KR100497491B1 - apparatus for preventing the developer wraparound in a wet electrophotograph type printer - Google Patents

Abstract

The developer wrap-around apparatus of the wet electrophotographic printer of the present invention includes a variable radius portion formed at both ends of the developing roller, and a matching portion formed in a shape corresponding to the shape of the variable radius portion of the developing roller at both ends of the metering roller. Equipped. According to the present invention, since the variable radius portion and the mating portion are provided at both ends of the developing roller and both ends of the metering roller, respectively, and are in contact with each other, it is possible to prevent the developer wraparound from being formed on the developing roller and the photosensitive member during development.

Description

Apparatus for preventing the developer wraparound in a wet electrophotograph type printer}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet electrophotographic printer using a high concentration liquid developer, and more particularly, to a wet electrophotographic printer for preventing developer wraparound from being formed on a developing roller and a photosensitive member during development. Relates to a wraparound preventing device.

In general, an electrophotographic printer forms a latent electrostatic image on a photosensitive medium such as a photosensitive belt or photosensitive drum, develops the electrostatic latent image with a developer having a predetermined color, and transfers the image onto a recording sheet to obtain a desired image. The electrophotographic printer is classified into wet and dry according to the type of developer used. In the wet type, a liquid developer in which powder toner is mixed with a volatile liquid carrier is used as a developer.

A liquid electrophotographic printer using such a liquid developer uses a toner having a particle size of about 0.5-5 μm or less, so that an image of higher quality than a dry printer using a powdered toner can be obtained when developing an electrostatic latent image. In addition, the damage caused by harmful toner dust can be prevented, and its use is gradually increasing.

However, wet electrophotographic printers generally use low density liquid developers of 3% solids or less to achieve an appropriate image density. Therefore, in order to obtain an appropriate image density, a complicated ink delivery system for supplying and recovering a sufficient liquid developer to the developing region of the developing apparatus is required, which increases the volume and complexity of the developing apparatus. It has a disadvantage.

In addition, an apparatus for controlling the concentration of the liquid developer is also required in order to obtain an appropriate image concentration upon replenishment of the developer according to the change of the toner particles after development.

Therefore, it is necessary to eliminate or simplify the developer feeder in order to prevent the wet electrophotographic printer from being enlarged or complicated, and therefore, 3% instead of the liquid developer of 3% solid or less, which is generally used. The use of wet electrophotographic printers with high concentrations of liquid developer above solids is increasing.

Referring to FIG. 1, a general electrophotographic printer using a high concentration of liquid developer is shown schematically.

This wet electrophotographic printer moves on tracks such as photosensitive bodies 9, such as OPC drums (organic photoconductive drums), laser scanning units 11, charging rollers 12, developing devices 13, and photosensitive belts. The transfer belt 10, the primary and secondary rollers 21 and 22 for circulating the transfer belt 10 along the path on the caterpillar, the first transfer roller 8 for transferring the image to the transfer belt 10, And a second transfer roller 23 for transferring the image onto the recording paper P, a fixing roller 25 for fixing the image, and a cleaning blade 51 for removing the image remaining on the transfer belt 10. The components of the printer interact with each other to sequentially perform an image forming process such as charging, exposing, developing, transferring, fixing, and the like to form a desired image on the recording paper P. FIG.

In general, in the case of a color printer, four laser scanning units 11 for color printing and three with four colors: black, yellow, cyan, magenta It includes four developer units 13 each containing a high concentration of liquid developer 48 of -40 solid%.

As shown in FIG. 2, each developing device 13 includes a storage unit 6 for storing a high concentration of liquid developer 48, a developing roller 7 located under the photosensitive member 9, and a developing roller ( 7) The development roller 14 is formed by a deposit roller 14 and a deposit roller 14 which are installed at the lower part and apply electric force to the liquid developer 48 to form a charging developer layer on the developing roller 7. 7) Applying a predetermined voltage to the charging developer layer formed in FIG. 7 so that a larger amount of toner adheres to the developing roller 7, while regulating the charging developer layer to a developer layer having a constant toner amount or concentration (% solid), the developing roller A metering roller 15 for supplying a nip between the 7 and the photosensitive member 9 and a cleaning roller 16 for cleaning the developing roller 7 are provided.

The deposit roller 14 and the metering roller 15 have a constant toner amount or concentration regardless of the concentration of the liquid developer 48 at a high concentration of 3-40 solid%, or the liquid developer 48 changed during use. To the nip between the developing roller 7 and the photoconductor 9.

The operation of the wet electrophotographic printer configured as described above is as follows.

