JP2006243129A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize a characteristic of liquid toner and to obtain uniform image quality by supplying to a developing device while a dispersant concentration of carrier liquid in a tank is made constant with a simple constitution. <P>SOLUTION: An image forming apparatus using the liquid toner with the carrier liquid dispersed in the toner is provided with a recovery carrier liquid transporting path transporting the carrier liquid recovered from a recovery position by dropping due to gravity and a new carrier liquid supplying path which supplies the new carrier liquid from a new carrier liquid replenishing tank by dropping due to gravity is joined to a part of the recovery carrier liquid transporting path. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that develops an electrostatic latent image formed on a photoreceptor with liquid toner in which toner particles are dispersed in a carrier liquid.

  2. Description of the Related Art Conventionally, there is known an image forming apparatus that develops an electrostatic latent image using a liquid toner obtained by dispersing toner in a carrier liquid. In such an image forming apparatus, a technique for collecting and reusing liquid toner is also known.

Japanese Patent Laid-Open No. 10-282969 (hereinafter referred to as “known example”) collects liquid toner that has not been used for development in an image forming apparatus that develops an electrostatic latent image with liquid toner, It is disclosed that a concentrated liquid and a carrier liquid or a low-concentrated liquid are separated and collected in separate containers, and these are mixed as appropriate, adjusted to a predetermined concentration, and then reused. In addition, it is disclosed that the recovered carrier liquid is recovered in a new carrier tank and used in a state where the new carrier liquid and the recovered carrier liquid are mixed.
By the way, according to a known example, in the case of an apparatus for applying a pre-wet liquid onto a photoconductor, the pre-wet liquid and the liquid toner are mixed in the developing process, so that the concentration of the recovered liquid toner is lowered. The collected liquid is separated into a high concentration liquid and a carrier liquid or a low concentration liquid, and a part of the low concentration liquid is mixed with the high concentration liquid as necessary to adjust to a predetermined concentration and reused. be able to. Therefore, in normal operation, the carrier liquid or the low concentration liquid is surplus, and a new carrier is not required and is used as an auxiliary. In other words, when the toner in the container is discarded because it is used for fine adjustment of the toner density / viscosity after the above toner density adjustment or dust is mixed into the toner in the developing container, it is mixed with new high-concentration toner. In this case, a toner liquid having a predetermined concentration is produced.
JP-A-10-282969

On the other hand, in the case of an apparatus that does not use a pre-wet liquid, the concentration of the recovered toner liquid is not reduced by the pre-wet liquid, so the concentration of the recovered liquid is not necessarily lower than the predetermined concentration. When only solid printing is performed, toner particles are not consumed at all, and only the carrier liquid is consumed. In this case, it is necessary to replenish a new carrier liquid in order to make the recovered liquid have a predetermined concentration. In normal printing as well as in such extremely low printing density, when printing with a printing density lower than the limit printing density determined by the apparatus setting, it is necessary to continue to supply the carrier liquid for toner density adjustment.
However, the new carrier liquid does not contain a dispersant, whereas the recovered carrier liquid contains a dispersant. This is because there exists a dispersant that is separated from the toner particles by an electric field applied at the development nip and a dispersant that is originally suspended in the carrier liquid as an excess dispersant. Thus, in a configuration in which the recovered carrier liquid is simply recovered from the upper portion as in a known example in a state where the dispersant is present in the recovered carrier liquid, the concentration of the dispersant is not present in the recovered carrier liquid in the initial use state. At the time of adjustment, a pure carrier liquid is supplied to the developing device, but as the operation of the apparatus proceeds, the concentration of the dispersant in the recovered carrier liquid increases. As a result, since the concentration of the dispersant in the carrier liquid supplied to the developing device changes, the characteristics of the liquid toner whose concentration has been controlled fluctuate, resulting in a problem that a uniform image quality cannot be obtained.

  The present invention solves the above-described problems and stabilizes the characteristics of the liquid toner by supplying a constant concentration of the dispersant in the carrier liquid in the tank to the developing device with a simple configuration, thereby obtaining a uniform image quality. An object is to provide a forming apparatus.

  In order to solve the above-mentioned problems, the first invention provides a recovered carrier liquid transport path for transporting a carrier liquid recovered from a recovery position by gravity drop in an image forming apparatus using liquid toner in which toner is dispersed in a carrier liquid. And a new carrier liquid supply path for supplying a new carrier liquid from a new carrier liquid supply tank by gravity drop is partly joined to a part of the recovered carrier liquid transport path.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, a flow rate adjusting valve is provided downstream of a junction portion between the recovered carrier transport path and the new carrier liquid supply path.

