JP3141904B2 - Image forming device - Google Patents

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 transfer paper and fixing the toner image to form an image.

[0002]

2. Description of the Related Art An image forming apparatus in an electrophotographic copying machine, a laser printer, a facsimile or the like, for example, an image forming apparatus in an electrophotographic copying machine using a laser beam is configured as shown in FIG. Is provided with an image carrier (photoreceptor) 2, a primary charger 3, a developing machine 4, a pre-transfer charger 5, a transfer charger 6 having a hallow baffle 6 a around the image carrier 2, and a peeling device. A charger 7 for use, a cleaner 8 and the like are sequentially disposed. The surface of the image carrier 2 is uniformly charged by the primary charger 3 and then image-exposed by the image exposure mechanism 9 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 to the paper feed mechanism 11.
Then, the visible image is transferred to a sheet by a transfer charger 6, and the sheet is sent to a fixing unit 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. The image exposure mechanism 9 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. It is. In this copying process, both single-sided copying and double-sided copying are performed similarly.

[0003]

Conventionally, there has been usually no change between single-sided copying and double-sided copying. In recent years, products that switch the output level of the transfer current applied to the transfer charger to obtain the optimum transfer image quality have only been commercialized. However, even the method of switching the transfer current of the transfer charger has not yet been able to satisfy all the image qualities in duplex copying. In particular, due to the curl of the transfer paper after single-sided copying that occurs during double-sided copying, poor transfer at the leading and trailing ends (white spots, blurred images, double images, missing images) has no definitive effective means. In general, the transfer failure occurred up to about 7 to 8 mm on the second surface, especially at the rear end. In addition, high-end machines and poles, which are not equipped with automatic double-sided machines, and some low-end machines, products using a bias transfer roll have been commercialized.
A high-end machine is too expensive for a sheet / minute class, and a low-grade machine has a problem in reliability / lifetime, and a machine suitable for a general-purpose machine class has not been put to practical use.

The present invention has been made in view of the above, and has been described in the related art.
It is an object of the present invention to provide an image forming apparatus capable of improving transfer failure due to white spots at the rear end of face copying.

[0005]

In order to achieve the above-mentioned 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, the toner image on the image carrier is transferred onto a sheet by the transfer beam of the transfer corotron of the transfer charger. In addition, metal transfer assist rollers 13, 13a, and 13a are located at positions within the transfer beam irradiation range of the transfer corotron 6b.
13b and 13c are provided between the image carrier 2.2a and the image carrier 2.2a so as to allow the paper 18 to pass through, and the gap between the image carrier 2 and the transfer auxiliary rollers 13, 13a and 13b is provided as an image carrier. Body 2
In this configuration, one end in the width direction of the sheet 18 to be passed through is narrowed on the one side end reference position side conveyed so as to pass through the same reference position, and the opposite side is widened. The image carriers 2, 2a and the transfer assist rollers 13, 13
The gaps between the holes a, 13b, and 13c are in the range of 0.1 to 1.0 mm, preferably 0.1 to 0.4 mm, and the diameter is 10 mm or less, preferably 4 to 7 mm. Further, the diameter of the transfer assisting rollers 13a and 13b is gradually reduced from the one-side end reference position side to the opposite side, and the gap with the image carrier 2 is made wider on the opposite side than the one-side end reference position side.
The transfer assist roller 13 is inclined with respect to the axis of the image carrier 2 in the direction in which the paper 18 enters, and is opposed to the image carrier 2. Further, 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, a metal transfer auxiliary roller is provided to the transfer charger.
The transfer assisting roller is supported together with a harrow baffle 6a disposed on the upstream side in the direction of entry of the sheet 18, the gap between the image carrier and the transfer assisting roller is set to a range of 0.1 to 1.0 mm, and further grounded. It is a configuration provided.

[0006]

[Operation] Entrance of the transfer charger 6 in the entry direction of the paper 18
The paper 18 entering from the side is guided to the gap between the image carrier 2 and the transfer auxiliary rollers 13, 13a, 13b, 13c, and the paper 18 at this time is transferred to the transfer auxiliary rollers 13, 13a, 13c.
b, 13c, it is suppressed to the image carrier 2 side. At this time,
The transfer assist rollers 13, 13a, 13b, 13c are located 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 and trailing ends of the paper 18 are transferred. Even when the paper 18 passes through an area subjected to the action of the electric field, the leading end and the trailing end of the sheet 18 are pressed so as to be in contact with the image carrier 2 side.

[0007]

Embodiment An embodiment of the present invention will be described with reference to FIG. Note that 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 paper entering direction and within the irradiation range of the transfer beam of the transfer corotron 6 b of the transfer charger 6.
A transfer assist roller 13 made of metal is provided rotatably so as to face each other at a slight distance of, for example, 0.1 to 1.0 mm.

