JPH11109758A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a constitution of a transfer separation electrifier capable of preventing the 'forward scattering' phenomenon of toner in the transfer separation process of an image forming device. SOLUTION: A transfer electrifier 1 is disposed, and a paper guide 5, a needle electrode 8 and an insulating sheet 15 are disposed in this order on the downstream side of the electrifier 1 in the moving direction of transfer paper 7, and the end face of the sheet 15 on the transfer paper 7 side is made saw- toothed. By removing charge accumulated on the sheet 15 and the paper guide 5 and reducing a potential difference between an image part and a non-image part on the surface of the transfer paper 7, the toner transferred to the transfer paper 7 is prevented from being made irregular.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as a printer or a copying machine that utilizes an electrostatic transfer process.

[0002]

2. Description of the Related Art In recent years, in an image forming apparatus, a transfer charger for transferring toner on a photoreceptor to transfer paper by corona discharge has a function of efficiently transferring toner to transfer paper and a function of preventing transfer paper from jamming. There is a demand for a function of guiding the transfer paper to pass smoothly through the transfer charger and a device for preventing the toner transferred to the transfer paper from being electrostatically disturbed when passing through the transfer charger.

Hereinafter, a transfer charger of a conventional image forming apparatus will be described. FIG. 3 is a cross-sectional view of a transfer charger and its periphery in a conventional image forming apparatus. Conventionally, a transfer charger of this type of image forming apparatus includes a transfer charger case 1, a charging wire 2, a static elimination case 3, a static elimination wire 4, and a paper guide 5, and a corona discharge of the charging wire 2 on the photosensitive drum 6. (Not shown) is transferred to a transfer paper 7 and the photosensitive drum 6
After the transfer paper 7 is separated from the transfer charger 7, the transfer paper 7 is smoothly passed through the transfer charger while preventing the transfer paper 7 from contacting the transfer charger case 1 with the paper guide 5.

FIG. 4 shows a conventional example of a transfer charger which is disclosed in Japanese Utility Model Application Laid-Open No. 63-200854, which is a further simplified version of the example shown in FIG. 3 is different from FIG. 3 in that it is constituted by the transfer charger case 1 and the charging wire 2 in FIG. 3, and in FIG. 4, the pointed electrode 8 as a static elimination needle plays the role of separating the transfer paper 7. Such a simple configuration is widely used especially in low-speed machines.

[0005]

However, in the above-mentioned conventional configuration, the "forward jump" phenomenon in which the toner transferred to the transfer paper 7 is scattered forward from the predetermined position in the traveling direction of the transfer paper 7 before being fixed. May have occurred. The cause is that when the transfer paper 7 passes over the paper guide 5,
In particular, in a low-humidity environment, the discharge current of the static elimination wire or the static elimination needle attenuates due to the electrostatic charge accumulated in the transfer paper surface of the image area where toner is attached and the non-image area where toner is not attached. 5, the toner 9 before fixing, which has been transferred to the transfer paper 7 as shown in FIG.
This is because the transfer paper 7 is drawn to a position 11 in the forward direction of the transfer paper 7 shown in FIG. Conventionally, in order to prevent this “front jump” phenomenon, the shape of the paper guide 5 is devised, the volume is reduced to reduce the amount of accumulated static electricity, or a flexible insulating guide film is used. A method has also been adopted in which the transfer paper is provided so as to be in contact with the paper guide and the transfer paper is not brought into contact with the paper guide. Among these measures, the method of providing a guide film was the most effective.However, in a low-humidity environment, static electricity was also accumulated in the guide film, and there was a problem that “front jump” could not be completely eliminated. Was.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a transfer / separation charger which does not have a "front jump" phenomenon.

[0007]

In order to solve this problem, an image forming apparatus according to the present invention transfers a developed image from a photoreceptor to a transfer sheet by a transfer unit, and then transfers the transfer sheet to a polarity opposite to that of the transfer unit. In the image forming apparatus, the transfer member is separated from the photoreceptor by a separation unit having a pointed electrode to which a voltage is applied. An electrode and an insulating sheet are arranged in this order, and the end face of the insulating sheet on the transfer paper side is formed in a saw-tooth shape.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention described in the claims of the present invention
After transferring the developed image from the photoreceptor to transfer paper by transfer means, the transfer paper is separated from the photoreceptor by separation means having pointed electrodes to which a voltage having a polarity opposite to that of the transfer means is applied. In the forming apparatus, a transfer charger, and a paper guide, a pointed electrode, and an insulating sheet are disposed in this order on the downstream side of the transfer charger in the transfer paper moving direction, and an end surface of the insulating sheet on the transfer paper side is saw-toothed. It removes the charge accumulated on the insulating sheet and paper guide,
It has the function of weakening the electric field intensity between the transfer paper and the photosensitive drum, and preventing the toner transferred to the transfer paper from being disturbed by the influence of the accumulated charge.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block sectional view for explaining the transfer / separation structure of the present invention, and the same components as those of the conventional example are denoted by the same reference numerals. In the figure, reference numeral 12 denotes a charger, 13 denotes exposure light, 14 denotes a developing device, and 15 denotes an insulating sheet such as an insulating film or sheet.

