JPH04255878A - Developing device - Google Patents

Abstract

PURPOSE:To provide a developing device where developer is completely prevented from being suspended from the developing device so as to prevent contamination in a copying machine, etc., image quality is prevented from being deteriorated, and the spark discharge of an electrode for preventing the scattering of the developer and an electrostatic latent image carrier is prevented so as to prevent the breakage of the electrostatic latent image carrier. CONSTITUTION:In a developing device which is provided with a developer carrier 2 which holds the developer T on its periphery and an electrostatic latent image 9 formed on the electrostatic latent image carrier 1 is visualized by splashing the developer T from the carrier 2, the electrode 5 for preventing the scattering of the developer whose surface is coated with an insulating film or a semiconductive film is laid on the downstream side of a developer splashing area interposed between the carriers 1 and 2, and specified bias voltage is impressed on the electrode 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus using an electrophotographic method, such as an electrophotographic copying machine or a laser beam printer.

0002

[Prior Art] Various types of developing methods have been proposed for visualizing an electrostatic latent image formed on an electrostatic latent image carrier, depending on the type of developer and image forming conditions. ing. In a typical development method, a two-component developer consisting of toner and carrier is attracted to a developer carrier containing a magnet to form a developer magnetic brush, and this magnetic brush is transferred to an electrostatic latent image carrier. There is a so-called magnetic brush development method in which development is carried out by bringing the developer into contact with the electrostatic latent image carrier, or a one-component developer consisting only of toner is made into a thin layer on the surface of the developer carrier, and the thin layer of developer is flown toward the electrostatic latent image carrier. There is a so-called touch-down development method in which development is carried out using the same technique.

FIG. 5 shows an example of a developing device that employs the latter touchdown developing method, and shows a one-component developing device that uses magnetic toner as a developer. Specifically, a hopper a that accommodates the developer T and a rotatable cylindrical sleeve b1 include a magnet roll b2 having a plurality of magnetic poles, and the developer T is transferred to the sleeve b1 by magnetic force.
It is composed of a developer carrier b that is attracted to the developer carrier b, and a developer regulating member c that thins the developer T conveyed by the sleeve to a predetermined thickness and triboelectrically charges the developer T.

FIG. 6 also shows an example of a developing device employing the latter touchdown developing method, and shows a one-component developing device using non-magnetic toner. In this device, since it is impossible to attract the developer T onto the sleeve b1 by magnetic force, a developer supply roll d is arranged adjacent to the developer carrier b, and this supply roll d carries out the development in the hopper a. It is configured to force the agent T to adhere to the sleeve b1.

In the one-component developing device configured as described above, in order to fly the developer T formed into a thin layer on the developer carrier b toward the electrostatic latent image carrier e, an AC power source g and a DC power source are used. A DC superimposed AC voltage is applied to the developer carrier b from h. As a result, as shown in FIG. 7, the developer T charged to a predetermined charge is transferred to the developer carrier b by the action of the alternating current electric field.
The developer T moves back and forth in a region A between the developer and the electrostatic latent image carrier e (hereinafter referred to as a developer flying region), and the developer T becomes cloud-like, moving in pieces in the atmosphere. On the downstream side of the developer flying area A, there are a developer carrier b and an electrostatic latent image carrier e.
As the distance from the electrostatic latent image carrier e gradually increases, the strength of the electric field acting on the area becomes weaker, so the cloud-like developer T is attracted to the electrostatic latent image f on the electrostatic latent image carrier e and develops it. , and when the electrostatic latent image f does not exist, it is pulled back to the developer carrier b.

In the one-component developing device shown in FIGS. 5 and 6, the developer T selectively adheres to the electrostatic latent image f to visualize it as described above, but at this time, All the developer T that was migrating in the developer flying area A is transferred to the electrostatic latent image carrier e.
Or, it does not adhere to any of the developer carriers b. In other words, some of the developer drifts out of the developing device and adheres to the surface of the electrostatic latent image carrier regardless of the presence or absence of an electrostatic latent image, or adheres to the paper conveyance path or optical system parts within the machine. . For this reason, conventional one-component developing devices have had the problem that the quality of recorded images tends to deteriorate.

