JPH01227175A - Electrostatic latent image developing device - Google Patents

Abstract

PURPOSE:To stably and certainly bring a thin film member into contact with a device roller by pressing the thin film member against the roller by means of a guide member having a prescribed pressing angle. CONSTITUTION:A thin film member 11 is closely adhered to the peripheral surface of a drive roller 10 and the angle of a guide member 9 provided on the surface facing a photosensitive drum 100 is set to 180-250 deg.. Moreover, a layer thickness regulating member 12 is fitted to the back of a supporting member 6 provided above the drive roller 10 and comes into contact with the thin film member 11 at the leading edge section. Since the thin film member 11 having a longer circumferential length than the drive roller 10 has is provided against the roller 10 in such a way, a space is formed between the member 11 and roller 10 in the section facing the photosensitive drum 100. Therefore, the thin film member covering the space 11 can be brought into contact softly and stably with the surface of the drum 100 with a very low pressure-contacting force in the developing area and, at the same time, the layer thickness regulating member 12 can be pressed against the roller 10 with a strong pressing force.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a developing device used in electrophotographic copying machines, printers, and the like. More specifically, the present invention relates to a developing device capable of stably supplying a uniformly charged thin layer of toner to an electrostatic latent image formed on the surface of a photoreceptor in a copying machine or the like.

Conventional technology An electrophotographic copying machine or an electrostatic copying machine uses a developing device to supply charged toner to an image carrier (photoreceptor) on which an electrostatic latent image has been formed to develop (visualize) the image. Transfers and fixes the toner image onto a transfer material such as paper.

In developing devices used in such electrophotographic copying machines and the like, especially in developing devices that use non-magnetic toner as a -component developer, it is important to supply a thin layer of uniformly charged toner to the surface of the photoreceptor. .

Conventionally, such a developing device supplies non-magnetic toner to the surface of an elastic developing roller, and presses a layer thickness regulating member to the elastic developing roller to form a thin layer of charged toner on the outer peripheral surface of the roller. A method has been proposed in which a toner image is formed by direct contact with the surface of a photoreceptor (see Japanese Patent Application Laid-Open No. 143831/1983).

However, in order to form the charged toner thin layer, it is necessary to bring the layer thickness regulating member into contact with the roller surface with a pressure above a certain level, and therefore the developing roller is required to have relatively high hardness.

On the other hand, in order to prevent damage to the photoreceptor and destruction of the image at the contact portion between the developing roller and the photoreceptor, it is desirable that the hardness of the developing roller be as low as possible. As described above, there are completely contradictory requirements regarding the surface hardness of the developing roller, and an actual developing roller cannot satisfy both of these requirements.

In addition, a conductive thin film is arranged on the surface of a roller made of a foamable soft conductive elastic material, and toner is electrically adhered to the surface using a magnetic brush, and the toner is applied by contact between the roller and the photoreceptor surface. It has also been proposed that the electrostatic latent image is developed by attaching it to the electrostatic latent image (Japanese Patent Laid-Open No. 55-7776).
(See Publication No. 4).

However, even with a developing roller using such a foam material, the pressing force against the photoreceptor cannot be made sufficiently small, especially when a difference in circumferential speed is provided between the roller surface and the photoreceptor surface.
A problem exists with destructive development of the image on the photoreceptor.

In view of the above-mentioned problems, the inventors of the present invention have created a combination of a drive roller and a slightly elongated cylindrical thin film sheathed on the drive roller, thereby creating a sufficient space between the drive roller and the layer thickness regulating member in the toner supply section. The electrostatic latent image carrier (photoreceptor drum)
We have previously proposed a developing device that can supply toner to an electrostatic latent image while maintaining stable and light contact with the electrostatic latent image carrier. In a developing device with such a structure,
The running stability of the thin film, the stability of contact with the photoreceptor, and even the toner thin layer are affected by the method of contact between the thin film member and the drive roller. An object of the present invention is to provide such a developing device in which the running of the thin film and the contact with the photoreceptor are stable.

Means for Solving the Problems The present invention provides: (i) a rotationally driven drive roller; (11) a cylindrical thin film member that is wrapped around the drive roller and has a circumference slightly longer than the circumference of the drive roller; (iii) having an inner surface that substantially corresponds to the outer shape of the drive roller, and connecting both ends of the drive roller to 18 mm via a thin film member;
A guide member that presses from 0 to 250 degrees: and (1v) presses the thin film member onto the outer peripheral surface of the thin film member.

The present invention provides an electrostatic latent image developing device characterized by comprising a layer thickness regulating member that forms a thin layer of charged toner.

