JPH10167516A - Sheet carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly carry sheets irrelevant to the thickness, types, and curled shapes of the sheets by forming the shapes of faces for sucking the sheets of a sheet carrier into upward bending shapes in the direction crossing at right angles with the carrying direction of the sheets. SOLUTION: A plurality of carrier belts 41 of a sheet carrier 4 formed by divided in the direction crossing at right angles with the carrying direction of sheets 3 have a plurality of suction holes 46 respectively and are so arranged with difference in level that their central part, becomes the highest and gradually becomes lower toward the end parts as drawing an arc in the direction crossing at right angles with the carrying direction of the sheets 3. The rotations of these carrier belts 41 are driven by a drive roll 45 arranged in the opposite side of the carrier face by a motor 47. Carrier guides 42 are also formed into arc in the direction crossing at right angles with the carrier direction of the sheet 3 and provided with a lot of suction holes 48. The suction force of a suction fan which is incorporated in the sheet carrier 4 is the lowest in its central part and gradually becomes stronger towards the end parts.

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 used in an image forming apparatus such as an electrophotographic copying machine or a printer, and more particularly to a transfer section for transferring a toner image onto a sheet and a transfer section onto the sheet. The present invention relates to a sheet conveying device that is disposed between a fixing unit that fixes a formed toner image and conveys a sheet.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus such as an electrophotographic copying machine or a printer, a toner image formed on a photosensitive drum is transferred onto a sheet at a transfer section, and then the toner image is transferred. In order to convey the fixed sheet to the fixing device in a stable state, the suction fan sucks the sheet, conveys the sheet to the fixing unit by a sheet conveying device that performs belt conveyance, and heat and heat is generated by the fixing device provided in the fixing unit. There is a type in which a toner image is melted and fixed on a sheet by pressure to form an image.

In the above-described image forming apparatus such as a copying machine and a printer, a sheet such as a transfer sheet is fed from a feed tray housed in the main body of the image forming apparatus due to an installation space of the apparatus. Therefore, the sheet receiving the transfer of the toner image is conveyed from the paper feed tray to the transfer section through a so-called U-turn-shaped conveyance path, and the sheet may be curled upward or downward. Further, in the image forming apparatus described above, curling may occur, for example, when the moisture content of a sheet such as a transfer sheet is unevenly distributed in a peripheral portion or the like in a high-humidity environment, in a paper feed tray or in a transport path. . Further, among the above-described image forming apparatuses, an apparatus that forms a color image may use a sheet whose surface is coated as a sheet in order to improve the color developability of the color image. When a color image is formed on a sheet to which a color is applied, in particular, a sheet coated on one side, the sheet may also be curled.

However, in the above-described image forming apparatus, if the sheet is curled upward in front of the fixing device, when the sheet is conveyed to the fixing device by the sheet conveying device, the sheet is moved immediately before the fixing roll. Since the posture when entering the conveyance guide can be regulated, paper jams, broken ears, and unsteady sheet behavior when the sheet enters the nip portion of the fixing roll cause paper wrinkles. The problem arises. In particular, in an image forming apparatus using a so-called belt nip type fuser that is suitable for fixing a color image, when a sheet is fixed by passing through the belt nip fuser, the sheet faces downward due to the characteristics of the belt nip fuser. If the first side is printed and fixed during double-sided printing, the front and back sides will be inverted and the curl will be upward when the second side is fixed, as described above. However, there is a problem that the above problem is easily caused. Also, in addition to the belt nip fuser, even in a normal fixing device in which a pair of rolls are pressed against each other, if the nip width of the rolls is increased to improve the fixing property, the sheet is likely to curl, and Similar problems arise. Furthermore, curl is likely to occur even when toner is printed in multiple layers due to colorization in recent years, and stability in sheet conveyance is an important problem.

However, in a belt conveying device using a suction fan, the required suction force varies depending on the thickness, type, and curl shape of the sheet. If a sufficient suction force cannot be obtained depending on the state, there is a problem that when the sheet enters the fixing device, the ear breaks, jams, and paper wrinkles occur.

Therefore, as a technique for solving such a problem, for example, JP-A-04-121357, JP-A-03-293253, and JP-A-07-530 are disclosed.
No. 89 is disclosed.

