JPH0497376A - Developing device - Google Patents

Abstract

PURPOSE:To form a stable and uniform toner thin layer and to prevent the occurrence of the defect of an image caused by fogging by providing plural doctor blades having electret layers. CONSTITUTION:Nonmagnetic one-component toner T is supplied to a developing sleeve 1, and a first doctor blade 21 is provided with a gap (d1) on the periphery of the developing sleeve 1. A second doctor blade 21 is provided with a gap (d2) on the downstream of the doctor blade 21, and the toner T on the developing sleeve 1 passes the gaps with respective to these doctor blades, and supplied to a photosensitive drum 1. Furthermore, at this time, the doctor blades 21 and 22 have electrets E1 and E2 covering the vicinities of the top ends, respectively. Therefore, the electrostatically napping action of the nonmagnetic one- component toner T can be carried out. Thus, the uniform stable toner thin layer can be formed. Moreover, the occurrence of the defect of the image caused by the fogging is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a developing device, and more specifically, a doctor blade having an electret layer cuts toner on a developing sleeve to form a uniform thin layer of toner. The present invention relates to a developing device that supplies toner to a photoreceptor.

[Prior Art] Conventionally, in a developing device of an image forming apparatus, for example, as shown in FIG. 3, toner T on a rotatable developing sleeve 1 is
In order to maintain appropriate image quality by supplying a uniform amount to the photoreceptor drum 3, a single doctor blade 2 on the developing sleeve 1 cuts the toner T to form a constant thin layer of toner. ing.

[Problems to be Solved by the Invention] However, since the doctor blade 2 is conventionally used alone and cuts the toner at once with its narrow tip, the limiting force exerted by the doctor blade 2 on the toner is extremely large. It takes a short time and it is difficult to form stable and uniform Nr@.
There was a problem.

In addition, since it is not affected by electrostatic influence from the doctor blade 2, toner with a small amount of charge is also carried to the developing area.
There is a problem in that uncharged toner unnecessarily adheres to areas of the photoreceptor drum 3 where there is no latent image, causing image defects called fog.

The present invention aims to solve such problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides the following developing device.

That is, the present invention is a developing device equipped with a plurality of doctor blades each having an electret layer.

[Function] In the above configuration, the developing device repeatedly cuts the toner by using a plurality of doctor blades each having an electret layer.

In other words, the amount of toner is appropriately reduced by cutting the ears with the doctor blade in the previous stage, so as not to disturb the potential distribution of the doctor blade in the latter stage, and the doctor blade in the latter stage cuts the ears accurately with fine adjustment. . Therefore, the plurality of doctor blades act to accurately equalize and stabilize the thickness of the toner by providing multiple stages.

Further, since the plurality of doctor blades repeatedly cut the toner, the toner has many chances to be charged. Therefore, the plurality of doctor blades act to increase the amount of charge on the toner.

[Example] Regarding an example of the present invention, how the configuration of the present invention is actually embodied will be described below with reference to the drawings, along with its operation.

FIG. 1 is an explanatory diagram of one embodiment of the present invention. In the figure, 1 is a rotatable developing sleeve, and non-magnetic to component toner is supplied to this developing sleeve 1. As shown in FIG.

A first doctor blade 21 is provided on the circumferential surface of the developing sleeve 1 with a gap of dl, and a second doctor blade 22 is provided downstream of the first doctor blade 21 with a gap of dl. .

The toner T on the developing sleeve 1 passes through the gap between these doctor blades and is supplied to the photoreceptor tram 3.

The size of these two gaps, dl and dl, is dl = d2 or d,>dl It is set in one circle.

Further, these doctor blades 21 and 22 are respectively provided with electrets E and E2 that cover the vicinity of their tips.

Here, this electret is a polymer material that can semi-permanently maintain an electrically polarized state at a high voltage.For example, the material itself maintains its polarity even without connecting a power supply circuit that applies a bias voltage. It is said that the name electret was given to magnets because it is similar to how permanent magnets can maintain their magnetic poles for long periods of time.

Electret has an extremely simple structure and can be made lightweight and compact, so as technology advances in the polymer field, it has recently become a material commonly used in ultra-small microphones, speakers, and other audio equipment.

