JPS60134263A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent contamination of an optical system, electrically charging system and conveying system and to form a stable image for a long period of time by providing a means for sticking the developer scattering from a developing device to a latent image holding member. CONSTITUTION:A wind conducting path 19 of which the aperture is directed to a photosensitive drum 11 is provided to the lower part of a developing device. The flow of air i formed in the direction of an arrow (a) in the path 19 by a fan 20 which is an air blowing means driven by an electric power source. OPC or alpha-Si, alpha-Se or the like is used for the drum 11 so that even if the voltage VL in the bright part maintains a certain specified voltage without decreasing down to 0V in the stage of using a Carlson process. The toner scattered from a developing part A is flows into the aperture of the path 19 by gravity and drum wind. This toner is brought in proximity to the drum 11 by the wind delivered from the path 19 and is stuck to the drum 11 by the static force between the electric charge possessed by the toner and the surface potential of a photosensitive body and is thus prevented from scattering in the device and contaminating the inside of the machine.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus having a developing device for developing a latent image formed on the surface of a latent image holding member in electrophotography, electrostatic recording, magnetic recording, or the like. In particular, by making the surface of the developer carrier on which a thin layer of toner is formed and held face the surface of the latent image holding member (facing with a small gap or facing in contact), the toner on the side of the thin toner layer is formed into a latent image. The present invention relates to an improvement in an image forming apparatus that develops a latent image with toner by selectively transferring the latent image to the surface of a holding member in accordance with the latent image pattern.

FIG. 1 shows the schematic structure of a typical image forming apparatus using mono-component magnetic toner in the developing part of this type of image forming apparatus (
The surface of the latent image holding member and the thin toner layer are a single sleeve, which is rotated in the direction of arrow a. Hereinafter, the member 1 will be referred to as a developing sleeve or simply a sleeve. The developing sleeve 1 rotates by one rotation of the fixed magnet roll 2, which is a fixed magnet roll which is a magnetic field generating member and which is inserted into the inner space of the sleeve 1. Reference numeral 3 denotes a toner hopper as a developer supply means for the developing sleeve 1, and the developing sleeve 1 is disposed with its substantially right half circumference inserted into the toner hopper 3. Reference numeral 4 is a developer layer thickness regulating member that is provided at the center of the upper path of the developing sleeve l with an appropriate minute gap α (for example, 2
The magnetic blades are arranged close to each other while maintaining a gap of 40 μm, and the layer thickness of the magnetic toner is formed to be thinner than this gap α. The gap α is smaller than the gap β between the sleeve and the latent image holding member, and is set so that one layer of toner coated on the sleeve does not come into contact with the latent image holding member. 5 is a one-component magnetic toner which is a developer contained in the hopper 3; 6 is a developing sleeve l on the side opposite to the hopper 3 side, with a minute gap β (for example, 300μ) maintained between the developing sleeve l and the sleeve surface; This is a latent image holding member that approaches and passes, and rotates in the direction b, which is the same direction at the closest portion to the rotational movement of the surface of the developing sleeve 1 in the direction a. The closest portion of both members 1.6 is referred to as a developing section A for convenience.

The magnet roll 2 inserted into the inner space of the developing sleeve l has an upper surface position corresponding to the magnetic blade 4, and a developing section A.
A magnetic pole 21 (cut magnetic pole N1 22 (developing magnetic pole 81),
23 (carrier magnetic pole N2).

24 (82) are arranged.

The latent image holding member 6 is, for example, a xerographic photoreceptor on which an electrostatic latent image is formed by the Carlson process,
A photoreceptor having an insulating layer on the surface with an electrostatic latent image formed by the NP process described in Publication No. 910, an insulator having a latent image formed by an electrostatic recording method, an insulator having an electrostatic latent image transferred by a transfer method. electrostatic latent image (or t
It is a member on which a magnetic latent image is formed and retained, and in the following description, it is also referred to as a photosensitive drum or simply a drum.

The circumferential speed of the member 6 in the developing section A and the circumferential speed of the toner layer on the developing sleeve l must be equal. This is because, as described in Japanese Patent Application Laid-Open No. 55-120042, if the circumferential speeds of the two are different, directionality will appear in the developed image. Taking advantage of the fact that the circumferential speed of a single layer of supported toner is slightly faster, the circumferential speed of the developing sleeve l is slightly slower than the circumferential speed of the latent image holding member 60, thereby reducing unevenness in the developed image due to directionality. This is to eliminate

On the other hand, as described above, it is necessary to hold the latent image holding member 6 and the developing sleeve l with a small gap β (for example, 300 μ). This has conventionally been achieved by the method shown in FIG.

FIG. 2 is a plan view of the developing section A seen from the X direction in FIG. , is of a type in which this is brought into contact with the latent image holding member 6, and the developing sleeve 1 and the spacer roller 7 are designed to rotate at independent angular velocities.

