JPH06214468A - Image forming device - Google Patents

Abstract

PURPOSE:To improve defective transfer in terms of void on an end part after copying a second surface in the case of both sides copying. CONSTITUTION:As to an image forming device in which a toner image on an image carrier is transferred to a paper by means of a transfer beam from the transfer corotron of a transfer charger by making the paper travel synchronously with the moving of the image carrier between the image carrier and the transfer charger; a metallic transfer auxiliary roller 13 is provided of the entrance side of the charger 6 in the advancing direction of the paper 18 and on a position within a range irradiated with the transfer beam of the transfer corotron 6b in a state where a space capable of making the paper 18 pass through is provided between the image carrier 2 and the roller 13, and the roller 13 is grounded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for transferring a toner image formed on an image carrier to a transfer paper and fixing it to form an image.

[0002]

2. Description of the Related Art An image forming apparatus for an electrophotographic copying machine, a laser printer, a facsimile, etc., for example, an image forming apparatus for an electrophotographic copying machine using a laser beam is as shown in FIG. Is provided with an image carrier (photoreceptor) 2, and a primary charger 3, a developing device 4, a pre-transfer charger 5, a transfer charger 6 having a halo baffle 6a, and a peeler around the image carrier 2. A charging charger 7, a cleaner 8 and the like are sequentially arranged, the surface of the image carrier 2 is uniformly charged by the primary charger 3, and then an image exposure mechanism 9 performs image exposure to form an electrostatic latent image. The electrostatic latent image is developed into a visible image by the developing device 4, and the paper in the paper tray 10 is fed by the paper feeding mechanism 11
Then, the visible image is conveyed toward the image carrier 2 and transferred to a sheet by the transfer charger 6, and the sheet is sent to the fixing device 12 to be fixed to form a copy. The image exposure mechanism 9 is a laser system including a laser oscillator, a rotating mirror, and a plurality of mirrors, and is configured to receive image information from an office automation device such as an external computer or a word processor and perform image exposure on an image carrier. There is. In this copying process, both single-sided copying and double-sided copying are performed.

[0003]

In the past, it was usual that no particular difference was made between single-sided copying and double-sided copying. In recent years, most of the products have been commercialized that try to obtain the optimum transfer image quality by switching the output level of the transfer current applied to the transfer charger. But,
Even with the method of switching the transfer current of the transfer charger, it has not been possible to satisfy all of the copy image qualities for double-sided copying. In particular, due to the curl of the transfer paper after single-sided copying that occurs during double-sided copying, there is no definitive effective means for defective transfer at the leading and trailing edges (white spots, image blurring, double-colored images, image defects), so there is no choice. In general, the above-mentioned transfer failure occurs on the second surface, especially on the rear end, up to about 7 to 8 mm. In addition, high-end machines and some low-end machines that do not have automatic both sides have commercialized products using a bias transfer roll, but 10-40 sheets /
The high class machines are too expensive for minute class machines, and the low class machines have problems with reliability / life, and those suitable for general purpose machine classes have not been put to practical use.

The present invention has been conceived in view of the above, and it is possible to perform double-sided copying when the conventional double-sided copying is performed up to about 7 to 8 mm.
An object of the present invention is to provide an image forming apparatus capable of improving a transfer failure due to blanking or the like of the trailing end portion of the first copy.

[0005]

In order to achieve the above object, an image forming apparatus according to the present invention runs a sheet between an image carrier and a transfer charger in synchronization with the movement of the image carrier. In the image forming apparatus in which the toner image on the image carrier is transferred onto the paper by the transfer beam of the transfer corotron of the transfer charger, the transfer charger 6 is provided at the entrance side of the paper 18 in the entrance direction. In addition, at a position within the irradiation range of the transfer beam of the transfer corotron 6b, the metal transfer auxiliary roller 13
Is provided between the image carrier 2 and the image carrier 2 so that the paper 18 can pass therethrough, and the transfer auxiliary roller 13 is grounded. Then, the image carrier 2 and the transfer assist roller 1
3 to 0.1-1.0 mm, preferably 0.1-1.0 mm
The range is 0.4 mm, and the diameter is within 10 mm, preferably 4 to 7 mm.

[0006]

[Working] Paper 1 guided by hello baffle 6a
8 is guided to the gap between the image carrier 2 and the transfer assist roller 13, and the paper 18 at this time is held by the transfer assist roller 13 toward the image carrier 2. At this time, the transfer assist roller 13
Is located within the irradiation range of the transfer beam of the transfer corotron 6b of the transfer charger 6 and is made of metal, so that when the leading edge and the trailing edge of the paper 18 pass through the area where the transfer electric field is applied. However, the leading end and the trailing end of the sheet 18 are held in contact with the image carrier 2 side. Further, since the transfer assisting roller 13 is grounded, it is not charged, and therefore dirt due to static electricity is prevented.

[0007]

EXAMPLE An example of the present invention will be described with reference to FIG. The same components as those of the conventional example shown in FIG. The image carrier 2 is located at the entrance side of the transfer charger 6 in the sheet entry direction and at a position within the transfer beam irradiation range of the transfer corotron 6b of the transfer charger 6.
A metal transfer auxiliary roller 13 is rotatably provided so as to face each other with a slight distance of 0.1 to 1.0 mm.

As shown in FIGS. 3 and 4, the transfer assisting roller 13 has a pair of bearings 15 whose both ends are rotatably supported in the vertical direction with respect to the shield case 14 of the transfer charger 6. It is rotatably supported at the tip. The bearing 15 is urged by a torsion spring 16 so that the roller supporting side approaches the image carrier 2 side.
As shown in FIG. 5A, the transfer assisting roller 13 is provided with rolling contact portions (tracking portions) 17, 17 whose both ends have a diameter that creates a step corresponding to the gap with respect to the image carrier 2. The rolling contact portions 17, 17 are rollingly driven by both ends of the image carrier 2 in accordance with the biasing rotation of the bearing 15 by the torsion spring 16.

The outer diameter of the transfer auxiliary roller 13 is preferably within 10 mm, preferably 4 to 7 mm so as not to obstruct the transfer beam from the transfer corotron 6b. The transfer auxiliary roller 13 is used as the shield case 1.
It is grounded together with 4. The rolling parts 17, 17 are made of an elastic semiconductive member such as synthetic resin. The gaps are positioned on the extension of the guide surface of the hello baffle 6a by the contact portions 17 and 17 abutting on the image carrier 2. Since the transfer auxiliary roller 13 and the halo baffle 6a are supported on the shield case 14 side of the transfer charger 6, they can keep the positional relationship between the transfer charger 6 and the transfer corotron 6b constant. . Further, these can be attached and detached integrally with the transfer charger 6. And the above hello baffle 6a
Is grounded via a constant voltage element 19. Further, guide plates 20 and 21 for introducing and guiding the paper 18 to the transfer portion
A power supply 22 is connected to the power source 22 and a shoot bias of a constant voltage is applied to the power source 22.

In the above structure, the sheet 18 sent from the sheet feeding mechanism 11 is guided by the transfer charger 6 by the halo baffle 6a, and the image carrier 2 and the transfer auxiliary roller 1 are guided.
It is guided to a gap between the transfer roller 3 and 3, and moves into the gap and moves above the transfer corotron 6b. At this time, since the transfer auxiliary roller 13 is arranged at a position approximately at the end of the transfer electric field (line of electric force) exerted by the transfer corotron 6a on the transfer, the leading end and the rear end of the paper 18 act on the transfer electric field. Even when passing through the receiving area, the leading end and the trailing end of the paper 18 are suppressed so as to be forcibly brought into contact with the image carrier 2. Further, at this time, since the transfer assist roller 13 is grounded, it is not charged with an electrostatic voltage, and therefore the transfer assist roller 13 is not electrostatically soiled. Further, the hello baffle 6a is grounded via the constant voltage element 19, and the guide plate 2
Since the shoot bias is applied to 0 and 21, the transfer failure does not occur even in the high water content paper.

FIGS. 6A, 6B, and 6C show a rear-end transfer defect (white spots) on the second surface during double-sided copying in the conventional technique.
Data is shown, and 6 mm of 50 copies in each of the lab shown in (a), the 28 ° C. and 85% environment shown in (b), and the 10 ° C. and 30% environment shown in (c).
Many white spots occurred over the entire range.

On the other hand, in the above-described embodiment of the present invention, the trailing edge transfer defect (white spot) on the second side during double-sided copying is shown in FIG.
As shown in (a), (b), and (c), any of the laboratory shown in (a), 28 ° C. and 85% environment shown in (b), and 10 ° C. and 30% environment shown in (c). Also in the case of 50 copies, the white spot width was significantly narrowed and the number of copies was also reduced.

8 (a) and 8 (b) show the effect of the transfer assist roller 13 at the time of high-moisture-content paper, single-sided copying. In the conventional case, as shown in FIG. 7 (a), 50 sheets are copied. Among them, the white spots of 6 mm or less and 12 mm or more occurred on all the sheets, whereas the white spot amount of all the sheets was 3 mm or less as shown in FIG. 7B in the embodiment of the present invention. It was

[0014]

According to the present invention, the transfer electric field can be surely applied to the image carrier even in the case of corrugated paper containing moisture and corrugated paper or curled downward paper after passing through the fixing device during automatic double-sided stacking. Even if the paper has such a curl, it is possible to suppress the white spot transfer failure at the end portion in the traveling direction of the paper within a maximum of 5 mm. Further, according to the present invention, the transfer assist roller 13 for achieving the above-mentioned effects
By grounding, it is possible to prevent the transfer auxiliary roller 13 from being soiled due to charging.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory view showing a conventional example of an electrophotographic copying machine to which the present invention is applied.

FIG. 2 is a schematic configuration explanatory view showing an electrophotographic copying machine to which the present invention is applied.

FIG. 3 is a sectional view showing a main part of the present invention.

FIG. 4 is a perspective view showing a main part of the present invention.

FIG. 5 is a plan view showing an embodiment of a transfer auxiliary roller.

FIGS. 6A, 6B, and 6C are diagrams showing the trailing edge whiteout amount of the second side in double-sided copying according to the related art.

7 (a), (b) and (c) are diagrams showing the trailing edge whiteout amount of the second side in double-sided copying in the apparatus of the present invention.

8 (a) and 8 (b) are diagrams showing a defect amount due to white spots at the leading end and the trailing end in the prior art and the device of the present invention when performing simplex copying on a high water content paper.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Device body, 2 ... Image carrier, 6 ... Transfer charger, 6a
... Hello baffle, 13 ... Transfer assist roller, 14 ... Shield case, 15 ... Bearing, 16 ... Torsion spring, 17 ... Rolling contact part, 18 ... Paper, 19 ... Constant voltage element, 2
0, 21 ... Guide plate, 22 ... Power supply.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Furuyama 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd. (72) Inventor Kazuhiro Yoshihara 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (3)

[Claims] 1. A sheet of paper is run between an image carrier and a transfer charger in synchronism with the movement of the image carrier, and a transfer beam from a transfer corotron of the transfer charger transfers the image onto the image carrier. In an image forming apparatus configured to transfer a toner image onto a sheet of paper, a transfer of metal is performed at a position on the entrance side of the transfer charger 6 in the direction of entry of the paper 18 and within the irradiation range of the transfer beam of the transfer corotron 6b. An image forming apparatus characterized in that an auxiliary roller 13 is provided with a gap enough to pass a sheet of paper 18 between the image carrier 2 and the transfer auxiliary roller 13 is grounded. 2. A gap between the image carrier 2 and the transfer auxiliary roller 13 is 0.1 to 1.0 mm, preferably 0.1 to 0.4 m.
The image forming apparatus according to claim 1, wherein the range is m. 3. The image forming apparatus according to claim 1, wherein the transfer auxiliary roller 13 has a diameter of 10 mm or less, preferably 4 to 7 mm.