JP2011095421A - Extracting device and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extracting device that can reliably separate a dispersoid and dispersion medium, even when the concentration of the dispersoid changes. <P>SOLUTION: The carrier liquid extracting device 500 includes: a liquid tank 510 storing liquid developer LD; a measuring roller 520 for scooping liquid developer LD; a toner recovery roller 530 carrying a thin layer TL of the liquid developer LD on a periphery 53S; a carrier liquid recovery roller 540 for separating a carrier liquid from the thin layer TL; and a charging device 550 for charging toner in the thin layer TL to a positive potential. When the toner concentration in the liquid developer LD in the liquid tank 510 is detected by a toner concentration sensor 512 and the toner concentration is higher than a fixed value, the operation of the carrier liquid extracting device 500 is stopped. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an extraction apparatus that separates and extracts a liquid sample containing a dispersoid and a dispersion medium, and an image forming apparatus to which the same is applied.

  A technique for executing a predetermined process using a liquid carried on a peripheral surface of a roller or the like is used in many fields such as a printing technique. For example, such a technique is applied to a wet image forming apparatus using a liquid developer (for example, a copier, a printer, a facsimile, or a multifunction machine having these functions).

  The liquid used for processing often contains a dispersion medium and a dispersoid. For example, in the above-described image forming apparatus, a liquid developer containing toner as a dispersoid and a carrier liquid as a dispersion medium is used. The dispersion medium plays a role of, for example, promoting uniformity of dispersion of the dispersoid and performing uniform and / or stable processing. In certain processes, it may be desired to recover and reuse the dispersion medium.

  Patent Document 1 discloses a recycling apparatus for recovering a dispersion medium. This recycling apparatus has a structure in which a conductive roller is disposed with a minute gap inside the conductive pipe, and a liquid developer is injected into the gap. By forming an electric field between the conductive pipe and the conductive roller, the toner and the carrier liquid are separated, and the carrier liquid is then collected.

JP 2003-270957 A

  However, the recycling apparatus of Patent Document 1 requires a lot of time to separate the toner and the carrier liquid, and cannot be mounted when the wet image forming apparatus intends to perform high-speed printing processing. If the gap between the conductive pipe and the conductive roller can be made as small as several microns, it is possible to increase the separation speed between the toner and the carrier liquid. It is practically impossible to confront each other on the order of several microns from the viewpoint of component accuracy and device configuration.

  Further, the toner concentration in the collected liquid developer may change due to various factors. In the case where separation of the toner and the carrier liquid is attempted by applying an electric field to the liquid developer, if such a change in the toner concentration in the liquid developer occurs, the separation may not be performed satisfactorily. is there.

  The present invention has been made in view of the above problems, and an extraction apparatus capable of reliably separating a dispersoid and a dispersion medium even when a situation in which the concentration of the dispersoid changes occurs, and the application thereof An object of the present invention is to provide an image forming apparatus.

  An extraction apparatus according to an aspect of the present invention is an extraction apparatus that separates the dispersoid and the dispersion medium from a liquid sample containing the dispersoid and the dispersion medium, and extracts them, and the peripheral surface includes the dispersoid and the dispersoid. A first roller that carries a thin layer of a liquid sample containing a dispersion medium and rotates around an axis, a liquid tank that stores the liquid sample, and a circumference of the first roller using the liquid sample in the liquid tank A thin layer forming means for forming the thin layer of the liquid sample on the surface; and the dispersion medium in the thin layer is electrically adsorbed on the peripheral surface of the first roller from the thin layer to the dispersion medium. Separating means for separating the particles, concentration detecting means for detecting the concentration of the dispersoid in the liquid sample, and at least the thin layer forming means and the first according to the concentration detection result of the dispersoid by the concentration detecting means. By controlling the driving of the roller, the extraction device can be operated or Characterized in that it comprises a control means for the stop state, the (claim 1).

  According to this configuration, the thin layer of the liquid sample is carried on the peripheral surface of the first roller, and the dispersoid in the thin layer is electrically adsorbed on the peripheral surface of the first roller, whereby the dispersoid is Since it is unevenly distributed on the peripheral surface of the first roller, the dispersoid and the dispersion medium can be easily separated. Here, depending on the concentration of the dispersoid in the liquid sample, the viscosity of the liquid sample changes, and due to this viscosity change, the thickness of the thin layer formed on the peripheral surface of the first roller can also change. This affects the electrical adsorption characteristics of the dispersoid on the peripheral surface of the first roller, and can affect the separation performance between the dispersoid and the dispersion medium. Therefore, in the present invention, the concentration of the dispersoid in the liquid sample is detected by the concentration detection means, and the extraction device is put into an operating state or a stopped state by the control means according to the detection result. Therefore, when the concentration of the dispersoid is a concentration that makes it difficult to set the thin layer to a desired thickness, the extraction device is stopped and the separation and extraction of the dispersoid and the dispersion medium are temporarily stopped. Operation can be planned. Thereby, even if the situation where the density | concentration of the dispersoid in a liquid sample changes arises, a reliable separation of a dispersoid and a dispersion medium can be performed.

  In the above configuration, when the concentration detection unit detects that the concentration of the dispersoid is the first concentration, the control unit sets the extraction device in the operating state, and the concentration detection unit detects the concentration of the dispersoid. However, when it is detected that the second concentration is higher than the first concentration by a predetermined value or more, it is desirable that the extraction device be in the stopped state (claim 2).

  According to this configuration, when the concentration of the dispersoid in the liquid sample increases from the first concentration to the second concentration for some reason, the extraction device is stopped. As a result, the formation of the thickened thin layer accompanying the increase in the concentration of the dispersoid is suppressed. In other words, the extraction device is prevented from operating in a situation where it is difficult to reliably separate the dispersion medium and the dispersoid in a state where the concentration of the dispersoid is high. Separation can be performed.

  The said structure WHEREIN: It is desirable to provide the stirring means which stirs the said liquid sample in the said liquid tank (Claim 3). According to this configuration, it is possible to suppress sedimentation of the dispersoid and maintain a state in which the dispersoid is uniformly dispersed in the dispersion medium.

  In this case, it is provided with a conduit for intermittently supplying the liquid sample to the liquid tank, and drive control means for controlling the drive of the stirring means, and the drive control means operates the extraction device by the control means. It is desirable to operate the stirring means regardless of the state or the stopped state.

  According to this configuration, since the liquid sample is intermittently supplied to the liquid tank, for example, even if the concentration of the dispersoid temporarily increases, the concentration of the dispersoid from the pipe line to the liquid tank thereafter. A low liquid sample may be supplied. Here, since the stirring means always operates and stirs the liquid sample, the dispersoid can be kept uniformly dispersed in the dispersion medium even during the stop period of the extraction apparatus. Therefore, it is possible to accurately detect the concentration by the concentration detection means, and thus it is possible to accurately determine the operation start timing of the extraction device.

  In the above-described configuration, the separation unit is in contact with the first roller and separates the dispersion medium from the thin layer carried by the first roller, and the separation member is in contact with the first roller. A charging device for charging the dispersoid in the thin layer carried by the first roller at a position upstream of the position in the rotational direction of the first roller, and electrically charging the charged dispersoid to the first roller. It is desirable to include an electric field forming means for forming an electric field to be adsorbed on the peripheral surface.

  According to this configuration, the dispersoid in the thin layer is charged by the charging device, and the charged dispersoid is electrically attracted to the peripheral surface of the first roller by the electric field formed by the electric field forming means. The Then, the dispersion medium is separated from the thin layer by the separation member that is in contact with the first roller. Therefore, it is possible to realize a configuration in which the dispersoid is securely adsorbed to the peripheral surface of the first roller.