[0007] The problem caused by the developer migrating in the developer flying region drifting out of the developing device is not unique to single-component developing devices; This is a problem common to component developing devices and the like.

In order to solve these problems, the applicant of the present application installed a developer scattering prevention electrode in the vicinity of the downstream side of the developer flying area, and applied a DC bias voltage to this developer scattering prevention electrode. We have previously proposed a developing device that applies .

According to this proposal, an electric field is formed in a fixed direction between the developer scattering prevention electrode and the electrostatic latent image carrier or the developer carrier, so that the developer is transported from the developer flying region to the outside. Therefore, it is possible to prevent the image quality from deteriorating due to the above reasons.

0010

[Problems to be Solved by the Invention] However, the following new problems have arisen in this proposed developing device. In other words, since the distance between the electrostatic latent image carrier and the developer scattering prevention electrode is extremely short, minute conductive substances such as metal powder mixed in the developer float in the developer flying area and flow between the two members. If this occurs, spark discharge is likely to occur. For this reason, for example, when the electrostatic latent image carrier is a photoconductive drum, the photoconductive layer is destroyed, resulting in image loss during subsequent image formation.

The present invention has been made in view of the above-mentioned problems, and its purpose is to completely prevent the developer from drifting out of the developing device by installing an electrode for preventing developer scattering. Another object of the present invention is to provide a developing device capable of preventing spark discharge between an electrode for preventing developer scattering and an electrostatic latent image carrier.

0012

[Means for Solving the Problems] In order to achieve the above object, the developing device of the present invention includes a developer carrier around which developer is held, and the developer is caused to fly from the developer carrier. In a developing device that visualizes an electrostatic latent image formed on an electrostatic latent image carrier, on the downstream side of the developer flying region between the electrostatic latent image carrier and the developer carrier, there is a A developer scattering prevention electrode whose surface is covered with an insulating film or a semiconductive film is installed, and a predetermined bias voltage is applied to this developer scattering prevention electrode.

[0013] In such technical means, the electrode for preventing scattering of developer can sufficiently exhibit its intended function if the surface of the conductive wire is coated with a semiconductive film or an insulating film. , from the viewpoint of smoothly guiding the airflow generated in the developer flying area as the developer carrier rotates to the developer carrier side or the electrostatic latent image carrier side, and preventing the developer from drifting out of the device. For example, the cross-sectional shape may be one that actively divides the airflow into two, for example, a substantially triangular shape.

Furthermore, from the purpose of the present invention, which is to prevent spark discharge between the electrostatic latent image carrier and the developer scattering prevention electrode, the volume resistivity of the coating film of the developer scattering prevention electrode is It is required that the film has a resistance of at least 10 4 Ω·cm or more, and may be either a semiconductive film or an insulating film. However, coating with a semiconductive film reduces the amount of charge on the surface of the coating film, making it difficult for the developer to adhere to the surface of the developer scattering prevention electrode.

[0015] Furthermore, since the developer contains a small amount of developer that is charged to the opposite polarity, these developers will adhere to the developer scattering prevention electrode, and if left as is, the attached developer will disappear. is deposited and comes into contact with the developer carrier and the electrostatic latent image carrier. Therefore, in order to eliminate such inconveniences, it is preferable to provide a cleaning member that periodically removes the developer from the surface of the developer scattering prevention electrode.

Furthermore, a developing device to which such technical means can be applied is one in which the electrostatic latent image carrier and the developer carrier are not in contact with each other, and the developer migrates between the two carriers. It can be applied to any material that can develop an electrostatic latent image.

[0017]

[Operation] According to the above technical means, a developer scattering prevention electrode to which a predetermined bias voltage is applied is installed on the downstream side of the developer flying region between the electrostatic latent image carrier and the developer carrier. At the same time, the surface of this electrode is coated with an insulating film or a semiconductive film, which prevents cloud-shaped developer from drifting outside the developing device, and prevents conductive substances from being contained in the developer. Even if mixed, spark discharge will not occur between the electrostatic latent image carrier and the developer scattering prevention electrode.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The developing device of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 schematically shows a one-component developing device to which the present invention is applied. This one-component developing device uses developer T consisting only of magnetic toner.
A developer carrier (hereinafter referred to as a developer roll) 2 disposed opposite to the electrostatic latent image carrier 1, a developer regulating member 3 disposed such that its tip is in pressure contact with the developer roll 2, and the developer T
and a developer scattering prevention electrode 5 installed on the downstream side of the developer flying area A sandwiched between the developing roll 2 and the electrostatic latent image carrier 1.

First, the developing roll 2 includes a magnet roll 21 which is magnetized with a plurality of magnetic poles (N..., S...) having different polarities and magnetic forces and is fixedly supported on a frame (not shown), and this magnet roll 21. It consists of a cylindrical sleeve 22 that rotates around the circumference of the magnet roll 21, and as the sleeve 22 rotates, the developer T is attracted, transported, and released from the sleeve 22 according to the magnetic pattern of the magnet roll 21. It has become. In this embodiment, the sleeve 22 is made of phenolic resin with a resistance value of 5 x 109 Ωcm and molded into a cylindrical shape with a wall thickness of 1.0 mm, and its surface has a JIS 10-point average roughness of RZ = 4.3 μm. A semiconductive sleeve was used that was polished in the longitudinal direction so that

The hopper 4 is disposed so as to cover the side of the developing roll 2 from below, and the stored developer T is deposited on the back side of the developing roll 2, causing the developer T to be deposited on the sleeve after passing through the developing area. The structure is such that the developer T can be continuously supplied to the surface of 22. In this embodiment, as the developer T contained in the hopper 4, magnetic toner containing 48% by weight of magnetic powder is used.

On the other hand, the developer regulating member 3 is made of SUS3
Spring plate member 31 with a thickness of 0.1 mm made of 04CSP3/4H material (tensile strength 95 kgf/mm2, yield strength 68 k
gf/mm2) at the tip of the soft elastic member 3 made of silicone rubber.
2 (rubber hardness: 50°, thickness: 1 mm, width: 15 mm) bonded by vulcanization. Further, the arrangement is such that the position of the soft elastic member 32 in pressure contact with the sleeve 22 is -140° in the rotational direction of the sleeve 22 from the position where the developing roll 2 and the electrostatic latent image carrier 1 face each other. Further, it is fixed to the frame 6 so that the direction of the free end coincides with the direction opposite to the direction of rotation of the sleeve 22.

The developer scattering prevention electrode 5 has a core material 51 made of a non-magnetic SUS wire with a diameter of 50 to 100 μm and a thickness of 2 to 10 μm, as shown in the cross section of FIG.
, is coated with a semiconductive film (coated film of carbon-containing acrylic resin) 52 having a volume resistivity of 104 to 108 Ω·cm, and is 100 μm to 1 mm from the electrostatic latent image carrier 1,
At a distance of 250 μm to 1 mm from the developing roll 2,
It is stretched parallel to the developing roll 2 with a tension of 50 to 200 gf by a frame 7 shown in FIG. In addition, the frame body 7
is supported by a frame (not shown) via a rotating shaft 71, and the developer scattering prevention electrode 5 is held at the above-mentioned predetermined position by the elastic force of a spring (not shown).

A felt cleaning member 8 is disposed below the developer scattering prevention electrode 5 in parallel with the electrode 5, and is periodically cleaned, for example, once every 10 copying operations of a copying machine. The developer T attached to the electrode 5 can be removed by rotating the frame 7 using a driving means (not shown) such as a solenoid and pushing the electrode 5 into the concave groove 8a formed in the cleaning member 8. It is now possible to do so.

Using the one-component developing device of this embodiment constructed as described above, an attempt was made to develop the electrostatic latent image 9 formed on the electrostatic latent image carrier 1. Incidentally, as the electrostatic latent image carrier 1, a photoconductive drum having a negatively charged organic photoreceptor on its surface is used, and after its surface is uniformly charged to, for example, -800V, it is exposed to light to remove the background portion. An electrostatic latent image of -120V was formed. Further, the gap width between the developing roll 2 and the electrostatic latent image carrier 1 was set to 150 μm, and the AC power source 10 and the DC power source 11 were connected to the sleeve 22 of the developing roll 2 to generate a frequency of 2.4 kHz.
Peak-to-peak voltage 1600V, DC component -200V
A DC superimposed AC voltage of 200 V was applied, while a DC power supply 12 was connected to the developer scattering prevention electrode to apply a DC voltage of 200 V.

At this time, according to the developing device of this embodiment,
Since a developer scattering prevention electrode 5 to which a DC voltage is applied is provided on the downstream side of the developer flying area A, the developer T that attempts to drift out from the developing device is separated from the electrode 5 and the electrostatic latent image carrier. 1 or the developing roll 2. Therefore, when the developer T approaches the area where the developer scattering prevention electrode 5 is installed, as shown in FIG. The developer T migrating on the electrostatic latent image carrier 1 side from the electrode 5 is attracted to the electrostatic latent image carrier 1 side, so that the developer T is prevented from drifting out of the developing device.

Further, since the developer scattering prevention electrode 5 is covered with the semiconductive film 52, spark discharge does not occur between the electrode 5 and the electrostatic latent image carrier 1, and static This makes it possible to prevent damage to the latent image carrier 1.

When the inventors of the present application actually took copies to confirm the effect of the above structure, they found that in the structure without the developer scattering prevention electrode 5 and the cleaning member 8, the developer accumulated at the bottom of the developing device With the configuration of this embodiment, stains did not occur on the copy paper until the number of copies was 50,000, and the effect of the present invention could be confirmed. Ta.

It goes without saying that the present invention can be applied not only to the magnetic one-component developing device of the above embodiment, but also to a non-magnetic one-component developing device as shown in FIG. 6, to obtain similar effects. .

[0029]

As explained above, according to the developing device of the present invention, since the electrode for preventing developer scattering is provided on the downstream side of the developer flying area, the developer does not drift out of the developing device. There is no risk of contaminating the inside of the copying machine or the paper, reducing image quality, and since the developer scattering prevention electrode is coated with a semiconductive film or an insulating film, damage to the electrostatic latent image carrier due to spark discharge is avoided. This makes it possible to prevent

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a first embodiment of a developing device according to the present invention.

FIG. 2 is an enlarged view showing a cross section of an electrode for preventing developer scattering.

FIG. 3 is a perspective view showing an electrode for preventing developer scattering and a cleaning member.

FIG. 4 is a conceptual diagram showing the migration of developer in a developer flying region in the present invention.

FIG. 5 is a schematic diagram showing a conventional magnetic one-component developing device.

FIG. 6 is a schematic diagram showing a conventional non-magnetic one-component developing device.

FIG. 7 is a conceptual diagram showing the migration of developer in a developer flying region.

[Explanation of symbols]

1 Electrostatic latent image carrier 2 Developer carrier (developing roll) 5 Developer scattering prevention electrode 8 Cleaning member 9 Electrostatic latent image T Developer

Claims (2)

[Claims] Claim 1: A developer carrier that holds a developer around its periphery is provided, and an electrostatic latent image formed on the electrostatic latent image carrier by flying the developer from the developer carrier to form a visible image. In the developing device, which is equipped with a surface coated with an insulating film or a semiconductive film to prevent developer scattering, the surface is coated with an insulating film or a semiconductive film on the downstream side of the developer flying region between the electrostatic latent image carrier and the developer carrier. A developing device comprising an electrode and applying a predetermined bias voltage to the developer scattering prevention electrode. 2. The developing device according to claim 1, further comprising a cleaning member for removing developer attached to the developer scattering prevention electrode.