First, as a print command is applied, the photosensitive member 9 is formed with a charge layer corresponding to an image to be printed by the charging roller 12 and the laser scanning unit 11, that is, an electrostatic latent image, and the portion where the electrostatic latent image is formed. The toner of the developer layer having a constant toner amount formed on the developing roller 7 from the liquid developer 48 of the storage portion 6 by the deposit roller 14 and the metering roller 15 is attached to the toner image. Is formed.

At this time, the liquid developer 48 is formed as a charging developer layer on the developing roller 7 by the electric force of the deposit roller 14, and a predetermined amount of toner is applied while a predetermined voltage is applied by the metering roller 15. It is formed in the developing roller 7 by the developer layer which has.

The image developed on the photosensitive member 9 by the developing device 13 is transferred from the photosensitive member 9 to the transfer belt 10 by the voltage and pressure of the first transfer roller 8 located inside the transfer belt 10. The car is transferred. The image transferred to the transfer belt 10 moves up to the second transfer roller 23 as the transfer belt 10 is rotated by the primary and secondary rollers 21 and 22, so that the transfer of the second transfer roller 23 is performed. The secondary paper is transferred to the recording paper P by the voltage and the pressure.

The image transferred to the recording paper P is fixed to the recording paper P by the fixing roller 25 and the fixing backup roller 26 to finally form a desired image.

After the image transferred to the transfer belt 10 is transferred onto the recording paper P, the transfer belt 10 is continuously rotated by the primary and secondary rollers 21 and 22 so as to be on the side of the primary roller 21. It moves to the cleaning blade 51 installed to be in contact with the image forming surface of the transfer belt 10, where the developer residue (normally not 100% transferred to the recording paper, 90-98% remaining on the surface of the transfer belt 10). Only transferred) is removed from the transfer belt 10 by the cleaning blade 51 and recovered to the waste developer storage 52 for the next image printing.

The transfer belt 10 from which the residual developer residue has been removed is operated as described above to proceed with the electrostatic latent image formation and development of the next image through the photosensitive member 9, the laser scanning unit 11, and the developing apparatus 13 again. Repeat.

However, the conventional printer constructed as described above uses a charging developer layer formed on the developing rollers 7, 7 ′, 7 ″ by the deposit roller 14, as shown in FIGS. 3A, 3B, and 3C. The surface of the metering rollers 15, 15 ', 15 ", which is made of a developer layer having a certain toner amount or concentration, has a structure in which the surface of the metering rollers 15, 15', 15" abuts in parallel with the surface of the developing rollers 7, 7, 7 ', 7 ". .

Therefore, as shown in FIG. 4, the metering roller 15 rotates while forming the nip with the developing roller 7 while the charging developer layer is formed on the developing roller 7 by the deposit roller 14. The liquid developer 48, which is pushed toward both surfaces of the metering roller 15 when regulated by a developer layer of a constant toner concentration, is already fixed by a nip between the developing roller 7 and the metering roller 15. Flows into the space between the surface 17 of the developing roller 7 and the metering roller 15 where the developer layer is regulated, or, if severe, transfers to the photosensitive member 9 through the developing roller 7 and wraps. By forming the around 18, a toner of a designed amount or concentration or more is partially or wholly supplied to the nip between the developing roller 7 and the photosensitive member 9.

In this manner, the toner above the designed amount or concentration supplied to the nip between the developing roller 7 and the photosensitive member 9 not only causes the image quality to deteriorate, but also after the image is transferred onto the recording paper P, the photosensitive member ( The amount of developer residue remaining on the surface of 9) and recovered to the waste developer storage 52 by the cleaning blade 51 increases the consumption of the developer unnecessarily.

The present invention has been made to improve the above problems, the main object of the present invention is to prevent the development of the developer wraparound (wraparound) on the developing roller and the photosensitive member during development, the end of the development roller during development While the developer wraparound is prevented from forming in contact with the end of the ring roller, the developer wraparound generated between the end of the developing roller and the end of the metering roller is prevented from contacting the surface of the photosensitive member. The present invention provides a wraparound prevention device for a wet electrophotographic printer that is recovered by a metering roller without being transferred to a photosensitive member.

In order to achieve the above object, the present invention provides a developer storage space for storing a liquid developer, a photosensitive member for forming a latent image, and a developer storage space for forming a visible image on the photosensitive member according to the latent image while rotating facing the photosensitive member. A wet electrophotographic printer comprising a developer conveying body for conveying a developer supplied from a photosensitive member, the developer conveying body having a first portion having a substantially constant first radius parallel to the photosensitive member, and along a longitudinal axis; A second portion having a variable radius extending beyond at least one end of the first portion and consisting of second radii less than the first radius; And at least one developer concentration regulating roller which is formed to have a shape to match the developer conveying body and regulates at least one of an amount and a concentration of toner particles in the liquid developer supplied to the developer conveying body. A developer wraparound prevention device for an electrophotographic printer is provided.

