JPS62105170A - Developing device - Google Patents

Abstract

PURPOSE:To entirely prevent generation of toner coagulation having the possibility to be generated between peripheral surfaces of an elastic regulating plate and a developing roller, by forming a shape of a part of a pressure welding part to the developing roller of the regulating plate, to a projecting shape. CONSTITUTION:The shape of the pressure welding part to the developing roller 2 of an elastic regulating plate 7 is formed to a projecting shape, and as for an opposed part E', a distance to the developing roller 2 is enlarged, and a scattering toner which has been generated by the pressure welding part of the elastic regulating member does not reach the part E'. This scattering toner is scattered roughly in the direction along the surface of the developing roller, and it does not occur that the scattering toner is accumulated in a surface F part. The scattered toner does not adhere to the surface of the vicinity of the abutting part to the developing roller 2 of the elastic regulating plate 7. Also, in this developing device, even in case of an operation extending over many hours, no blocking toner is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a developing device in an image forming apparatus such as a copying machine or a printer that uses electrophotography.

Conventional technology The developing methods used in developing devices for electrophotography and electrostatic recording devices using dry toner can be roughly divided into two types: methods using two-component developers and methods using single-component developers. be done.

The method using a two-component developer differs from the method using a single-component developer, that is, the method using a developer containing only toner, because it uses a mixed developer of carrier and toner, so the mixing ratio of toner and carrier is kept constant. This method requires a toner concentration detection device to maintain the toner concentration, and has drawbacks such as deterioration of image quality due to deterioration of the carrier and periodic replacement of the carrier.

Therefore, recently, a method using the above-mentioned one-component type developer has been attracting attention.

In this case, there are various methods for applying electric charge to the toner, but most of the methods that have been put into practical use are methods using triboelectric charging. That is, the toner is charged to a desired positive or negative polarity by rubbing the toner with a substance appropriately selected for the toner. In particular, there are many developing devices in which charging is performed by friction between a layer of toner carried on the surface of a developing roller and a blade for regulating the thickness of this layer to a constant value. At this time, what becomes a problem is so-called blocking toner generated at the friction portion. This is because toner particles each having a diameter of about several tens of micrometers aggregate with each other at the frictional part to form a lump of about several hundred micrometers in size, which has a fatal adverse effect on development performance. This problem is especially serious when the fulcrum position of the blade, the contact position between the blade and the developing roller (the toner layer), and the rotating direction of the developing roller have a certain relationship.

FIG. 3 shows a developing device described in Japanese Unexamined Patent Publication No. 64-43038. This developing device forms a uniform thin layer of toner on the surface of the developing roller to improve image quality. 1 is a photosensitive drum that rotates in the direction of arrow &. 2 is a developing roller, which rotates at a constant speed in the direction of the arrow. A multipolar magnet 3 is arranged inside the developing roller 2. 4 is a toner container containing magnetic toner 6
is stored. The developer roller 2 is in contact with the toner spool in the container 4 in the lower region of its rotational movement and is adapted to draw up this magnetic toner 5 along the path of upward movement.

Reference numeral 6 denotes a rigid plate that removes a part of the thick toner layer 51 sent from the container 6, and removes a part of the toner layer 51 that is as thin as or thinner than the gap between the drum 1 and the developing roller 2 in the developing section. 62. Reference numeral 7 denotes a toner regulating plate made of a flexible elastic material such as rubber, which is disposed downstream of the rigid regulating member 6 with respect to the rotational path of the developing roller 2 and upstream of the developing section. This elastic regulating plate 7 has one end supported by a support member 71 and the other end surface facing the developing roller 2.
is pressed against the peripheral surface of the member, and a close contact portion is formed between the two members. This elastic regulating plate γ regulates the thin layer 62 of toner formed by the rigid regulating member 6 into an even thinner layer 53 . With this elastic regulating plate 7,
A uniform layer of toner of 100 μm or less is formed on the developing roller 2, and the elastic regulating plate 7 causes friction between the toner and the toner, thereby giving the toner the expected charge polarity.

