JPH0656291A - Sheet sucking/conveying device for image forming device - Google Patents

Abstract

PURPOSE:To suck a sheet to a conveyor belt without generating wrinkles and floating of the sheet and provide a good image by pressing the conveyed sheet to the upper face of the conveyor belt with an auxiliary roll on the upstream side than a pressing roll prior to the pressing roll, correcting wrinkles and warp deformation, and feeding the sheet downstream. CONSTITUTION:A holding roll 10 pressing a fed sheet P prior to a pressing roll 3 is provided upstream a conveyor belt 1 on a bus line and downstream the pressing roll 3 on the bus line. The auxiliary roll 10 is made freely rotatable, it has the same outer diameter as that of the pressing roll 3, and its rotary axis is located in the plane formed by the surface containing the axis of the pressing roll 3. The sheet P is adapted to the upper face of the conveyor belt 1 by the auxiliary roll 10 in advance and fed, and wrinkles and warp deformation can be vanished before suction. The sheet P having undulations or wrinkles, particularly the sheet P partially containing water, can be closely stuck on the upper face of the conveyor belt 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying device of an image forming apparatus such as an electrophotographic copying machine or an ink jet printer, and more particularly to a sheet suction device capable of adsorbing without wrinkling or floating on the sheet. Concerning a carrier device.

[0002]

2. Description of the Related Art Conventionally, in a device such as an electrophotographic copying machine, a system in which an image is electrostatically adsorbed on a carrier sheet to write an image is adopted. And this system
For example, as described in Japanese Patent Application Laid-Open No. 55-32079, a transfer drum system in which a corotron and a facing roll are combined is most common.

However, in such a paper suction method, if the carrier sheet has irregularities for some reason during suction, a gap is often formed between the paper and the carrier sheet.

In order to prevent the occurrence of such a gap between the carrying sheet and the paper, as described in Japanese Patent Laid-Open No. 2-157779, a pair of corrections for unevenness of the carrying sheet near the suction portion are made. It has already been proposed to correct with a roll.

However, for a sheet having undulations, for example, even if a straightening roll is used, the distortion of the sheet itself cannot be corrected. Further, due to the curvature of the transfer drum, the sheet will be deformed again after passing through the rolls, and will be adsorbed to the peripheral surface of the transfer drum while having a float.

On the other hand, in the electrophotographic copying machine, in order to prevent the deformation of the carrier sheet and allow the sheet to be conveyed, a system for conveying the sheet by a tensioned endless belt is adopted. As an example, FIG. 7 shows an outline of a system of a tandem type full-color electrophotographic copying machine in which visible image forming units of four colors are arranged along a sheet conveying path.

In the figure, a toner image (visible image) corresponding to each color of yellow, magenta, cyan, and black is formed along the conveyance path of the sheet P between the sheet supply tray 120 and the fixing device 113. A set of visible image forming units 100 is arranged. Further, a closed-loop conveyor belt 1 for conveying the paper is incorporated so that it can travel in the direction of the arrow in the figure.

The visible image forming unit 100 includes a charging device 107, a latent image writing means 102, a developing device 103 and a cleaner 10 around an electrostatic latent image carrier 101 such as a photosensitive drum.
6 is arranged. Then, a toner image corresponding to the image information of each color is formed on the electrostatic latent image carrier 101, and the toner image is sequentially electrostatically transferred by the transfer corotron 105 onto the paper P conveyed by the conveyor belt 1. Therefore, the sheet P carried out from the supply tray 120 is held on the conveyor belt 1 by the electrostatic attraction force of the sheet attracting corotron 4 at a predetermined timing, and then the visible image forming units 100 are advanced in accordance with the progress thereof. Then, the toner images of respective colors are sequentially transferred to carry a full-color toner image.

FIG. 8 is an enlarged view showing the outline of the suction portion of the paper P.

The conveyor belt 1 is hung around the drive roll 2 and runs, and an adsorption corotron 4 is arranged inside the path line of the conveyor belt 1. A pressing roll 3 for pressing down the paper P and pressing it against the upper surface of the conveyor belt 1 is rotatably incorporated in a portion located above the path line and substantially above the suction corotron 4. The pressing roll 3 is grounded.

