JPH0651642A - Excess developer removing device - Google Patents

Abstract

PURPOSE:To obtain the sufficient removing efficiency of excess developer without causing irregularities in a toner image by providing a nozzle blowing off air in the vicinity of the downstream side of a developing electrode. CONSTITUTION:Since a gap formed by the opposed surface 3e of the developing electrode 3 and the outer peripheral surface of a rotating drum 1 is successively supplied and filled with the developer, an electrostatic latent image on photosensitive paper 9 which reaches the gap is developed and becomes a visible image. When the photosensitive paper 9 at a part where the electrostatic latent image is developed comes off from the opposed surface 3e of the electrode 3 by the rotation of the drum 1 and passes the side surface 3d on the downstream side of the electrode 3, the developer sticking and remaining on the surface is pressed back to the side surface 3d by air flow blown off from the nozzle 5a of an excess developer removing device 5, and flows down with the air flow falling along the side surface 3d, and is recovered in a developer recovery drain 4. Thus, the excess developer is recovered with high removing efficiency without causing the irregularities of the toner image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for removing excess developer in a wet electrophotographic apparatus.

[0002]

2. Description of the Related Art In a wet electrophotographic apparatus in which an electrostatic latent image is formed on a photosensitive material and the latent image is developed by a wet developing apparatus to be visualized, an image after passing through the developing apparatus is formed. Inevitably, the developer remains on the surface of the carrier,
If this residual developer is left unattended, the quality of the finished image will be degraded. Therefore, conventionally, after a toner image is formed on the surface of an image carrier by a developing device, excess developer remaining on the surface of the image carrier is removed by an excess developer removing device such as a so-called blade device, corona squeeze device, and air knife device. I am trying to do it. Among these surplus developer removing devices, the removing device using the air knife device has the advantage that the toner image on the surface of the image carrier is less disturbed and the structure is relatively simple. Widely used.

[0003]

However, the conventional excess-developing solution removing device using the air knife device has a serious drawback in that the removal efficiency of the excess developing solution is low and the developing solution removing action cannot be sufficiently achieved. there were. In addition, if the amount of air supplied to the air knife device is increased to increase the ejection efficiency and the jet air pressure is increased too much, the toner image on the surface of the image carrier is disturbed, or the developer is bubbled or scattered. However, there is a problem in that the amount of the developer evaporates.

[0004]

DISCLOSURE OF THE INVENTION The inventors of the present invention have found that the shape of a developing electrode for supplying a developing solution to the surface of an image bearing member, and the shape of the developing electrode, in order to realize a sufficient excess developing solution removing action by an air knife device. As a result of intensive studies on the position of the electrode with respect to the rotary drum and the positional relationship between the developing electrode 3 and the nozzle of the air knife, the inventors have invented a surplus developer removing device which can solve the above problems by the following means. is there.

That is, the invention according to claim 1 is an apparatus for removing excess developer used in a wet electrophotographic apparatus for supplying a developer to a photosensitive material on which a latent image is formed to develop a visible image. A rotary drum that carries the photosensitive material and is driven to rotate about a substantially horizontal axis, and the entire facing surface of the rotary drum on the upstream side in the rotation direction of the rotary drum from immediately below the rotary drum or An excess developing solution removing device, characterized in that a nozzle that has a developing electrode disposed in the majority thereof and that blows out the air supplied from the air supplying device is provided in the vicinity of the downstream side of the developing electrode. " Is what

According to a second aspect of the present invention, "the interval between the developing electrode and the nozzle is such that no reservoir of the developing solution is formed between the developing electrode and the nozzle, and the developing solution is provided in the nozzle. Is a distance that does not propagate. The apparatus for removing excess developer according to claim 1, wherein

The invention according to claim 3 is that "the downstream side surface of the developing electrode forms an obtuse angle with respect to a tangent plane of the outer peripheral surface of the rotary drum immediately above the downstream side surface. The excess developer removing device according to claim 1 or 2, "is provided.

The invention according to claim 4 is characterized in that "air diverting means is provided for diverting the air generated by the air supply device and supplying the diverted air to the developing particle fixing device and the nozzle, respectively. The excess developer removing device according to any one of claims 1 to 3. "

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing a schematic configuration around a surplus developer removing device according to an embodiment of the present invention. Reference numeral 1 is a rotating drum, which carries a photosensitive paper 9 on its outer peripheral surface and is driven to rotate in the direction of arrow A. Reference numeral 2 is a developing device, which is shown in FIG.
In general, it is roughly constituted by a developing electrode 3 extending in a direction slightly shorter than the generatrix of the rotary drum 1 in the direction perpendicular to the paper surface, and a developing solution collecting drain 4 for collecting the developing solution overflowing from the developing electrode 3. There is.