As shown in FIGS. 3 and 4, the transfer assist roller 13 has a pair of bearings 15 whose both ends are rotatably supported in a vertical direction with respect to a case 14 of the transfer charger 6.
It is rotatably supported at the tip of. The bearing 15 is biased by a torsion spring 16 in a direction in which the roller support 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 generates a step corresponding to the gap with respect to the image carrier 2. The rolling contact portions 17, 17 are in rolling contact with both ends of the image carrier 2 in accordance with the biasing rotation of the bearing 15 by the torsion spring 16.

The transfer support roller 13 has an outer diameter of 10 mm.
Within, preferably, 4-7 mm is suitable and is electrically grounded. The rolling portions 17, 17 are made of an elastic semiconductive member such as a synthetic resin.
The gap is positioned on the extension of the guide surface of the hello baffle 6a by the contact of the rolling contact portions 17 with the image carrier 2. Since the transfer assisting roller 13 and the hello baffle 6a are supported on the case 14 side of the transfer charger 6, they can maintain a constant positional relationship with the transfer corotron 6b of the transfer charger 6. These can be detached integrally with the transfer charger 6.

In the above configuration, the sheet 18 sent from the sheet feed mechanism 11 is guided by the hello baffle 6a by the transfer charger 6, and the image carrier 2 and the transfer assisting roller 1 are guided.
3 and enters the gap and moves above the transfer corotron 6b. At this time, since the transfer assisting roller 13 is disposed at a position where the transfer corotron 6a substantially applies to the transfer electric field (line of electric force) exerted on the transfer, the leading end and the rear end of the sheet 18 act on the transfer electric field. Even when the sheet 18 passes through the receiving area, the leading end and the trailing end of the sheet 18 are suppressed so as to be forcibly brought into contact with the image carrier 2.

FIGS. 6 (a), 6 (b) and 6 (c) show defective transfer of the trailing edge of the second side during double-sided copying in the prior art (white spots)
The data are shown in FIG. 5 (a), 50 copies in a laboratory at 28 ° C. and 85% environment shown in FIG. 5 (b), and at 50 ° C. and 30% environment shown in FIG.
In many cases, white spots were generated.

On the other hand, in the above-described embodiment of the present invention, the rear end transfer failure (white spot) on the second side during double-sided copying is shown in FIG.
As shown in (a), (b) and (c), any 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) Also in the case of 50 copies, the white spot width was remarkably narrowed and the number of copies was also reduced.

FIGS. 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. Among them, the white spots of 6 mm or less to 12 mm or more occurred in all the sheets, whereas in the embodiment of the present invention, as shown in FIG. 8B, the white spots of all the sheets were 3 mm or less. Was.

Since the gap between the image carrier 2 and the transfer auxiliary roller is narrow, the surface of the transfer auxiliary roller is easily stained by the toner from the image carrier 2 or the like due to the transfer operation to the paper 18. For this reason, the portion where the frequency of the paper 18 passing is low,
That is, by increasing the gap between the portion farther from the side registration side position and the image carrier 2, it is useful to prevent the transfer assist roller from being stained.

FIGS. 5B and 5C show an embodiment of the present invention . That is, the one shown in FIG. 5B is a reference position (side registration position)
The other side of the rolling contact portion 17b while the diameter D ₁ of the rolling contact portion 17a of the location) side is the diameter gap between the one end reference position side is the predetermined 0.1~1.0mm have diameter D ₂ is larger than this, the gap is so large little by little as the distance from one end reference position. In addition,
The one-side end reference is usually called a side resist.
This is when the paper 18 of different width is passed
One side in the width direction of each of the sheets 18 having different widths
That is, the edges are conveyed so as to pass through the same reference position .

In the embodiment shown in FIG. 5 (c) , the diameters of the rolling contact portions 17, 17 on both sides of the transfer assist roller 13b are the same, and the diameter of the transfer assist roller 13b is set at the one end reference position.
It is formed on the stepped so that the diameter decreases away from the location side. Note that the change in the diameter may be tapered instead of being stepped.

FIGS. 9A and 9B show another embodiment of the present invention, in which the axis of the transfer auxiliary roller 13 is indicated by an arrow with respect to the axis of the image carrier 2. For the feed direction
One end is inclined to the reference position side. As a result, the gap between the transfer assisting roller 13 and the image carrier 2 is increased on the side opposite to the one-side end reference position side, and the transfer assisting roller 13 at the intermediate portion causes the paper 18 to move toward the image carrier 2. It is easy for both ends of the paper 18 to enter the gap without impairing the pressing.