In a preferred embodiment, the developer conveying member is configured in the form of a roller, and at least a part of the second portion is formed to be tapered at an angle toward the end of the developer conveying member so as not to contact the photosensitive member. Optionally, the developer carrier has at least a portion of the second portion tapered, convex tapered, concave tapered, stepped tapered, jar shaped, and at least It may be configured in the form of a roller formed in one of two or more angles tapered form.

The developer concentration regulating roller includes at least one end portion formed to have a shape to mate with the second portion of the developer conveying body in compression contact with the second portion of the developer conveying body.

Further, the second portion of the developer conveyance body is terminated at the second radius of the variable radius located at the point where the contact with the developing concentration regulating roller is terminated, and the end portion of the developing concentration regulating roller is a liquid developer with the developing concentration regulating roller. The same radius as the third radius of the end portion corresponding to the second radius of the variable radius of the second portion located at the point of terminating contact with the second portion for recovery, a radius smaller than the third radius, and smaller than the third radius It is preferable to further include an extended surface portion formed to have one of the variable radius.

In addition, the end portion of the developing concentration regulating roller is preferably composed of an elastic material.

Hereinafter, a developer wraparound prevention apparatus for a wet electrophotographic printer according to the present invention will be described in detail according to the accompanying drawings.

Referring to FIG. 5, a developing apparatus 113 and a photosensitive member 109 of a wet electrophotographic printer to which the developer wraparound prevention apparatus 100 of the present invention is applied are partially illustrated.

As the developing apparatus 13 described with reference to FIG. 1, the developing apparatus 113 includes a storage unit (not shown) for storing a high concentration of liquid developer, a developing roller 107 disposed under the photosensitive member 109, A developing roller (not shown) and a developing roller (not shown) are provided below the developing roller 107 and apply electric force to the liquid developer to form a charging developer layer on the developing roller 107. The developer roller 107 is regulated by a developer layer having a constant toner amount or concentration while applying a predetermined voltage to the developer layer formed at 107 so that a larger amount of toner adheres to the developer roller 107. And a metering roller 115 for supplying to the nip between the photosensitive member 109 and a cleaning roller (not shown) for cleaning the developing roller 107.

The deposit roller and the metering roller 115 may be formed of the developer roller 107 with a high concentration of a liquid developer of 3-40 solid%, or a certain amount of developer concentration regardless of the concentration of the liquid developer changed during use. It serves to supply the nip between the photosensitive member 109.

The developer wrap-around prevention apparatus 100 of the present invention is composed of two wrap-around prevention portions 100a and 100b installed at each end of each of the developing roller 107 and the metering roller 115.

Each of the wrap around prevention parts 100a and 100b, for example, the wrap around prevention part 100a shown on the right side of FIG. 5, is substantially parallel to the photosensitive member 109 to prevent wraparound from occurring during development. Second radiuses R that are smaller than the first radius R ₁ so as to extend beyond the right end of the cylindrical surface 122 of the developing roller 107 with a constant first radius R ₁ and do not contact the photoreceptor 109. A variable radius portion 108a having a variable radius R _{2 composed of 21} -R _2N ; And a mating portion formed at a corresponding right end of the metering roller 115 to have a form that matches the variable radius portion 108a of the developing roller 107 so as to be in compression contact with the variable radius portion 108a of the developing roller 107. 116a.

In this embodiment, the variable radius portion 108a is formed in a tapered shape having a truncated conical tapered surface 118a formed to be inclined toward the axis 107a from the circumferential surface toward the end so as not to contact the photosensitive member 109, The mating portion 116a is configured in the form of an inverse taper having a truncated conical tapered surface 118a and an inverted truncated conical tapered surface 119a of opposite shape.

The inverted truncated conical tapered surface 119a of the mating portion 116a has an extended surface 121a extending in the axial direction at the point where contact with the truncated conical tapered surface 118a of the variable radius portion 108a ends.

The extending surface 121a is a second radius R _2N of the variable radius R ₂ located at the point where the inverted truncated conical tapered surface 119a terminates contact with the truncated conical tapered surface 118a of the variable radius portion 108a. ) and formed to have a small variable-radius than the third radius (R ₃₎ with the same radius, the smaller radius than the third radius (R _3), or a third radius (R ₃₎ of the corresponding inverse truncated to a conical tapered surface (119a) It is desirable to.

