JPS6167050A - Stain preventing method of electrophotographic device - Google Patents

Abstract

PURPOSE:To eliminate the sticking of toner, to prevent staining with the toner, and to improve the quality of a copy by holding members at the periphery of an image carrier at nearly the same potential with toner present at its periphery. CONSTITUTION:A paper feeding device 3 consists of a couple of rollers 3a and a guide 3b which adjoin thereto and has its tip nearby the image carrier, and the guide 3b is formed of a conductive member. The guide 3b is connected to the DC output terminal of a transformer 5 so as to apply a voltage (bias) having the same potential with toner present nearby, specially, on the image carrier. A resistor 7 for short-circuit protection is inserted at a proper position of a lead wire 6. It is difficult to measure directly the potential of the toner nearby the guide 3b, specially, on the image carrier, so the DC developing bias potential is considered as an approximate value of the potential of toner by a means of applying the bias to a developing sleeve, so this value is used as a substitute and the independent method is usable.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a method for preventing members disposed close to the periphery of an image bearing member in an electrophotographic apparatus such as a copying machine from being contaminated by toner smudge. Regarding.

(Prior Art) For example, in a dry type copying machine, the surface of an image bearing book such as a photosensitive drum is charged to impart photosensitivity, and an electrostatic latent image is formed. developing,
A known configuration is known in which toner is transferred to a transfer material, residual toner is cleaned by a cleaner, and the next copying process is started.

However, in recent years, there has been a demand for smaller copying machines.
Equipment or members surrounding the image carrier are arranged as close as possible to the image carrier to reduce the size of the machine. As is known, toner on an image carrier originally has a certain potential, and therefore, if a member close to the image carrier is a grounded conductive member, the image carrier Some of the toner on top is transferred to and collected on such conductive member, contaminating it. Moreover, in the method of applying bias in the developing process, the developing bias is, for example, 700 V% when the image carrier is idling, and 200 to 40 V% during copying.
Since a DC voltage of 0 V is superimposed and the surface of the image bearing member is charged, the toner may reach a potential sum of several hundred volts due to these charges. With such high potential toner, the adhesion of the toner to the conductive member is further increased.

Furthermore, in the above process, the toner remaining on the image carrier is not completely removed by the cleaner, so there is a small amount of toner scattered or leaked from the cleaner or developing device on the inner surface of the image carrier and in the air inside the machine. The toner also adheres to the conductive member.

(Problems to be Solved by the Invention) As mentioned above, the toner carried on the surface of the image carrier (including during copying and idle linking) and the toner remaining inside the machine have a relatively high potential. Some of the toner adheres to the conductive member disposed close to the image carrier, and even during idle linking, a small amount of toner is observed to adhere to the member. Dirt causes problems such as deteriorating the quality of copies.

For example, if toner adheres to and stains the guide or transfer member of a paper feeder that is close to the image carrier, the back side of the copied paper will become stained. In the past, attempts have been made to solve this problem by using an insulating material or varistor to electrically interrupt the member close to the image carrier, or to remove the toner by sucking polluted air near the member. However, neither was successful.

SUMMARY OF THE INVENTION An object of the present invention is to provide a stain prevention method that can prevent a conductive member disposed close to the periphery of a stone image carrier in an electrophotographic apparatus from being soiled by toner.

(Means for Solving the Problems) A method for preventing contamination of an electrophotographic apparatus according to the present invention provides a method for preventing contamination of an electrophotographic apparatus according to the present invention. It is characterized by applying a voltage of approximately the same potential as the toner above to prevent toner from adhering.

(Function) Therefore, in the stain prevention method of the present invention, since the conductive member near the image bearing member is always kept at almost the same potential as the toner on the image bearing member existing in the vicinity, the toner is It bounces off the member and therefore leaves the member as soon as it comes into contact with it, so it does not stick to it and therefore does not cause dirt.