  In this case, it is desirable that the separation member is a second roller that carries the dispersion medium on its peripheral surface and rotates about its axis. According to this configuration, a nip portion is formed by the first roller and the second roller, and the dispersoid is adsorbed on the peripheral surface of the first roller when the thin layer passes through the nip portion. While the dispersion medium is recovered by the second roller.

  In the above configuration, the thin layer forming means is disposed so that a peripheral surface thereof is in contact with the liquid sample in the liquid tank, rotates about an axis, and transports the liquid sample along the peripheral surface. A third roller, which is in contact with the first roller at a position upstream of the charging device in the rotational direction of the first roller to form a nip portion; It is desirable that the thin layer is formed on the peripheral surface of the first roller by passing the liquid sample conveyed on the peripheral surface of the first roller through the nip portion.

  According to this configuration, the liquid sample in the liquid tank is pumped up by the third roller, and the liquid sample on the peripheral surface of the third roller is transferred to the first roller at the nip portion. Then, since it passes through the nip portion, the delivered liquid sample is carried as a thin layer on the peripheral surface of the first roller. Therefore, the thin layer can be formed easily and stably.

  In the above-described configuration, there is further provided driving means for rotating the first roller and the third roller about their respective axes, and the driving means rotates the first roller and the third roller in opposite directions. In addition, it is desirable to rotate the third roller so that the rotational peripheral speed of the third roller is faster than the rotational peripheral speed of the first roller. According to this configuration, the thickness unevenness of the thin layer carried on the peripheral surface of the first roller can be reduced. Thereby, when the dispersoid is charged by the charging means, it is possible to prevent charging unevenness as much as possible. Therefore, the dispersoid can be reliably adsorbed on the peripheral surface of the first roller, and the separation performance can be improved.

  In the above configuration, the electric field forming means may be a power source that applies a negative electric field to the first roller, and the charging device may be configured to positively charge the dispersoid in the thin layer ( Claim 9). According to this structure, the structure which makes a dispersoid electrically adsorb | suck on the surrounding surface of a said 1st roller can be achieved simply.

  In the above configuration, it is preferable that the liquid sample is a liquid developer, the dispersoid is a toner, and the dispersion medium is a carrier liquid. According to this configuration, the extraction apparatus according to the present invention can be applied to a wet image forming apparatus.

  A wet image forming apparatus according to another aspect of the present invention includes the above-described extraction device (claim 11). That is, an image forming apparatus, a photosensitive drum carrying a toner image on a peripheral surface thereof, a developing unit for supplying a liquid developer containing toner and carrier liquid to the photosensitive drum, the toner and the carrier A developer generating unit that generates a liquid developer having a mixed ratio with the liquid, and a first supply system that supplies the developer generating unit with a toner concentration higher than that of the developer used in the developing unit. A second supply system for supplying the carrier liquid to the developer generating unit, and a third supply system for supplying the liquid developer generated by the developer generating unit to the developing unit via a reserve tank A liquid developer that is supplied to the developing unit and that is not consumed in the developing unit or the photosensitive drum, and a recovery system that supplies the liquid developer to the developer generating unit; Provided Wherein the collected liquid developer to separate toner and said carrier liquid, characterized in that it comprises an extraction device according to the to extract these (claim 12).

  According to the present invention, the extraction device is activated or stopped by the control means according to the concentration of the dispersoid in the liquid sample. Therefore, since the separation and extraction of the dispersoid and the dispersion medium in a situation where the formation thickness of the thin layer is expected to be inappropriate is avoided, both can be reliably separated as a result, for example, It is possible to prevent the dispersion medium from being collected in a state where the dispersoid is mixed in the dispersion medium.

It is a figure which shows the structure of the carrier liquid extraction apparatus which concerns on embodiment of this invention. It is a figure for demonstrating the effect | action of the charging device in the said carrier liquid extraction apparatus. It is a schematic diagram for demonstrating operation | movement of the said carrier liquid extraction apparatus. 6 is a graph showing a relationship between toner density and output of a toner density sensor. It is a figure of the tabular form which shows evaluation of the extraction state of a carrier liquid. 1 is an overall schematic cross-sectional view of a color printer according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the color printer, excluding a portion of a liquid developer circulation device. It is sectional drawing which expands and shows one of the image formation parts. It is a block diagram of a liquid developer circulation device.

[Exemplary Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration of a carrier liquid extraction device 500 (extraction device) according to an embodiment of the present invention. This carrier liquid extraction apparatus 500 is applied to a wet image forming apparatus using a liquid developer (liquid sample), and from a liquid developer used for image formation, a toner solid content (hereinafter simply referred to as a dispersoid). It is an apparatus for separating a “toner” or “toner particle”) and a carrier liquid as a dispersion medium, and recovering the carrier liquid for reuse. The carrier liquid extraction device 500 includes a liquid tank 510, a measuring roller 520 (third roller), a toner recovery roller 530 (first roller), a carrier liquid recovery roller 540 (second roller), a charging device 550, and a control device 500A (control). Means).

  The liquid tank 510 is a box that opens upward, and the liquid developer LD is stored in the tank. A developer supply pipe 511 (a pipe line for intermittently supplying a liquid sample) is connected to the liquid tank 510, and the liquid developer LD collected in the image forming unit is sequentially developed by driving a pump (not shown). It is intermittently supplied into the liquid tank 510 through the supply pipe 511. As the liquid tank 510, a metal or resin container having excellent thermal conductivity, or a ceramic container can be used. In this embodiment, a toner concentration sensor 512 (concentration detection unit), a stirring member 513 (stirring unit), and a stirring drive unit 514 (drive control unit) are attached to such a liquid tank 510.

  The toner concentration sensor 512 detects the toner concentration in the liquid developer LD stored in the liquid tank 510. The toner concentration sensor 512 is, for example, a light transmission type sensor, and utilizes the fact that the light transmission amount changes depending on the density of toner particles in the liquid developer LD. The toner concentration sensor 512 is disposed in the liquid tank 510, and the sensor probe portion is disposed at a position where it can come into contact with the liquid developer LD. For example, the sensor probe unit includes a light emitting element that generates near infrared light (emission peak wavelength: 940 nm) and a light receiving element that receives infrared light (light receiving peak wavelength: 1000 nm) with a predetermined gap. Arranged ones can be used. Output data (output voltage) corresponding to the density of toner particles from the toner density sensor 512 is given to the control device 500A as toner density data.

  The stirring member 513 constantly stirs the liquid developer LD stored in the liquid tank 510, and maintains a state where the toner is uniformly dispersed in the carrier liquid. The stirring member 513 includes a stirring blade disposed in the liquid tank 510 and a stirring shaft that transmits a rotational force to the stirring blade. Although FIG. 1 shows an example in which one stirring member 513 is arranged, a plurality of stirring members 513 may be arranged in the liquid tank 510.

  The agitation drive unit 514 includes a motor and a gear connected to the output shaft of the motor, and generates a rotational force for rotationally driving the agitation member 513. The stirring drive unit 514 basically rotates the stirring member 513 at all times. As a result, the toner density can be accurately detected by the toner density sensor 512. As will be described in detail later, when the toner concentration in the liquid developer LD in the liquid tank 510 exceeds a certain value, the operation of the carrier liquid extraction device 500 is stopped. Even during the stop period, the agitation driving unit 514 rotates the agitation member 513 so that the toner is uniformly dispersed in the carrier liquid.

  The metering roller 520 is a roller made of a cylindrical body made of a metal excellent in lyophilicity with respect to the liquid developer LD, and rotates counterclockwise around the rotation shaft 52A. In the present embodiment, the measuring roller 520 is made of stainless steel and has a surface roughness of the peripheral surface 52S of JIS roughness shape parameter (JIS B0601-1994) having a maximum height Ry of 6.3. ing. The lower portion of the metering roller 520 is immersed in the liquid developer LD stored in the liquid tank 510, and the upper portion of the measuring roller 520 is assembled to the liquid tank 510 so that the upper portion protrudes upward from the opening of the liquid tank 510. Yes. Accordingly, a part of the peripheral surface 52S of the measuring roller 520 is always in contact with the liquid developer LD in a state where an appropriate amount of the liquid developer LD is stored in the liquid tank 510.