Incidentally, in FIG. 2, the latent image holding member 6 and the developing sleeve 1 are each driven by a gear (not shown). Also, the first
In the figure, reference numeral 9 denotes a bias power supply for forming an alternating electric field between the developing sleeve l and the image holding member 6;
Alternating current with superimposed direct current.

Alternating voltage such as distorted wave alternating current, square wave, pulse wave, etc. is supplied, and its value is 1000 to 200 peak-to-peak.
0 V is appropriate.

In FIG. 2, a latent image holding layer 62 made of a photosensitive layer or an insulating layer is coated or pasted on the surface of the image holding member 60 at a position corresponding to the central image area.

This latent image holding layer 62 has a maximum voltage of V depending on the latent image to be formed.
to a minimum of vL1. - million a
The base holding member 60 and the substrate 61 are normally made of a conductive material, and the surface potential thereof is the ground potential.

By the way, conventionally, when a bias voltage is applied to the minute gap β, the toner coated in a thin layer on the developing sleeve l flies between the roller and the drum, and the latent image is spread according to the surface position of the latent image holding member 60. The image is developed. During this flight, a small portion of the toner is affected by gravity.

The latent image holding member 60 may separate from the developing section A due to the laminar flow caused by the rotation of the latent image holding member 60, and may not adhere to the image holding member 6 or one image on the developing sleeve, becoming scattered toner and contaminating the inside of the image forming apparatus. Ta. When this scattered toner adheres to optical equipment, charging equipment, etc., the surface potential on the latent image holding member 6 is disturbed, and white streaks, black streaks, black spots, etc. may appear on the image.

Furthermore, if the scattered toner falls onto the copy paper conveyance path, the copy paper may be stained.

An object of the present invention is to provide an image forming apparatus that prevents contamination of optical equipment, charging equipment, and conveyance equipment by suppressing toner scattering from the conventional developing section described above, and forms stable images over a long period of time. do.

The present invention is an image forming apparatus that is provided with a means for causing scattered toner generated in a developing section to adhere to a latent image holding member, thereby preventing the inside of the image forming apparatus from becoming contaminated.

Embodiments of the present invention will be described in detail below with reference to the drawings.

[Embodiment 1] FIG. 3 is a schematic cross-sectional view of an image forming apparatus according to the present invention. The same members as in FIG. 1 are given the same reference numerals and detailed explanations will be omitted. In the figure, reference numeral 10 denotes a scattering prevention magnetic pole fixed inside the latent image holding member (photosensitive drum) 6. This anti-scattering magnetic pole 10 needs to be placed away from the developing section A and at a distance from the developing poles (S, ) ZZ so that they do not affect each other. Further, it is preferable that the scattered toner be attracted to the latent image holding member 6 before being diffused. Therefore, as shown in FIG. 3, the anti-scattering magnetic pole 10 is 700 to 8
The above conditions can be satisfied by having a magnetic flux density of 0.00 Gauss, facing the lower part of the developing device, and setting the gap γ between the lower part of the developing device and the latent image holding member within 5 circles. In the image forming apparatus set in this way, the anti-scattering magnetic pole lo
Since the scattered toner generated in the developing section A is attracted onto the latent image holder by magnetic force without affecting the development phenomenon in the developing section A, the amount of toner scattering into the image forming apparatus is significantly reduced. It became possible.

In FIG. 3, an N pole, which is different from the developing magnetic pole 22, is used as the anti-scattering magnetic pole 10, but it may of course be an S pole. Further, an electromagnet may be used instead of a permanent magnet.

[Example 2] In Example 1, the scattered toner was attached to the latent image holding member using magnetic force, but in order to improve color reproducibility, when non-magnetic toner was used as the toner, , magnetic force cannot be used. FIG. 4 shows an example in which non-magnetic toner is used. As an example of a method for developing non-magnetic toner, the present applicant has already published a patent application in 1983-212.
The developing method described in No. 320 can be applied. FIG. 4 shows the developing method.

In the figure, reference numeral 11 denotes an electrophotographic photosensitive drum, which holds a latent image formed by a latent image forming means (not shown), and rotates in the direction of the arrow to pass through the development position shown. A non-magnetic sleeve 12, which is a developer holding member that holds developer, faces the photosensitive drum 11 with a predetermined gap therebetween, and this sleeve 12 rotates in the direction of arrow a. A container 13 made of a non-magnetic material such as resin or aluminum is located above the sleeve 12 and stores a mixture of a non-magnetic developer 14 and magnetic particles 15, and downstream of the container 13 in the rotational direction of the sleeve, A magnetic blade 16 is screwed.

On the other hand, a magnet 17 is provided on the opposite side of the sleeve 12 to the magnetic blade 16.

In the above configuration, the magnetic particles 15 in the container 13 form a magnetic brush 18 due to the magnetic field generated between the S pole of the magnet 17 and the magnetic blade 16.