In the suction portion of the paper P having such a structure,
While the paper P is passing between the pressing roll 3 and the conveyor belt 1, the suction corotron 4 is maintained in the discharge state, and the electrostatic attraction force is applied to the entire surface of the paper P.

[0012]

However, in such a system, the deformation of the conveyor belt 1 itself does not occur, but when the electrostatic attraction force is applied to the entire surface of the paper P, the paper P is not deformed.
Wrinkles and floating are likely to occur on the paper P at the stage of adsorbing the paper onto the upper surface of the transport belt 1.

For example, in the case of the paper P that is partially deformed by absorbing moisture as shown in FIG. 9A or the curled paper P shown in FIG. 9B, such wrinkles and The occurrence of floating appears remarkably. Therefore, when the paper P is adsorbed on the upper surface of the conveyor belt 1 in this state, the paper P is adsorbed on the conveyor belt 1 with wrinkles and floats as shown in FIG. Will be transported. Then, if the paper P is directly sent to the transfer unit or the like, a part of the toner image is not transferred from the photoconductor drum to the paper P. As a result, as shown in FIG.
White spots Q are partially generated in the image, and the reliability of the copying machine itself is impaired.

Such a problem occurs not only in the electrophotographic copying machine but also in the ink jet printing. Further, in the case of an inkjet printer, there is a problem in that in the case of a distorted image or color, color misregistration occurs due to the difference in paper height.

An object to be solved in the present invention is to properly adsorb a sheet onto a conveyor belt without causing wrinkles or floating so that a good image can be obtained.

[0016]

SUMMARY OF THE INVENTION The present invention is directed to a visible image forming unit for transferring a visible image to a sheet according to image information, and a sheet along a predetermined path in which the visible image forming units are arranged. An image forming apparatus including: a conveyance belt that adsorbs and conveys the sheet; an adsorption corotron that adsorbs the sheet onto the conveyance belt; and a pressing roll that is disposed at a position facing the adsorption corotron and that urges the sheet toward the conveyance belt. In the above area, at least one auxiliary roll that rolls down the paper toward the upper surface of the conveyor belt is arranged in a region where the leading edge of the paper is landed on the upper surface of the conveyor belt and upstream of the pressing roll. It is characterized by

[0017]

The auxiliary roll, which is arranged on the upstream side of the pressing roll, presses down the sheet conveyed toward the upper surface of the conveying belt prior to the pressing roll, corrects wrinkles and warp deformation, and flows downstream. Therefore, compared to the case where the suction corotron and the pressing roll adsorb the paper to the conveyor belt, the auxiliary roll allows the paper to be preliminarily fitted to the upper surface of the conveyor belt and the paper can be fed, and wrinkles are formed before the suction corotron sucks the paper. It is possible to dissipate the warp deformation.

Further, although the sheet is attracted by the pressing roller and the sheet tends to be deformed due to the constraint, it is possible to prevent the sheet from being deformed on the upstream side which is not attracted.

Further, if the pressure lower surface of the paper by the auxiliary roll is made to be substantially the same as that by the pressing roll,
The rolling point applied to the paper does not move up and down, which is effective in preventing warp deformation.

If the auxiliary roll is used as a conductor and is grounded, electric charges are not injected even when the paper is passed, and the wrinkling of the paper due to static electricity is prevented. The chute is arranged so that the position of the leading edge of the sheet toward the auxiliary roll side is adapted to the positional relationship between the auxiliary roll and the upper surface of the conveyor belt, and the restraining force acts on the sheet in the conveying direction. With this, wrinkles and deformation can be removed more effectively.

If a speed relationship is set so that the speed of the supplied paper and the traveling speed of the conveyor belt are substantially the same or the speed of the paper is slightly higher, the occurrence of wrinkles can be suppressed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the essential parts of a paper suction device of the present invention.

The sheet suction device is incorporated in the system described with reference to FIG. 7. Like the one shown in FIG. 8, the drive roll 2 for running the conveyor belt 1 is incorporated in the pass line. . Similar to the conventional example in FIG. 8, the suction corotron 4 is arranged at a position included in the pass line and the pressing roll 3 is arranged outside the pass line so as to face the suction corotron 4. Is.

The conveyor belt 1 is supported by a plurality of support rolls 5 so as to travel along a substantially horizontal path line, and a pair of registration rolls 6 and 7 for feeding the paper P from the paper feed tray to the conveyor belt 1 side are provided on the entrance side. Deploy. Further, a chute 8 and a lower chute 9 for guiding the paper P to the conveyor belt 1 are incorporated.

An auxiliary roll 10 is provided above the pass line of the conveyor belt 1 and downstream of the pressing roll 3 so as to press down the supplied paper P prior to the pressing roll 3. This auxiliary roll 10 can freely rotate, its outer diameter is the same as that of the pressing roll 3, and its rotation axis is located in the plane formed by the plane including the axis of this pressing roll 3. Under these built-in conditions, the auxiliary roll 10 rotates in the clockwise direction in the figure in conjunction with the passage of the paper P supplied to the conveyor belt 1.

In the example of FIG. 1, the center of rotation of the auxiliary roll 10 is located slightly offset from the vertical line of the rotary shaft of the drive roll 2 to the pressing roll 3 side. Then, the shape dimensions of the lower ends of the chute 8 and the lower chute 9 are appropriately set according to the position of the auxiliary roll 10.

FIG. 2 shows an example in which the position of the auxiliary roll 10 is changed.

As shown, one auxiliary roll 10 is
It is positioned so as to have a rotation axis on the vertical line of the rotation axis of the drive roll 2.

The position of the auxiliary roll 10 with respect to the pressing roll 3 is set such that the distance between the outer peripheral surfaces facing each other is in the range of 10 to 30 mm. The auxiliary roll 10 is a conductor and is grounded. As a result, the charge injection into the paper P due to the charging of the auxiliary roll 10 itself can be eliminated.

FIG. 3 shows an example in which, in addition to the auxiliary roll 10, another auxiliary roll 11 is arranged between the pressing roll 3 and the auxiliary roll 11. Even in this case, the conditions such as the position and posture of the auxiliary roll 11 with respect to the pressing roll 10 and the ground contact are exactly the same as those in the examples of FIGS. 1 and 2.

As for the positional relationship between the auxiliary roll 10 located at the right end and the chute 8 and the lower chute 9, as shown in FIG. 4, the extension line of the lower chute 9 includes a drive roll in a vertical plane including the axis of the drive roll 2. The direction of the peripheral surface is 2. As a result, the leading edge of the paper P fed by sliding on the lower chute 9 is sandwiched between the auxiliary roll 10 and the conveyor belt 1.

FIG. 5 shows an example in which the positional relationship between the chute 8 and the lower chute 9 is changed with respect to the arrangement of the auxiliary rolls 10 and 11 similar to that shown in FIG.

As shown in the enlarged view of FIG. 6, the chute 8 and the lower chute 9 are installed so that their lower ends are located at substantially the same level as or higher than the horizontal plane including the rotation axis of the auxiliary roll 10. Has been. Due to the positional relationship between the auxiliary roll 10 and the chute 8 and the lower chute 9 as shown in FIG. 6, the sheet P fed from the lower chute 9 is slightly bent downward by the auxiliary roll 10. I will pass.

1 to 6, one or two auxiliary rolls 10 and 11 are provided on the upstream side of the pressing roll 3 in the conveying line. Therefore, the deformation (waviness) of the sheet P on the upstream side, which occurs when the sheet P is attracted to the transport belt 1 by the pressing roll 3, can be reduced by these auxiliary rolls 10 and 11. Therefore, the passing paper P is uniformly brought into close contact with the upper surface of the conveyor belt 1 by the suction corotron 4, and wrinkles and floating of the paper P are prevented.

Further, since the auxiliary rolls 10 and 11 are conductors and are grounded, no charge is injected into the paper P due to the charging of the auxiliary rolls 10 and 11 themselves. Therefore, the paper P
It is possible to more effectively suppress wrinkles and deformation of the.