The rotation speed control device of the conveyance suction fan according to the above-mentioned Japanese Patent Application Laid-Open No. 04-121357 discloses a detection device which controls the rotation speed of the conveyance suction fan based on the distance between the conveyance suction fan and the transfer paper on the conveyance belt. By providing a means for adjusting and controlling, the transfer paper is transported to the fixing unit with an appropriate suction force according to the paper quality, and the transporting paper in the fixing unit is prevented from being transported poorly such as creases, wrinkles, and jams. is there.

In the sheet conveying apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 7-53089, the sheet enters a nip portion downstream of the sheet conveying apparatus by forming the sheet conveying surface into a curved shape in a direction in which the sheet is sucked. It is configured to absorb the shock when performing.

Further, the paper suction type conveying apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 3-293253 has a sheet opening / closing means for changing an opening state of a suction hole according to the size detection of the sheet being conveyed. It is configured to reduce air leaks not covered by the above and secure a stable suction force.

[0010]

However, the prior art described above has the following problems. That is, in the case of the apparatuses disclosed in JP-A-04-121357 and JP-A-3-293253, the detecting unit detects the conveyance suction fan based on the distance between the conveyance suction fan and the transfer paper on the conveyance belt. Because it is configured to provide means for adjusting and controlling the number of rotations, the thickness of the paper,
It is necessary to detect various factors such as the type and curl shape, and complicated control must be performed depending on the state. In addition, the control based on the suction force of the sheet cannot control the position of the sheet in a range that does not reach the suction when the sheet enters the fixing device, so that the problem at the time of entering the fixing device cannot be solved.

Further, in the case of the sheet conveying apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 7-53089, normal sheet conveyance can be stabilized and a shock at the time of entry can be absorbed.
For a sheet having an upward curl such as the second side during double-sided printing by a belt nip fuser, there is a problem that the conveyance is rather unstable. further,
Since the angle at which the sheet enters the fixing device is restricted, there is a problem that it is not suitable for a belt nip fuser.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a belt which does not depend on the thickness, type, curl shape, etc. of a sheet to be conveyed. It is an object of the present invention to provide a sheet conveying device that does not cause any trouble when a sheet enters the fixing device even when a nip type fixing device or the like is used.

[0013]

According to a first aspect of the present invention, there is provided a sheet provided on a path for conveying a sheet from a transfer section to a fixing section of an image forming apparatus and having a toner image transferred thereon. In a sheet conveying apparatus of an image forming apparatus provided with a suction conveying means for conveying while suctioning, the shape of a surface of the sheet conveying apparatus on which a sheet is adsorbed is curved upward in a direction orthogonal to the sheet conveying direction. It is configured so as to have a bent shape.

According to a second aspect of the present invention, there is provided the sheet conveying apparatus according to the first aspect, wherein the suction and conveying means reduces the sheet attraction force at both ends in a direction orthogonal to the sheet conveying direction. , Is set to be stronger than the central part.

Further, according to a third aspect of the present invention, in the sheet transporting device according to the first or second aspect, a leading end of the sheet transported by the suction transporting unit is disposed in a fixing unit of the image forming apparatus. After being nipped by the fixing device, the suction unit of the suction conveyance unit is shut off to stop the suction of the sheet, and the sheet is fed by the conveyance force of the fixing device. Do the suction,
It is configured to convey the next sheet.

[0016]

According to the present invention, in a sheet conveying apparatus that conveys a sheet while sucking the sheet, the sheet can be utilized by using a conveying surface having a shape curved upward in a direction orthogonal to the sheet conveying direction. With a simple configuration, it is possible to eliminate problems such as broken ears, jams, and paper wrinkles that occur when entering the fixing device.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings.

FIG. 2 shows an embodiment of an image forming apparatus to which the sheet conveying device according to the present invention is applied.