  The measuring roller 520 is rotationally driven by the first drive unit 521. The first driving unit 521 includes a motor that generates a rotational driving force and a gear mechanism that transmits the rotational driving force to the rotation shaft 52A of the measuring roller 520. When the metering roller 520 is rotated, the peripheral surface 52S immersed in the liquid developer LD moves upward, and the liquid developer LD is attached to the peripheral surface 52S due to surface tension. Accordingly, when the metering roller 520 rotates, a predetermined amount of the liquid developer LD is pumped from the liquid tank 510 along the peripheral surface 52S according to the wettability of the peripheral surface 52S with respect to the liquid developer LD.

The toner recovery roller 530 is a roller that carries a thin layer TL of liquid developer on its peripheral surface 53S and rotates clockwise around the rotation shaft 53A. In the present embodiment, a roller having a structure in which an outer layer 53C made of conductive rubber is provided on a conductive metal core 53B is used as the toner collection roller 530. The conductive rubber is urethane having a hardness of 30 degrees and a volume resistivity of 10 ⁵ Ω · cm according to JIS-A. A fluororesin coating layer is applied to the surface of the urethane outer layer 53C in order to promote the releasability of the toner.

  The circumferential surface 52S of the metering roller 520 comes into contact with the circumferential surface 53S of the toner collecting roller 530 in a pressed state, so that both rollers 520 and 530 form a first nip portion N1. A charging device 550, which will be described later, is disposed so as to face the outer peripheral portion of the toner collection roller 530. The formation position of the first nip portion N1 is upstream of the rotation direction of the toner collection roller 530 with respect to the arrangement position of the charging device 550. Position.

  The toner collection roller 530 is rotationally driven by the second drive unit 531. The second driving unit 531 includes a motor that generates a rotational driving force and a gear mechanism that transmits the rotational driving force to the rotation shaft 53 </ b> A of the toner recovery roller 530. A voltage is applied to the rotating shaft 53A from the first power source 532 (electric field forming means). The rotating shaft 53A is electrically connected to the metal core 53B and the outer layer 53C, and the peripheral surface 53S of the toner collection roller 530 is charged by applying a voltage from the first power source 532 to the rotating shaft 53A. In the present embodiment, the first power source 532 applies a voltage of −400 V to the rotating shaft 53A to charge the peripheral surface 53S to a negative potential.

  The toner collecting roller 530 is attracted to the circumferential surface 53S of the toner collecting roller 530 at a position downstream of the second nip portion N2 between the toner collecting roller 530 and the carrier liquid collecting roller 540 described below in the rotation direction. A first blade 533 for scraping off the toner that is present is disposed. The tip of the first blade 533 is in contact with the peripheral surface 53S from the rotation direction of the toner recovery roller 530 and the counter direction. The toner collected by the first blade 533 is collected in a toner collection container 534 and guided to a toner disposal container (not shown) through a toner disposal pipeline 535.

  The carrier liquid recovery roller 540 is pressed against the toner recovery roller 530 to form the second nip portion N2, and separates the carrier liquid from the thin layer TL of liquid developer carried on the peripheral surface 53S of the toner recovery roller 530. And a roller for carrying the carrier liquid on the peripheral surface 54S. In this embodiment, a stainless steel roller having good wettability with respect to the carrier liquid is used as the carrier liquid recovery roller 540.

  The carrier liquid recovery roller 540 is driven to rotate counterclockwise around the axis of the rotation shaft 54A by the third drive unit 541. The third driving unit 541 includes a motor that generates a rotational driving force, and a gear mechanism that transmits the rotational driving force to the rotation shaft 54 </ b> A of the carrier liquid recovery roller 540. The rotating shaft 54A is electrically connected to the ground path 542, whereby the carrier liquid recovery roller 540 is set to the ground potential. Accordingly, an electric field is formed between the carrier liquid recovery roller 540 and the toner recovery roller 530 such that the former peripheral surface 54S is zero potential and the latter peripheral surface 53S is −400V.

  A second blade 543 that scrapes off the carrier liquid carried on the peripheral surface 54S of the carrier liquid recovery roller 540 is disposed at a position downstream of the second nip portion N2 in the rotation direction of the carrier liquid recovery roller 540. Yes. The tip of the second blade 543 is in contact with the circumferential surface 54S from the rotation direction of the carrier liquid recovery roller 540 and the counter direction. The carrier liquid recovered by the second blade 543 is recovered in the carrier liquid recovery container 544 and guided to an apparatus (for example, the carrier tank 274 shown in FIG. 9) that reuses the carrier liquid through the carrier liquid recovery conduit 545.

  The charging device 550 applies a voltage to the thin layer TL of the liquid developer carried on the toner recovery roller 530 to charge the toner of the thin layer TL. The charging device 550 is a corotron charging device provided with a charge wire, and the toner collection roller is located upstream of the second nip portion N2 in the rotation direction of the toner collection roller 530 (downstream side of the first nip portion N1). It is arranged to face the circumferential surface 53S of 530. The charging device 550 may be a scorotron charging device or a roller charging device.

  A charging voltage is applied to the charging device 550 from the second power supply 551. In the present embodiment, the second power supply 551 supplies a positive potential of +4 kV to the charge wire. As a result, the toner in the thin layer TL is charged in the range of about + 10V to + 60V. As described above, since the peripheral surface of the toner recovery roller 530 is charged with a negative potential of −400 V, the toner charged to a positive potential is electrically adsorbed on the peripheral surface 53S of the toner recovery roller 530. . Here, if the charging voltage of the toner is +10 V or less, there is a tendency that the electric attractive force to the peripheral surface 53S cannot be sufficiently secured. On the other hand, if it exceeds + 60V, the adhesion force of the toner to the peripheral surface 53S is increased. It tends to be too strong and difficult to be scraped off from the peripheral surface by the first blade 533.

  The control device 500A controls the operations of the first driving unit 521, the second driving unit 531, the third driving unit 541, the first power source 532, and the second power source 551, thereby driving the rollers 520, 530, and 540. The charging operation by the charging device 550 and the bias application operation to the toner collecting roller 530 are controlled. Particularly in the present embodiment, the control device 500A selects the execution or stop of each of the above-described operation controls in accordance with the toner density data given from the toner concentration sensor 512, thereby causing the carrier liquid extraction device 500 to be in an operating state or a stop. State. A specific control operation of the control device 500A will be described in detail later.

  Next, the operation of the carrier liquid extraction apparatus 500 will be described with reference to FIGS. 2 and 3 in addition to FIG. When the carrier liquid extraction device 500 is operated, the metering roller 520, the toner collection roller 530, and the carrier liquid collection roller 540 are driven to rotate counterclockwise, clockwise, and counterclockwise, respectively. The rotational peripheral speed of each roller can be set to 1330 mm / s for the metering roller 520, 1200 mm / s for the toner recovery roller 530, and 1200 mm / s for the carrier liquid recovery roller 540, for example.

  By the rotation of the metering roller 520, the liquid developer LD in the liquid tank 510 adheres to the peripheral surface 52S with surface tension, is pumped, and is transported to the first nip portion N1. As the liquid developer LD pumped up passes through the first nip portion N1, a thin layer TL of the liquid developer LD is carried on the peripheral surface 53S of the toner recovery roller 530. Here, the thin layer TL is desirably a layer having a thickness of about 4 to 9 microns, particularly about 6 to 7 microns, and a uniform thickness.