Then, as the sleeve 12 rotates while holding the magnetic brush 18, the magnetic particles and the non-magnetic developer are stirred and mixed. In this state, on the magnetic blade side of the container 13, due to the presence of this blade 16, the non-magnetic developer 14
The mixture of magnetic particles 15 is prevented from moving by this blade, rises, and circulates in the direction of arrow C.

As a result, the non-magnetic developer is frictionally charged by the magnetic particles or the magnetic particles. reach the opposite position.

At the position where the photoreceptor drum and the developing sleeve face each other,
As in the developing device shown in FIG. 1, by applying an alternating voltage to the sleeve from the power source 9, the non-magnetic toner is developed according to the surface potential on the photosensitive drum.

An air guide path 19 with an opening facing the photosensitive drum is provided in the γ portion of the developing device configured as described above, and air flow is formed in the direction of arrow d by a fan 20, which is an air blowing means driven by a power source (not shown). do.

In such an image forming apparatus, O2 is used as a photosensitive drum.
When a PC, α-8t, α-8s, etc. are used and the Carlson process is used, even the bright area voltage vL does not become 0V and is maintained at a certain constant voltage. The toner scattered from the developing section A flies to the opening of the air guide path 19 due to gravity and drum wind. This toner approaches the photoreceptor drum by the wind sent out from the air guide path 19, and is attached to the photoreceptor drum by the electrostatic force between the charge of the toner and the surface potential of the photoreceptor, and is transferred into the image forming apparatus. It will not spread and pollute the cabin. Of course, it is undesirable to use strong winds that adversely affect the developing section when blowing air from the air guide path, so the wind force should be selected appropriately.

[Example 3] In Example 2, wind force was used as the scattering prevention means, but mechanical force may also be used. FIG. 5 shows such an example. In FIG. 5, the same members as in FIG. 4 are denoted by the same reference numerals, and detailed explanations are omitted.

In the figure, reference numeral 25 denotes a urethane rubber roller, which is placed in light contact with or close to the photoreceptor drum 11, and is indicated by the arrow e.
It rotates at the same speed as the photoreceptor drum 11 in the direction.

Development is carried out in a manner similar to that shown in FIG. Since the lower part of the image forming apparatus is closed by the rubber roller 25, the toner scattered from the developing section A falls onto the rubber roller.

The toner that has fallen onto the rubber roller comes into contact with the photoreceptor drum as the rubber roller rotates, and is attracted to the photoreceptor drum by electrostatic force. At this time, light toner is scraped off from the photosensitive drum 11 and the rubber roller 25 by a scraper 26 so as not to disturb the image formed on the photosensitive drum. The scraped off toner is collected in a collection container 27. However, the toner remaining on the urethane rubber roller 25 does not last long. In order to prevent the scattered toner from being pressed against the rubber roller, the rubber roller may be coated with a resin or the like that is charged to the same polarity as the toner.

In the detailed explanation of the present invention, an example in which development is performed by non-contact jumping development using l-component magnetic or non-magnetic toner has been shown, but the present invention can also be applied to a contact type developing device.

Further, the present invention can also be applied to a developing device using a two-component developer. Furthermore, in addition to the embodiments shown in FIGS. 3 to 5, it goes without saying that the present invention includes all other modifications in which scattered toner is attached to the photosensitive drum.

As explained above, the present invention has a simple configuration in which the toner scattered from the developing section is attached to the photoreceptor drum.
Equipment in an image forming apparatus, especially the optical system.

Preventing dirt on the charging system and transport system and forming stable images over a long period of time 73;

[Brief explanation of drawings]

FIG. 1 is a sectional view of the developing unit of the image forming apparatus, FIG. 2 is an explanatory diagram showing a method for positioning the developer carrier and the latent image holding member, and FIG. 3 is the developing unit of the image forming apparatus according to the present invention. 4 and 5 are cross-sectional views showing other embodiments of the present invention. In the figure, 1 and 12 are developing sleeves, 2 is a bias power source, 10 is a scattering prevention magnetic pole, 14 is a non-magnetic toner, 1
7 represents a magnet, 19 represents an air guide path, 2o represents a fan, and 25 represents a rubber roller. Applicant Canon Co., Ltd.

Claims (3)

[Claims] (1) An image forming apparatus in which a developing device is disposed opposite to a latent image holding member, characterized in that the image forming apparatus has a means for causing developer that is about to be scattered from the developing device to adhere to the latent image holding member. (2) The image forming apparatus according to claim 1, wherein the adhering means is a scattering prevention magnetic pole disposed inside the latent image holding member. (3) The image forming apparatus according to claim 1, wherein the adhering means comprises an air blowing means and an air guide path with an opening directed toward the latent image holding member. (Me) The image forming apparatus according to claim 1, wherein the adhesion means is a roller that is brought into contact with or in close proximity to the latent image holding member.