(Example) Next, the present invention will be described in detail with reference to the drawings. 1st
The figure illustrates the case where the present invention is applied to a paper feed guide of a paper feed device in a copying machine, and in the figure (1)
(2) is a developing device, (3) is a paper feeding device, and (4) is a corona waste electric device for transfer. In this example, the image carrier (1) has a drum shape that rotates in the direction of arrow A, but the present invention is also applicable to belt or flat plate shapes. The developing device (2) is a magnetic brush type developing device of known construction, and its sleeve is biased with an alternating current voltage superimposed with a direct current voltage of appropriate polarity. Although magnetic toner is used in this column, a two-component developer may also be used, for example. An AC power supply (111) and a transformer (5) are provided to supply the AC voltage and DC voltage. Note that the AC power supply Ut- may be omitted depending on the case. On the other hand, the developing device (2)
A surface electrometer (8) is arranged to measure the surface potential of the bright part of the electrostatic latent image on the image carrier (υ) at the upstream position of the image carrier (υ). (5).Thus, the electrometer (8) is connected via this transformer (5).
) is superimposed on the sleeve with an optimum value of DC voltage corresponding to the surface potential of the image carrier (1) detected by the electrostatic latent image, for example, a value of several tens of v'l added to the detected potential. An optimal developed image can be formed.

The paper feeding device (3) includes a pair of rollers (3a) and a guide (3b) adjacent thereto and whose tip is close to the image carrier 1 (11).
The guide (3b) is made of a conductive member.

The guide (3b) is connected to the DC output terminal of the transformer (5) in order to apply a voltage (bias) having approximately the same potential as the toner existing in the vicinity, particularly the toner on the image carrier. A resistor (7) for protecting the engine is inserted into an appropriate position of the lead wire (6).

Since it is difficult to directly measure the potential of the toner present near the guide (3b), especially the toner on the image carrier, in the method of applying a bias to the developing sleeve as described above, the DC developing bias Since the electric potential can be regarded as an approximate value of the toner electric potential, such a value is used as a substitute, and thereby the present invention can be carried out by simple means.

In addition, in the - example, the DC voltage is 700 V during idle link.

Suitable results were obtained when the peak voltage applied to the sleeve was controlled to be approximately 800 to 1500 V during copying, with the voltage being 200 to 400 V.

FIG. 2 shows another embodiment, in which also a paper feeding device (
Case 3) is shown, in which the same parts as in FIG. 1 are given the same reference numerals. In addition, in this row, a conductive guide roller (3c) is provided at the tip of the guide (3b), and a DC voltage source (121) is used to apply a DC bias to the guide (3b) and the roller (3C). In this example, the sleeve of the developing device (2) is grounded, and assuming that the potential of the toner is an unchanging constant potential, the guide potential is approximately equal to this assumed potential, for example, a potential of 200 to 300 V. (3b).This method allows implementation with simple means similar to the previous embodiment.

Note that in the first embodiment described above, the value of the DC component of the developing bias corresponding to the surface potential of the image carrier is used as the toner potential, but other potentials may be used instead of the toner potential. It is obvious that this is a good idea, and it goes without saying that the potential of the toner may be measured and used in some cases.

Further, the present invention may be applied to all members disposed close to the periphery of the image carrier, but it may be applied only to some of them, for example, only to the guide of the paper feeding device as in the above-mentioned embodiment. It is clear that it is good.

(Effects of the Invention) As described above, according to the present invention, the members around the image carrier are kept at almost the same potential as the toner existing in the vicinity, so there is no toner adhesion and no toner stains. Prevented. Therefore, the maintenance cycle can be lengthened, and the quality of the copies can be improved without staining the copies for a long period of time.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing one embodiment of the present invention, and FIG. 2 is a schematic diagram of another embodiment.

Claims (2)

[Claims] (1) A voltage of approximately the same potential as the toner on the image carrier carried near the member is applied to a conductive member disposed close to the periphery of the image carrier carrying the toner image. . A method for preventing staining of an electrophotographic apparatus, characterized in that the adhesion of toner to the member is prevented. (2) A method for preventing stains in an electrophotographic apparatus according to claim 1, wherein the member is a paper feed guide having one end close to the image carrier.