The extended surface 121a does not transfer the generated wrap around 117 toward the photosensitive member 109 even if a small amount of wrap around 117 occurs between the inverted truncated conical tapered surface 119a and the truncated conical tapered surface 118a. It serves to recover toward the metering roller 115.

The matching portion 116a is preferably formed of an elastic material so as to add a contact pressure sufficient to contact the variable radius portion 108a of the developing roller 107 to prevent the wraparound from being formed.

The matching portion 116a is fitted to the step 115a formed at the end of the metering roller 115.

In order to fix the mating portion 116a to the end of the metering roller 115, the ring-shaped stopper 120a has an interference fit or screw type metering roller 115 after the mating portion 116a is fitted to the step 115a. Is fixed to the end of the

The wraparound prevention part 100b shown on the left side of FIG. 5 has the same configuration as the wraparound prevention part 100a described above.

The operation of the developer wraparound prevention device 100 of the wet electrophotographic printer of the present invention configured as described above will be described with reference to FIG. 5.

First, when a printing command is given, the liquid developer contained in the storage unit of the developing apparatus 113 is formed as a charging developer layer on the developing roller 107 rotating at a constant speed by the electric force of the deposit roller, and then metering. A predetermined voltage is applied by the roller 115 and is formed in the developing roller 107 as a developer layer having a constant toner amount.

At this time, the liquid developer that rotates while pushing toward both surfaces of the metering roller 115 is formed by the elastic compression contact between the variable radius portions 108a and 108b and the matching portions 116a and 116b. Passing through the nip between the developing roller 107 and the metering roller 115 along both ends is blocked from flowing onto the developer layer formed on the cylindrical surface 122 of the developing roller 107.

At this time, even if some of the developer forms a small amount of wrap around 117 at both ends of the developing roller 107, the variable radius portions 108a and 108b formed at both ends of the developing roller 107 are exposed to the photosensitive member 109. The metering roller 115 has a wraparound 117 having the truncated conical tapered surfaces 118a and 118b which do not come into contact with the reverse truncated conical tapered surfaces 119a and 119b of the mating portions 116a and 116b. By having the extension surfaces 121a and 121b to be recovered, the wraparound 117 is recovered toward the metering roller 115 without being transferred to the photosensitive member 109.

In this manner, while the developer layer having a constant concentration is formed by the deposit roller and the metering roller 115, the photosensitive member 109 is formed with an electrostatic latent image corresponding to the image to be printed by the charging roller and the laser scanning unit.

Thereafter, when the developing roller 107 having the developer layer having a constant concentration rotates while facing the photosensitive member 109 on which the electrostatic latent image is formed, the developer layer formed on the developing roller 107 is exposed to the photosensitive member 109 and the developing roller. Due to the difference in voltage applied to 107, electrostatic force, and the like, the image is moved to an electrostatic latent image formed on the photoconductor 109 and developed into a toner image.

Thereafter, the toner image is formed into a desired image on the recording paper through a sequential image forming process such as transfer and fixing as described with respect to the printer shown in FIG. 1, and the developer residue remaining on the transfer belt to which the toner image is transferred. Is removed by the cleaning blade and returned to the waste developer reservoir.

6A to 6G, variations of the wraparound prevention part of the developer wraparound prevention device 100 of the present invention (only the left wraparound prevention part is illustrated) are illustrated.

The wraparound prevention parts 100b ', 100b ", 100b"', 100b "", 100b "" ', and 100b "" "of the variants have variable radius parts 108b', 108b", 108b "'and 108b" ". , 108b "" ', 108b "" ") and mating portions 116b', 116b", 116b "', 116b" ", 116b" "', 116b" "") are sawtooth or Tapered form (Fig. 6a), convex tapered form (Fig. 6b), concave tapered form (Fig. 6c), stepped tapered form (Fig. 6d), bent form ( 6E), and the same configuration and operation as the wraparound prevention portion 100b described in connection with Fig. 5, except that it is configured for compression contact in two angles in tapered form (FIG. 6F). Detailed configuration and operation description of these modifications will be omitted.

As described above, the apparatus for preventing the wrap-around of the wet electrophotographic printer of the present invention is installed at both ends of the developing roller and at both ends of the metering roller such that the variable radius portion and the mating portion are compressed to contact each other. This prevents the developer wraparound from forming.

In the above, certain preferred embodiments of the present invention have been illustrated and described. However, the present invention is not limited to the above-described embodiments, and any person having ordinary skill in the art to which the present invention pertains without departing from the spirit and spirit of the present invention as claimed in the claims may have various modifications and Modifications may be made.

1 is a schematic diagram of a typical wet electrophotographic printer.

2 is a schematic diagram illustrating a developing device and a photosensitive member of the wet electrophotographic printer shown in FIG. 1;

3A, 3B, and 3C are schematic views illustrating installation examples of the developing roller and the metering roller of the developing apparatus of the wet electrophotographic printer shown in Fig. 1;

4 is a schematic diagram illustrating a process in which wraparound occurs in an installation example of the developing roller and the metering roller shown in FIG. 3A.

5 is a schematic view of a developing apparatus and a photosensitive member to which a developer wrap-around prevention device according to the present invention is applied.

6A, 6B, 6C, 6D, 6E, and 6F are partial schematic views illustrating modifications of the wraparound prevention portion of the developer wraparound prevention apparatus according to the present invention.

* Description of the symbols for the main parts of the drawings *

7, 107: developing roller 8, 23: pre roller

9, 109: photosensitive member 10: transfer belt

11: laser scanning unit 13, 113: developing device

14: deposit roller 15, 115: metering roller

16: cleaning roller 25: fixing roller

48: developer

100a, 100b, 100b ', 100b ", 100b"', 100b "", 100b "" ', 100b "" ": Wrap-Around Protection

108a, 108b, 108b ', 108b ", 108b"', 108b "", 108b "" ', 108b "" ": Variable radius

116a, 116b, 116b ', 116b ", 116b"', 116b "", 116b "" ', 116b "" ": matching part

121a, 121b, 121b ', 121b ", 121b"', 121b "", 121b "" ', 121b "" ": extended surface

Claims (9)

A developer storage space for storing a liquid developer, a photosensitive member for forming a latent image, and a developer supplied from the developer storage space to rotate to face the photosensitive member to form a visible image on the photosensitive member according to the latent image; In the wet electrophotographic printer comprising a developer conveying body to the photosensitive member, The developer conveying body comprises a first portion having a first radius substantially constant parallel to the photosensitive member, and second radii extending beyond at least one end of the first portion along a longitudinal axis and smaller than the first radius A second portion having a variable radius; And at least one end portion formed to have a shape to mate with the second portion of the developer conveyance to be in compression contact with the second portion of the developer conveyance, the liquid development being supplied to the developer conveyance And a developer concentration regulating roller for regulating at least one of an amount and a concentration of toner particles in the agent. The wet electrophotographic printer of claim 1, wherein the developer conveying member is formed in a roller shape, and at least a part of the second portion is tapered at an angle toward an end portion so as not to contact the photosensitive member. Developer wraparound prevention device. delete 3. The apparatus of claim 2, wherein the end portion of the development concentration regulating roller comprises an elastic material. The method of claim 2, The second portion terminates at a second radius of the variable radius located at a point where the contact with the developing concentration regulating roller ends; The end portion of the developing concentration regulating roller has a radius equal to a third radius of the end portion corresponding to the second radius of the variable radius of the second portion located at a point where contact with the second portion ends; And an extension surface portion formed to have one of a radius smaller than a third radius and a variable radius smaller than the third radius. A developer storage space for storing a liquid developer, a photosensitive member for forming a latent image, and a developer supplied from the developer storage space to rotate to face the photosensitive member to form a visible image on the photosensitive member according to the latent image; In the wet electrophotographic printer comprising a developer conveying body to the photosensitive member, The developer conveying body comprises a first portion having a first radius substantially constant parallel to the photosensitive member, and second radii extending beyond at least one end of the first portion along a longitudinal axis and smaller than the first radius Have a variable radius, at least partially tapered, convexly tapered, concave tapered, stepped tapered, jar-shaped, bent, and at least two angles tapered A roller form including a second portion formed in one of the forms; And a developing concentration regulating roller which is formed to have a form to match the developer conveying body and regulates at least one of an amount and a concentration of toner particles in the liquid developer supplied to the developer conveying body. Developer wraparound prevention device for photo printers. 7. The developer concentration regulating roller according to claim 6, wherein the developer concentration regulating roller includes at least one end portion formed to have a shape to mate with the second portion of the developer conveying body in compression contact with the second portion of the developer conveying body. A developer wrap-around device for a wet electrophotographic printer, characterized in that. 8. The apparatus of claim 7, wherein the end portion of the development concentration regulating roller comprises an elastic material. The method of claim 7, wherein The second portion terminates at a second radius of the variable radius located at a point where the contact with the developing concentration regulating roller ends; The end portion of the developing concentration regulating roller has a radius equal to a third radius of the end portion corresponding to the second radius of the variable radius of the second portion located at a point where contact with the second portion ends; And an extension surface portion formed to have one of a radius smaller than a third radius and a variable radius smaller than the third radius.