In FIG. 2, reference numeral 1 denotes a photosensitive drum as an image carrier, and the photosensitive drum 1 is rotated at a predetermined speed along a direction indicated by an arrow by a driving means (not shown). Has become. Although not shown, known image forming units such as a primary charging unit, an image exposing unit, a developing unit, and a cleaning unit that uniformly charge the surface of the photosensitive drum 1 are provided around the photosensitive drum 1. And on the surface of the photosensitive drum 1,
By a known image forming process, a toner image corresponding to an image of a document (not shown) or image information is formed. The image carrier is, for example, a photosensitive drum or a photosensitive belt as described above in the case of a monochrome image forming apparatus, but is a photosensitive drum or a photosensitive body in the case of a color image forming apparatus. In addition to the belt, the intermediate transfer body belt may be used. However, in any case, the configuration around the image carrier is the same as that of the conventional apparatus.

The toner image formed on the surface of the photosensitive drum 1 is brought into contact with the surface of the photosensitive drum 1 at a predetermined timing by a transfer roll 2 to which a predetermined transfer voltage is applied. The image is transferred onto a sheet 3 conveyed to a transfer section where the drum 1 and the transfer roll 2 come into contact.
In addition, as a transfer means, the transfer is performed in the same manner as in the conventional apparatus using the transfer roll 2, but it is needless to say that a corotron may be used instead of the transfer roll 2.

The sheet 3 onto which the toner image has been transferred from the photosensitive drum 1 is conveyed to a fixing device 5 via a sheet conveying device 4, and the fixing device 5 forms the toner image on the sheet 3 by heat and pressure. The image is fixed and discharged to the outside of the apparatus, thereby completing the image forming process. Here, as the fixing device 5, a belt 52 rotatably supported by a plurality of rolls is pressed against a lower portion of the heat roll 51, and a nip having a large area is formed between the heat roll 51 and the belt 52. The heat roll 51 is formed by passing a sheet through a nip portion between the heat roll 51 and a belt 52 for applying pressure.
The toner image is fixed on the sheet 3 by heat and pressure by a heating unit (not shown) disposed inside the printer, and is suitable mainly for fixing a color image.
When forming images on both sides of the sheet 3,
The sheet 3 having the toner image fixed on one side is again conveyed to the transfer section with the front and back reversed through a conveyance path for duplex copying (not shown), and the toner image is transferred and fixed on the back surface of the sheet 3. May be configured.

The sheet conveying device according to this embodiment is configured such that the shape of the surface of the sheet conveying device on which the sheet is sucked is curved upward in a direction perpendicular to the sheet conveying direction. Have been. Further, in the suction conveyance means, the sheet suction force at both ends in the direction orthogonal to the sheet conveyance direction is set to be stronger than that at the center. Further, after the leading edge of the sheet conveyed by the suction conveyance unit is nipped by a fixing device arranged in a fixing unit of the image forming apparatus, the suction unit of the suction conveyance unit is shut off to stop the suction of the sheet, The sheet is fed by the conveying force of the fixing device, and after the trailing end of the sheet leaves the suction conveyance unit, suction is performed again, and the next sheet is conveyed.

That is, the sheet conveying device 4 applied to the image forming apparatus according to the first embodiment has the configuration shown in FIGS.
As shown in FIG. 7, the sheet 3 including the transport belt 41, the transport guide 42, and the suction fan 43, on which the unfixed toner image is transferred at the transfer unit, is subjected to a pressure difference caused by the suction fan 43, and the transport belt 41 and the transport guide 42 The sheet is conveyed to the fixing device 5 in a state of being sucked. The conveyor belt 41
Includes a plurality of idlers 44 and the like, and a drive roll 45
Are rotatably arranged.

The conveying belt of the sheet conveying device 4 is divided into a plurality (five in the illustrated example) in a direction orthogonal to the conveying direction of the sheet 3. Each has a plurality of suction holes 46, and is arranged with a step so that the center is the highest so as to draw an arc shape in a direction perpendicular to the sheet conveying direction and becomes lower toward the ends. These transport belts 41 are driven to rotate by a motor 47 by a drive roll 45 disposed on the opposite side to the transport surface.

Further, the conveyance guide 42 of the sheet conveyance device 4 is also formed in an arc shape in a direction orthogonal to the conveyance direction of the sheet 3 and has a plurality of suction holes 48.