Further, in the example shown in FIGS. 5 and 6, after the paper P comes out from the lower chute 9, the auxiliary roll 10
It is bent downward by and draws a gentle S-shaped path. In this case, the paper P is bent downward at the portion in contact with the peripheral surface of the auxiliary roll 10, and the posture of the paper P in the pass direction is restricted. Therefore, as compared with the case where the auxiliary roll 10 simply presses the paper P against the upper surface of the conveyor belt 1, the occurrence of wrinkles and deformation is reliably prevented.

Further, the traveling speed of the conveyor belt 1 is made substantially equal to the speed of the paper P fed toward the upper surface thereof. With such a speed relationship, the relative speed between the conveyor belt 1 and the paper P can be made close to zero, and for example, when the traveling speed of the conveyor belt 1 is slower than the speed of the paper P, wrinkles in the paper P are likely to occur. And deformation can be prevented.

Next, the evaluation by tests by each structural example of the conveying apparatus of the present invention including the conventional example of FIG. 8 will be shown in order.

The apparatus used for the test is the electrophotographic copying machine shown in FIG. 7, and is a system for supplying the paper P from the chute 8 and the lower chute 9 onto the conveyor belt 1.

Test Example 1 Test Conditions: Device Configuration [1] Conventional Example FIG. 8 Outer Diameter of Pressing Roll 3: 8.9 mm Paper P is 5 mm above the conveyor belt 1 in front of the pressing roll 3.
Rush into the vicinity.

[2] Present Invention FIG. 1 Auxiliary Roll 10 Outer Diameter 8.9 mm, Material SUS A = 20 mm Paper P is 5 m above the conveyor belt 1 in front of the auxiliary roll 10.
Rush into the vicinity of m.

[3] Present Invention FIG. 3 Auxiliary Rolls 10, 11 Outer Diameter 8.9 mm, Material SUS B = 11 mm, C = 14 mm Paper P is 5 m above the conveyor belt 1 in front of the auxiliary roll 10.
Rush into the vicinity of m.

Paper conditions Basis weight 64 gsm state Partially hydrous paper 250 sheets left as they are in a high humidity environment.

(28 ° C., 85%, 15 hours) Wrinkles only in the peripheral area.

Size A3 Longitudinal feed Other conditions Speed of conveyor belt 160 mm / s Circumferential speed of registration rolls 6, 7 160 mm / s Adsorption corotron 4, pressing roll 3 current 6 μA Pressing roll 3 and auxiliary rolls 10 and 11 load 200 gf Pressing roll 3 and auxiliary rolls 10 and 11 Grounding test environment 28 ° C, 85% Evaluation characteristics: Proportion of transfer omission excluding front and rear ends Test result: Ratio of occurrence of transfer omission Situation [1] 96% Large omission [2] 21% Undulation Only the lower layer of the large paper stack is removed [3] Only the lower layer with a large 15% swell is removed. As is clear from the above test results, in the suction conveyance device of the present invention, the occurrence of transfer omission occurs. The effect of preventing is great. In addition, the rate of occurrence of transfer omission changes depending on the water content or deformation of the paper P, and the undulation of the paper P is small when the time is shorter than the test conditions or when left for a long time (48 hours or more). It was also confirmed that the apparatus of the present invention hardly causes the transfer omission even under the condition that the transfer omission occurs in the apparatus.

[Test Example 2] A comparative test of [4] was carried out under the above apparatus conditions [2] when only the auxiliary roll 10 was not grounded. The other conditions are the same as in Test Example 1. Test results: Rate of occurrence of transfer omission Situation [2] 21% Not dependent on the number of continuous copies.

[4] 35% It becomes worse when the number of continuous copies is large.

In the case of the configuration [4], the auxiliary roll 10 is gradually charged by the passage of paper, and after a certain number of sheets, the auxiliary roll 10 is weak, but the sheet P and the conveyance belt 1 start to be attracted to each other. Due to such an influence, the rate of occurrence of transfer omission during copying of the paper P is increased as compared with the case where the auxiliary roll 10 is grounded.

From this, it is preferable that the auxiliary roll 10 is not charged, and by using the material of the conductor grounded, it is possible to suppress the occurrence of transfer omission.
It should be noted that as the actual material of the auxiliary roll 10, metals such as SUS, Al, and Cu to which toner is hard to adhere, and conductive rubber capable of making the nip portion uniform are suitable.

[Test Example 3] Under the test conditions of Test Example 1, the distance between the auxiliary roll 10 and the pressing roll 3 was changed, and the test was conducted as follows.

[2] Present Invention FIG. 1 Auxiliary Roll 10 Outer Diameter: 8.9 mm, Material: SUS A = 20 mm The paper P rushes into the vicinity of 5 mm above the conveyor belt 1 in front of the auxiliary roll 10.

[5] Present Invention FIG. 2 Auxiliary Roll 10 Outer Diameter: 8.9 mm, Material: SUS D = 10 mm The paper P rushes in the vicinity of 5 mm above the conveyor belt 1 in front of the auxiliary roll 10.

[6] Present Invention FIG. 2 Auxiliary Roll 10 Outer Diameter: 8.9 mm, Material: SUS D = 30 mm The paper P rushes into the vicinity of 5 mm above the conveyor belt 1 in front of the auxiliary roll 10.

[7] Present Invention FIG. 2 Auxiliary Roll 10 Outer Diameter: 8.9 mm, Material: SUS D = 40 mm The paper P rushes into the vicinity of 5 mm above the conveyor belt 1 in front of the auxiliary roll 10.

Test result: Configuration D dimension Transfer drop occurrence rate Situation [5] 10 mm 16% Good [2] 20 mm 21% Good [6] 30 mm 28% Good [7] 40 mm 73% Bad In case of [7], auxiliary Roll 10 and pressing roll 3
The sheet P floats between the sheet and.

From the above test results, it was found that in the case of [7], the auxiliary roll 10 was not effective in suppressing the deformation of the paper 10. In addition, another test was performed and the D dimension was 30 mm.
It was also confirmed that the occurrence rate of transfer omission increases from around the point of exceeding. The lower limit of the D dimension is restricted by the outer diameters of the pressing roll 3 and the auxiliary roll 10, and the limit is about 10 mm in a practical range. If the D dimension is in the range of at least 10 mm to 30 mm, it is effective in suppressing the occurrence of wrinkles and deformation of the paper P.

TEST EXAMPLE 4 Under the test conditions of TEST EXAMPLE 1, the path of the paper sheet entering the auxiliary roll was changed as follows.

[3] Present Invention FIG. 3 Auxiliary Rolls 10, 11 Outer Diameter: 8.9 mm, Material: SU
SB = 11 mm, C = 14 mm The paper P rushes into the vicinity of 5 mm on the conveyor belt 1 before the auxiliary roll 10.

[8] Present Invention FIG. 5 Auxiliary Rolls 10, 11 Outer Diameter: 8.9 mm, Material: SU
SB = 11 mm, C = 14 mm The sheet P is guided so as to hit the first auxiliary roll 10 and forms an S shape along the auxiliary roll 10 and rushes onto the conveyor belt 1 (FIG. 6).

Test results: From the above test, it is found that the introduction path of the paper P is substantially S-shaped so that the deformation of the paper P can be suppressed, the floating of the paper P on the pressing roll 3 portion can be prevented, and the occurrence of transfer omission can be eliminated. It was

[Test Example 5] Under the test conditions of Test Example 1, a test was carried out by changing the feeding speed of the paper entering the auxiliary roll as follows.

In each test, the auxiliary roll 10,
11 is an outer diameter: 8.9 mm, the material is SUS,
The conditions of the roll distance E = 11 mm and F = 14 mm are common. The paper P is guided so as to hit the first auxiliary roll 10 and has a common condition that the paper P is S-shaped along the auxiliary roll 10 and rushes into the conveyor belt 1.