The photosensitive drum 6 takes a negative charge over the entire surface thereof due to the negative corona discharge action of the charger 12 while rotating in the direction of arrow 16. In the next process, the surface charge disappears due to the action of the exposure light 13 of the document irradiated by the optical means, but the surface charge of the portion not irradiated with the exposure light 13 remains on the surface of the photosensitive drum 6 (electrostatic latent). Image formation). The surface charge remaining on the surface of the photosensitive drum 6 electrostatically attracts the toner 9 positively charged by the developing device 14 which is the next process, and is visualized (formation of a visible image). ).

On the other hand, the transfer paper 7 supplied to the surface of the photosensitive drum 6 by the paper feeding means is given a negative electric field by the corona discharge action of the charging wire 2 in the transfer charger case 1 in the following process. The toner 9 on the surface of the drum 6 is electrostatically attracted to the surface of the transfer paper 7 (transfer operation).

The transfer paper 7 is provided on the downstream side of the transfer charger case 1 in the transfer paper moving direction in the following process, and has an insulating property formed so that the transfer paper 7 does not fall into the transfer charger case 1 and jam. While passing over the paper guide 5, the photosensitive drum 6 is electrostatically moved by the positive electric field effect of the sharp electrode 8 serving as a static elimination needle disposed downstream of the transfer paper in the moving direction of the transfer paper in the vicinity of the paper guide 5. Separated. Further, an insulating sheet 1 such as a Mylar film provided downstream of the pointed electrode 8 in the transfer paper moving direction and in contact with the paper guide 5.
The sheet guide 5 and the insulating sheet 15 take on a positive charge 17 due to the frictional charging with the transfer sheet 7 and the positive electric field action of the pointed electrode 8 at this time. . When the positive charge 17 becomes large due to the influence of low humidity or the like, the discharge current of the pointed electrode 8 is attenuated to cause insufficient elimination of the transfer paper 7 and the image portion where the toner 9a adheres and the toner 9a A potential difference is generated on the surface of the transfer paper 7 on the non-image portion where the transfer paper 7 is not adhered, and the transferred toner 9a is attracted to the non-image portion forward in the moving direction of the transfer paper 7, that is, on the downstream side in the moving direction, as shown in FIG. ,
Since the distal end shape 18 of the insulating sheet 15 is formed in a sharp sawtooth shape of 0.1 mmR or less, the electric field strength E = 30R
As shown in the calculation formula of [KV], the electric field intensity becomes 3 KV at the maximum, and the electric field intensity can be kept small enough not to affect the toner 9a. As a result, it is possible to prevent the toner from moving and skipping when the transfer paper is separated from the photosensitive drum, and to stabilize copy quality.

[0013]

As described above in detail, according to the present invention, after a developed image is transferred from a photoreceptor to a transfer paper by a transfer means, the transfer paper is applied to a pointed shape to which a voltage having a polarity opposite to that of the transfer means is applied. In an image forming apparatus configured to be separated from the photoreceptor by a separating unit having an electrode, a transfer charger, and a paper guide, a pointed electrode, and an insulating sheet are arranged in this order on a downstream side of the transfer charger in a transfer sheet moving direction. The insulating sheet has a sawtooth-shaped end surface on the transfer paper side of the insulating sheet, removes electric charges accumulated in the insulating sheet and the paper guide, and reduces a potential difference between an image portion and a non-image portion on the transfer paper surface. At a minimum, an effect of preventing the toner transferred to the transfer paper from being disturbed can be obtained. That is, an effect is obtained in which stable transfer and separation operations can be performed without causing image disturbance such as forward skipping due to the influence of an electric field generated near the toner.

[Brief description of the drawings]

FIG. 1 is a block sectional view showing a configuration of the present invention.

FIG. 2 is an enlarged plan view of a main part of the insulating sheet of the present invention.

FIG. 3 is a block sectional view of a conventional transfer charging unit.

FIG. 4 is a block sectional view of another conventional transfer charging unit.

FIG. 5 is an enlarged cross-sectional view of a main part, illustrating an operation at the time of conventional transfer separation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transfer charger case 3 Static elimination case 5 Insulator 6 Photoreceptor drum 7 Transfer paper 8 Pointed electrode 9 Toner 14 Developing device 15 Insulation sheet

Claims (1)

[Claims] After transferring a developed image from a photoreceptor to a transfer sheet by a transfer unit, the transfer sheet is separated from the photoreceptor by a separation unit having a pointed electrode to which a voltage having a polarity opposite to that of the transfer unit is applied. In the image forming apparatus,
A transfer charger, and a paper guide, a pointed electrode, and an insulating sheet are disposed in this order on the downstream side of the transfer charger in the transfer paper moving direction, and the end surface of the insulating sheet on the transfer paper side is formed in a sawtooth shape. An image forming apparatus comprising: