JPH07334009A - Developing device for wet type image forming device - Google Patents

Abstract

PURPOSE:To instantaneously and uniformly micronize high solidity toner and dispersedly replenish the toner without causing clogging due to the toner, as for a developing device for a wet type image forming device provided with a dispersing means for replenishing high concentration developer to a developer tank after the high concentration developer is prepared by micronizing the high solidity toner and dispersing the toner in the dispersing agent. CONSTITUTION:The dispersing means 17 is constituted of a grinding driving body 33 having such a structure that a cylindrical fixed external blade with plural slit holes formed in the circumferential wall and a cylindrical rotary internal blade with plural slit holes formed in the circumferential wall are combined, and a dispersing room 34 for housing and installing the grinding driving body 33 and also for storing the supplied high solidity toner and the dispersing agent at the time of preparing the high concentration developer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device of a wet image forming apparatus which visualizes an electrostatic latent image as a monochromatic image or a color image with a liquid developer, and particularly, to replenish high solid toner. Meanwhile, the present invention relates to a developing device having a mechanism for keeping the concentration of the liquid developer constant.

[0002]

2. Description of the Related Art As a developing device in a conventional wet image forming apparatus, a high solidity toner having a composition having a toner content larger than that of a dispersion liquid is micronized and replenished as fine toner particles to obtain a liquid developer. It is known to keep the concentration constant.

A developing device of this type, which employs means for finely dispersing high-solidity toner into fine particles and well dispersing it in a developing solution, is, for example, a rotating blade having a blade in a casing installed in a developing solution tank. By rotating the body at high speed, the high solidity toner supplied into the casing is crushed into fine particles, and thereafter, only the toner having a predetermined particle size or less is provided on the lower surface of the casing. It has been proposed to selectively replenish and disperse in a developing solution by passing through a mesh for separation (JP-A-64-38773).

In addition to the above, a rotating roll such as a bristle brush roll, a mesh roll or a sponge roll is used in the dispersion chamber installed in the developer tank, or another member such as a blade is also used (first ~ Fig. 5, Fig. 10
(FIGS. 13 to 13), the structure is made finer by the action of rubbing high solidity toner or the like, or is composed of a fixed base having a notch in the outer peripheral portion and a turntable rotating at a high speed on the upper surface of the fixed base. 6 to 9), a high-concentration toner is supplied between the opposing surfaces and finely divided by the shearing force received from the notch when the toner is discharged, thereby forming a high-concentration developer, It has been proposed to replenish the tank with a high-concentration developing solution (Japanese Patent Laid-Open No. 63-109479).
Issue).

[0005]

However, in such a conventional developing device, in the former case, in addition to the low pulverizing ability of the high solidity toner by the rotor having the blades, the predetermined particle diameter is required. Since only the finely divided toner passes through the mesh and is supplied to the tank at any time, it takes time for the developer in the tank to reach the required concentration by replenishing the toner. There's a problem. For example, such a developing device cannot support a high-speed type wet image forming apparatus. Further, in the case of this developing device, the mesh is apt to be clogged due to the lump of toner, and as a result, there is a problem that means for preventing the clog is required.

On the other hand, in the latter case, the device tends to be complicated regardless of the structure, and
There is a problem that the pulverizing ability for uniformly pulverizing high solidity toner in a short time is low. Further, in any structure using a rotating roll or a rotating disk, there is a fear that clogging due to toner lumps may occur, and a countermeasure against it is necessary.

The present invention has been made to solve the above technical problems, and the purpose thereof is to:
It is an object of the present invention to provide a developing device for a wet image forming apparatus capable of instantly and uniformly miniaturizing and replenishing high solidity toner without causing clogging by toner.

[0008]

A developing device for a wet image forming apparatus according to the present invention includes a developing section for developing an electrostatic latent image on a latent image carrier in a wet image forming apparatus with a liquid developer, and this developing section. And a dispersion tank for preparing a high-concentration developer solution in which the high-solidity toner is made into fine particles and dispersed in a dispersion solution, and the high-concentration developer solution is supplied to the developer tank. In a developing device including means, the dispersing means is arranged in a non-contact state inside a cylindrical fixed outer blade having a plurality of slit holes formed in a peripheral wall and the opening lower end of the outer blade to rotate at an ultrahigh speed. The crushing driving body having a structure in which a cylindrical rotating inner blade having a plurality of slit holes formed in the peripheral wall are combined, and the high solidity toner and the dispersion liquid which are housed and installed in the crushing driving body are supplied. When preparing high-concentration developer And it is characterized in that it is composed of a dispersion chamber for distillation.

Further, in the developing device of the present invention, in the above-mentioned technical means, the dispersion chamber has a cylindrical shape, and the inner diameter of the dispersion chamber is 1.5 to 2. It is characterized in that it is set within a range of 0 times. With this structure, the convection of the liquid in the dispersion chamber can be efficiently generated, and as a result, the high solidity toner can be miniaturized more efficiently.

In such technical means, the gap between the fixed outer blade and the inner rotating blade is preferably 20 μm or less. If this gap exceeds 20 μm, the ability of the high-solidity toner to be atomized by convection is reduced, and moreover, between the fixed outer blade and the inner rotating blade that rotates at a very high speed, and further, between the slits of both blades. Sound waves (or high frequencies) are less likely to be generated.

The rotating inner blade is usually 10,000 to 2
50,000 rpm range, 20,000r if possible
Rotate at a super high speed of pm or more. By rotating the rotary inner blade at an ultrahigh speed in this manner, it is possible to reliably generate the ultrasonic wave (or high frequency) as described above.

Further, the amount of the dispersion liquid supplied to the dispersion chamber is
It is preferable to adjust the liquid surface so that the height is about 1 cm or less from the upper surface of the fixed outer blade. By controlling the height of the liquid surface of the dispersion liquid in this way, liquid convection in the dispersion chamber can be efficiently generated.

[0013]

According to the present invention, due to the rotation of the rotary inner blade in the crushing driving body, the convection of the liquid is generated in the dispersion chamber from the inside of the rotary inner blade to the outside of the fixed outer blade through the slit. The mass of high-solidity toner carried by this convection is between the fixed outer blade and the rotating inner blade (between the slits of both blades).
In, it is mechanically crushed and pulverized. Moreover, due to the ultra-high speed rotation of the rotating inner blade, ultrasonic waves (or high frequencies) are generated between the fixed outer blade and the rotating inner blade (between the slits of both blades), and the ultrasonic waves mechanically miniaturize the ultrasonic waves. The lumps of high-solidity toner are finely crushed.

Due to the synergistic action of such mechanical pulverization action and pulverization action by ultrasonic waves, the high-solidity toner is finely and uniformly pulverized in a very short time (toner particles having a particle size of about 3 μm). At the same time, it is uniformly and satisfactorily dispersed in the dispersion liquid.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 and 2 show an embodiment of the present invention. FIG. 1 is a view showing a color wet image forming apparatus to which the developing device of the present invention is applied, and FIG. 2 is a main part of the developing device.

In FIG. 1, 1 is a latent image bearing drum as a latent image bearing member on which an electrostatic latent image is formed, 2 is a charger for precharging the latent image bearing drum 1 for each image forming cycle of each color. Reference numeral 3 is a laser writing device for writing an electrostatic latent image corresponding to an image for each color, and 4 to 7 are liquid developing devices for supplying the liquid developer for each color and developing for each color, 8
Is a transfer drum which holds the recording paper in advance and rotates following the latent image holding drum 1 for each image forming cycle for each color.
Is a cleaning device, 10 is a discharge lamp for removing residual charges on the latent image bearing drum 1, 11 is a transfer device for transferring the toner image on the latent image bearing drum 1 to recording paper, and 12 is recording paper.

Basically, all of the liquid developing devices 4 to 7 should be supplied to the developing section 13 for developing the electrostatic latent image formed on the latent image bearing drum with the liquid developer, and the developing section 13. A developer tank 15 for containing the liquid developer 14,
Dispersing means 17 for replenishing the high-concentration developing solution to the developer tank 15 after preparing the high-concentration developing solution in which the high-solidity toner supplied from the high-solidity toner bottle 16 is finely divided and dispersed in the dispersion. It is equipped with. Further, the developing unit 13 includes a developing shoe 18 arranged in the vicinity of the latent image carrying drum 1, and a collecting roll 19 for collecting the excess developing solution, which is arranged on the rear side of the developing shoe 18. Has been done. In FIG. 1, 20 is a pipe for conveying a developer for supplying the developer from the developer tank 15 to the developing section 13 by a pump 21, 22 is a pipe for collecting a developer, 23 is a rotary blade for stirring liquid, and 24 is a concentration measuring sensor. Are shown respectively. Although the developer tanks and the dispersing means in the liquid developing devices 5, 6 and 7 are omitted for convenience of illustration, the configurations are the same except that the colors of the developers are different.