[8] Present Invention FIG. 5 Feed Speed of Registration Rolls 6, 7 to the Conveyor Belt 1: ± 0% [9] Present Invention FIG. 5 Feed Speed of Registration Rolls 6, 7 to the Conveyor Belt 1: + 0.5% [10 ] The present invention Fig. 5 Feed speed of the registration rolls 6, 7 to the conveyor belt 1: + 1% [11] Present invention Fig. 5 Feed speed of the registration rolls 6, 7 to the conveyor belt: + 2% Test result: Speed relationship Proportion [8] 0% 0% [9] + 0.5% 10% [10] + 1% 30% [11] + 2% 70% From the above test results, the delivery speed from the registration rolls 6 and 7 is that of the conveyor belt 1. It turns out that it is better not to be so large compared to the speed of. Further, if the feeding speed is too high, the sheet P forms a loop while entering the auxiliary roll 10, and the effect of restraining the sheet P passing in the S shape along the peripheral surface of the auxiliary roll 10 is weakened. Will end up.

Here, the conveyor belt 1 and the registration rolls 6, 7
If the speed difference between the feeding speeds is 0, it is more effective for the transfer omission. However, a load is applied to the driving of the conveyor belt 1, which causes color misregistration. Therefore, in the practical range, the cash register rolls 6, 7
It is preferable that the feeding speed from the carrier is within the range of 0 to + 0.5% as compared with the speed of the conveyor belt 1.

In the embodiment, one or two auxiliary rolls are used.
However, three or more may be arranged. Further, although a color copying machine has been exemplified as an example of the system, the suction conveyance device of the present invention can be applied to the field of a single-color copying machine, a full-color inkjet printer, and the like.

[0066]

EFFECTS OF THE INVENTION Paper can be fed by an auxiliary roll in advance so that it fits on the upper surface of the conveyor belt, and when the paper is transferred to the upper surface of the conveyor belt, the paper is attracted to the conveyor belt by a suction corotron and a pressing roll. Compared with the structure, it is possible to dissipate wrinkles and warp deformation before adsorption. Therefore, even if the paper has undulations or wrinkles, especially if the paper partially contains water, it can be brought into close contact with the upper surface of the conveyor belt, and white spots can be prevented from occurring in the transfer process. Regardless of which, good image formation can be maintained.

[Brief description of drawings]

FIG. 1 is a diagram showing a main part of a suction conveyance device of the present invention.

FIG. 2 is a diagram showing an example in which the arrangement of auxiliary rolls in FIG. 1 is changed.

FIG. 3 is a diagram showing an example in which two auxiliary rolls are arranged.

FIG. 4 is an enlarged view of a main part showing an arrangement of a conveyor belt and a chute in FIG.

5 is a diagram showing an example in which the arrangement of auxiliary rolls in FIG. 3 is changed.

6 is an enlarged view of a main part showing an arrangement of a conveyor belt and a chute in FIG.

FIG. 7 is a diagram showing an outline of a color copying machine provided with a paper suction transport device.

FIG. 8 is a diagram showing a conventional example of a sheet suction conveyance device.

FIG. 9 is a diagram showing wrinkles and warp deformation of a sheet.

FIG. 10A shows a state in which a wrinkled and deformed sheet remains on the conveyor belt as it is, and FIG. 10B shows occurrence of white spots after copying. FIG.

[Explanation of symbols]

1 conveyor belt, 2 drive rolls, 3 pressing rolls,
4 adsorption corotron, 5 support rolls, 6 registration rolls, 7 registration rolls, 8 shoots, 9 lower shoots, 1
0 auxiliary roll, 11 auxiliary roll, P paper

Claims (1)

[Claims] 1. A visible image forming unit for transferring a visible image to a sheet according to image information, and a conveyor belt for adsorbing and conveying the sheet along a predetermined path in which the visible image forming units are arranged, In an image forming apparatus including an adsorption corotron that adsorbs the sheet onto the conveyance belt, and a pressing roll that is disposed at a position facing the adsorption corotron and that urges the sheet toward the conveyance belt, the leading end of the sheet is Paper suction in an image forming apparatus in which at least one auxiliary roll for declining the paper toward the upper surface of the conveyor belt is arranged upstream of the pressing roller in a region to be landed on the upper surface of the conveyor belt. Transport device.