By the way, as shown in FIGS. 4A and 4B, the manner in which the elastic regulating plate 7 comes into pressure contact with the developing roller includes forward direction pressure contact and reverse direction pressure contact with respect to the rotational direction of the developing roller 2. According to this reference, forward pressure welding refers to a pressure welding mode as shown in FIG. 4(A). That is, according to the explanation in this reference,
With the plate 7 arranged so that the distance between it and the circumferential surface of the developing roller 2 gradually decreases in the direction of rotation of the developing roller 2,
A state in which the plate 7 is in pressure contact with the developing roller 2 is defined as a state in which the plate 7 is in pressure contact with the developing roller 2, as shown in FIG. This refers to a state in which the developing roller 2 is pressed against the developing roller 2 in a state in which the developing roller 2 is provided so as to gradually increase in the direction. In FIG. 4(A), a relatively thick layer of toner is formed, which has the advantage of improving the image density of the developed toner layer. It is explained that the slits formed by the toner have the advantage of preventing passage of large particles in a single layer of toner, thereby making it possible to develop and form a fine-grained toner image.

Additionally, this reference contains the following statement: That is, if toner aggregates or the like become loose due to some accident between the elastic regulating plate 7 and the circumferential surface of the developing roller 2, slight unevenness may occur in the thin toner layer that is formed. In order to form a more uniform layer of toner, the elastic regulating plate may be vibrated perpendicularly or parallel to the direction of movement of the toner carrying surface, or in another direction, while keeping it in pressure contact with the toner carrying surface. There is a description that it can be smoothed out, and there is also a description of a device that applies such vibration to the elastic regulating plate.

Problems to be Solved by the Invention The present invention attempts to completely eliminate the generation of toner aggregates that may occur between the elastic regulating plate and the circumferential surface of the developing roller, as mentioned in the cited example above. It is something. The occurrence of this toner agglomerate actually causes a much more serious problem than that mentioned in the above cited example. That is,
These aggregates easily grow to a size of several hundred micrometers, and are attached to a single layer of toner on the surface of the developing roller at the so-called developing section where the photosensitive drum and the developing roller face each other as the developing roller rotates. carried to. In this developing section, the distance between the photosensitive drum and the developing roller, the so-called development gap, is usually about 100 to 200 μm, so that the above-mentioned aggregates, ie, Pro 9. Large pieces of king toner eat into this development gap and contaminate the surface of the photosensitive drum on which the electrostatic latent image is formed, resulting in a fatal deterioration of image quality. In addition, blocking toner smaller than the above-mentioned development gap will not get stuck in the development cuff, but its adhesion to the toner layer is small, so while the development roller is rotating, the toner will fall from the surface and be used in devices such as copying machines and printers. Contaminates the interior significantly. In the cited example above, as mentioned above, a method of vibrating the elastic regulating plate is proposed as a means of preventing the generation of blocking toner, but this method not only makes the device complicated and expensive, but also Even when the elastic regulating plate that regulates the toner layer thickness is vibrated, it is extremely difficult to control the vibration of the regulating plate so that the toner layer thickness remains constant.

The present invention aims to provide a means for reliably solving the above problems with a simple structure.

Means for Solving the Problems A technical means of the present invention for solving the above-mentioned problems is to make the shape of the portion of the regulating plate in pressure contact with the developing roller locally convex.

action The operation of this technical means will be explained.

Although the validity of this technical means has not been fully elucidated theoretically, it has been obtained and fully confirmed as an experimental fact, so at this stage we cannot fully understand its effects theoretically. I can't fully explain it. Therefore, I will explain this with some consideration.

When experiments were conducted on the generation of blocking toner using the configurations (M) and (B) in Figure 4, the amount of blocking toner generated was overwhelmingly larger in the configuration CB). ) and 中) are considered to have a fundamental difference. By the way, in the configuration (B), toner adhesion is observed on the downstream surface of the portion of the regulating plate 7 in pressure contact with the developing roller on the downstream side when viewed from the rotating direction of the developing roller, that is, on the portion E.

We will discuss why this toner adhesion to portion E occurs.

In (B), the elastic regulating plate 7 tries to rotate clockwise around the attached fulcrum 1 due to the friction of the pressure contact portion with the developing roller 2 rotating in the direction of the arrow.
In other words, the developing roller 2 receives a moment in the direction of the developing roller 2. the result.