In each of the above embodiments, the transfer assist roller 1
Although the rolling contact portions provided at both end portions of the transfer assist rollers 3, 13a and 13b are shown as being integrated with the transfer assist roller, one of the rolling contact portions is rotatable with respect to the transfer assist roller via a bearing or the like. It may be. According to this, the transfer assist roller is rotated by the image carrier 2 by only one of the rolling contact portions, and the fixed difference due to the difference in outer diameter between the two rolling contact portions is absorbed, and the transfer assist roller is rotated. Wear of the contact portion is reduced.

FIG. 10 shows still another embodiment of the present invention, in which rolling contact portions 20 and 20 having a larger diameter than the image bearing surface are provided on both sides of the image bearing member 2a. The transfer assisting roller 13c formed in the first embodiment is spring-biased by the same mechanism as in the above embodiments.

[0020]

According to the present invention, the transfer electric field can be ensured even when the paper is wavy due to moisture and the paper curls downward after passing through the fixing device during automatic double-sided stackless operation in a state in which the paper is securely in contact with the image carrier. Even in the case of paper having such a habit, it is possible to suppress the whiteout transfer failure at the end in the running direction to a maximum of 5 mm.

[Brief description of the drawings]

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

FIG. 2 is a schematic structural 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.

FIGS. 5A, 5B and 5C are plan views showing different embodiments of the transfer assisting roller. FIGS.

FIGS. 6A, 6B and 6C are diagrams showing the trailing edge blanking amount of the second side in duplex printing according to the related art.

FIGS. 7A, 7B, and 7C are diagrams showing the amount of white spots at the rear end of the second side in duplex copying in the apparatus of the present invention.

8 (a) and 8 (b) are diagrams showing the amount of defects due to white spots at the leading and trailing edges in the conventional art and the apparatus of the present invention during single-sided copying on highly water-containing paper.

FIGS. 9A and 9B are explanatory views showing different arrangement examples of the transfer assisting roller.

FIG. 10 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 ... Image carrier, 6 ... Transfer charger, 6a
... Hello baffle, 13, 13a, 13b, 13c, 1
3d: transfer assist roller, 14: case, 15: bearing, 1
6 ... torsion spring, 17, 17a, 17b, 2
0: transfer part, 18: paper.

Continued on the front page (72) Inventor Masahiko Kitamura 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Kazuhiro Yoshihara 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (56) References Special 63-212973 (JP, A) JP-A-2-123962 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/16

Claims (6)

(57) [Claims] 1. A sheet is run between an image carrier and a transfer charger in synchronization with the movement of the image carrier, and a transfer beam from a transfer corotron of the transfer charger is transferred onto the image carrier. In an image forming apparatus in which a toner image is transferred onto a sheet, a metal transfer is performed at a position on the entrance side of the transfer charger 6 in the direction of entry of the sheet 18 and within the irradiation range of the transfer beam of the transfer corotron 6b. Auxiliary rollers 13, 13a, 13b, 1
3c, the gaps enough to allow the paper 18 to pass through the image carriers 2, 2a.
Between the image carrier 2 and the transfer assist roller 1
The gap between the paper carrier 3, 13a, and 13b is changed in the axial direction of the image carrier 2, and the one-side end reference position is conveyed so that one end in the width direction of the sheet 18 to be passed passes through the same reference position. An image forming apparatus having a narrow side and a wide opposite side. 2. An image carrier 2, 2a and a transfer assist roller 1.
The gap with 3,13a, 13b, 13c is 0.1 to 1.0
2. The image forming apparatus according to claim 1, wherein the distance is set in a range of 0.1 mm to 0.4 mm. 3. The transfer assist rollers 13, 13a, 13b,
2. The image forming apparatus according to claim 1, wherein the diameter of 13c is within 10 mm, preferably 4 to 7 mm. 4. The transfer auxiliary roller 13a has a diameter gradually reduced from the one-side end reference position side to the opposite side, and the gap with the image carrier 2 is made wider on the opposite side than the one-side end reference position side. The image forming apparatus according to claim 1, wherein: 5. The image forming according to claim 1, characterized in that oppositely arranged is inclined to the image carrier 2 in the approach direction of the sheet 18 to transfer the auxiliary roller 13 to the axis of the image carrier 2 apparatus. 6. A transfer beam from a transfer corotron of the transfer charger by moving a sheet between the image carrier and the transfer charger in synchronization with the movement of the image carrier. In an image forming apparatus in which a toner image is transferred onto a sheet, a metal transfer is performed at a position on the entrance side of the transfer charger 6 in the direction of entry of the sheet 18 and within the irradiation range of the transfer beam of the transfer corotron 6b. Auxiliary roller to transfer charger
The transfer assisting roller is supported together with a harrow baffle 6a disposed on the upstream side in the direction of entry of the sheet 18, the gap between the image carrier and the transfer assisting roller is set to a range of 0.1 to 1.0 mm, and further grounded. An image forming apparatus, comprising: