit 8a in the second embodiment, and FIG. 9 is a plan view of the outer cylinder 41 in FIG. 8 cut along the arrow FF from above. FIG.

  As shown in FIG. 8, the surplus developer conveying pipe 8a has an outer cylinder 41. The outer cylinder 41 is formed in a circular cross section using a resin material having high hermeticity and insulating properties. ing. One end portion of the relay pipe 45 communicates with the inlet of the first cyclone unit 9, and the other end portion of the relay pipe 45 is connected to the upper end portion of the surplus developer transport pipe line 8 a (that is, the outer cylinder 41). Connected and communicated.

  As shown in FIGS. 8 and 9, a cylindrical electrode plate 42 made of a conductive metal member is located on the inner wall of the surplus developer delivery path (conveyance path) on the inner wall of the outer cylinder 41. Is provided. In addition, a charging wire 43 extends in the center portion of the outer cylinder 41 in the longitudinal direction so as not to contact the electrode plate 42 in the delivery path. That is, the charging wire 43 is provided at the approximate center of the cylindrical electrode plate 42 and in the transport direction of the surplus developer by the charging wire fixing bracket 44 fixed to the seating surface 45a formed on the inner surface of the relay pipe 45 with the screw 46. Is supported in a parallel form and droops. The charging wire fixing bracket 44 is made of a conductive metal material. The charging wire 43 whose upper end is fixed to the fixing bracket 44 protrudes toward the center of the electrode plate 42 so that the cylindrical electrode plate 42 is not in contact with the lower developer transporting line 8a. The lower end is fixed to an arm (not shown). The electrode plate 42 and the charging wire 43 constitute a first electrode and a second electrode.

  An AC bias is applied to the charging wire 43, and an electric field (see arrow E in FIG. 9) is generated between the charging wire 43 and the grounded (grounded) electrode plate. . The relay pipe 45 is connected to the inflow port of the first cyclone unit 9. At this time, the toner and the carrier that have overflowed from the developer discharge port 7 and are conveyed by air as a mixture with air from the lower side of FIG. Is positively charged and electrostatically adsorbed.

  In this embodiment, by setting the AC bias value of the charging wire 43 as 8 [kvpp] and the distance between the charging wire 43 and the electrode plate 42 as 30 [mm], the toner and the carrier conveyed inside the electrode plate 42 An electric field sufficient to remove the charge is generated.

  The electrostatically adsorbed toner and carrier are neutralized while being conveyed through the electrode plate 42 that is the conveying path, and the adsorbing force is lost (or reduced), and most of the excess developer is returned to the individual particle state. After that, it passes through the relay pipe 45 and flows into the first cyclone unit 9.

  Also in the second embodiment having the above configuration, the same operational effects as the first embodiment can be obtained, and the electric field can be more efficiently distributed from the charging wire 43 located in the central portion of the electrode plate 42. An effect can also be obtained.

  Note that the configuration of the electrostatic attraction force reducing means and the cyclone conditions are not limited to the configurations of the first and second embodiments described above, and the charge eliminating effect for separating the electrostatically attracted toner and the carrier is provided. Any device can be used as long as it exhibits upstream of the first cyclone unit 9.

1 is a schematic configuration diagram of an image forming apparatus including a toner separation device according to the present invention. FIG. 3 is an enlarged schematic diagram illustrating a developing device and a toner separation device. FIG. 3 is a cross-sectional view illustrating in detail a main part of an excess developer conveyance conduit in the first embodiment. It is the plane sectional view which cut the outer cylinder in Drawing 3 along arrow BB, and was seen from the upper part. It is sectional drawing which shows the principal part of the 1st cyclone unit in 1st Embodiment in detail. It is the plane sectional view which cut the cyclone outer cylinder and the cyclone inner cylinder in Drawing 5 along arrow CC, and was seen from the upper part. It is a simple theoretical diagram of the particle separation limit cyclone radius for every inflow air velocity. It is sectional drawing which shows the principal part of the excess developer conveyance pipe line in 2nd Embodiment in detail. It is the plane sectional view which cut the outer cylinder in Drawing 8 along arrow FF, and was seen from the upper part. It is explanatory drawing which simplified and modeled the state of the centrifugation in a cyclone. It is explanatory drawing which simplified and modeled the state of the centrifugation in a cyclone. It is explanatory drawing which simplified and modeled the state of the centrifugation in a cyclone.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing device 5 Developing sleeve 6 Toner collection and replenishing means (replenishing device)
7 Developer discharge port 8a, 8b Excess developer transport line 9 Cyclone separation means (first cyclone unit)
10 Waste carrier recovery unit (deteriorated developer storage unit)
11 Second cyclone separating means (second cyclone unit)
12 Duct 13 Fan 14 Filter 15 Outer cylinders 16a, 16b Electrostatic adsorption force reducing means, first and second electrodes (electrode plates)
17 Relay pipes 18 and 19 Second electrostatic attraction force reducing means (cyclone outer cylinder, cyclone inner cylinder)
21 Document Placement Table 22 Exposure Optical System 24 Charger 25 Laser Scanner 25a Laser Light 26 Transfer Charger 27 Cleaning Device 28 Timing Roller Pair 29, 30 Transport Roller Pair 31A, 31B Paper Feed Cassette 32A, 32B Paper Feed Roller 33 Fixing Device 34 Paper discharge tray 41 Outer cylinders 42, 43 Electrostatic adsorption force reducing means, first and second electrodes (electrode plate, charging wire)
44 Charging wire fixing bracket 45 Relay pipe 46 Screw 51 Pipe line 52 Small diameter powder 53 Large diameter powder U Image forming apparatus (copier)

Claims (8)

In a toner separation device for separating toner from a developer including toner and carrier,
A cyclone separating means for separating the toner and carrier in the developer;
Prior to delivery of the developer to the cyclone separating means, and electrostatic attraction force reducing means for reducing the electrostatic attraction force between the toner and the carrier by applying a charge to the developer,
A toner separator. The electrostatic attraction force reducing means is disposed so as to face the delivery path of the developer to the cyclone separating means, and has first and second electrodes that are held at different potentials and generate an electric field therebetween. Have
The toner separation device according to claim 1. The electrostatic attraction force reducing unit includes an AC voltage applying unit that forms an AC electric field between the first electrode and the second electrode and generates a discharge therebetween.
The toner separating apparatus according to claim 2. The first and second electrodes are electrode plates arranged to face each other on the inner surface of the delivery path,
The toner separation device according to claim 2 or 3. The first and second electrodes are an electrode plate disposed on an inner surface of the delivery path, and a charging wire extending so as not to contact the electrode plate in the delivery path.
The toner separation device according to claim 2 or 3. The cyclone separating means has a cyclone outer cylinder and a cyclone inner cylinder each having conductivity,
The cyclone outer cylinder and the cyclone inner cylinder constitute second electrostatic attraction force reducing means for generating an electric field between them held at different potentials.
The toner separation device according to claim 1. A second cyclone separating unit that takes in an air-fuel mixture obtained by mixing the toner separated by the cyclone separating unit and separates a toner having a predetermined specific particle diameter from the toner;
Toner collection / replenishment means for collecting the toner having the specific particle size separated by the second cyclone separation means and replenishing the developing device;
The toner separating device according to claim 1. A toner separation device according to any one of claims 1 to 7,
A waste carrier recovery unit that recovers the carrier separated by the toner separation device,
An image forming apparatus.

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