According to the device of the present invention, since the drive roller is covered with a thin film member having a slightly longer circumference, a space is created between the thin film member and the drive roller at the portion facing the photoreceptor drum. It is formed. Therefore, in the developing region, the thin film member covering the space can be stably soft-touched to the surface of the photoreceptor drum with a very low pressure contact force, and in the region where a thin layer of charged toner is formed on the thin film member. By bringing the thin film member and the drive roller into close contact with each other, the layer thickness regulating member can be pressed against the drive roller with a strong pressing force.

EXAMPLES Hereinafter, the present invention will be explained in more detail by way of examples with reference to the accompanying drawings.

FIG. 1 is a sectional view showing a developing device (1) of the present invention.

The developing device (1) is arranged adjacent to a photosensitive drum (100) that is rotationally driven in the direction of arrow (a).

The developing device (1) includes a drive roller (10) that is a rotating body;
A cylindrical thin film member (11) mounted on the drive roller, and a guide member (10) that presses the thin film member against the drive roller (10).
9), a layer thickness regulating member (12) that is pressed against the outer surface of the thin film member, and a casing (3) that supports and accommodates these members and stores toner (To).

First, a drive roller (lO) that performs rotational driving is made of a conductive member such as aluminum coated with an elastic member such as rubber or plastic that has conductivity, and a developing bias voltage is applied to the drive roller (lO). Further, the drive roller may be manufactured from a conductive material such as aluminum whose surface has been roughened by blasting.

Next, the thin film member (11) is made of a cylindrical film having a circumference slightly longer than the outer circumference of the drive roller (10), and is wrapped around the drive roller (lO) so that the thin film member (11) is not attached to the drive roller. Form a slight slack.

Preferred materials for such a thin film member include a soft resin sheet, a resin sheet with carbon or metal fine powder added thereto, a metal thin film such as nickel or aluminum, and a laminated sheet of the resin sheet and metal thin film. The thin film member and the driving roller each have a massing coefficient between the inner surface of the thin film member and the roller surface that is larger than a massing coefficient between the guide and the regulating layer thickness regulating member that presses the outer surface of the thin film member, and the thin film member is stabilized by the driving roller. It is set to be driven.

The guide member (9) has an arcuate inner surface with an angle θ substantially corresponding to the outer shape of the drive roller. Therefore, by bringing the thin film member (11) into close contact with the periphery of the drive roller (10), the slack of the thin film member (11) is concentrated at the opening angle of 360°-θ of the guide member provided on the surface facing the photoreceptor drum. As a result, a certain space (S) is formed. The angle θ of the guide member is set to 180 to 250°.

If θ is smaller than 180°, the thin film member cannot run stably because the contact area is small, and the member stops running, causing noise in the image. Further, when the thin film member is strongly pressed against the photoreceptor, the thin film member escapes in the vertical direction as shown in FIG. 2, and sufficient pressure contact force cannot be obtained. D, (image density) decreases. Further, the degree of deformation of the thin film member is different between the axial end portions and the center portion, and as a result, the state of pressure contact with the photoreceptor in the developing section becomes non-uniform, making it impossible to obtain a uniform image.

On the other hand, when θ is larger than 250° as shown in FIG. Note that the inner arc of the contact portion may be partially discontinuous as long as it substantially forms an arc, and may be partially discontinuous as long as it has a shape that allows the thin film member to substantially come into close contact with the drive roller. good.

The guide member may be made of synthetic resin such as polyethylene, polypropylene, nylon, polyacetal, phenol resin, or fluorine resin;
Alternatively, a material in which a polyethylene, nylon, or Teflon film is provided on the contact surface with the thin film member (11), or a material in which the film is provided on the surface of a foam material is used.

Note that the outer peripheral surface of the drive roller (10) and the thin film member (11)
The coefficient of friction with the inner peripheral surface of 70. If the coefficient of friction between the outer peripheral surface of the thin film member (11) and the guide member (9) is μ, then μ
m) A relationship of μ2 is given, and the drive roller (10)
When rotates in the direction of arrow (b), the thin film member (
11) also moves in the same direction.

Furthermore, the layer thickness regulating member (12) is attached to the back side of the support member (6) provided on the top of the drive roller (10), and contacts the thin film member (11) at its tip.

The material of the layer thickness regulating member may be a non-magnetic metal thin plate material such as stainless steel or phosphor bronze, a plastic material such as Teflon or nylon, or a composite material made by bonding these materials together. Any material used for the thickness regulating member can be suitably used, and a material having elasticity is preferable. As such a material, it is preferable to use a more negative material in the triboelectrification series for positive (+) toner, and a more positive material for negative (-) toner. For example, for a positive donor, a sheet of fluororesin such as Teflon or a coating thereof is suitable, and for a negative toner, a polyamide film such as nylon or its coating is suitable.