As shown in FIG. 3, the suction fan 43 is disposed inside the sheet conveying device 4, and the suction force of the suction fan 43 is weakest at the central portion, and gradually decreases toward the ends. The suction force is set so as to gradually increase according to the size, number, position, and the like of the suction holes 46. It is configured so that it can be adsorbed to the surface. In the illustrated example of FIG. 3, a shielding plate 49 is provided between the upper end surfaces of the transport belt 41 and the transport guide 42 and the suction fan 43, and the transport direction of the sheet 3 provided on the shielding plate 49. The opening width of the elongated suction opening 49a along the length of the suction opening 49a at the center is
The opening width of the suction fan 43 is set to be narrower, and the opening width is gradually increased toward the suction opening 49a at the end. The suction force of the suction fan 43 is weakest at the center, and is suctioned toward the end. The force is configured to gradually increase.

In the above configuration, in the image forming apparatus to which the sheet conveying apparatus according to the first embodiment is applied, as described below, the belt is independent of the thickness, type, curl shape, etc. of the sheet to be conveyed. Even when a nip-type fixing device or the like is used, no problem occurs when a sheet enters the fixing device.

That is, in the image forming apparatus according to the first embodiment, as shown in FIG. 2, after the toner image formed on the photosensitive drum 1 is transferred onto the sheet 3 by the transfer roll 2, The sheet 3 to which the unfixed toner image has been transferred is conveyed to the fixing device 5 via the sheet conveying device 4, and the unfixed toner image is fixed on the sheet 3 by heat and pressure by the fixing device 5. An image is formed.

At this time, the sheet 3 onto which the toner image has been transferred at the transfer portion below the photosensitive drum 1 is transferred from the suction holes 48 and 46 of the conveyance guide 42 and the conveyance belt 41 by the suction fan 43 of the sheet conveyance device 4. By aspirating,
The sheet is conveyed by being attracted to the step of the conveyance belt 41 and the arc-shaped conveyance surface of the sheet conveyance guide 42, and conveyed to the fixing device 5.
After the leading end of the sheet 3 is nipped by the fixing device 5, the suction means including the suction fan 43 is shut off so as not to apply a load to the sheet 3 and the toner image transferred onto the sheet 3. Then, the suction of the sheet 3 is stopped, the sheet 3 is fed by the conveying force of the fixing device 5, and after the rear end of the sheet 3 has left the conveying belt 41, the suction by the suction fan 43 is performed again to remove the next sheet 3. It is designed to be sucked and transported.

As described above, in the sheet conveying device 4 according to the above-described embodiment, as shown in FIG. 1, the shape of the sheet conveying surface is formed in an arc shape in a direction orthogonal to the conveying direction of the sheet 3, and The sheet 3 is sucked and adsorbed along, and as shown in FIG. 4, an arc-shaped curl is forcibly added to the sheet 3 so that the sheet 3 can be uniformly formed regardless of the thickness, type, and curl shape of the sheet 3. It is possible to convey the sheet 3 having an upward curl generated at the time of double-sided printing.
Even if the suction force is partially reduced when the sheet 3 is conveyed to the fixing device 5 or the like, as shown in FIG. 5, the sheet 3 to which the upward arc-shaped curl is forcibly added is stiffened (stiffness). The conveyance posture of the sheet 3 is stable, and there is no occurrence of broken ears, jam, and paper wrinkles. Further, since the suction force at both ends in the axial direction is set higher than that at the center, even if a sheet 3 or a thick paper having a large curl is sent, it can be stably conveyed along an arc. Further, when the sheet enters the fixing device 5, the suction fan 43 is shut off and the sheet 3 is fed by the conveying force of the fixing device 5, so that the transferred toner image and the sheet 3 are not added. , Sheet 3 can be conveyed.

Further, in the sheet conveying device 3, the sheet 3 is forcibly added with an arc-shaped curl.
Is conveyed to the fixing device 5, even if the leading end of the sheet 3 leaves the sheet conveying device 3 and no longer receives the suction force, the leading end of the sheet 3 curled upward in an arc shape (rigidity). Is transported to the nip portion of the fixing device 5 while being slightly pressed by a transport guide disposed between the sheet transporting device 3 and the fixing device 5.
For this reason, the leading end of the sheet 3 is deformed flat by the conveyance guide immediately before entering the fixing device 5.
As described above, the conveying posture of the sheet 3 is stabilized,
Jams and paper wrinkles can be reliably prevented from occurring.