  For the formation of the desirable thin layer TL, the nip depth D1 of the first nip portion N1 and the rotational peripheral speed difference between the metering roller 520 and the toner recovery roller 530 shown in FIG. It has a relatively large effect compared to the factors. The nip depth D1 for forming the thin layer TL having a thickness of about 6 to 7 microns is, for example, 0.1 mm. Further, in order to form the thin layer TL2 having substantially no thickness unevenness as shown in FIG. 3C, not the thin layer TL1 having thickness unevenness as shown in FIG. 3B. The ratio of the rotational peripheral speed of the metering roller 520 to the rotational peripheral speed of the counter-rotating toner recovery roller 530 is preferably set to about 1: 0.9, and the metering roller 520 is rotated relatively quickly. The rotational peripheral speeds of the above two rollers are set based on this ratio, and the first driving unit 521 and the second driving unit 531 change the measuring roller 520 and the toner collection roller 530 according to the setting. Drive to rotate.

  The thin layer TL whose thickness is too thick or the thin layer TL1 having uneven thickness as shown in FIG. 3B can inhibit the toner from being optimally charged by the charging device 550. Further, such a thin layer TL or TL1 may have a problem that a part thereof cannot pass through the second nip portion N2. When this problem occurs, as shown in FIG. 3A, a liquid pool B (build-up) is generated at a position immediately upstream of the second nip portion N2. When the liquid reservoir B grows, it gradually drops and causes the problem of contaminating the surroundings.

  The thin layer TL formed on the peripheral surface 53S of the toner recovery roller 530 is conveyed to the position where the charging device 550 is disposed by the clockwise rotation of the toner recovery roller 530. As described above, the charging device 550 is supplied with electric energy from the second power source 551 and applies a voltage of +4 kV to the thin layer TL present on the peripheral surface 53S of the toner recovery roller 530. On the other hand, the first power source 532 applies a voltage of −400 V to the rotation shaft 53A of the toner recovery roller 530, and the peripheral surface 53S is charged to a negative potential.

  Referring to FIG. 2, the toner particles T are irregularly suspended in the thin layer TL before passing through the charging device 550. On the other hand, since the voltage E is applied to the charging device 550 when the thin layer TL passes the position where the charging device 550 is disposed, the toner particles T in the thin layer TL have a positive potential (+ 10V to + 60V). As a result, in the thin layer TL after passing through the charging device 550, the toner particles T are electrically strongly attached to the peripheral surface 53S of the toner recovery roller 530 charged to a negative potential. Therefore, a layer structure in which the toner particles T are located immediately above the peripheral surface 53S and the carrier liquid C is positioned on the outer periphery thereof is formed.

  Thereafter, the thin layer TL moves toward the second nip portion N2. As described above, since the carrier liquid recovery roller 540 is at the ground potential, the toner particles T do not transfer to the peripheral surface 54S of the carrier liquid recovery roller 540, but are electrically applied to the peripheral surface 53S of the toner recovery roller 530. Passing through the second nip portion N2 while maintaining the state of being adsorbed to. On the other hand, since the peripheral surface 54S has good wettability with respect to the carrier liquid C, the carrier liquid C adheres to the peripheral surface 54S. As a result, after passing through the second nip portion N2, the toner particles T are transported along the peripheral surface 53S of the toner recovery roller 530 and the carrier liquid C is transported along the peripheral surface 54S of the carrier liquid recovery roller 540, respectively. Will be.

  The toner particles T on the peripheral surface 53S are scraped off by the first blade 533 (FIG. 1) and recovered in the toner recovery container 534. Note that the toner particles T and the carrier liquid C are not completely separated in the second nip portion N2, and the recovered material recovered in the toner recovery container 534 includes some carrier liquid C. Further, the carrier liquid C on the peripheral surface 54S is scraped off by the second blade 543 (FIG. 1) and recovered in the carrier liquid recovery container 544.

  The above is a series of operations of the carrier liquid extraction device 500. As described above, in this embodiment, it is important to form a thin layer TL having a predetermined thickness on the peripheral surface 53S of the toner collection roller 530. The thickness of the thin layer TL is in the liquid tank 510. There may be a case where it varies depending on the toner concentration of the liquid developer LD contained therein. The change in the thickness of the thin layer TL affects the charging characteristics of the thickness of the thin layer TL, and may make it difficult to separate the toner particles T and the carrier liquid C from each other.

  That is, the toner concentration in the liquid developer collected from the wet image forming unit is, for example, about 5%. If the liquid developer has such a toner concentration, the rotational peripheral speeds of the metering roller 520 and the toner recovery roller 530 and the nip depth D1 of the first nip portion N1 are set as in the first embodiment. A thin layer TL having a thickness of about 6 to 7 microns can be formed on the peripheral surface 53S of the toner recovery roller 530. However, the toner density may be high for some reason. For example, when the toner image carried on the photosensitive drum continues to be collected without being transferred to the paper due to the occurrence of paper jam or the like, or the toner is intentionally applied to the photosensitive drum during maintenance or the like. When the solid liquid is collected and collected, the toner concentration of the collected liquid developer increases. For example, when the toner concentration is increased to about 15%, the viscosity of the liquid developer increases, and as a result, when the rotational peripheral speed and the nip depth D1 are the same, the thickness of the thin layer TL tends to increase. This tendency becomes more prominent when the toner concentration is increased to about 30%. When the thin layer TL is thickened, the toner particles in the thin layer TL are not sufficiently charged, and it is difficult to realize a clear layer separation between the toner particles T and the carrier liquid C as shown in FIG.

  In view of this point, in this embodiment, when the toner concentration sensor 512 detects a high toner concentration exceeding a predetermined value during the operation (operating state) of the carrier liquid extraction device 500, the control device 500A extracts the carrier liquid. The operation of the device 500 is stopped. That is, when the toner concentration in the liquid developer LD is a concentration that makes it difficult to set the thin layer TL to a desired thickness, the carrier liquid extraction device 500 is stopped and the toner and the carrier liquid are separated and extracted. Is temporarily stopped. Then, when the toner concentration sensor 512 detects that the toner concentration is an appropriate value, the control device 500A restarts the operation of the carrier liquid extraction device 500. As a result, even if a situation occurs in which the toner concentration in the liquid developer LD changes, the toner and the carrier liquid can be reliably separated as a result.

  FIG. 4 is a graph showing the relationship between the toner concentration in the liquid developer LD and the output of the toner concentration sensor 512. The output voltage of the toner density sensor 512 changes as shown in FIG. 4 according to the toner density. For example, when the operation of the carrier liquid extraction device 500 is stopped when the toner concentration reaches 15%, the carrier liquid extraction device 500 determines whether or not the output voltage of the toner concentration sensor 512 exceeds 340 mV. It is set to a stopped state or an operating state. The toner concentration that determines whether or not to operate the carrier liquid extraction device 500 is determined in consideration of the charging voltage of the thin layer TL and the bias voltage applied to the toner recovery roller 530.

  FIG. 5 is a table format showing the evaluation of the extraction state of the carrier liquid. Here, when the toner density is 5% (normal time), 15% higher than this, and 30% higher than this, the charge bias supplied to the charge wire of the charging device 550 and the toner collection roller 530 are supplied. Using the applied roller bias as a parameter, how much toner remains in the carrier liquid separated by the carrier liquid recovery roller 540 is evaluated. When the toner concentration in the carrier liquid is 0.1% or less, it is given that the carrier liquid and the toner can be satisfactorily separated from each other, and a mark that does not satisfy this condition is given a cross mark. ing.

  Based on the result of FIG. 5, if the charge bias of the charging device 550 is a constant value of 4 kV, the compensation with the roller bias of the toner recovery roller 530 does not show an effect when the toner concentration is 15%. To. Therefore, the toner concentration that determines whether to operate the carrier liquid extraction device 500 can be set to 15%.

