JPS59129880A - Developing device - Google Patents

Abstract

PURPOSE:To feed stably a toner to a feed roller, to form a uniform thin layer and to execute a good friction charging by making a control roller having elasticity contact by pressing to a toner feed roller by forming a nip, and providing a toner carrying means. CONSTITUTION:The surface of a toner feed roller 2 consisting of a metallic sleeve of stainless steel, etc. is processed to a rough surface, and a control roller 3 having an intermediate elastic layer 3c forms a nip and is made to contact by pressing to said roller, and a circumferential speed of the control roller 3 is set so as to be a little slower than the feed roller 2. Also, in order to feed a toner into the nip, an impeller consisting of an arm 9 and an elastic body 10 is provided. Therefore, even in case of an original having a lot of overall black parts, the toner is fed enough to the nip, and no under-development occurs. In this regard, a uniform thin layer of the toner is formed by forming the nip, and also a good friction charging can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device using insulating powder toner.
In particular, the present invention relates to a developing device used to develop an electrostatic latent image formed on a photoreceptor or an insulating material, or a magnetic latent image formed on a magnetic material.

Conventionally, various developing methods have been proposed for developing the latent spots formed on an image bearing member such as the above-mentioned photoreceptor.

For example, as a clear image method for plasticizing an electrostatic latent image, a one-component development method is widely known in which development is performed using only toner without using carrier particles.

This method is further divided into those using magnetic toner and those using non-magnetic toner.

However, in either case, it is required to form a uniform layer of toner on the surface of a means such as a roller that supplies toner to the image carrier, or to sufficiently charge this single layer of toner. be. It becomes more difficult to uniformly apply toner to the surface of such a toner supply means as the coating layer becomes thinner and rougher.

In order to solve this problem, an elastic blade plate is pressed against the surface of the toner supply means according to the moving direction of the supply means, and the toner is passed between these blade plates and the supply means, thereby making the layer thin and It has been proposed to perform charging at the same time. However, with the above configuration, foreign matter tends to get stuck between the supply means and the elastic blade, and as a result,
A streaky area is formed on the supply means due to the toner being applied.
This area cannot be developed and becomes thicker, reducing the quality of the image obtained by development.

Furthermore, when non-magnetic toner is used, since it cannot be transported by a magnetic field, it is more difficult to coat and transport the toner onto the supply means than with magnetic toner.

An object of the present invention is to solve the problems of the conventional image forming apparatus using the toner of the above-described one-component developer. More specifically, it is an object of the present invention to provide a parent image device that can efficiently supply toner to a toner supply means. Furthermore, it is an object of the present invention to provide a plasticizing device which has a simple structure and is capable of forming a uniform thin layer on the surface of a toner supplying means, regardless of whether the toner is magnetic or non-magnetic, and can maintain this state stably.

A viewing body device of the present invention that achieves the above object includes a toner storage container that stores insulating powder toner, and a toner storage container that is located at a toner outlet portion of the storage container and rotates to supply the toner to an image carrier. a toner supply means, and an amount of toner applied that prevents the toner from flowing out from the toner outlet portion and forms a single layer of toner with a constant thickness on the surface of the toner supply means; at least one of the toner supplying means and the application amount regulating means is elastic, and the toner supplying means and the application amount regulating means are disposed so that they form a nip and come into pressure contact with each other, and the toner supplying means and the coating amount regulating means are disposed on the upstream side of the toner controlling means. A toner conveying means for actively feeding toner into the nip portion is provided near the supply means.

Hereinafter, the present invention will be explained in more detail according to examples and diagrams thereof.

FIG. 1 shows a sectional view of essential parts of a developing device to which the present invention can be applied. In the figure, 1 is a photosensitive drum that rotates in the direction of the arrow, and an electrostatic image is formed by a latent image forming means (not shown).
formed on its surface. A toner supply roller 2 facing the photosensitive drum 1 at the developing position supplies insulating non-magnetic toner on its surface to the photosensitive drum 1 while rotating in the direction of the arrow.

The toner supply roller 2 is made of a metal sleeve made of stainless steel or aluminum, or a hard synthetic resin that is hardened.

A regulating roller 3 for regulating the amount of toner applied is opposed to the roller 2 upstream of the development position, and the toner 4 flows out from the toner storage section by this regulating roller 3 and the supply roller 2. I have stopped doing that for a while. This regulation roller 3 rotates in the same direction as the position 7 facing the supply roller 2, and its speed is different from that of the supply roller 2. They form a nip and are pressed against each other.