In addition, as the layer thickness regulating member (12), as shown in FIG. 1, a contact rigid body such as a metal round rod (12b) that contacts the thin film member (11) is provided at the tip of the thin plate-like elastic member (12a). is preferable.

A toner storage tank (15) is provided in the casing (3). The toner storage tank (15) is provided with an agitator (14) that rotates in the direction of the arrow (c), and moves the toner (TO) stored therein in the direction of the arrow (c) while preventing blocking.

The toner used in the apparatus of the present invention is preferably a so-called -component type non-magnetic toner, but a magnetic toner or the like may also be used. In addition, in order to bring the thin film member into close contact with the drive roller, a magnet is placed inside the drive roller.
It is also possible to use magnetic adsorption force to layer a thin film made of a magnetic material.

Next, the operation of developing using the apparatus of the present invention will be explained with reference to FIG.

The drive roller (lO) and the agitator (14) are rotated in the directions of arrows (b) and (c), respectively, by a drive source (not shown), and the toner (TO) is forcibly moved in the direction of arrow (c). It will be done. On the other hand, the thin film member (11) rotates in the direction of arrow (b) together with the drive roller (10) due to frictional force with the drive roller (10). Toner storage tank (15)
The toner (TO) inside adheres to the surface of the thin film member (11) by contact with the thin film member (11) and electrostatic force, and is transported in the direction of arrow (b). The toner (To) is taken into the tip (13) formed by the thin film member (11) and the layer thickness regulating member (12), reaches the pressure contact part of the layer thickness regulating member (12), and is removed from the thin film member (12). 11) is uniformly coated in a thin layer on the surface of the material, and triboelectrically charged to a predetermined positive or negative polarity.

The thin layer toner (To) held on the thin film member (11) by the electrostatic force due to its own charging further moves and is carried to the part facing the photoreceptor drum (100) (development area (X)), The surface potential of the photoreceptor drum (100) and the drive roller (1
Due to the electric field based on the voltage difference between the toner and the bias voltage applied to the photoreceptor drum (100), the toner moves to the electrostatic latent image formed on the surface of the photoreceptor drum (100) to form a toner image.

Here, the thin film member (1) in contact with the photoreceptor drum (100)
1) has a space (S) between it and the drive roller (10) and is in a non-contact state with the drive roller, so the thin film member (11) is able to hold the photoreceptor drum ( 10
0) to form a uniform toner image on the electrostatic latent image on the photoreceptor drum (100). It is also possible to create a speed difference between the circumferential speed of the photoreceptor drum (100) and the speed of the thin film member (11), so that the toner image once formed on the photoreceptor drum (100) is transferred to the thin film member. It will not be destroyed by physical forces such as rubbing force.

To + remaining on the thin film member (11) in the development area (X)
-(To) continues with the thin film member (11) and the arrow (
b) conveyed in the direction.

Next, an agitator (14) is placed on the surface of the thin film member (11).
), the toner (TO) is supplied again, a uniform thin layer of charged toner is formed at the pressure contact portion of the layer thickness regulating member (12), and the above operation is repeated again.

Effects of the Invention According to the developing device of the present invention, stable running of the thin film member is ensured by pressing the thin film member against the drive roller by the guide member having a predetermined suppression angle, and in addition, in the developing area, the thin film member It is possible to make stable and accurate contact with the photoreceptor drum with a sufficient nip width and extremely low pressure contact force, and it can supply toner uniformly to the electrostatic latent image, producing a stable image with no density unevenness. can be formed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the developing device of the present invention, FIG. 2 is a partial sectional view showing the case where a guide member with a small pressing angle is attached, and FIG. 3 is a partial sectional view showing the case where a guide member with a large pressing angle is installed. It is a diagram. The main symbols in the figure are as follows. ■, developing device, 3: casing, 9 guide member, lO
: Drive roller, 11: Thin film member, 12: Layer thickness regulating member.

Claims (1)

[Claims] (1) A drive roller that is rotationally driven; a cylindrical thin film member that is externally mounted on the drive roller and has a circumference slightly longer than the circumference of the drive roller; an inner surface that substantially corresponds to the outer shape of the drive roller; A guide member that presses both ends of the drive roller over a range of 180 to 250° via a thin film member; and a layer thickness regulating member that presses the thin film member to form a thin layer of charged toner on the outer peripheral surface of the thin film member. Characteristic electrostatic latent image developing device.