  In this case, when the toner density sensor 512 detects that the toner density in the liquid developer LD is the normal density (for example, the toner density is 5%; the first density), the control device 500A performs the first drive. 521, the second driving unit 531, the third driving unit 541, the first power source 532, and the second power source 551 are activated, and the rollers 520, 530, and 540 rotate at 1330 mm / s, 1200 mm / s, and 1200 mm / s, respectively. The carrier liquid extraction device 500 is in a state in which the charging device 550 generates a 4 kV charge bias and the first power source 532 applies a −400 V roller bias to the rotation shaft 53A of the toner recovery roller 530. Is in the operating state. Thereby, an operation of separating the liquid developer LD collected in the liquid tank 510 into toner and carrier liquid is executed.

  On the other hand, when it is detected that the toner density is a high density (for example, the toner density is 15%; the second density) that is higher than the normal value by a predetermined value or more, the control device 500A stops the active operation of each of the above parts. Then, the carrier liquid extraction device 500 is brought into a stopped state. Accordingly, it is possible to prevent the carrier liquid separation operation from being performed in a state where the thin layer TL is formed on the peripheral surface 53S with an inappropriate thickness due to the rise of the clay of the liquid developer LD. . Note that the control device 500A keeps the stirring drive unit 514 active at all times. Therefore, the stirring member 513 stirs the liquid developer LD in the liquid tank 510 even when the carrier liquid extraction device 500 is in a stopped state or an operating state.

  The liquid developer LD collected in the image forming unit is intermittently supplied to the liquid tank 510 through the developer supply pipe 511. Therefore, even if the toner concentration temporarily rises to about 15%, the toner concentration of the liquid developer LD that is normally collected is about 5%. Therefore, when a certain amount of collection proceeds, the toner concentration reaches the normal level. Return. When it is confirmed from the output value of the toner density sensor 512 that the toner density has returned from the high density level to the normal level, the control device 500A puts the carrier liquid extraction device 500 into the operating state again.

  Note that the liquid developer LD having a low toner concentration may be intentionally supplied to the liquid tank 510 in order to forcibly reduce the toner concentration of the liquid developer LD having a high concentration. As a specific method, a method of forcibly forming an image close to white paper in the image forming unit and recovering the liquid developer LD containing almost no toner can be exemplified.

  According to the carrier liquid extraction device 500 according to the embodiment described above, the thin layer TL of the liquid developer LD is carried on the peripheral surface 53S of the toner recovery roller 530, and the thin layer TL is charged by the charging device 550. Thus, the toner particles T in the thin layer TL are electrically adsorbed on the peripheral surface 53S. As a result, the toner particles T can be unevenly distributed right above the peripheral surface 53S of the toner collection roller 530 in the thin layer TL, and the carrier liquid C can be easily separated by the carrier liquid collection roller 540. Therefore, the toner particles T and the carrier liquid C can be separated at a high speed.

  Further, when the toner concentration in the liquid developer LD is increased for some reason, the operation of the carrier liquid extraction device 500 is temporarily stopped, and the separation operation of the toner particles T and the carrier liquid C under the high toner concentration is performed. Is avoided. Accordingly, as a result, the toner particles T and the carrier liquid C can be reliably separated.

[Embodiment as Image Forming Apparatus]
FIG. 6 is a schematic configuration diagram of a color printer 1 (wet image forming apparatus) in which the above-described carrier liquid extraction device 500 is incorporated, and FIG. 7 is a schematic cross-sectional view of the color printer 1 excluding the liquid developer circulating device. FIG. 8 is an enlarged cross-sectional view of one of the image forming units. Although the image forming apparatus shown in FIGS. 6 to 8 is a color printer, it is a copier, a facsimile machine, a multifunction peripheral (MFP) including these functions, and other devices capable of forming an image on a sheet. It can also be a device.

  As shown in FIG. 6, the color printer 1 is arranged in an upper main body 1A that houses various units and parts for image formation and a lower portion of the upper main body 1A, and circulates liquid developer for each color. It is comprised from the lower main-body part 1B in which apparatus LY, LM, LC, LB is accommodated. Here, the piping connecting the upper main body 1A and the lower main body 1B is not shown.

  As shown in FIG. 7, the upper main body 1 </ b> A is formed by a tandem image forming unit 2 that forms a toner image based on image data, a paper storage unit 3 that stores paper, and an image forming unit 2. A secondary transfer unit 4 that transfers the toner image onto the paper, a fixing unit 5 that fixes the transferred toner image on the paper, a discharge unit 6 that discharges the fixed paper, and a paper storage unit 3. And a paper transport unit 7 for transporting paper from the discharge unit 6 to the discharge unit 6.

  The image forming unit 2 includes an intermediate transfer belt 21, a cleaning unit 22 for the intermediate transfer belt 21, and an image forming unit corresponding to each of yellow (Y), magenta (M), cyan (C), and black (Bk). FY, FM, FC, and FB.

  The intermediate transfer belt 21 is a belt-like member that has conductivity and is wider than the maximum length of paper in the direction perpendicular to the usable paper conveyance direction, and is an endless belt-like member. In FIG. 7, it is circulated and driven clockwise. In the circulation driving of the intermediate transfer belt 21, the surface facing outward is hereinafter referred to as a front surface, and the other surface is referred to as a back surface.

  Four image forming units FY, FM, FC, and FB are arranged near the intermediate transfer belt 21 and arranged between the cleaning unit 22 and the secondary transfer unit 4 of the intermediate transfer belt 21. Note that the order of arrangement of the image forming units FY, FM, FC, and FB is not limited to this, but this arrangement is preferable in consideration of the influence of the color mixture on the completed image.

  The image forming units FY, FM, FC, and FB include a photosensitive drum 10, a charger 11, an LED exposure device 12, a developing device 14, a primary transfer roller 20, a cleaning device 26, and a charge removal device 13. And a carrier liquid removing roller 30. Further, among the image forming units, the image forming unit FB located closest to the secondary transfer unit 4 is not provided with the carrier liquid removal roller 30, but the other configurations are the same.

  Corresponding to the image forming units FY, FM, FC, FB, liquid developer circulating devices LY, LM, LC, LB are provided, respectively, so that supply and recovery of the liquid developers of the respective colors are performed. Yes. The liquid developer circulating devices LY, LM, LC, and LB will be described in detail later.

  The photosensitive drum 10 is a cylindrical member, and can carry a toner image including toner charged on its surface (charged positively in this embodiment). The photosensitive drum 10 is a member that can rotate counterclockwise in FIGS. 7 and 8. The charger 11 is a device that can uniformly charge the surface of the photosensitive drum 10. The exposure device 12 has a light source such as an LED and irradiates light onto the surface of the uniformly charged photoreceptor drum 10 in accordance with image data input from an external device. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 10.

  The developing device 14 holds a liquid developer (liquid sample) containing toner (dispersoid) and a liquid carrier (dispersion medium) so as to face the electrostatic latent image on the surface of the photosensitive drum 10, thereby Toner is attached to the electrostatic latent image. Thereby, the electrostatic latent image is developed as a toner image.

  Referring to FIG. 8, the developing device 14 includes a developing container 140, a developing roller 141, a supply roller 142, a support roller 143, a supply roller blade 144, a developing cleaning blade 145, a developer recovery device 146, and a developing roller charger 147. Including.

  The developing container 140 is a container that receives a liquid developer including toner particles and a liquid carrier. As will be described later, the liquid developer is supplied from the supply nozzle 278 into the developing container 140 in a state where the density adjustment between the toner and the carrier has been performed in advance. The liquid developer is supplied toward the nip portion between the supply roller 142 and the support roller 143, and the surplus portion falls below the support roller 143 and is stored at the bottom of the developing container 140. The stored liquid developer is recovered by the liquid developer circulating device through the pipe 82 (see FIG. 9).