  According to a third aspect of the present invention, in the image forming apparatus of the first or second aspect, in the case of a color image forming apparatus, each image forming station is provided with a recovery carrier transport path and a new carrier liquid supply tank.

  According to a fourth aspect of the present invention, in the image forming apparatus of the first or second aspect, in the case of a color image forming apparatus, a recovery carrier liquid transport path and a new carrier liquid replenishing tank common to each image forming station are provided. To do.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects of the invention, the new carrier liquid supply tank is a replaceable cartridge.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect of the present invention, a check valve is provided at both the cartridge and the joint portion.

In the image forming apparatus using the liquid toner in which the toner is dispersed in the carrier liquid of the present invention, the image forming apparatus has a recovery carrier liquid transfer path for transferring the carrier liquid recovered from the recovery position by gravity drop, and the recovery carrier liquid transfer path Liquid toner concentration adjustment tank with a constant ratio of recovered carrier liquid and new carrier liquid in a steady state by partly combining a new carrier liquid supply path that supplies new carrier liquid by gravity drop from a new carrier liquid replenishment tank Therefore, the concentration of the dispersant in the carrier liquid supplied from the liquid toner concentration adjusting tank to the developing device is constant, and the characteristics of the liquid toner are stabilized, so that a uniform image quality image can be obtained.
When the replenishment amount is small relative to the amount of recovered carrier liquid due to the configuration in which the flow rate adjustment valve is provided downstream of the merged part of the recovered carrier transport path with the new carrier liquid supply path (for example, when all solid printing is performed continuously, etc.) ), The flow rate adjustment valve is throttled, and the new carrier liquid supply container can be used as a buffer for temporarily storing the recovered carrier liquid.
In the case of a color image forming apparatus, a recovery carrier transport path and a new carrier liquid supply tank are provided for each image forming station, so that the recovery carrier liquid and the new carrier liquid are supplied according to the amount of liquid toner consumed in each image forming station. The supply amount can be controlled.
In the case of a color image forming apparatus, it is possible to make the entire apparatus compact by providing a recovery carrier liquid transport path and a new carrier liquid supply tank common to each image forming station.
The new carrier liquid supply tank has a replaceable cartridge, which makes it easy for the user to install and remove.
By providing a check valve in both the cartridge and its joint, it is possible to prevent back flow of liquid from the cartridge and the joint when removed by the user.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the overall configuration of an embodiment of an image forming apparatus of the present invention. As shown in FIG. 1, the image forming apparatus according to this embodiment includes yellow, magenta, and cyan below an intermediate transfer belt 400 stretched around a drive roller 401, a cleaner backup roller 402, and auxiliary rollers 403 and 404, respectively. The image forming units Y, M, C, and K for black are arranged in a tandem configuration.

  An image forming procedure of the image forming apparatus according to the present embodiment will be described by using the black image forming unit K as a representative. The image forming units Y, M, and C for yellow, magenta, cyan, and black have the same configuration as the image forming unit for black, and description thereof is omitted.

  The photoconductor 100 composed of an organic photoconductor or an amorphous silicon photoconductor is uniformly charged by the charger 110 while a bias having the same polarity as the charge polarity of the liquid toner is applied from a power supply device (not shown). Is done.

  Next, an electrostatic latent image for black image is written on the uniformly charged photoreceptor 100 by a laser scanning optical system 200 disposed below each color image forming unit.

  The developing device 300 includes a container 320 that stores liquid toner. The container 320 includes a toner supply roller 305 provided with fine irregularities such as spiral grooves on the surface thereof, and a toner in which urethane rubber is provided at the tip of a flexible metal plate so as to contact the rotating toner supply roller 305. The regulating blade 306 scrapes off the liquid toner within the irregularities on the surface of the toner supply roller 305. The liquid toner contained in the irregularities on the surface of the toner supply roller 305 is transferred to the surface of the developing roller 301 by bringing the developing roller 301 having an elastic member such as conductive urethane rubber into contact with the surface of the metal core. An uneven pattern on the surface of the toner supply roller 305 by the leveling roller 308 applied to the developing roller 301 and rotated in contact with the developing roller 301 and applied with a bias having the same polarity as the charging polarity of the liquid toner higher than that of the developing roller 301 from a power supply device (not shown). Erasing and making the liquid toner film thickness uniform. The leveling roller blade 309 contacts the leveling roller 308 in the counter direction, and scrapes off the liquid toner adhering to the leveling roller 308. The liquid toner scraped off by the leveling roller blade 309 is returned to the storage part of the container 320 by gravity. In the developing device 300, a uniform liquid toner layer is formed on the developing roller 301, and the developing roller 301 to which a developing bias having the same polarity as the liquid toner is applied from a power supply device (not shown) is formed on the photosensitive member 100. The electrostatic latent image for black image is visualized with liquid toner by rotating in contact with the electrostatic latent image for image.

  In the liquid toner used in this embodiment, a solid particle having an average particle diameter of 1 μm in which a colorant such as a pigment is dispersed in a thermoplastic resin is dispersed in a liquid solvent such as an organic solvent, silicon oil, mineral oil, or edible oil. About 20% by weight dispersed while being added.

  The developing roller 301 may have a structure in which an elastic member such as conductive urethane rubber and a resin layer or a rubber layer are provided on the outer periphery of a metal core.

  The developing roller blade 307 is brought into contact with the surface of the developing roller 301 on the downstream side of the developing nip, and the liquid toner remaining as a developing residue is scraped off to clean the surface of the developing roller 301. The liquid toner scraped off by the developing roller blade 307 is conveyed and collected by gravity drop to the liquid toner concentration adjustment tank 340 (see FIG. 2) through the collection path 341 (see FIG. 2).

  The liquid toner image immediately after being formed on the photoconductor 100 by the developing roller 301 has a high carrier liquid ratio, and if color is superimposed on the intermediate transfer belt 400 by a transfer device described later, there is a possibility of causing an image flow. An excess carrier liquid is copied by a squeezing roller 330 that rotates in contact with the photoreceptor 100 while applying a bias having the same polarity as the charging characteristics of the toner, and a process of increasing the solid particle ratio in the visible image is performed. The carrier liquid copied onto the squeezing roller 330 is scraped off by the squeezing roller cleaner 331, and is transported to the liquid toner concentration adjusting tank 340 (see FIG. 2) via the recovered carrier liquid transporting path 342 (see FIG. 2) due to gravity drop. Collected.

  The squeezing roller 330 is preferably an elastic roller in which an elastic member such as conductive urethane rubber and a fluororesin surface layer are arranged on the surface of a metal core.

  Next, the visible image on the photoconductor 100 is applied to a primary transfer roller 405 that rotates in contact with the intermediate transfer belt 400 by applying a bias having a polarity opposite to the charging characteristic of the liquid toner from a power supply device (not shown). The image is primarily transferred to the transfer belt 400, and is superposed on a visible image of another color formed on the upstream side in the rotational direction of the intermediate transfer belt 400 by a similar image forming procedure to form a full color image.

  After the primary transfer, the electrostatic latent image is erased by the static elimination lamp 120 formed of a rod-shaped light source, and the liquid toner remaining in the primary transfer is scraped off by the photosensitive member cleaning blade 130 that is in contact with the photosensitive member 100.

  The used liquid toner scraped off by the photoconductor cleaning blade 130 is conveyed and collected by gravity drop to the liquid toner concentration adjustment tank 340 (see FIG. 2) via the collection carrier liquid carrying path 342 (see FIG. 2).

  Each color visible image formed on the intermediate transfer belt 400 proceeds to a secondary transfer portion constituted by the intermediate transfer belt 400, a driving roller 401, and a secondary transfer roller 430.

  Corresponding to the timing of image formation, a recording medium 501 such as paper stacked in a paper feed cassette 500 is separated by a pickup roller 502 and a separation pad 503, and a pair of conveying rollers 504, skew feeding of the recording medium, and the like. The sheet is fed to the secondary transfer section through a registration roller pair 505 that corrects the feeding timing.

  The secondary transfer roller 430 is urged by an urging means (not shown) to the driving roller 401 via the intermediate transfer belt 400, and an intermediate transfer is performed by applying a bias having a polarity opposite to the charging characteristics of the liquid toner from a power supply device (not shown). The full color image on the belt 400 is secondarily transferred to the recording medium 501.

  The secondary transfer roller 430 is an intermediate transfer belt 400 between the paper dust and the recording medium attached to the surface of the secondary transfer roller 420 by the secondary transfer roller cleaning blade 421 that is in contact with the secondary transfer roller 430 by the secondary transfer roller cleaner 420. The liquid toner adhering to is scraped off. Paper dust and liquid toner scraped off by the secondary transfer roller cleaning blade 421 are conveyed in the depth direction of FIG. 1 by the conveying screw 422 and collected in a waste toner container (not shown).

  After the secondary transfer, the intermediate transfer belt 400 is subjected to secondary transfer residual toner and paper dust remaining on the surface of the intermediate transfer belt 400 by a belt cleaning blade 411 in a belt cleaner 410 that contacts the cleaner backup roller 402 via the intermediate transfer belt 400. Is scraped off. The secondary transfer residual toner and paper dust scraped off by the belt cleaning blade 411 are transported in the depth direction of FIG. 1 by the transport screw 412 and collected in a waste toner container (not shown).

  A recording medium 501 carrying a secondary-transferred full-color image passes through a fixing device 600 including a heat roller 601 having a heating means inside and a pressure roller 602 having an elastic member such as rubber outside. While the thermoplastic resin in the full-color image is melted, it is pressure-fixed to the recording medium 501 to obtain a desired image.

  After the fixing, the recording medium 501 is discharged from the upper surface of the image forming apparatus by a pair of discharge rollers 506. When forming an image on the back side of the same recording medium 501, the recording medium 501 is switched back by a pair of discharge rollers 506 that can be rotated in the forward and reverse directions, and registered by a pair of refeed rollers 507, 508, and 509. The image is again transferred to the back surface of the recording medium 501 by the secondary transfer unit via the roller pair 505, and after the image is fixed by the fixing device 600, the upper surface of the image forming apparatus is discharged by the paper discharge roller pair 506.

  FIG. 2 is a view showing a reuse state of the liquid toner in the image forming apparatus of the present invention, and FIG. 3 is a partially enlarged view thereof. The container 320 for storing the liquid toner of the developing device 300 and the liquid toner concentration adjusting tank 340 communicate with each other via the communication path 343. A pump 344 for supplying the liquid toner adjusted to a predetermined concentration by the liquid toner concentration adjusting tank 340 to the liquid toner storage portion of the container 320 is disposed in the communication path 343.

  The liquid toner concentration adjustment tank 340 is provided with a stirring member 345 for stirring the carrier liquid and the toner. The liquid toner concentration adjustment tank 340 is provided with a concentration detection means (not shown) for detecting the concentration of the liquid toner. The liquid toner concentration adjustment tank 340 is supplied with toner (solid content concentration of 25%) from the toner tank 346 through the toner supply pipe 347. A pump 348 for supplying toner is disposed in the toner supply pipe 347. The toner is forcibly supplied by the pump 348 because the toner has high viscosity and low fluidity.

  The liquid toner scraped off from the surface of the developing roller 301 by the developing roller blade 307 is conveyed to the liquid toner concentration adjustment tank 340 through the recovery path 341 by gravity drop. Further, the used liquid toner scraped off from the surface of the photoconductor 100 by the photoconductor cleaning blade 130 is transported and collected to the liquid toner concentration adjustment tank 340 through the collection carrier liquid carrying path 342 by gravity drop.

  Further, excessive carrier liquid is copied by the squeezing roller 330 that rotates in contact with the photosensitive member 100, and the carrier liquid copied to the squeezing roller 330 is scraped by the squeezing roller cleaner 331, and the recovered carrier liquid is conveyed by gravity drop. Via a path 342, the liquid toner concentration adjustment tank 340 is conveyed and collected. Further, a recovered carrier liquid that is scraped from the intermediate transfer belt 400 after the secondary transfer by the belt cleaning blade 411 may be used.

  A new carrier liquid supply path 350 for supplying a new carrier liquid from the new carrier liquid supply tank 349 by gravity drop is joined in the middle of the recovered carrier liquid transport path 342. Since the recovered carrier liquid and the new carrier liquid have low viscosity, they can be transported by gravity drop without using a pump. Since the recovered carrier liquid and the new carrier liquid are supplied together to the liquid concentration adjustment tank 340, the concentration change of the dispersant in the recovered carrier liquid is reduced by the new carrier liquid not containing the dispersant, and the liquid toner concentration The characteristics of the liquid toner supplied from the adjustment tank 340 to the developing device 300 are stabilized, and a uniform image quality image is obtained.

A flow rate adjustment valve 351 is disposed downstream of the junction between the recovered carrier liquid transport path 342 and the new carrier liquid supply path 350. When the replenishment amount is small with respect to the recovered carrier liquid amount (for example, when all the solid printing is continuously performed), the flow rate adjustment valve 351 is throttled and the new carrier liquid replenishment container is used for temporarily storing the recovered carrier liquid. It can be used as a buffer.

  In the embodiment of the present invention shown in FIGS. 2 and 3, each of the image forming stations Y, M, C, and K of the color image forming apparatus is provided with a recovery carrier liquid transport path 342 and a new carrier liquid supply tank 349. However, as shown in FIG. 4, a recovery carrier liquid transport path 342 and a new carrier liquid supply tank 349 that are common to the image forming stations Y, M, C, and K for color image formation may be provided. Good.

  A flexible pipe such as a Tygon tube can be used as the pipe for the recovered carrier liquid transfer path 342 and the like. By making the piping flexible, the degree of freedom of arrangement of the apparatus increases. In order to ensure fluidity, the pipe diameter may be changed in various places.

  FIG. 5 shows an embodiment in which the new carrier liquid supply tank 349 is a replaceable new carrier liquid cartridge 352. (The toner tank is not shown in FIG. 5) A bifurcated portion is formed in a part of the recovered carrier liquid transport path 342, a joint 353 is formed in the recovered carrier liquid transport path 342, and the recovered carrier liquid is transported to the joint 353. A path-side check valve 354 is disposed. In addition, a new carrier liquid cartridge side check valve 355 is disposed at the junction of the new carrier liquid cartridge 352. By using the new carrier liquid replenishing tank 349 as a cartridge, the user can easily replace the cartridge, and by providing check valves on both, the ejection of liquid during cartridge replacement can be prevented.

It is a figure which shows one Embodiment of this invention. It is a figure which shows one Embodiment of this invention. It is a figure which shows one Embodiment of this invention. It is a figure which shows one Embodiment of this invention. It is a figure which shows one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100: Photoconductor, 110: Charger, 120: Static elimination lamp, 130: Photoconductor cleaning blade, 200: Laser scanning optical system, 300: Development apparatus, 301: Development roller, 305: Toner supply roller, 306: Toner regulation blade 307: developing roller blade, 308: leveling roller, 309: leveling roller blade, 320: container, 330: squeezing roller, 331: squeezing roller cleaner, 340: liquid toner concentration adjustment tank, 341: recovery path, 342: Collection carrier transport path, 343: communication path, 344: pump, 345: stirring member, 346: toner tank, 347: toner supply pipe, 348: pump, 349: new carrier liquid supply tank, 350: new carrier liquid supply path, 351: Flow rate adjusting valve, 352: New carrier liquid cartridge, 353: Joint part, 354 :: Collected carrier liquid transport path side check valve, 355: New carrier liquid cartridge side check valve, 400: Intermediate transfer belt, 401: Drive roller, 402: Cleaner backup roller, 403, 404: Auxiliary roller 405: primary transfer roller, 410: belt cleaner, 411: belt cleaning blade, 412: transport screw, 420: secondary transfer roller cleaner, 421: secondary transfer roller cleaning blade, 422: transport screw, 430: secondary transfer Roller, 501: Recording medium, 502: Pickup roller, 503: Separation pad, 504: Conveyance roller, 505: Registration roller, 506: Paper discharge roller pair, 507, 508, 509: Refeed roller pair, 600: Fixing device 601: heat roller, 602: pressure roller,

Claims (6)

In an image forming apparatus using liquid toner in which toner is dispersed in a carrier liquid, the image forming apparatus has a collection carrier liquid conveyance path for conveying the carrier liquid collected from the collection position by gravity drop, and a part of the collection carrier liquid conveyance path An image forming apparatus comprising: a new carrier liquid supply path for supplying a new carrier liquid from a new carrier liquid supply tank by gravity drop. The image forming apparatus according to claim 1, wherein a flow rate adjustment valve is provided downstream of a joining portion between the collection carrier transport path and the new carrier liquid supply path. 3. The image forming apparatus according to claim 1, wherein in the case of a color image forming apparatus, a recovery carrier transport path and a new carrier liquid supply tank are provided for each image forming station. 3. The image forming apparatus according to claim 1, wherein in the case of a color image forming apparatus, a recovery carrier liquid transport path and a new carrier liquid replenishing tank common to each image forming station are provided. 5. The image forming apparatus according to claim 1, wherein the new carrier liquid supply tank is a replaceable cartridge. The image forming apparatus according to claim 5, wherein a check valve is provided in both the cartridge and a joint portion thereof.

Images