In the color wet type image forming apparatus having such a basic structure, the surface of the latent image bearing drum 1 is preliminarily uniformly charged by the charger 2, and then the charged surface of the latent image bearing drum 1 is charged. The electrostatic latent image of a predetermined color is written by the laser writing device 3, and the latent image is formed by the liquid developer 4 to 4.
No. 7 makes a visible image with a developer of a predetermined color, and then the toner image on the drum 1 is transferred to the recording paper 12 on the transfer drum 1. It is designed to be repeated for each image.

Next, the dispersion means 17 in each of the liquid developing devices 4 to 7 will be described. This dispersion means 17 is shown in FIG.
As shown in FIG. 3 and FIG. 3, a crushing drive body 33 having a structure in which a fixed outer blade 30 and a rotating inner blade 31 are combined with each other, and a high solidity toner and a dispersion liquid which are supplied while the crushing drive body 33 is housed and installed. And a dispersion chamber 34 for storing the high concentration developing solution at the time of preparation thereof.

The fixed outer blade 30 has a cylindrical shape with an open lower surface, and a plurality of slit holes 35 are formed in the peripheral wall of the cylinder, and the notch blade 3 is provided at the tip of the opening.
6 is formed. The fixed outer blade 30 is fixed to a support member 37 having one end attached to the apparatus body. One of the rotating inner blades 31 has a cylindrical shape with an open lower surface, and similarly to the fixed outer blade 30, a plurality of slit holes 38 are formed in the peripheral wall of the cylinder and the opening tip portion is formed. A notch blade 39 is formed. The rotary inner blade 31 is disposed inside the lower end of the opening of the fixed outer blade 30 at a predetermined interval, and at the same time, is directly connected to a rotary shaft 41 which is rotated by a rotary drive source 40 such as a motor or the like. It is designed to rotate at high speed.

The dispersion chamber 34 has a cylindrical shape as a whole, and a bottom cover 43 having a structure that can be opened and closed by a solenoid 42 is provided in the lower portion of the cylinder.
The crushing driving body 33 is installed at a position which has a predetermined height above the bottom cover 43 and which corresponds to the central portion inside the cylinder. Further, the high solidity toner bottle 16 is installed at the opening of the upper portion of the cylinder of the dispersion chamber 34 so as to be able to supply the high solidity toner, and the recovered developer (which is mainly dispersed) is returned by the developer recovery pipe 22. Liquid) is supplied via the electromagnetic valve 44 to the recovered developer supply pipe 22a.
Is installed.

Further, as shown in FIG. 4, the inner diameter dimension R of the dispersion chamber 34 is within a range of 1.5 to 2.0 times the outer diameter dimension L of the fixed outer blade 30 in the crushing driving body 33. Is set to.

The liquid developing device provided with the dispersing means 17 having such a structure operates as follows.

The liquid developer 14 stored in the developer tank 15 at a predetermined reference concentration is supplied to the developing section 13 through the developer conveying pipe 20 by the pump 21 which operates at a predetermined developing timing. At the same time, a part of it passes through the concentration measuring sensor 24 via another concentration measuring pipe 20a and is then returned to the tank 15. On the other hand, the liquid developer supplied to the developing unit 13 and used for the development passes through the developer collecting pipe 20 and the tank 15
Returned inside. As described above, the liquid developer is used while being circulated between the developer tank 15 and the developing section 13.

At this time, the concentration of the liquid developer in the tank 15 is measured by the concentration measuring sensor 24, and the detected concentration data is sent to the concentration detecting / comparing / judging circuit 46 via the wiring 45, and the liquid concentration is measured. Is determined. When the circuit 46 determines that the measured density is lower than the reference value, an operation signal for supplying toner to predetermined device parts is supplied from the circuit 46 to the wiring 4 at a predetermined timing.
It is sent via 5 as appropriate.

The operation signal is first sent to the solenoid 42, and the operation closes the bottom lid 43 of the dispersion chamber 34. Subsequently, by operating the electromagnetic valve 44, a part of the recovered developer recovered from the developing unit 13 and returned through the developer recovery pipe 22 passes through the recovered developer supply pipe 22 a and is transferred into the dispersion chamber 34. Is supplied to. At this time, the electromagnetic valve 44, as shown in FIG.
The operation time is controlled so that the liquid surface S of the recovered developer (dispersion liquid) supplied into the inside is at a height of 1 cm or less from the upper surface of the fixed outer blade 30 constituting the crushing driving body 33.

Subsequently, a predetermined amount of high-solidity toner is supplied from the bottle 16 into the dispersion chamber 34 in which the liquid is accumulated, and at the same time, the driving motor 40 is rotationally driven to drive the crushing driving body 33.
The rotating inner blade 31 is rotated at an ultrahigh speed for a predetermined time. As a result, the high-solidity toner is pulverized and finely dispersed in the collected developer (dispersion liquid) to prepare a high-concentration developer.

When the high-concentration developer is prepared in the dispersion chamber 34, the bottom lid 43 is opened by the solenoid 42, and the high-concentration developer is replenished in the developer tank 15. And
This high-concentration developing solution is mixed with the liquid developer already in the tank by the stirring rotary blade 23. The concentration of the entire developer in the tank is made uniform. At the same time, the concentration of the liquid developer in the tank 15 to which the high-concentration developer has been replenished and mixed has a concentration measuring sensor 2
4 is measured. That is, the above operation is repeated until the measured density reaches the reference value.

It is presumed that the high solidity toner is made finer by the dispersing means 17 as follows.

That is, as shown in FIG. 5a, when the rotary inner blade 31 of the crushing driving body is rotated, the liquid in the dispersion chamber 34 is centrifugally generated by the rotation of the inner blade, and the slit hole 3 is formed.
8 through the slit holes 35 of the fixed outer blade 30 to radially and violently collide with the inner wall of the dispersion chamber 34, and the liquid is attracted and enters the inner blade 3 from the lower opening of the rotating inner blade 31. As a result, convection of the liquid occurs in the entire dispersion chamber 34 as indicated by the arrow in the figure.

By such convection, as shown in FIG. 5B, the high solidity toner 50 supplied into the dispersion chamber 34 is guided to the lower portion of the opening of the rotary inner blade 31, and the notch of the rotary inner blade 31 is cut. Just before the crushed crushed toner lump 50a is crushed by the blade 39 and is discharged from the rotary inner blade 31 side to the outside of the fixed outer blade 30 by the convection of the liquid, the crushed toner lump 50a is shown in FIG. So that the slit hole 3 of the rotary inner blade 31
8 and the slit holes 34 of the fixed outer blade 30 are crushed by the shearing force, and the finer toner 50b is obtained.

Further, as shown in FIG. 5d, the rotating inner blade 31 of the crushing driving body is rotated at a very high speed to allow the fixed outer blade 3 to rotate.
Between 0 and 0, in fact, slit holes 34, 38 in both blades
Since the ultrasonic wave (or high frequency) P is generated during the interval, the ultrasonic toner further miniaturizes the fine toner 50b, and thus the ultrafine toner 50 having a particle diameter of about 3 μm.
c. Further, this ultrasonic wave is always accumulated in the toner mass (toner masses 50, 5) while the rotary inner blade 31 is rotating at a high speed.
0a and 50b), the pulverization and miniaturization of the toner are greatly promoted. The above miniaturization is performed in an extremely short time, that is, almost instantly.

Next, the following tests were conducted on the pulverizing performance of the dispersing means in the developing device of the present invention.