  The support roller 143 is disposed substantially at the center of the developing container 140 and is in contact with the supply roller 142 in a manner of supporting from below, thereby forming a nip portion. The supply roller 142 is arranged not diagonally above the support roller 143 but obliquely upward in the direction away from the supply nozzle 278, and a groove for holding the liquid developer is provided on the peripheral surface thereof. As indicated by dotted arrows in the figure, the support roller 143 rotates counterclockwise and the supply roller 142 rotates clockwise.

  The liquid developer supplied from the supply nozzle 278 is temporarily retained upstream in the rotation direction of the nip portion, and is held in the groove of the supply roller 142 as both rollers 142 and 143 rotate. Carried up. The supply roller blade 144 is in pressure contact with the peripheral surface of the supply roller 142 and regulates the amount of liquid developer held by the supply roller 142 to be a predetermined amount. Excess liquid developer scraped off by the supply roller blade 144 is received at the bottom of the developing container 140.

  The developing roller 141 is disposed in the upper opening of the developing container 140 so as to be in contact with the supply roller 142. The developing roller 141 is rotated in the same direction as the supply roller 142 (the surface of the developing roller 141 moves in the opposite direction to the surface of the supply roller 142 in the nip portion where the developing roller 141 and the supply roller 142 abut), thereby The liquid developer held on the peripheral surface of the supply roller 142 is delivered to the peripheral surface of the developing roller 141. Since the layer thickness of the liquid developer on the supply roller 142 is regulated to a predetermined value, the layer thickness of the liquid developer layer formed on the surface of the developing roller 141 is also maintained at a predetermined value.

  The developing roller charger 147 moves the toner in the developer layer carried on the developing roller 141 to the surface side of the developing roller 141 by applying a charging potential having the same polarity as the charging polarity of the toner, thereby improving the developing efficiency. It fulfills the action of The developing roller charger 147 faces the circumferential surface of the developing roller 141 on the downstream side in the rotation direction of the developing roller 141 in contact with the supply roller 142 and on the upstream side in contact with the photosensitive drum 10. It is provided as follows.

  The developing roller 141 is in contact with the photosensitive drum 10. A toner image corresponding to the instructed image data is formed on the surface of the photosensitive drum 10 by the potential difference between the electrostatic latent image potential on the surface of the photosensitive drum 10 and the developing bias applied to the developing roller 141. .

  The developing cleaning blade 145 is disposed so as to contact the downstream side in the rotation direction of the contact portion of the developing roller 141 with the photosensitive drum 10, and the liquid development on the surface of the developing roller 141 that has completed the developing operation on the photosensitive drum 10 is performed. Remove the agent.

  The developer recovery device 146 recovers the liquid developer removed by the development cleaning blade 145 and sends the liquid developer to the pipe 81 of the liquid developer circulation device. The liquid developer flows down along the surface of the development cleaning blade 145. Since the viscosity of the liquid developer is high, the developer recovery device 146 is provided with a feed roller for assisting in feeding the liquid developer.

  The primary transfer roller 20 is disposed on the back surface of the intermediate transfer belt 21 so as to face the photosensitive drum 10. A voltage having a polarity opposite to that of the toner in the toner image (minus in this embodiment) is applied to the primary transfer roller 20 from a power source (not shown). That is, the primary transfer roller 20 applies a voltage having a polarity opposite to that of the toner to the intermediate transfer belt 21 at a position in contact with the intermediate transfer belt 21. Since the intermediate transfer belt 21 has conductivity, the applied voltage attracts toner to the surface side of the intermediate transfer belt 21 and its periphery. The intermediate transfer belt 21 functions as an image carrier that carries a toner image and conveys it to a sheet.

  The cleaning device 26 is a device for cleaning the liquid developer remaining without being transferred from the photosensitive drum 10 to the intermediate transfer belt 21, and includes a residual developer conveying screw 261 and a cleaning blade 262. . The residual developer conveying screw 261 is a member for conveying the residual developer scraped by the cleaning blade 262 and stored in the cleaning device 26 to the outside of the cleaning device, and is disposed in the cleaning device 26. Yes.

  The cleaning blade 262 is a member for scraping off the liquid developer remaining on the surface of the photosensitive drum 10 and is a plate-like member extending in the direction of the rotation axis of the photosensitive drum 10. The end of the cleaning blade 262 is in sliding contact with the surface of the photosensitive drum 10, and scrapes off the liquid developer remaining on the photosensitive drum 10 as the photosensitive drum 10 rotates.

  The static eliminator 13 has a light source for static elimination, and removes the liquid developer by the cleaning blade 262 and removes the surface of the photosensitive drum 10 with light from the light source in preparation for the next round of image formation.

  The carrier liquid removal roller 30 is a substantially cylindrical member that can rotate in the same direction as the photosensitive drum 10 around a rotational axis parallel to the rotational axis of the photosensitive drum 10. The carrier liquid removing roller 30 is disposed on the side where the secondary transfer unit 4 is disposed with respect to the position where the photosensitive drum 10 and the intermediate transfer belt 21 are in contact with each other, and the carrier liquid is removed from the surface of the intermediate transfer belt 21. The member to be removed.

  Returning to FIG. 7, the paper storage unit 3 is a part for storing paper for fixing the toner image, and is disposed at the lower part of the upper main body 1A. The paper storage unit 3 has a paper feed cassette that stores paper.

  The secondary transfer unit 4 is a part for transferring the toner image formed on the intermediate transfer belt 21 to a sheet, and is a support roller 41 that supports the intermediate transfer belt 21 and a second roller disposed opposite to the support roller. And a next transfer roller 42.

  The fixing unit 5 is a part for fixing the toner image on the sheet, and is disposed on the upper side of the secondary transfer unit 4. The fixing unit 5 includes a heating roller 51 and a pressure roller 52 disposed to face the heating roller 51.

  The discharge unit 6 is a portion from which the paper on which the toner image has been fixed by the fixing unit 5 is discharged, and is disposed at the top of the color printer 1. The paper transport unit 7 includes a plurality of transport roller pairs, and transports the paper from the paper storage unit 3 to the secondary transfer unit 4, the fixing unit 5, and the discharge unit 6.

  FIG. 9 is a block diagram showing an outline of the entire liquid developer circulating device LY. The other liquid developer circulating devices LM, LC, LB have the same configuration. This liquid developer circulation device LY circulates the residual developer (mixture of toner and carrier liquid) scraped from the surface of the developing roller 141 by the developing cleaning blade 145 after supplying the liquid developer to the photosensitive drum 10. It is a device to let you reuse.

  The liquid developer circulation device LY includes a residual developer tank 271, a developer container 272, a solid content concentration detection device 273, a carrier tank 274, a toner tank 275, a stirring device 276, a developer reserve tank 277, and a liquid developer supply device. 278, a liquid developer separation device 28 (extraction device), a plurality of pumps P1 to P12, and a control unit 560. Here, as the liquid developer separating device 28, any of the carrier liquid extracting devices 500 and 500A to 500C of the first to fourth embodiments described above is applied.

  The residual developer tank 271 is a tank that is connected to the developing device 14 via the first pipe 81 and the second pipe 82 and can store the liquid developer recovered from the developing device 14 side. A first pump P1 and a fifth pump P5 are attached in the middle of the first pipe 81 and the second pipe 82, respectively.

  The liquid developer scraped from the surface of the developing roller 141 by the developing cleaning blade 145 after supplying the toner to the photosensitive drum 10 is sent to the residual developer tank 271 through the first pipe 81 by driving the first pump P1. It is done. Further, the liquid developer stored in the developing container 140 without being supplied from the supply roller 142 to the developing roller 141 in the developing container 140 is driven to the residual developer tank 271 through the second pipe 82 by driving the fifth pump P5. Sent.