The structure of this regulation roller is such that a rigid core 3a serving as a rotation center axis is used.
and an intermediate elastic layer i3b and a surface elastic layer 3C surrounding this core 3a.
have. As the intermediate elastic layer 3b, a particularly flexible resin such as a foamed resin having continuous or discontinuous cells or silicone rubber can be used. The rubber hardness of the elastic body used for these intermediate elastic layers 3b is 30 degrees to 90 degrees in Asker-F.
The hardness of the rubber is determined in consideration of forming a nip without applying more pressure than necessary between the two rollers.

If the intermediate elastic layer 3b has open cells and the toner enters into the cells and changes its elasticity, or if the toner composition causes deterioration, the intermediate elastic layer 3b
It is preferable to provide a surface elastic layer 3C around b. As such a surface elastic layer 3c, for example, a resin tube with a rubber hardness of about 0.3 to 2 mm and Asker C and 80 to 90 degrees is used. It may be covered with.

Of course, if the surface of the elastic layer 3b has undesirable porosity, large open cells, or a relatively smooth surface and is not affected by toner, there is no need to further provide a surface elastic layer.

The surface layer of the regulating roller 3 regulates the thickness of the toner adhesion layer to the supply roller at the nip portion with the supply roller, and also performs frictional electrification on the toner.

This frictional charging is mainly performed between the surface of the supply roller in the nip portion and the toner, and it is preferable to select a material for the surface of the supply roller that can frictionally charge the toner on the supply roller to a predetermined polarity. For example, Teflon (trade name) may be used to positively charge the toner, and synthetic resin such as nylon (trade name) may be used to charge the toner negatively. however,
If the surface of the regulation roller is made smooth by using a material with low frictional resistance such as Teflon, the toner will easily pass through the nip, and the toner thickness may not be controlled or the toner may not be charged sufficiently by friction. This may occur.

In such a case, the problem can be solved by roughening the surface of the regulating roller. In addition, the nip width at the nip portion is
・Set by taking into consideration conditions such as the pressure between the rollers 3, the elastic force of the regulating roller 3, and the difference in circumferential speed between the two rollers.

In the developing device shown in FIG. 1, the storage section for the toner 4 is constituted by both rollers 2113 and the casing 5 of the device. Further, film-like seal members 6 and 7 are provided between the housing 5 and each of the rollers 2 and 3 to prevent the toner from leaking from the storage portion of the supply roller in the developing device shown in FIG. The rotation of the roller 2 and the regulating roller 3 will be described. It has already been mentioned that on the Kimio side, both rollers rotate in the same direction at the nip part, but regarding the speed, the circumferential speed of the regulating roller should be lower than the circumferential speed of the supply roller, or the rollers should rotate in the opposite direction. is preferred.

On the other hand, if the side circumferential speeds are exactly the same, the toner on the supply roller may be caught between the supply roller and the regulation roller and pass through as is.

This kind of passage of toner causes the toner on the supply port, -ra, to not generate the appropriate amount of triboelectric charge required during development.
This may cause the latent image to not be sufficiently developed, or even cause the toner on the supply roller to scatter.

Therefore, both rollers preferably change their circumferential speed,
When moving in the same direction as shown in FIG. 1, the amount of change is preferably such that the speed of the regulating roller 4 is at least 5 times slower than the supply roller 3, preferably at least 50 times slower. Furthermore, the rotation of the regulation roller 4 may be not only continuous rotation but also intermittent rotation.

The effect of rotating the supply roller 2 and the regulation roller 3 in this way is to discharge the solidified toner and foreign matter caught between the nip out of the nip, and to prevent the presence of streaks of toner on the supply roller 2. Prevent areas from occurring. Further, it is preferable that at least one side is flushed, since the toner is prevented from slipping on the roller, the toner is loosened between the nip, and at the same time sufficient charging is achieved.

Next, the developing operation by the developing device shown in FIG. 1 will be explained briefly.

In Fig. 1, as the supply roller 2 rotates, the toner on the roller 2 moves to the position of the regulation roller 3.Then, a nip is formed between the two rollers that are in pressure contact with each other. The toner that has arrived is charged to a predetermined polarity due to frictional electrification as it passes through a regulating roller that rots at a different rate than the supply roller, and at the same time is regulated to a fixed layer thickness, and then transferred to the current image on the photosensitive drum 1. At this developing position, the drum 1 and the roller 3 face each other with a gap of 100 to 500 μm, and the toner is transferred to the photosensitive drum 1 by the action of the alternating electric field generated by the alternating current bias applied between the two members. It flies to the latent image and completes development.

By the way, in the plastic imaging apparatus shown in FIG. 1, a positive latent image is formed on the photosensitive drum 1 based on an original with many solid black areas or a high overall image density, and development of the dark areas of the image is continuously repeated. When developed, the lack of five images may become noticeable in the developed image. The reason for this is that due to the continuous removal of a large amount of toner, the amount of toner between the supply roller and the regulation roller, especially right before the nip portion, decreases or even disappears. As a result, toner is no longer supplied between the nip, and active application of toner to the supply roller 2 is stagnated, resulting in a shortage of toner on the roller 2.

The conditions under which this phenomenon occurs vary depending on the fluidity of the toner, the peripheral speed of the supply roller, and the diameters of the supply and regulation rollers. This problem is particularly likely to occur when the fluidity of the toner is low, when the circumferential speed of the supply roller is high, when the diameter of both legs is large, and when the space on the upstream side of the nip is narrow.

FIG. 2 is an enlarged sectional view of the nip portion for explaining the cause of toner shortage on the upstream side of the nip.

As shown in the figure, the toner 4 on the upstream side of the nip portion moves in the direction of rotation of the roller 2 by the surface of the supply roller 2, collides with the surface of the regulation roller 3 just before the nip, and this roller 3
rise along the surface of the

Therefore, if the toner 4 splatters immediately before the nip, or if the space between the two rollers on the upstream side of the nip is narrow, the above region B is likely to occur.

Even if the surface of the supply roller 2 is roughened to solve this problem, the toner on the roller 2 does not hold an electric charge, so it hardly sticks due to mirroring force, and it sticks weakly due to friction due to the toner's own weight. Not too much. Therefore, even if the surface of the supply roller is smoothed, the flow direction of the toner is bent due to the presence of the suppression roller 3, and the occurrence of the above-mentioned curved region B cannot be avoided.

FIG. 3 is a sectional view of a device showing an embodiment of a configuration that solves the above problem.

In the figure, 7 is an impeller which is a toner conveying means, and the rotation center M
Arms 9 were extended in all directions of 8, and an elastic body 10 made of a flexible sheet was attached to the tip of each arm 9. The elastic body 10 is constructed by wrapping one end of a synthetic resin filament around an arm, or by fitting a molded body of soft resin onto the arm 9. By configuring the elastic body 10 in this way, the impeller 7 can be placed as close as possible to the supply roller and the regulation roller, and if there is an elastic body at the tip of the arm, these rollers can be protected from damage due to friction of the arm. This has the effect of not only protecting the toner but also allowing the toner to be gently (forcibly) fed into the nip.

The major difference between this impeller 7 and the conventional stirring wheel for preventing toner crosslinking is that it is disposed as close to the nip as possible and is used to feed the toner into the nip. . Therefore, if the impeller 7 is provided in the toner 4 whose blade tips are not close to both rollers, toner cannot be smoothly supplied to the nip portion.

Further, when a rotating body as shown in FIG. 3 is used as a toner conveying means, the direction of rotation is not particularly limited, but regardless of the difference in diameter between the supply roller and the regulation roller, the toner is conveyed to the nip portion along the supply roller. Just rotate it in the direction that it will go in.

That is, the supply roller and the rotating body are rotated in the same direction at opposing positions.

FIG. 4 is a perspective view of the impeller 7, in which reference numeral 11 indicates a binding member for fixing the arm 9 on the shaft 8. The bow neutral body 10 is constructed by wrapping one end of a polyethylene terephthalate film with a thickness of 50 μm around the arm 9 and fixing it with adhesive.

Figure 5 shows another embodiment of the present invention, in which 12 is a photosensitive drum rotating in the direction of the arrow, and a supply roller 13 similar to the above is opposed to the photosensitive drum 12 and rotating in the direction of the arrow. . In other words, the rejection roller 14 has a rigid core 1 that is the center of rotation.
4a, an intermediate elastic layer 14b, and a surface elastic layer 14c, and rotates in the direction of the arrow at a circumferential speed of one-tenth that of the supply roller [2]. The housing 15 of the plastic waste device constitutes a toner storage section upstream of the developing position of the photosensitive drum. In the toner 16 of this reservoir there is a rotating arm 17 for preventing crosslinking of the toner. A rotary impeller 18, which is the toner conveying means of the present invention, is located very close to the supply and regulation rollers 13 and 14, which also function to prevent the toner from flowing out on the toner outlet side of the toner storage section. This impeller 18 has a rotating shaft 18a having a hexagonal cross section,
The toner that is supplied by the above configuration and located upstream of the second part formed by the regulating rollers 13 and 14 is attached to the lower part of the nip part. Even if it is, it is scooped up by the impeller 18, and at the same time, it is forcibly fed toward the nip portion. In the figure, numerals 19, 20, and 21 indicate sealing members for preventing toner from flowing out.

[Experiment 1] As a supply roller, a stainless steel bar with a diameter of 30 mm was cast with urethane rubber of 10 degrees of rubber hardness Asker-C on a stainless steel core metal with a diameter of 8 mm, and the maximum outer diameter was 28 mm. was covered with a Teflon heat-shrinkable tube to make the outer diameter 30 mm. Then, create a developing device with the configuration shown in Figure 1,
Both rollers were pressed together with a width of approximately 2 mm, and the width of the two rollers was approximately 2 mm.

When operating the developing device with the above configuration, the supply roller was driven at a circumferential speed of 120 mm/sec, and the regulation roller was rotated at 0.17 m$sec. At the development position, the gap between the photosensitive drum and the toner supply roller is 300μ, and a development bias of 1.6kHz is applied between the two members at a frequency of 1.6kHz.
A pressure of 3 kVpp (beak-to-beak Ichikawa) was applied, and a total of 16 images were formed from a completely black original on the photosensitive drum.
A latent image of 00■ was repeatedly developed. The toner used was a black toner with relatively poor fluidity, containing 95 parts of polystyrene having no magnetic component and 5 parts of a charge control agent, and having an average particle size of 10 microns.

As a result, the image density of the copies began to decrease after 20 copies were made from an A4 size (JIS standard) original.

Next, in the toner storage section of the developing device, the tips of the elastic bodies of the rotating blades as shown in FIG. It was rotated in the same direction at a position facing the roller. The rotational speed was set to 1/20 of that of the supply roller. Then, continuous copying was carried out under the same conditions as in the above experiment.

As a result, even though 1000 copies were made from the same A4 size original, no change was observed in the image density of the copies.

As described above, there is a toner storage container that stores insulating powder toner, a toner supply means that is located at the toner outlet of the storage container and rotates to supply the toner to the image carrier, and this supply means. rotates opposite to the supply means and prevents toner from flowing out from the toner outlet portion in cooperation with the toner supply means;
and a toner application amount regulating means for forming a single layer of toner of a constant thickness on the surface of the toner supplying means, at least one of the toner supplying means and the application amount regulating means has elasticity, and both means are configured to prevent a nip. In a developing device arranged so as to form and press the toner, it is possible to use not only magnetic toner, which can easily transport the toner, but also non-magnetic toner. Further, by forming a nip and rotating regulating means facing the supply roller, the toner application amount is made uniform and at the same time, the function of sufficiently charging the toner is stably maintained.

However, since both supply and regulation means form a nip and face each other, insufficient toner may be applied to the supply means. Possible causes of this include the fluidity of the toner and the shape of the space upstream of the nip in the toner storage section.

However, by configuring the developing device by arranging the toner conveying means upstream of the nip, the toner can be stably supplied to the supplying means without being affected by the fluidity of the toner or the shape of the space upstream of the nip. It was possible to supply the power.

Although only a rotary body is illustrated in the above embodiment as this toner conveying means, it may of course be a plate-shaped or link-shaped moving body that reciprocates in the direction of feeding the toner to the two-tube portion. Furthermore, this conveying means does not necessarily have an elastic body, and may be a blade wheel or an arm made of a rigid body, but an elastic body may also be used.A roller as in the above embodiment can be used as the supply means and the rejection means. In addition to the shape, it may also be a belt-shaped rotating body that rotates endlessly.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a developing device to which the present invention can be applied, FIG. 2 is an explanatory diagram showing the movement of toner on the upstream side of the nip portion by a supply roller and a regulation roller, and FIG. 3 is a diagram illustrating the present invention. FIG. In the figure, 1 is a photosensitive drum, 2 is a supply roller, 3 is a regulation roller, 4 is a toner, 7 is a rotary impeller which is a toner conveying means, 12 is a photosensitive drum, 13 is a supply roller, 14 is a regulation roller, 16 is a Toner, 18 indicates a rotating impeller.

Claims (3)

[Claims] (1) a toner storage container for storing insulating powder toner;
A toner supply means is located at the toner outlet of the storage container and rotates to supply the toner to the image bearing member; and a toner application amount regulating means for preventing the toner from flowing out and forming a single layer of toner of a constant thickness on the surface of the toner supplying means, and at least one of the toner supplying means and the application amount regulating means has elasticity. and a toner conveying means for feeding the toner into the nip portion near the toner supplying means on the upstream side of the regulating means. A developing device characterized by: (2) The developing device according to claim (1), wherein the toner supply means and the application amount regulating means are rotated at different circumferential speeds. Solution λ (3) Claims characterized in that the surface of the toner supply means is hardened; Claims (1) or (2) Claims characterized in that the toner application amount regulating means has elasticity. The developing device according to item (1) or item (2).