The elastic regulating plate attempts to press against the developing roller with even greater force, and the above-mentioned moment becomes even greater. As a result of this amplification effect, the elastic regulating plate obtains sufficient frictional force at the portion in pressure contact with the developing roller and begins to move as the developing roller rotates. Next, as the elastic regulating plate 7 begins to rotate clockwise around the fulcrum 71 as the developing roller 2 rotates, the deformation of the elastic regulating plate 7 increases, so that the inside of the elastic regulating plate 7 Then, the internal stress that tries to return the elastic regulating plate 7 to its original position increases. Finally, this internal stress overcomes the above-mentioned frictional force, and the elastic regulating plate 7 slips at the pressure contact portion with the developing roller 2, in other words, the toner on the surface of the developing roller is removed from the developing roller. Return to the original position by rubbing in the opposite direction to the direction of travel. Therefore, the elastic regulating plate 7 repeats the movement due to the friction described above and the movement back to its original state, so that it ends up vibrating to rub the toner on the developing roller. Due to the action of this vibration, a part of the toner on the surface of the developing roller is scattered and attached to the E section of the surface of the elastic regulating plate 7, which is charged with the opposite polarity to the toner, near the pressure contact part with the developing roller 2. It seems to be.

On the other hand, in (A), the elastic regulating plate 7 is in pressure contact with the developing roller, and has a frictional force that causes vibrations that rub the toner on the developing roller surface in a direction opposite to the direction of rotation of the developing roller. does not work, the amount of scattered toner generated is sufficiently small, and since the regulating plate does not extend to the downstream side K from the pressure contact portion, there is no surface to which the scattered toner adheres. It seems that the scattered toner adhering to the elastic regulating plate 7 grows into blocking toner by some mechanism.

Therefore, by making the shape of the portion of the regulating plate 7 in pressure contact with the developing roller locally convex, and making the pressure contact with the developing roller at the convex portion, the area near the pressure contact portion is as shown in FIG.
Compared to case B), since the distance between the developing roller surface and the regulating member surface is sufficiently long, toner is less likely to adhere to the regulating member surface, and the generation of blowing toner can be eliminated. .

Embodiment FIG. 1 shows an embodiment of the present invention in a form corresponding to FIG. 4(B). The same reference numerals as in FIG. 4(B) represent the same contents.

In this embodiment, as shown in the figure, the shape of the portion of the elastic regulating plate in pressure contact with the developing roller 2 is convex.

As a result, part E' corresponding to part E in (■) in Figure 4 has a larger distance from the developing roller than in the past, and the scattered toner generated at the pressure contact part of the elastic regulating member is transferred to part E'. It will never reach that point. Moreover, this scattered toner is scattered in the direction along the surface of the developing roller, and the scattered toner does not accumulate on the surface F portion.

In this manner, in this embodiment, the scattered toner does not adhere to the surface of the elastic regulating plate in the vicinity of the contact portion with the developing roller. Further, in the developing device of this embodiment, blocking toner is not generated even during long-time operation. Regarding the specific specifications of this embodiment, the elastic regulating plate 7 is made of Si rubber, has a thickness of 3+ nm at the convex portion, 2 mm at the other portions, and has a hardness of about 60°.

FIG. 2 shows another embodiment of the invention. Here, by providing the groove 8 in the elastic regulating plate 7 near the part where it comes into pressure contact with the developing roller 2, the shape of the part of the elastic regulating plate 7 where it comes into pressure contact with the developing roller 2 is made locally convex. As in the case of the embodiment shown in FIG. 1, generation of blocking toner can be reliably prevented.

Effects of the Invention As described above, the present invention has a simpler configuration and structure than the conventional one,
The present invention provides a developing device that can reliably prevent the generation of bronzing toner, and can realize copying machines, printers, etc. with high reliability at low cost.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a developing device in an embodiment of the present invention, FIG. 2 is a sectional view of a main part of a developing device in another embodiment of the present invention, and FIGS. 3 and 4 are a sectional view of a main part of a developing device in a conventional example. FIG. 2 is a diagram of the principle of the device. 2...Developing roller, 5...Toner, 7
...Elastic regulation plate, 8...Groove, 71...
...Mounting is a fulcrum.

Claims (1)

[Claims] An elastic regulating plate for regulating the layer thickness of the developer on the surface of the developing roller is pressed into contact with a rotating cylindrical developing roller carrying developer on its surface, and this elastic regulating plate is
It is fixed relative to the developing roller at a fulcrum position where a moment in the direction of biting into the developing roller is applied due to the frictional force received at the pressure contact portion with the developing roller when the developing roller rotates, and A developing device in which the shape of the pressure contact portion of the elastic regulating plate with the developing roller is locally convex.