By using this electret in a doctor blade, the non-magnetic component toner can be electrostatically restricted, that is, it can have a cutting action.

In this embodiment, a case is described in which electret El-E2 having the same polarity as the toner T is used.

FIG. 2 is an explanatory diagram of the operation of the same embodiment, and as shown by the arrow, the toner T conveyed on the circumferential surface by the developing sleeve 1 rotating counterclockwise is transported to the gap dl (
1) and has the same polarity as the toner T, when the toner T is cut into ears by the first doctor blade 21, a large amount of the toner T is removed by electrostatic repulsion. be limited.

This larger amount of toner than necessary disturbs the state of the potential distribution of the electret, so by limiting the amount of toner with the first stage (in this case, the first) doctor blade,
without interfering with the action (electrostatic repulsion or adsorption force) of the electret of the subsequent (second in this case) doctor blade;
Efficiency and stability can be achieved.

This is precisely the reason for providing multiple doctor blades.

This first doctor blade 2. As a result, the quantitatively limited toner T is repeatedly limited in the next second doctor blade 2□, so that a thinner, more uniform, and stable toner layer can be formed.

In this case, even if the gap d2 with the developing sleeve 1 is set to 1-d2, which is the same size as the gap d in the case of the first doctor blade, the toner T is further Stably formed to a thin and uniform thickness.

However, if the gap d2 of this second doctor blade 2° is set to a gap d>d2 smaller than the gap d1 of the first doctor blade 21, the toner T will be formed into a thin, uniform layer. layers can be formed.

In the embodiment described above, the electret El-E2 of each toctor bullet has the same polarity as the toner T,
Each of the electrets E1 and E2 is not limited to the same polarity as the toner T shown in the above embodiment; Other embodiments (not shown) may be used in which the polarity is set to be opposite to that of the toner.

That is, in the case of this other embodiment, each electret El"E2 forms a thin toner layer by peeling off the upper part of the toner on the developing sleeve with the adsorption force due to electrostatic opposite polarity. can.

Furthermore, the two electrets E and E2 are not limited to having the same polarity as each other, but may also have other (not shown) embodiments, such as one having the same polarity as the toner and the other having the opposite polarity to the toner. It may be.

In this case, one electret with the same polarity as the toner presses down the toner with repulsive force, and then the other electret with the opposite polarity peels off the upper part of the same toner with adsorption force, thereby transferring the toner onto the developing sleeve. It is possible to form a thin layer of

Although the embodiments described so far refer to two doctor blades, each with an electret, this is not limited to two, but may also include three, four, or more. You can.

As described above for each embodiment, the present invention is a developing device equipped with a plurality of doctor blades each having an electret layer, and is capable of limiting the toner on the developing sleeve in multiple steps in multiple stages. This makes it possible to form a more stable toner layer with a uniform fiF8.

In addition, by having these multiple electrets,
Since there are more opportunities to be charged, the amount of toner charge increases and the toner is more likely to be attracted to the latent image on the photoreceptor drum 3, resulting in a higher development density and a clearer image.

Furthermore, by increasing the amount of charge and decreasing the amount of uncharged toner, fogging is eliminated and image defects can be prevented.

[Effects of the Invention] As described above, according to the present invention, since a plurality of doctor blades each having an electret layer are provided, the amount of toner is appropriately squeezed by the doctor blade at the front stage, and the effect of fine adjustment is achieved by the doctor blade at the rear stage. Being able to cut the ears,
Can form a uniform and stable toner thin layer. Therefore, during development, image quality can be maintained well without unevenness.

In addition, since a plurality of doctor blades each having an electret layer are provided, the toner is given the opportunity to be charged multiple times, increasing the amount of charge, thus increasing the electrostatic adsorption force and improving the developed density. It is possible to form clear images.

Furthermore, since the amount of charge increases, unnecessary uncharged toner is reduced, and image defects due to fogging can be eliminated.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of the same embodiment, and FIG. 3 is an explanatory diagram of a conventional example. ...Developing sleeve, -First doctor blade, 22...Second doctor blade, -E2...Electred. Special attorney: Suzuki Junya Sanda Kogyo Co., Ltd.

Claims (1)

[Claims] A developing device equipped with multiple doctor blades each having an electret layer.