JPS5995556A - Toner concentration uniformizing device - Google Patents

Abstract

PURPOSE:To make effectively a distribution of toner concn. in a developer uniform by forming a distributing means for supplying the toner throughout its transfer course region near the transfer course of a developer of a transfer means for transferring it in the direction intersecting the circulating direction of the developer. CONSTITUTION:The developer D is delivered from the bottom of a casing to a developing roll 21 through scooping rolls 23, 22, and the developer D passed through a developing section flows on a separator 26, and again recovered in the developer storing casing to make circulation. A part of the developer D is introduced into a toner concn. sensor 28 to detect toner concn. and the toner is replenished in accordance with its result through a toner replenishing pipe 27 by action of a screw 280 into the developer D. A part of the developer D passed through the developing section but not recovered in the casing is brought into a pipe 30 for distributing the toner and transferred from the opposite side to this side by action of a screw 30 through the pipe 30, and dropped through holes 302 into the bottom of the casing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner concentration leveling device, that is, a device for uniformizing the toner concentration distribution in a developer.

Conventionally, magnetic development methods and cascade development methods are well known as development methods using a powdered developer formed by mixing carrier and toner.

In such a developing system using a powder developer, the toner concentration distribution in the developer tends to be biased compared to a developing system using a liquid developer.

If a deviation occurs in the toner concentration distribution in a powder developer, image density unevenness will occur in a visible image obtained by development. Therefore, it is necessary to make the toner concentration distribution in the developer uneven.

Conventionally, as a method for uniformizing the toner concentration distribution in a developer as a mixed system of carrier and toner, for example, the developer is stirred by a stirring means such as a stirring blade, and the toner diffusion effect due to stirring is utilized. A well-known method is to even out the toner concentration distribution.

However, unlike in the case of liquids, when it comes to powder, the effect of stirring only extends to the vicinity of the area where the stirring is currently being performed, and the action of stirring evens out the toner concentration in the entire developer. It is not easy to do this, and it is often impossible to even out the toner concentration distribution, which changes as development is carried out, and as development is carried out continuously, density unevenness gradually occurs in the visible image.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a new type of toner density leveling device that has an excellent leveling effect.

The present invention will be described below with reference to illustrated embodiments.

FIG. 1 schematically shows an example of a developing device to which the present invention is applied. This developing device is of a magnetic development type.

The electrostatic latent image to be developed is formed on a drum-shaped latent image holder 1, moves as the latent image holder 1 rotates in the direction of the arrow, and is developed as it passes through the developing section. It becomes a visible image.

Reference numeral 2 indicates a developing device. 2o is a casing, 21 is a developing roller, 22 and 23 are pumping rollers, 24 is a screen agitator, 25 is a doctor, 26 is a separator, 27 is a toner supply pipe, 28 is a toner concentration sensor, Reference numeral 29 indicates a fin, reference numeral 3o a toner distribution pipe, and reference numeral 31 a guide.

The developer is a powder, a mixture of a magnetic carrier and toner, and is stored at the bottom of the casing 20. That is, the bottom of the casing 20 is a developer reservoir.

Both the developing roller 21 and the pumping rollers 22 and 23 have magnets arranged in a predetermined arrangement in the inner space of a non-magnetic sleeve. These rollers 21. , 22
．． The sleeves 23 each rotate in the direction of the arrow. The developer material is magnetically held on the circumferential surface of the sleeve and transported by rotation of the sleeve.

When the developer fluid flows, the carrier and toner rub against each other, and the toner is triboelectrically charged to a polarity opposite to that of the electrostatic latent image to be developed.

During development, the developer is transferred to the developing section, that is, the developing roller 2.
1 and the latent image holding member 1 are circulated in close opposition to each other.

That is, shortly before the electrostatic latent image to be developed reaches the developing section, for example, about 2 seconds, the developing roller 21
, the respective sleeves of the pumping rollers 22, 23 start rotating in the direction of the arrow. Then, the developer reservoir is first drawn up by the pumping roller 23 from the bottom of the casing which is the developer reservoir, transferred to the developing roller 21 via the pumping roller 22, and conveyed to the developing section by the developing roller 21. However, other than that, the amount of conveyance is regulated to an appropriate amount by the doctor 25.

In this way, when the electrostatic latent image on the latent image holder 1 passes through the developing section, it is developed by the supplied developer with a magnetic brush and becomes a visible image.

The developer layer that has passed through the developing section is then transferred to the developing roller
21, flows over the separator 26, and is collected again in the developer reservoir 9. Thus, the developer fluid is circulated to the developing section.

This developer circulation path is indicated by a chain arrow. Each arrow is
It shows the circulation direction at that position. Therefore, in FIG. 1, if we consider the direction perpendicular to the drawing, this direction is perpendicular to the developer circulation direction at each point.

Therefore, in FIG. 1, the direction intersecting the drawing is referred to as the direction intersecting the developer circulation direction.

When the development is completed, the sleeves of the pumping rollers 22, 23 and the screen agitator 24 stop rotating.