Further, the developing device 2 is constructed so that it can be raised and lowered between at least two positions, a developing position (state of FIG. 1) and a retracted position lowered in the direction of arrow B, by an elevating device (not shown). In the state of the developing position, a predetermined gap (hereinafter referred to as “gap”) is formed between the facing surface 3e of the developing electrode 3 and the outer peripheral surface of the rotating drum 1, and the facing surface 3e of the developing electrode 3 is formed. , All or most of its surface is at the lowest position of the rotary drum 1 (hereinafter referred to as "drum lowest point 1a").
Say. ) Is configured to be located on the upstream side. Furthermore, when the developing device 2 is in the developing position, the angle formed by the tangent plane at the drum lowermost point 1a of the rotary drum 1 and the downstream side surface 3d of the developing electrode 3 is an obtuse angle. And the nozzle 5a, as will be described later.
The flow of air blown from is configured to be along the side surface 3d.

The developing solution supplied from a developing solution storage tank (not shown) is supplied to the developing solution supply port 3a of the developing electrode 3 and passes through the developing solution supply path 3b in the developing electrode 3 to communicate with the gap to the developing solution outlet. 3 c, the gap is filled with the developing solution, and most of the developing solution overflowing from the gap is on the downstream side surface 3 of the developing electrode 3.
It is adapted to flow down to the developer collecting drain 4 through the d. Incidentally, in this way, the developer collecting drain 4
The developer collected in (1) is again collected by the hose (not shown) or the like into the above-mentioned developer storage tank and circulated. Further, reference numeral 5 is a surplus developer removing device, which is a blower 5c for accelerating and sending out air, and two nozzles 5a extending over a range slightly shorter than the generatrix of the rotary drum 1 in the direction perpendicular to the paper surface in FIG. , 5b.

The photosensitive paper 9 carried on the outer peripheral surface of the rotary drum 1 is uniformly charged by a well-known charger (not shown) as the rotary drum 1 rotates in the direction of arrow A, and then not shown. It is scanned by a well-known optical device, and an electrostatic latent image is formed and moved to the developing device 2. Development electrode 3
As described above, since the developing solution is successively supplied and filled in the gap formed by the facing surface 3e and the outer peripheral surface of the rotating drum 1, the electrostatic latent image on the photosensitive paper 9 reaching here reaches It is developed into a visible image. In this way, the photosensitive paper 9 in the portion where the electrostatic latent image has been developed deviates from the facing surface 3e of the developing electrode 3 by the rotation of the rotary drum 1 and passes through the side surface 3d on the downstream side of the developing electrode 3. Due to the air flow blown from the nozzle 5a of the developer removing device 5, the developer remaining on the surface thereof is pushed back toward the side surface 3d of the developing electrode 3 and flows down together with the air flow descending along the side surface 3d. And collected in the developing solution collecting drain 4.

Then, the photosensitive paper 9 from which the excess developing solution has been removed
Is transported further downstream by the rotation of the rotary drum 1, heated by the thermal fixing device 6, and the airflow generated by the blower 5c is diverted and is supplied from the nozzle 5b to be dried and fixed. As described above, in the fixing process of the present apparatus, since the air flow is supplied at the same time as the heat by the heat fixing device 6, the fixing process can be performed quickly and surely. Is obtained by diverting the air flow generated by the blower 5c of the excess developer removing device, and therefore, it is not necessary to separately provide a blower, which contributes to downsizing of the device.

Next, the positional relationship between the developing electrode 3 and the nozzle 5a and the shape of the developing electrode 3, which are essential parts of the present invention, will be described with reference to FIGS. FIG. 2A is a partially enlarged view showing the positional relationship between the developing electrode 3 and the nozzle 5a of the present invention, and the nozzle 5a is provided in the vicinity of the downstream side of the developing electrode 3. In this case, the side surface 3d of the developing electrode 3 and the nozzle 5
The distance G1 from a is such that the maximum allowable value is determined by the characteristics of the photosensitive paper, the properties of the developing solution, the rotation speed of the rotating drum, etc., and after considering these parameters,
It may be set in a range such that the developer does not pool between the developing electrode 3 and the nozzle 5a and the developer does not reach the nozzle. According to experiments conducted by the present inventors, when the gap G1 is set to an appropriate value equal to or less than the maximum value, the liquid pool 7a is provided between the developing electrode 3 and the nozzle 5a (see FIG. 3A). ) Was not observed, and it was confirmed that almost all of the excess developer flowed down along the side surface 3d on the downstream side of the developing electrode.

On the other hand, as shown in FIG. 3A, when the gap G2 is set to be equal to or larger than the maximum value, the liquid pool 7a is provided between the downstream side surface 3d of the developing electrode 3 and the nozzle 5a.
Was confirmed to occur. In the case of FIG. 3 (A), since the gap G2 between the developing electrode 3 and the nozzle 5a is relatively large, the developing solution 7 receives a force to push it back to the developing electrode 3 side by the airflow blowing from the nozzle 5a, but at the same time, the rotating drum. By the rotation of 1 in the direction of arrow A, a force in the same direction as the rotating direction of the rotary drum 1 acts on the developing solution 7, so that the developing solution 7 pushed back by the nozzle 5a becomes droplets,
It is considered that the liquid pool 7a is generated between the developing electrode 3 and the nozzle 5a. Further, in the case of FIG. 3, when all the facing surfaces 3e of the developing electrode 3 are on the upstream side of the drum lowermost point 1a, gravity also acts on the developing solution 7 and the rotating drum 1 It is considered to be a force that pulls the developer 7 in the direction of arrow A, which is the direction of rotation.

