JPH06214476A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent a void on the tailing edge part of the second copy in both-side copying and a failure in a transfer. CONSTITUTION:A metallic auxiliary roller for a transfer 13 is provided so as to obtain a gap by which sheets of paper 18 can pass between the roller 13 and an image carrier 2, on an entrance side in the advancing direction of the paper 18 of a transfer electrifier 6 and at a position within an irradiation range of the transfer beam of a transfer corotron 6b. The gaps are formed on both end parts of either of the auxiliary roller for the transfer 13 or the image carrier 2, to provide transfer contact parts 17 for the transfer contact of the auxiliary roller for the transfer 13 with the image carrier 2. Moreover, the auxiliary roller for the transfer 13 is freely rotatably supported on a bearing 15 pressed to the side of the image carrier 2 by a spring and freely turnably supported on the side of the shield case 14 of the transfer electrifier 6 and a stopper part 15a abutting on a hollow-baffle 6 fixed on the side of the shield case 14 in a state where the bearing 15 is turned beyond the transfer contact of the auxiliary roller for the transfer 13 with the side of the image carrier 2 is provided on the bearing 15, and simultaneously, the auxiliary roller for the transfer 13 and the bearing 15 supporting it are 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 configured to transfer the toner image on the image carrier onto the paper by the transfer beam of the transfer corotron 6b of the transfer charger, the transfer charger 6 is provided at the entrance side of the paper 18 in the approach direction. A transfer assist roller 13 made of metal is provided at a position within the transfer beam irradiation range of the transfer corotron 6b so as to have a gap between the image carrier 2 and the paper 18, and the transfer assist roller 13 is provided. 13 or both end portions of the image carrier 2 are provided with transfer contact portions 17 for the transfer assist roller 13 to contact the image carrier 2 with the above gap, and the transfer assist roller 13 is used for transfer. Image bearing on the shield case 14 side of the charger 6. The body 2 side by spring-loaded and rotatably supported on the rotatably supported by bearings 15, the bearing 15,
The stopper portion 1 comes into contact with the halo baffle 6a fixed to the shield case 14 side in a state in which the bearing 15 is rotated more than the transfer auxiliary roller 13 rolls to the image carrier 2 side.
5a is provided, and the transfer assist roller 13 and the bearing 15 that supports the transfer assist roller 13 are grounded.

[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. The transfer assist roller 13 when the transfer charger 6 is detached from the image forming apparatus is provided with a stopper portion 15a of a bearing 15 that supports the transfer auxiliary roller 13.
By contacting the halo buckle 6a, further rotation is prevented. At this time, hello baffle 6a
The charged potential is grounded via the bearing 15.

[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 auxiliary roller 13 has a pair of conductive members 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 of the bearing 15. And this bearing 15 is the torsion spring 1
At 6, the roller support side is spring-biased in a direction toward the image carrier 2 side. The bearing 15 includes the bearing 1
There is provided a stopper portion 15a which comes into contact with the halo baffle 6a fixed to the shield case 14 via an insulator in a state in which the transfer assist roller 13 supported by the roller 5 is rotated more than rolling contact with the image carrier 2 side. .

As shown in FIG. 5A, the transfer assisting roller 13 has rolling contact portions (tracking portions) 17 and 17 each having both ends thereof having a diameter that creates a step corresponding to a gap with respect to the image carrier 2.
Is provided, and the torsion spring 1 of the bearing 15 is provided.
The rolling contact portions 17, 17 are rollingly driven by the both ends of the image carrier 2 in accordance with the biasing rotation of the image carrier 6.

The outer diameter of the transfer assisting roller 13 is set so as not to interrupt the transfer beam from the transfer corotron 6b.
It is suitable to be within 4 mm, preferably 4 to 7 mm, and electrically grounded. 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.

In the above structure, the paper 18 fed from the paper feeding mechanism 11 is guided by the transfer charging device 6 by the hello 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.

When a trouble such as a paper jam (jam) occurs at the transfer portion during the copying operation, the transfer charger 6 is pulled out from the apparatus main body and inspected. At this time, the transfer auxiliary roller 13 and the halo are used. The baffle 6a is pulled out integrally with the transfer charger 6. At this time, the transfer assist roller 13 is separated from the image carrier 2 and therefore tries to rotate further upward due to the spring bias, but the bearing 15 supporting this is rotated by the hello baffle 6a.
Since it abuts against the stopper via the stopper portion 15a, any further unnecessary rotation is prevented. Therefore, when the transfer charger 6 is inserted again into the apparatus main body, the transfer auxiliary roller 13 does not interfere.

On the other hand, when the transfer charger 6 is pulled out, the halo baffle 6a is grounded by contacting the bearing 15 which is grounded via the shield case 14. Therefore, the electric charge charged on the halo baffle 6a during the copying operation is quickly grounded by the drawing operation of the transfer charger 6, and an operator who handles the electric charge does not get an electric shock.

FIGS. 6A, 6B, and 6C show the trailing edge transfer defects (white spots) on the second side during double-sided copying in the prior art.
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. 8 (a), 50 sheets are copied. Among them, white spots of 6 mm or less and 12 mm or more occurred on all sheets, whereas in the embodiment of the present invention, the white spot amount of all sheets was 3 mm or less as shown in FIG. 8B. It was

[0017]

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. In particular, according to the present invention, when the transfer charger 6 is taken in and out, for example, when clearing a paper jam, the transfer auxiliary roller 1 is used.
3 does not interfere with other members, and damage to them can be prevented. Further, when the transfer charger 6 is pulled out, the halo baffle 6a is automatically grounded, so that it is possible to prevent an inadvertent electric shock due to the electric charges charged on the halo baffle 6a.

[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 different examples of the transfer assist 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, 15a ... Stopper section, 16 ...
Torsion spring, 17 ... Rolling contact part, 18 ... Paper.

 ─────────────────────────────────────────────────── ─── 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 (1)

[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 is used to transfer the paper 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 a transfer beam irradiation range of the transfer corotron 6b. The auxiliary roller 13 is provided with a gap enough to allow the paper 18 to pass through between the image carrier 2 and the transfer assist roller 13 or the image carrier 2 and the above-mentioned gap is formed at both ends of the image carrier 2. Roller 13 is provided with rolling contact portions 17 and 17 for rolling contact with the image carrier 2, and the transfer assisting roller 13 is biased toward the image carrier 2 by the shield case 14 side of the transfer charger 6. Bearing 15 rotatably supported
Rotatably supported by the bearing 15, and the bearing 15 is brought into contact with the halo baffle 6a fixed to the shield case 14 side in a state in which the bearing 15 is rotated more than the transfer auxiliary roller 13 is rollingly contacted with the image carrier 2 side. The stopper 15a is provided, and the transfer assist roller 13 and the bearing 15 that supports the transfer assist roller 13 are provided.
An image forming apparatus having a grounded surface.