JPH06214478A - 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:This image forming device moving sheets of paper in synchronization with the movement of an image carrying zone between the image carrying zone and a transfer electrifier, so that a toner image on an image carrier is transferred on the sheets of paper 18 with transfer beams from the transfer corotron of the transfer electrifier is constituted as follows; metallic auxiliary rollers for a transfer 13 and 13a are provided so a to obtain gaps by which the paper 18 can pass between the rollers 13 and 13a and the image carriers 2 and 2a, on an entrance side in the advancing direction of the paper 18 of the transfer electrifier 6 and a position within the irradiation range of the transfer beam of the transfer corotron 6b, the gaps are formed on both end parts of one of the auxiliary rollers for the transfer 13 and 13b or the image carrier 2, to provide transfer contact parts 20 in the transfer contact with the image carrier 2 and 2a and further, these auxiliary rollers for the transfer 13 and 13a are pressed by springs on the sides of the image carriers 2 and 2a.

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. Then, in the image forming apparatus in which the toner image on the image carrier is transferred onto the sheet by the transfer beam of the transfer corotron of the transfer charger, at the entrance side of the transfer charger 6 in the approach direction of the sheet 18, In addition, metal transfer assisting rollers 13 and 13a are provided at positions within the transfer beam irradiation range of the transfer corotron 6b so that the paper 18 can pass therethrough and between the image carriers 2 and 2a, and Rolling contact portions 17, 17, 2 for rolling contact with the image supporting bodies 2, 2a by forming the above-mentioned gap at one end of each of the transfer assisting rollers 13, 13a or the image supporting bodies 2, 2a.
Nos. 0 and 20 are provided, and the transfer assisting rollers 13 and 13a are biased toward the image bearing members 2 and 2a by a spring.
Then, the image carrier 2, 2a and the transfer assist roller 13, 1
The gap with 3a is 0.1-1.0 mm, preferably 0.1
~ 0.4mm range, and its diameter within 10mm,
It is preferably 4 to 7 mm. The transfer assist roller 1
3, 13a is 100 to 150 g and is pressed against the image carrier 2, 2a.

[0006]

[Operation] The transfer assisting rollers 13 and 13a are spring-biased toward the image bearing members 2 and 2a.
Transfer unit 1 provided on the side of 13a or image carrier 2, 2a
7, 17, 20, and 20 are driven by rolling contact to move the image carrier 2, 2a.
It is rotated in the same circumferential direction as that of the image carrier 2 with a gap between the image carriers 2 and 2a. And hello baffle 6
The paper 18 guided by a is guided to the gap between the image carrier 2 and the transfer assisting rollers 13 and 13a.
Is suppressed by the transfer auxiliary roller 13 toward the image bearing members 2 and 2a. At this time, the transfer assisting rollers 13 and 13a are positioned within the irradiation range of the transfer beam of the transfer corotron 6b of the transfer charger 6 and are made of metal, so that the leading end portion and the trailing end portion of the paper 18 are transferred to the transfer electric field. Even when the sheet 18 passes through the area affected by the action, the leading edge and the trailing edge of the sheet 18 are held in contact with the image carrier 2 side.

[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. 5, the transfer assisting roller 13 is provided with rolling contact portions (tracking portions) 17, 17 having both ends thereof having a diameter that creates a step corresponding to the gap with respect to the image carrier 2, and the bearing 15 The rolling contact portions 17, 17 are adapted to follow the rolling contact with both ends of the image carrier 2 in accordance with the biasing rotation of the torsion spring 16 acting on the. The biasing force of the torsion spring 16 at this time is
The pressing force at is set to a force in the range of 100 to 150 g.

The outer diameter of the transfer assisting roller 13 is appropriately 10 mm or less, preferably 4 to 7 mm so as not to interrupt the transfer beam from the transfer corotron 6b, and is 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 transfer assisting roller 13 is spring-biased toward the image carrier 2 and is rotated and driven by the rolling contact parts 17, 17 provided on the transfer assisting roller 13 in accordance with the rotation of the image carrier 2. As a result, the transfer auxiliary roller 13 is rotated in the same circumferential direction as the circumferential direction of rotation of the image carrier 2. In this state, the paper 18 sent from the paper feeding mechanism 11 is guided by the transfer charger 6 by the halo baffle 6a to be guided to the gap between the image carrier 2 and the transfer auxiliary roller 13, and enters this gap. , Moving above the transfer corotron 6b. At this time, the transfer assist roller 13 moves the transfer corotron 6
Since a is located at a position approximately at the end of the transfer electric field (line of electric force) exerted on the transfer, even when the front end and the rear end of the paper 18 pass through the region where the transfer electric field is applied,
The leading edge and the trailing edge of the sheet 18 are suppressed so as to be forcedly contacted with the image carrier 2.

Further, at this time, even if a sheet having a normal thickness passes through the gap between the image carrier 2 and the transfer assist roller 13, this gap is constant, but the sheet having a thickness larger than the gap is used. When a sheet, an envelope, or the like passes, the gap between the sheets and the sheet is expanded against the bias of the spring, and a substantially constant pressing force is secured.

FIGS. 6A, 6B, and 6C show the trailing edge transfer defects (white spots) on the second side 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 duplex 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 assisting roller 13 at the time of single-sided copying with high water content paper. 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

Since the gap between the image carrier 2 and the transfer assisting roller 13 is narrow, the surface of the transfer assisting roller 13 is easily soiled by the toner from the image carrier 2 or the like due to the transfer action to the paper 18. Therefore, by increasing the gap between the image carrier 2 and a portion of the paper 18 which is less frequently passed, that is, a portion farther from the side resist side position, it is useful for preventing the transfer auxiliary roller from being soiled.

FIG. 9 shows another embodiment for this. That is, the rolling contact portions 20, 20 having a diameter larger than that of the image bearing surface are provided on both sides of the image bearing member 2a, and the transfer assisting roller 13a formed in a right columnar shape is formed on the rolling bearing portion 20a by the same mechanism as in the above-described embodiment. It is designed to be spring biased.

[0021]

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, the transfer assisting rollers 13 and 13a for forming a gap for passing the above-mentioned sheet between the image bearing members 2 and 2a are spring-biased toward the image bearing members 2 and 2a, and the rolling contact portion 17 provided on one of both sides. , 17 or 2
When a sheet or envelope having a thickness equal to or larger than the gap passes by being rolled and driven at 0 and 20, the gap is widened by the sheet, and a substantially constant pressing force can be secured.
The paper running safety can be maintained.

[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.

5A, 5B, and 5C are plan views showing different examples of the 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.

FIG. 9 is a perspective view showing another example of the rolling contact relationship between the image carrier and the transfer auxiliary roller.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Device main body, 2, 2a ... Image carrier, 6 ... Transfer charger, 6a ... Hello baffle, 13, 13a ... Transfer assist roller, 14 ... Shield case, 15 ... Bearing, 16 ... Torsion spring, 17, 20 … Transposition 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 (4)

[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. Auxiliary rollers 13 and 13a are provided so as to allow a space for the paper 18 to pass between them and the image bearing members 2 and 2a, and one end portion of one of the transfer assisting rollers 13 and 13a or the image bearing members 2 and 2a. Is provided with transfer portions 17, 17, 20, 20 for making contact with the image supporting members 2, 2a by forming the above-mentioned gaps. Further, the transfer assisting rollers 13, 13a are connected to the image supporting members 2, 2a. Characterized by spring bias toward 2a Image forming apparatus. 2. An image carrier 2, 2a and a transfer auxiliary roller 1
2. The image forming apparatus according to claim 1, wherein the gap between the image forming apparatus and the roller 13a is in the range of 0.1 to 1.0 mm, preferably 0.1 to 0.4 mm. 3. The diameter of the transfer assisting rollers 13, 13a is 10
3. The image forming apparatus according to claim 1, wherein the image forming apparatus has a thickness within 4 mm, preferably 4 to 7 mm. 4. The transfer assisting rollers 13, 13a are 100-
The image forming apparatus according to claim 1, wherein the image forming apparatus is pressed against the image bearing members 2 and 2a with a pressing force of 150 g.