  The developer container 272 is connected to the residual developer tank 271. The developer container 272 adjusts the toner concentration to an appropriate range by adding a developer having a toner concentration higher than that of the developer used in the developing device 14 or a carrier liquid to the residual developer. The toner density is adjusted to an appropriate range. The liquid developer whose toner concentration is adjusted is supplied to the developing device 14. The developer container 272 is connected to the residual developer tank 271 via a third pipe 83, and a second pump P2 is attached to the third pipe 83. The liquid developer in the residual developer tank 271 is sent to the developer container 272 through the third pipe 83 by driving the second pump P2.

  The solid content concentration detection device 273 is a device for detecting the toner concentration of the liquid developer in the developer container 272. A solid concentration detector 273 is connected to an annular fourth pipe 84 connected to the developer container 272. A fourth pump P4 is attached to the annular fourth pipe 84. The liquid developer in the developer container 272 is guided from the inlet end of the fourth pipe 84 to the solid concentration detector 273 by driving the fourth pump P4, and then the developer is accommodated from the outlet end of the fourth pipe 84. Returned to container 272.

  The carrier tank 274 is a tank that stores a carrier liquid. When the solid concentration detector 273 determines that the toner concentration in the developer container 272 is higher than the appropriate range, the carrier liquid is supplied from the carrier tank 274 into the developer container 272, and the container 272 The toner concentration of the liquid developer inside is lowered. The carrier tank 274 and the developer container 272 are connected by a fifth pipe 85, and the supply of the carrier liquid is executed by driving a third pump P3 provided in the middle of the fifth pipe 85.

  The toner tank 275 is a tank that stores a liquid developer having a toner concentration higher than that of the developer used in the developing device 14. When the solid content concentration detection device 273 determines that the toner concentration in the developer storage container 272 is lower than the appropriate range, a liquid developer having a high toner concentration is transferred from the toner tank 275 into the developer storage container 272. The toner concentration of the liquid developer in the container 272 is increased. The toner tank 275 and the developer container 272 are connected by a sixth pipe 86, and the supply of the liquid developer is executed by driving an eighth pump P8 provided in the middle of the sixth pipe 86.

  The stirring device 276 is a member for stirring the liquid developer in the developer container 272. The purpose of this stirring is to allow the toner or carrier liquid introduced into the developer container 272 for density adjustment to be uniformly mixed with the existing liquid developer in the developer container 272. This is to redisperse the toner that may aggregate in the liquid developer contained in the developer containing container 272. The stirring device 276 includes a rotating shaft and a stirring blade attached to the tip of the rotating shaft. A liquid level detecting member 276a is coaxially assembled to the rotating shaft. The liquid level detection member 276a is driven by a motor (not shown), and the amount of liquid developer is detected based on a change in the load of the motor caused by the liquid level detection member 276a coming into contact with the liquid level of the liquid developer. The

  The developer reserve tank 277 is a tank that stores a liquid developer to be replenished to the developing device 14. The developer reserve tank 277 is connected to the developer container 272 by a seventh pipe 871, and the liquid developer is removed from the developer container 272 by driving a sixth pump P6 provided in the middle of the seventh pipe 871. Receive the supply. Further, the developer reserve tank 277 is connected by a carrier tank 274 and a first direct connection pipe 910, and by a toner tank 275 and a second direct connection pipe 920, respectively. An eleventh pump P11 and a twelfth pump P12 are arranged in the first and second direct connection pipes 910 and 920, respectively, so that carrier and toner can be directly supplied from each tank to the developer reserve tank 277. The carrier and toner supply systems from these first and second direct connection pipes 910 and 920 are used to quickly develop liquid according to a known blending ratio at the start of use of the color printer 1 in which no recovered liquid developer has yet been generated. It is utilized when producing agents.

The supply nozzle 278 is a member for supplying the liquid developer stored in the developer reserve tank 277 to the developing device 14 (developing container 140). The supply nozzle 278 and the developer reserve tank 277 are connected by an eighth pipe 872, and the supply of the liquid developer is executed by driving a seventh pump P7 attached to the eighth pipe 872.
A direct connection conduit 910 extending from the carrier tank 274 to the developer reserve tank 277 and a direct connection conduit 920 extending from the toner tank 275 to the developer reserve tank 277 are provided. These direct connection pipes 910 and 920 are used to supply a predetermined amount of carrier and toner to the developer reserve tank 277 before circulation. This makes it possible to start the development process quickly.

  Although not shown, liquid level detection for detecting the liquid level in these tanks is provided at appropriate positions of the residual developer tank 271, the carrier tank 274, the toner tank 275, and the developer reserve tank 277. A device is provided.

  The liquid developer separation device 28 (extraction device) is a device that separates the toner and the carrier liquid from the residual developer collected by the cleaning device 26 and separately extracts the toner and the carrier liquid. The cleaning device 26 and the liquid developer separating device 28 are connected by a ninth pipe 881 to which a ninth pump P9 is attached. The residual developer in the cleaning device 26 is sent to the liquid developer separating device 28 by driving the ninth pump P9. A tenth pipe 882 to which a tenth pump P10 is attached is provided between the liquid developer separating device 28 and the carrier tank 274. The carrier liquid extracted by the liquid developer separating device 28 is sent to the carrier tank 274 by driving the tenth pump P10. Here, the developer supply pipe 511 in FIG. 1 corresponds to the ninth pipe 881, and the carrier liquid recovery pipe 545 corresponds to the tenth pipe 882.

  The control unit 560 includes a CPU (Central Processing Unit) that performs arithmetic processing, a ROM (Read Only Memory) that stores each control program, and a RAM (Random Access Memory) that temporarily stores data such as arithmetic processing and control processing. Etc. The controller 560 controls driving of the first to twelfth pumps P1 to P12, driving of a motor that operates the liquid level detection member 276a, and the like.

  Next, the operation of the color printer 1 will be described. Upon receiving an image formation instruction from a personal computer (not shown) connected to the color printer 1, the color printer 1 converts toner images of each color corresponding to the image data received with the creation instruction into image forming units FY, FM, FC, It is formed using FB. Specifically, an electrostatic latent image based on image data is formed on the photosensitive drum 10, and toner is supplied to the electrostatic latent image from the developing device 14. The images formed by the image forming units FY, FM, FC, and FB in this way are transferred to the intermediate transfer belt 21 and are superimposed on the intermediate transfer belt 21 to form a color toner image.

  In synchronization with the formation of the color toner image, the paper stored in the paper storage unit 3 is taken out from the paper storage unit 3 one by one by a paper feeding device (not shown), and is conveyed along the paper conveyance unit 7. . Then, the sheet is sent to the secondary transfer unit 4 in synchronization with the primary transfer to the intermediate transfer belt 21, and the color toner image on the intermediate transfer belt 21 is secondarily transferred to the sheet by the secondary transfer unit 4.

  The sheet on which the color toner image is transferred is further conveyed to the fixing unit 5 where the color toner image is fixed on the sheet by heat and pressure. Further, the paper is discharged outside the color printer 1 by the discharge unit 6. The toner remaining on the intermediate transfer belt 21 after the secondary transfer is removed from the intermediate transfer belt 21 by the cleaning unit 22 of the intermediate transfer belt 21.

  The liquid developer remaining on the developing roller 141 without being supplied to the photosensitive drum 10 during the image forming operation is scraped off by the developing cleaning blade 145 and collected in the residual developer tank 271 through the first pipe 81. . Further, the liquid developer collected in the developing container 140 without being supplied from the supply roller 142 to the developing roller 141 is also collected in the residual developer tank 271 through the second pipe 82. Further, the carrier liquid extracted by the liquid developer separating device 28 from the residual developer recovered by the cleaning device 26 is recovered to the carrier tank 274. In order to execute such liquid circulation, the first, fifth, ninth, and tenth pumps P1, P5, P9, and P10 are driven and controlled by the control unit 560.

  When the amount of liquid developer in the developer storage container 272 is exhausted, the control unit 560 drives the second pump P2 to supply the residual developer from the residual developer tank 271 to the developer storage container 272. When the developer container 272 is filled with the remaining developer, the solid concentration detector 273 detects the toner concentration of the liquid developer. In accordance with the detection result, the control unit 560 drives the third pump P3 or the eighth pump P8 to supply a necessary amount of carrier liquid or high-concentration liquid developer to the developer container 272. Thereafter, the toner concentration of the liquid developer is detected again by the solid content concentration detection device 273. If the toner concentration is within an appropriate range, the liquid developer is supplied to the developer reserve tank 277 as necessary.

  In the liquid developer separating device 28, the carrier liquid and toner particles are separated by the operation described in the previous embodiment of the carrier liquid extracting device 500. That is, the recovered liquid developer is introduced into the liquid tank 510 through the ninth pipe 881 (developer supply pipe 511). The carrier liquid separated by the carrier liquid recovery roller 540 is sent to the carrier tank 274 through the tenth pipe 882 (carrier liquid recovery conduit 545). On the other hand, the toner recovered from the toner recovery roller 530 is guided to a waste tank. According to the color printer 1 provided with such a liquid developer separation device 28, the separation speed between the toner and the carrier liquid can be increased, so that it is possible to cope with high-speed printing processing.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these, For example, the following modified embodiment can be taken.

  (1) In the above embodiment, the case where the liquid sample to be processed is the liquid developer, the dispersoid is the toner, and the dispersion medium is the carrier liquid is exemplified. The present invention is not limited to this, and can be widely applied to any liquid sample that includes a dispersoid and a dispersion medium and can charge the dispersoid. For example, a liquid sample in which the dispersoid is a pigment and the dispersion medium is moisture may be used.

  (2) In the above embodiment, the carrier liquid recovery roller 540 is exemplified as the separation member. Instead of such a roller member, a blade member whose tip is in contact with the peripheral surface 53S of the toner recovery roller 530 may be used as the separation member.

  (3) In the above embodiment, the thin layer TL is formed by passing the liquid developer LD pumped up by the metering roller 520 through the first nip portion N1 as the thin layer forming unit. Instead, the regulating blade member is used as a thin layer forming member with a predetermined interval (interval corresponding to the thickness of the thin layer TL) at a predetermined interval (interval corresponding to the thickness of the thin layer TL) on the peripheral surface 53S of the toner collecting roller 530. Also good.

  (4) In the above-described embodiment, the configuration including the carrier liquid recovery roller 540, the charging device 550, and the first power source 532 that applies a potential to the rotation shaft of the toner recovery roller 520 is exemplified as the separation unit. This is an example of the separation means, and other means can be applied as long as the toner and the carrier liquid can be separated. For example, a blade member may be used instead of the carrier liquid recovery roller 540.

1 Color printer (wet image forming device)
28 Liquid developer separation device (extraction device)
500 Carrier liquid extraction device (extraction device)
500A Control device (control means)
510 Liquid tank 511 Developer supply pipe (line for supplying liquid sample intermittently)
512 toner density sensor (density detection means)
513 Stirring member (stirring means)
514 Stirring drive unit (drive control means)
520 Weighing roller (third roller)
530 Toner recovery roller (first roller)
540 Carrier liquid recovery roller (second roller)
550 Charging device

Claims (12)

An extraction device for separating the dispersoid and the dispersion medium from a liquid sample containing the dispersoid and the dispersion medium, and extracting them.
A first roller carrying a thin layer of a liquid sample containing a dispersoid and a dispersion medium on its peripheral surface and rotating about an axis;
A liquid tank for storing the liquid sample;
A thin layer forming means for forming the thin layer of the liquid sample on the peripheral surface of the first roller using the liquid sample in the liquid tank;
Separation means for separating the dispersion medium from the thin layer in a state in which the dispersoid in the thin layer is electrically adsorbed on the peripheral surface of the first roller;
Concentration detecting means for detecting the concentration of the dispersoid in the liquid sample;
Control means for controlling the driving of at least the thin layer forming means and the first roller according to the concentration detection result of the dispersoid by the density detecting means, thereby bringing the extraction device into an operating state or a stopped state;
An extraction device comprising: The extraction device of claim 1,
The control means includes
When the concentration detection means detects that the concentration of the dispersoid is the first concentration, the extraction device is set to the operation state,
When the concentration detection unit detects that the concentration of the dispersoid is a second concentration that is higher than the first concentration by a predetermined value or more, the extraction device is set to the stopped state;
An extraction device characterized by that. The extraction device according to claim 1 or 2, further comprising:
An extraction apparatus comprising stirring means for stirring the liquid sample in the liquid tank. The extraction device of claim 3, further comprising:
A conduit for intermittently supplying the liquid sample to the liquid tank;
Drive control means for controlling the drive of the stirring means,
The extraction device characterized in that the drive control means operates the agitation means regardless of whether the control means places the extraction device in an operating state or a stopped state. In the extraction apparatus in any one of Claims 1-4,
The separating means includes
A separation member that contacts the first roller and separates the dispersion medium from the thin layer carried by the first roller;
A charging device that charges the dispersoid in the thin layer carried by the first roller at a position upstream of the first roller in the rotational direction of the first roller relative to the contact position of the separation member;
And an electric field forming means for forming an electric field for electrically attracting the charged dispersoid to the peripheral surface of the first roller. The extraction device of claim 5,
The extraction device, wherein the separation member is a second roller carrying the dispersion medium on a peripheral surface thereof and rotating around an axis. The extraction device according to claim 5 or 6,
The thin layer forming means is a third roller that is arranged so that a peripheral surface thereof is in contact with the liquid sample in the liquid tank, rotates about an axis, and conveys the liquid sample along the peripheral surface. And
The third roller is abutted against the first roller at a position upstream of the charging device in the rotation direction of the first roller to form a nip portion,
The liquid sample conveyed on the peripheral surface of the third roller passes through the nip portion, whereby the thin layer is formed on the peripheral surface of the first roller. The extraction device of claim 7, further comprising:
Drive means for driving the first roller and the third roller to rotate about their respective axes;
The driving means rotates the first roller and the third roller in opposite directions and rotates the third roller so that the rotational peripheral speed of the third roller is faster than the rotational peripheral speed of the first roller. Feature extraction device. In the extraction apparatus in any one of Claims 5-8,
The electric field forming means is a power source for applying a negative electric field to the first roller,
The charging device positively charges the dispersoid in the thin layer. In the extraction apparatus in any one of Claims 1-9,
An extraction apparatus, wherein the liquid sample is a liquid developer, the dispersoid is toner, and the dispersion medium is a carrier liquid.   A wet image forming apparatus comprising the extraction device according to claim 10. An image forming apparatus,
A photosensitive drum carrying a toner image on its peripheral surface;
A developing unit for supplying a liquid developer containing toner and a carrier liquid to the photosensitive drum;
A developer generating section for generating a liquid developer in which the mixing ratio of the toner and the carrier liquid is adjusted;
A first supply system for supplying a developer having a higher toner concentration than the developer used in the developing unit to the developer generating unit;
A second supply system for supplying the carrier liquid to the developer generator;
A third supply system for supplying the liquid developer generated by the developer generation unit to the development unit via a reserve tank;
A collection system for collecting the liquid developer supplied to the developing unit, which has not been consumed in the developing unit or the photosensitive drum, and supplying the liquid developer to the developer generating unit;
The extraction device according to claim 10 provided in the recovery system, separating the toner and the carrier liquid from the recovered liquid developer, and extracting them.
A wet image forming apparatus.

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