The developing roller 21 continues to rotate the sleeve. As a result, the developer stuck in the developing section and part of the doctor is sent to the separator 26 side via the developing section, and after a short period of time, for example, about 0.3 seconds, the developer is There will be no developer left near the area.

A portion of the separator 26 serves as a guide 263, and this guide 263 guides a portion of the developer flowing on the separator 26 to the tonneau concentration sensor 28.

The toner concentration sensor 28 detects the toner concentration in the developer flowing to the bottom of the casing 20, and the detection result is used to control l-ner replenishment.

Toner is replenished as follows. The toner replenishment pipe 27 extends in a direction perpendicular to the drawing, and one end thereof is connected to a toner tank, from which toner is replenished into the toner replenishment pipe 27.

A screw 280 is provided inside the toner replenishment pipe 27, and the toner replenished into the replenishment pipe 27 is conveyed in the longitudinal direction of the toner replenishment pipe 280 by the action of the screw 2800.

A plurality of replenishment holes 272 are bored in the toner replenishment pipe 27 at approximately equal intervals in the longitudinal direction, just like a vertical flute, and the toner conveyed by the screw 280 is
The developer is replenished into the tank through these replenishment holes 272.

Note that toner alone has poor fluidity, so a hole 271 is provided in the upper part of the toner supply pipe 27, and a part of the developer is poured from an opening 261 formed in the separator 26 corresponding to the hole 271. Fluidity is improved by pumping a portion of the toner and mixing it with replenishment toner.

Now, the leveling of toner density according to the present invention will be explained below.

The screw agitator 24 constitutes a transfer means.

When this screw agitator 24 rotates in the direction of the arrow, it transports the developer in a direction extending from the front side to the back side of the drawing in FIG. Hereinafter, this will be referred to as the developer being transported from the front side of the developing device 2 to the back side.

In any case, the screw agitator 24 transports the developer in a direction transverse to its circulation direction. Further, the rotation of the scree agitator 24 is controlled by the pumping roller 22.
．． The screen agitator 24 turns on and off in synchronization with the rotation of the sleeve 23, and when the sleeve rotates, the screen agitator 24
It also rotates. Therefore, the Sufu IJ w-agitator is
When the developer is circulated to the developing section, some of the developer is
Transfer in a direction that crosses the circulation direction.

Separator 26, toner distribution pipe 30, screw 310 disposed in this pipe 30, guide 31
constitutes the distribution means.

Here, referring to FIG. 2, the right side in FIG. 2 is the above-mentioned front side, and the left side is the back side.

A hole 262 is bored in the back side of the separator 26, and a hole 301 is bored in the back end of the pipe 30 in correspondence with this hole 262.

Hole 262 of separator 26 and hole 301 of pipe 3o
are communicated with each other by a guide 31, as shown in FIG. Therefore, when the developer is circulated to the developing section, a portion of the developer that has passed through the developing section and has not yet been collected in the developer reservoir section is transferred to the holes 262, guides 31, and holes 30.
1, 9 is inserted into the pipe 3o.

The taken in developer is transferred from the back side to the front side inside the pipe 3o by a screw 310 (FIG. 1) disposed inside the pipe 3o.

The pipe 30 also has a plurality of holes 302 drilled in the longitudinal direction of the pipe, just like the holes of a vertical flute.
The developer material transferred through the pipe 30 is passed through these holes 30.
2, it drops to the bottom of the casing.

As shown in FIG. 1, the fall position of the developer dropped from the pipe 3o is
The developer material is distributed in the vicinity of the transport path according to the arrangement of the holes 302 over the transport path area.

Now, how to even out the toner density using such an apparatus will be explained below.

During development, when the developer is circulated to the developing section, the developer that contributed to the development is transferred to the Sufu IJ w-agitator 24.
It will be collected in the vicinity of. During development, the toner in the developer is consumed, and the toner consumption is in the longitudinal direction of the developing section, that is, in the direction perpendicular to the drawing in FIG.
Because it is not necessarily uniform, as mentioned above, the souffle l)
The developer collected in the vicinity of the x-agitator 24 generally has a certain non-uniform l/ner density distribution in the direction of the transport path by the screw agitator 24, which is the transport means.

Now, let us assume that at a certain moment during development, a toner concentration distribution as shown in FIG. 3 occurs on the transport path of the screw agitator 24.

The left-right direction in FIG. 3 is the direction perpendicular to the drawing in FIG. 1, that is, the transfer path direction, and the right side in the drawing is the aforementioned front side, and the left side is the back side.

Assume that the toner density distribution is such that the high density portion is ρ0 and the low density portion is ρI. When the screw agitator 24 (FIG. 1) operates and the developer is transferred from the front side to the back side, this toner concentration distribution gradually shifts in the direction of the arrow. Of course, the shape of the toner concentration distribution will gradually collapse as the toner is transferred, since the diffusion effect also comes into play during the transfer process.However, for now, such a diffusion effect will be ignored, and as the toner is transferred, Assume that the toner concentration distribution in FIG. 3 moves in parallel to the left.

However, when the developer is transported in this manner, the developer is distributed and supplied to the transported developer at discrete positions on the transport path.