As a working sample of the present invention, the rotation speed of the crushing driving body 33 of the dispersing means 17 in the above-mentioned apparatus of the embodiment is 20,000 rpm or more, and the inner diameter of the cylindrical dispersing chamber 34 is about the outer diameter of the fixed outer blade 30. 2 times, set according to the conditions of the example except that the liquid level in the dispersion chamber 34 is set to a height of about 1 cm from the upper surface of the fixed outer blade 30 (Example A)
And a dispersion chamber 34 having a quadrangular shape and having the same inner diameter (distance between the inner surfaces facing each other) as the outer diameter of the fixed outer blade 30 at least twice (Example A) (Example B) was prepared. Further, for comparison, as shown in FIG. 7, a developing device using a conventional dispersion means having a structure in which a rotary blade 51 having a conventional blade shape is installed and rotated in a cylindrical dispersion chamber 34. Comparative Example C, and a developing device using a conventional dispersing means constituted by rotating a stirrer type rotary blade similar to the form of the stirring rotary blade 23 in the dispersion chamber was prepared as Comparative Example D.

Regarding the pulverizing performance of the high solidity toner by the apparatus of these Examples and Comparative Examples, the target toner particle size (3
μm) and the variation in toner particle size at that time were measured, and the results are also shown in FIG. The length (width) in the vertical axis in each data in the figure indicates the degree of variation in toner particle size.

From these results, Examples A and B according to the present invention
In the case of, in comparison with Comparative Examples C and D, when the high solidity toner is dispersed, the high solidity toner can be uniformly pulverized and dispersed in an extremely short time, and in addition, when the mesh clogging occurs. It has been confirmed that the following problems do not occur, and therefore the present invention is very effective in dispersing high solidity toner.

[0037]

As described above, according to the present invention,
Since the dispersing means mechanically grinds the high solidity toner and ultrasonically grinds (micronizes) them in the presence of the dispersion liquid, the high solidity toner can be instantly and uniformly micronized. Moreover, the finely divided toner can be replenished to the developer tank in a short time in the state of the high-concentration developer in which the toner is well dispersed in the dispersion liquid. Further, at this time, there is no fear that the toner will be clogged.
Therefore, the concentration of the liquid developer in the developer tank can be maintained at the reference concentration (constant) in a short time. Therefore, the device of the present invention can be sufficiently applied as a developing device of a high-speed type wet image forming apparatus.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment in which a developing device of the present invention is applied to a color wet image forming apparatus.

FIG. 2 is an enlarged schematic configuration diagram showing a main part of the developing device of FIG.

FIG. 3 is a partially cutaway side view showing an example of a crushing driving body in the dispersing means.

FIG. 4 is a top view for explaining the relationship between the crushing driving body and the dispersion chamber.

FIG. 5 is an explanatory diagram for explaining the refining action of the high-solidity toner by the dispersing unit.

FIG. 6 is a graph showing measurement data regarding the pulverization (miniaturization) ability of high-solidity toner.

FIG. 7 is an explanatory diagram showing an example of a conventional dispersing means (Comparative Example C).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Latent image carrier, 4-7 ... Developing device, 13 ... Developing part, 1
4 ... Liquid developer, 15 ... Developer tank, 17 ... Dispersing means, 30 ... Fixed outer blade, 31 ... Rotating inner blade, 33 ... Grinding driving body, 34 ... Dispersion chamber, 35, 38 ... Slit hole, R ... Dispersion Inner diameter of chamber, L ... Outer diameter of fixed outer blade.

Claims (2)

[Claims] 1. A developing unit for developing an electrostatic latent image on a latent image carrier in a wet image forming apparatus with a liquid developer, a developer tank for containing the liquid developer supplied to the developing unit, and In a developing device comprising a dispersing means for preparing a high-concentration developing solution in which a toner having a small solidity is finely dispersed and dispersed in a dispersing solution, the dispersing means is provided on the peripheral wall. A cylindrical fixed outer blade with a plurality of slit holes and a non-contact state inside the outer edge of the outer blade, which rotates at ultra-high speed, and a cylindrical rotation with a plurality of slit holes in the peripheral wall. It is composed of a crushing drive body having a structure in which an inner blade is combined, and a dispersion chamber for accommodating and installing the crushing drive body and storing the high solidity toner and the dispersion liquid supplied at the time of preparing a high concentration developer. Is characterized by A developing device of the wet image forming apparatus. 2. The apparatus according to claim 1, wherein the dispersion chamber has a cylindrical shape, and the inner diameter thereof is within a range of 1.5 to 2.0 times the outer diameter of the fixed outer blade of the crushing driving body. An image recording device characterized by being set.