On the other hand, in the case of FIG. 2A, since the gap G1 between the developing electrode 3 and the nozzle 5a is relatively small, the pressure of the air flow blown out from the nozzle 5a is at the opposing surface 3e of the developing electrode 3. Since the developer 7 directly acts on the rear end (the end on the most downstream side), the developer 7 remains separated from the photosensitive paper 9 without being conveyed toward the nozzle 5a while being attached to the photosensitive paper 9. It is considered to flow down the side surface 3d.
At this time, as described above, the angle formed by the tangent plane at the drum lowermost point 1a of the rotary drum 1 and the side surface 3d on the downstream side of the developing electrode 3 is an obtuse angle. The flow of air blown out from 5a flows down along with the developer 7 along the side surface 3d as shown by the arrow 8 without causing great turbulence.

Next, a case where the nozzles 5a are arranged at a gap G1 as shown in FIG. 2A and a gap G2 as shown in FIG. 3A.
In the case where the nozzle 5a is arranged in, the four line segments 10a to 10d parallel to the rotation direction (direction of arrow A) of the rotary drum 1 and orthogonal to these as shown in FIG. A case will be described in which a pattern composed of two line segments 11a and 11b in the same direction is to be developed. Figure 2 (B)
Is the gap G1 between the developing electrode 3 and the nozzle 5a in FIG.
Toner particles 7 to be used for development on the cross section of the photosensitive paper 9 when cut in the axial direction of the rotating drum 1 at a substantially intermediate point of
3C is a diagram schematically showing the state of FIG. 3C, and FIG. 3B is a cross-sectional view taken along the axial direction of the rotary drum 1 at a substantially midpoint of the gap G2 between the developing electrode 3 and the nozzle 5a in FIG. 3A. FIG. 6 is a diagram schematically showing a state of toner particles 7c and excess toner particles 7d that are used for development on the cross section of the photosensitive paper 9 in the case.

At the portion of the liquid pool 7a generated in the case of FIG. 3A, the bias voltage applied to the developing electrode 3 does not act, so that the excess toner particles 7d in the liquid pool 7a. Are collected by electrophoresis on the line segments 10a to 10d, which are the contours. The surplus toner particles 7d are made to flow in the direction opposite to the rotating direction of the rotary drum 1 (direction of arrow A), and so-called streak (on the right side of the line segment 11b in FIG. 3C) is called streak. 12a to 12d
Will occur. On the other hand, at the gap G1, the nozzle 5a
In the case of FIG. 2A in which the toner is arranged, as described above, since the excess toner does not flow and all of the excess toner flows down along the side surface 3d of the developing electrode 3, as shown in FIG. Only the toner particles 7c, which should be originally used for development, remain on the photosensitive paper 9 and remain, so-called streaks (tailing) in the non-image area (right side of the line segment 11b in FIG. 2C). The problem of is solved.

[0019]

As described above, according to the apparatus for removing excess developer of the present invention, sufficient efficiency of removing excess developer can be obtained without disturbing the toner image, and so-called streak and uneven development can be prevented. The problem can be solved and a high quality image can be obtained. Further, bubbling, scattering, evaporation and the like of the developing solution can be extremely reduced. Furthermore, since the air is diverted and supplied to the fixing device, the function of the fixing device can be improved, and at this time, it is not necessary to separately provide an air supply device for the fixing device, which contributes to downsizing of the device. It is a thing.

[Brief description of drawings]

FIG. 1 is a side view showing a schematic configuration around a surplus developer removing device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating the principle of the excess developer removing device according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating the principle of the excess developer removing device according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotating drum 2 developing device 3 developing electrode 4 developing solution collecting drain 5 surplus developing solution removing device 6 thermal fixing device 7 developing solution 9 photosensitive paper

Claims (4)

[Claims] 1. A surplus developer removing device used in a wet electrophotographic apparatus for supplying a developing solution to a photosensitive material on which a latent image is formed to develop it into a visible image. A rotary drum that is driven to rotate about a substantially horizontal axis, and a developing electrode in which all or most of the surface facing the rotary drum is arranged upstream of the rotary drum immediately below and in the rotational direction of the rotary drum. And a nozzle for blowing air supplied from the air supply device, the nozzle being provided in the vicinity of the downstream side of the developing electrode. 2. The distance between the developing electrode and the nozzle is a distance such that a reservoir of the developing solution is not formed between the developing electrode and the nozzle and the developing solution is not transmitted to the nozzle. The excess developing solution removing device according to claim 1. 3. A downstream side surface of the developing electrode forms an obtuse angle with respect to a tangential plane of an outer peripheral surface of the rotary drum immediately above the downstream side surface.
The excess developer removing device described. 4. An air diversion means is provided to divert the air generated by the air supply device and supply the air to the developing particle fixing device and the nozzle, respectively. Any one of the excess developer removing devices.