If the toner concentration of this developer distributed and supplied by the toner distribution pipe 30 is ρ2, the toner concentration ρ0
．． ρ1. The following five relationships are possible between ρ2.

(1) ρ2〉ρ0〉ρJ (eye) ρ2〉ρ0〉ρ1 (iii) ρ0〉ρ2〉ρ1 (IV) ρ2−ρj〈ρ0 (V)〈ρ1〈ρ0 First, considering the case (1) , in this case, the toner concentration ρ2 in the distributed developer is equal to the toner concentration ρ0. ρ].

Therefore, when the developer having a high toner concentration is distributed and supplied while the developer is being transported, the toner concentration of the developer being transported gradually increases. However, the effect of increasing toner concentration by distributing and supplying high toner concentration developer is
It is remarkable in the part No. 1, and it is easy in the part where the toner concentration ρ0 is high.

Therefore, while the developer having a high toner concentration ρ2 is being supplied and transported, the difference 1ρ0−ρ11 in the toner concentration of the developer being transported gradually becomes smaller, and eventually the toner concentration distribution becomes uniform. will be done.

Next, considering the case (eye), in this case, when the developer is distributed and supplied, the toner concentration does not change in the portion of the developer that is being transported and has a high toner concentration ρ0. This is because the toner concentration of the supplied developer is also ρ0.

However, 1·s-i of the region with low toner concentration ρ1
The intensity increases gradually as developer is distributed. In this way, differences in toner concentration are gradually smoothed out.

In case (iii), as developer is distributed and supplied, toner concentration decreases in areas with high toner concentration ρ0, and increases in toner concentration in areas with low toner concentration ρ1, causing the toner concentration to decrease. It will be evened out.

In case (Iv), the change in toner concentration due to distributed supply of developer occurs as a decrease in toner concentration in the region of high toner concentration ρ0, thereby smoothing out the non-uniformity of the toner concentration distribution.

In case (V), a developer with a low toner concentration is distributed and supplied, and the toner concentration ρ0. A decrease in concentration occurs at any part of ρ1, but the decrease in concentration at the part of concentration ρO is
This is more remarkable than the decrease in concentration at the site of concentration ρ1. Therefore,
The non-uniformity of the 1-ner concentration is gradually smoothed out.

Therefore, in any of the cases (i) to (V) above, the unevenness of the l-toner concentration in the developer being transported is gradually leveled out by the developer distributed and supplied. The leveling device can effectively equalize uneven toner density.

In addition, in the case of the example shown in Fig. 1, the screw agitator
During the transfer by the agitator 24, the diffusion effect caused by the agitation of the agitator 24 also effectively promotes the effects of the present invention.

Finally, the action of the fins 290 will be explained.

In FIG. 1, the fins 29 provided on the left side plate of the casing 20 are actually as shown in FIG.
There are multiple pieces.

Each of these fins 29 is slanted such that, in FIG. 2, the left side is higher and the right side is lower.

Therefore, when the developer pool is circulated to the developing section, the circulating developer pool is transferred in the direction of the arrow, that is, from the back side to the front side, by the action of these fins 29 when it is collected into the developer reservoir section. be done.

Incidentally, the transporting force of the screw agitator 24 is quite large, and unless some measure is taken, there is a risk that the presence of the developer will be concentrated toward the back of the developing device due to this transport. Therefore, one fin 29 is provided to maintain the balance with the transfer of the developer by the screw agitator 24 and to prevent the developer from being unevenly distributed in the developing device. The transfer force is matched to the transfer force of the screw agitator 24.

As described above, according to the present invention, it is possible to provide a toner concentration leveling device that is highly effective in uniformly leveling the toner concentration distribution in the developer.

In the above embodiment, the direction in which the developer is transported by the transport means;
Although the direction of transport by the distribution means is set to be opposite, these directions of transport may be the same.

Further, the transport direction may intersect with the developer circulation direction, but does not necessarily need to be perpendicular to the circulation direction as in the above example. Further, the distribution and supply of the developer may also be carried out continuously in one continuous position instead of at discrete positions as in the embodiment.

Further, the present invention is applicable not only to the above magnetic development method but also to a cascade development method.

[Brief explanation of the drawing]

FIG. 1 is a side view schematically showing only the essential parts of an example of a developing device embodying the present invention, FIG. 2 is a diagram for explaining distribution and supply of developer, and FIG. , is an explanatory diagram for explaining the leveling of toner density. ■ Latent image holder, 2 Developing device, 21...Developing roller, 26- Separator, 24 Screw agitator-130 pipe for distributing toner, 3
1..ga.f.do, 310 Scrikou, D..
developer.

Claims (1)

[Scope of Claims] A device for leveling the toner concentration in a powdered developer made by mixing a carrier and toner, wherein when the developer is circulated to a developing section, one part of the developer is a transport means for transporting a part of the developer in a direction intersecting the circulation direction of the developer; A distributing means that distributes continuously or at discrete positions in the vicinity of the transfer route by the transfer means, over the transfer route area, while transferring in the opposite direction or in the same direction as the transfer direction by the transfer means; Toner density leveling stool I having.