JPH0625890B2 - Developer supply device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a developer supply device, and more particularly, to a developer supply device that can be widely applied to an image forming apparatus employing a wet development system such as an electrophotographic copying machine and a facsimile. It is about.

(Prior Art) In a wet developing system in which a developing solution is supplied to the peripheral surface of a photosensitive drum carrying an electrostatic latent image to visualize the electrostatic latent image, as a means for supplying the developing solution, for example, Japanese Patent Application Laid-Open No. There is a technique disclosed in Japanese Patent Laid-Open No. 57-20056.

In this method, the liquid sprayed from the nozzle for supplying the developing solution is once abutted against the guide plate, and then flows down along the guide plate to reach the photosensitive drum, and further to the peripheral surface of the photosensitive drum. Accordingly, a liquid pool is formed between the developing roller and the developing roller which is provided near the photosensitive drum.

Further, as the other developer supplying means, the constitution as shown in FIG. 4 can be considered.

In this method, the opening 3 of the developing solution supply nozzle is arranged above the area where the photosensitive drum 1 and the developing roller 2 face each other. Therefore, the developer discharged from the opening 3 directly forms a liquid pool in the area where the photosensitive drum 1 and the developing roller 2 face each other. The position of the opening 3 in the longitudinal direction of the photosensitive drum axis is the center as shown in FIG.

In each of these conventional techniques, the developer stored in the liquid reservoir is intended to be uniformly supplied to the peripheral surface of the photosensitive drum via the narrow gap between the photosensitive drum 1 and the developing roller.

By the way, in the above-mentioned conventional technique, the developer discharged from the opening 3 contains bubbles due to the air contained in the tube at the time of starting, and the bubbles are also generated when the developer is deteriorated. It has a characteristic that it is likely to occur. In addition to this, by vigorously discharging from the opening 3,
Alternatively, when abutting against the guide plate, many bubbles are present in the liquid pool between the photoconductor drum and the developing roller, and these bubbles significantly reduce the developing performance and impair the image quality. There is.

Further, as shown in FIG. 5, the amount of the liquid pool is large only near the opening 3, and the amount of the liquid pool tends to be smaller as the distance from the opening 3 increases. For this reason, if the amount of liquid supplied from the opening 3 is increased, the load on the pump is increased and the temperature of the developing solution rises. In addition, a large amount of developing solution is directly applied to a part of the photoconductor to make the developing solution uniform. The image cannot be obtained. That is, an imbalance in the developer supply amount occurs between the vicinity of the opening 3 and a portion away from the opening 3, which causes uneven image density.

(Objective) Therefore, an object of the present invention is to supply a developing solution capable of extinguishing bubbles mixed in the developing solution in advance by a simple means and uniformly supplying the developing solution to the peripheral surface of the latent image carrier. To provide a device.

(Structure) In order to achieve the above object, the present invention places a developing roller close to the latent image carrier, and presses the scraper against the developing roller so that the liquid can be stored in the developing roller so that the developing roller and the scraper face each other. It is characterized in that the developing solution is once stored in the region and the stored developing solution is pumped into a liquid film shape as the developing roller rotates and supplied to the latent image carrier.

Hereinafter, a specific description will be given based on an embodiment of the present invention.

The example described below is for a transfer type electronic copying machine, in which a latent image carrier, for example, a developing roller that is rotationally driven while holding a minute gap on a photosensitive drum, develops an electrostatic latent image on the photosensitive member with a developing solution. The development roller is cleaned with a scraper that also functions as a liquid reservoir.

An example in which the photosensitive member is formed into a drum shape as the latent image carrier will be described below. However, the present invention is not limited to this, and the photosensitive member may be formed into a belt shape. Alternatively, it may be configured in a belt shape.

First, the copying process will be outlined.

In FIG. 1, the photosensitive drum 10 is rotationally driven in the direction of the arrow (clockwise) at a constant speed by a driving device during copying, and is uniformly charged by the main charger 11,
The original image IM is projected by the exposure device to form an electrostatic latent image on the photoconductor, and the eraser 12 eliminates the charge outside the image forming area.

The electrostatic latent image on the photoconductor drum 10 is visualized by a wet developing device 13 to which the present invention is applied, and is fed from a sheet feeding device (not shown) via a conveying roller 14 as indicated by a dashed arrow. It is transferred onto the transfer paper S by the transfer charger 15.

The transfer sheet S is separated from the photosensitive drum 10 by the separation roller 16 and conveyed by the conveyance belt 17, and thereafter, the toner is fixed by the fixing device and discharged to the outside.

After the transfer paper S is separated from the photosensitive drum 10, the cleaning unit 18 removes the residual toner, and the static eliminator lamp 19
The residual potential is removed by the (static eliminator or static eliminator) to prepare for the next copy.

The above is the outline of the copying process. Next, the wet developing device 13 to which the present invention is applied will be described.

In the wet developing device 13, a first developing roller 131, a second developing roller 132, and a squeeze roller 133 are axially supported in the developing container 130 in this order from the top. The first and second developing rollers 131 and 132 are held at a slight distance from the surface of the photosensitive drum 10. This interval is adjusted to, for example, 0.1 m, and is driven to rotate in the opposite direction (counterclockwise) to the photoconductor drum 10 as shown by an arrow by a drive device (not shown). Further, the tip ends of the scrapers 131A and 132A, whose base ends are fixed to the developing container 130, are in pressure contact with the first and second developing rollers 131 and 132, respectively, so that the liquid can be accumulated.
The toner on the developing roller is always cleaned.

Here, the pressure contact with which the liquid can be collected means that a scraper having a length in the axial direction of the developing roller is a substantially V-shaped facing area in which the free end of the scraper is in relation to the peripheral surface of the developing roller. And that the developing solution can be stored in the facing area there. Therefore,
The developer is stored in the facing area. Therefore, hereinafter, the developer stored in the facing area is referred to as a liquid reservoir.

Next, the position of the opening 20a of the liquid supply nozzle 20 is arranged in close proximity to the base end side of the scraper 131A as shown in FIG. 1 in order to supply the developing liquid without causing bubbles in the liquid reservoir. . Alternatively, as shown in FIG. 2, it is conceivable to dispose it close to the liquid reservoir or to immerse it. Alternatively, the developer flowing out of the opening 20a may be guided to the liquid reservoir via an appropriate liquid guide member.

By setting the opening 20a in this way, the generation of bubbles due to splashes or the like when flowing into the liquid reservoir is reduced as much as possible.

Further, most of the air bubbles in the liquid reservoir that are still generated even in this way disappear spontaneously in the course of the retention time as the liquid reservoir until being pumped up by the developing roller.

Nevertheless, the remaining bubbles are crushed and disappear in the process in which the developing solution is conveyed toward the photoconductor drum while being pumped in the form of a liquid film on the developing roller as the developing roller rotates. Thus, one of the objects of the present invention has been achieved.

Next, in the present invention, since the developing solution once having formed the liquid reservoir is successively supplied to the photosensitive drum through the developing roller, as long as the liquid reservoir is formed, the scraper and the developing roller are formed. The imbalance of the developing solution in the facing area due to the above does not cause a problem so much and the developing solution is uniformly supplied through the developing roller. Therefore, the remaining object of the present invention can be achieved. That is, as described in the prior art, the problem related to the imbalance of the developer supply amount with respect to the photoconductor due to the phenomenon that the liquid amount is large only in the vicinity of the nozzle opening and becomes smaller as the distance from the opening is eliminated. It

However, the smaller the imbalance of the liquid amount in the longitudinal direction in the liquid reservoir, the more preferable. Therefore, as shown in FIG. 3, the nozzle opening 20a is located at the central portion of the first developing roller 131 in the axial longitudinal direction.

By doing so, a sufficiently good liquid can be supplied by one liquid supply nozzle 20, but if several liquid supply nozzles are set, the center of the first developing roller 131 in the axial longitudinal direction will be the center. It can be said that it is preferable to arrange the nozzles at symmetrical positions, and to set the direction of the nozzle by inclining toward the central portion in order to form a more uniform liquid reservoir.

Thus, the photoconductor drum 10 via the first developing roller 131.
The developing solution supplied toward is stored in a region where the first developing roller 131 and the photoconductor drum 10 face each other, and gradually moves onto the photoconductor with the rotation of the photoconductor drum 10, and has an auxiliary developer supply function. Squeeze roller 1 through second developing roller 132
It is removed from the photoreceptor by 33 and a scraper 133A, and is recovered in a tank 22 through a recovery pipe 21 which opens at the bottom of the developing container 130. By the way, the supply of the developing solution to the solution supply nozzle 20 is performed by a pump P installed in the tank 22.
Via 23.

In addition to the above, the discharge pipe from the pump P is also connected to the developer concentration sensor 24 and the stirring nozzle 25.

Both ends in the longitudinal direction of the scrapers 131A and 132A are in an open state and flow down from the liquid reservoir. That is, scraper 13
The developer flowing down from 1A is received by the scraper 132A.
The developer flowing down from the scraper 132A is received by the developing container 130.

The scrapers 131A and 132A are each slightly longer than the axial length of each developing roller in order to function as a cleaning member. For example, each end is projected to the outside of the developing roller by about 1 to 2 mm.

In the present invention, it is necessary that a liquid pool is always formed in the area where the developing roller and the scraper face each other, and further, the developing liquid is pumped up from the liquid pool to form the developing roller and the photosensitive drum. Is formed in the longitudinal direction of the developing roller so that non-uniformity such as liquid shortage or uneven development does not occur at least in the area where the electrostatic latent image is present on the photoconductor when it reaches the interval. Need to be present.

Therefore, the supply amount of the developing solution from the solution supply nozzle is determined in consideration of the rotation speed of the developing roller, the developing solution viscosity, and the like, which are related to the scooping amount of the developing roller.

The developing roller is applied with a so-called developing bias at least during the developing process in order to prevent background stains.

In the experimental example, the scrapers 131A and 132A have a thickness of about 250μ.
m of Mylari film is used, both the first and second developing rollers 131 and 132 are driven at a peripheral speed of 200 to 300 mm / sec with a roller diameter of 22 mm, and a developer having a viscosity of 1.0 to 1.7 cp is supplied to the liquid supply nozzle 20.
From 1200 to 1500 ml / min, an appropriate amount of liquid reservoir was formed on the developing roller 131 in the axial direction of the developing roller 131 to obtain a good developing result.

(Effect) As described above, in the present invention, since the developing solution is extended between the developing roller and the scraper to store the developing solution, the developing solution is moved to the photosensitive drum side by the developing roller, so that the bubbles disappear. At the same time, the developing solution between the photoconductor and the developing roller forms a uniform reservoir, so that it is easy to obtain uniform image quality without image density unevenness or blurred images, which is convenient.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a transfer type electrophotographic copying machine to which the present invention is applied, FIG. 2 is an enlarged view of a main part of a wet developing device in the same figure, and FIG. 3 is a perspective view of a peripheral part of a first developing roller. FIG. 4 is a front view of the developing device section for explaining the prior art, and FIG. 5 is a perspective view for explaining the main part of the same figure. 10 ... Photosensitive drum, 20 ... Liquid supply nozzle, 131 ... First developing roller, 131A ... Scraper.

Claims (1)

[Claims] 1. In a wet development method in which a developing solution is supplied to the surface of a latent image carrier carrying an electrostatic latent image to visualize the electrostatic latent image, a developing roller is brought close to the latent image carrier. At the same time as disposing, the scraper is pressed against the developing roller so that the liquid can be stored, the developing solution is temporarily stored in the area where the developing roller and the scraper face each other, and the stored developing solution is formed into a liquid film with the rotation of the developing roller. A developer supply device characterized by supplying the latent image carrier while pumping it up.