Second Embodiment FIG. 6 shows a second embodiment of the present invention. The same parts as those of the above-described embodiment are denoted by the same reference numerals, and will be described. The fixing device 5 is not a fuser of a belt nip type, but a fixing device including a roll pair of a pressure roll and a heat roll. As described above, in the image forming apparatus having the fixing device 5 using the roll pair, the fixing device 5 from the sheet conveying device 4 is used.
It is good to set the angle of entry into the vehicle so that it is slightly upward.

Other configurations and operations are the same as those of the first embodiment, and therefore, description thereof will be omitted.

Third Embodiment FIG. 7 shows a third embodiment of the present invention. The same parts as those of the above-described embodiment are denoted by the same reference numerals, and will be described. Since the arc shape of the conveying belt and the conveying guide does not need to be constant, in the conveying direction, the conveying guide and the conveying belt are arranged so that the diameter of the arc becomes smaller toward the fixing device, and as the sheet is conveyed. Are arranged so as to gradually form an arc shape.

In such a case, even if the sheet 3 is a cardboard or a sheet curled upward largely, it can be surely curled in an upward arc.

The other constructions and operations are the same as those of the first embodiment, and a description thereof will be omitted.

Fourth Embodiment FIG. 8 shows a fourth embodiment of the present invention. The same parts as those of the above-described embodiment are denoted by the same reference numerals, and will be described. The transport belt 41 other than the central portion is disposed so as to be inclined, and the transport surface of the sheet transport device 4 is configured to be closer to an arc.

The conveying surface of the sheet conveying device 4 is shown in FIG.
As shown in (1), the conveyance belt of the sheet conveyance device 4 may be configured to be closer to an arc by supporting the conveyance belt other than the center portion with a roller 60 formed in an arc.

The other configuration and operation are the same as those of the first embodiment, and the description thereof will be omitted.

In the above-described embodiment, the suction means may be electrostatic suction instead of suction suction by a suction fan, and may be variable depending on the position and the state of the sheet by the suction force variable means.

[0041]

According to the present invention, the sheet conveying surface is formed into an arc shape in a direction perpendicular to the sheet conveying direction, and the sheet is sucked and adsorbed along the shape to force the sheet. By applying an arc-shaped curl to a sheet, it is possible to convey the sheet uniformly without depending on the thickness, type, and curl shape of the paper, and it has an upward curl that occurs during double-sided printing. For the sheet,
Even when the suction force is partially reduced when the sheet is conveyed to the fixing device or the like, the sheet conveyance posture can be stabilized by stiffening the sheet, and there is no occurrence of edge breaks, jams, and paper wrinkles. . Further, by setting the suction force at both ends in the axial direction higher than that at the center, even if a sheet or cardboard having a large curl is sent, it can be stably conveyed along the arc. Further, when the sheet enters the fixing device, the suction unit is shut off, and the sheet is conveyed by the conveying force of the fixing device.
The sheet can be conveyed without applying a load to the transferred toner image and sheet.

[Brief description of the drawings]

FIG. 1 is a front view illustrating a sheet conveying apparatus according to a first embodiment of the present invention;

FIG. 2 is a configuration diagram illustrating an embodiment of an image forming apparatus to which the sheet conveying device according to the present invention is applied.

FIG. 3 is a partially broken plan view showing the sheet conveying apparatus according to the first embodiment of the present invention.

FIG. 4 is a perspective view showing Embodiment 1 of the sheet conveying apparatus according to the present invention.

FIG. 5 is a perspective view illustrating a sheet conveying state according to the first embodiment of the sheet conveying apparatus according to the present invention.

FIG. 6 is a configuration diagram showing another embodiment of the image forming apparatus to which the sheet conveying device according to the present invention is applied.

FIG. 7 is a perspective view illustrating a sheet conveying apparatus according to a second embodiment of the present invention.

FIG. 8 is a front view illustrating a sheet conveying apparatus according to a third embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a sheet conveying apparatus according to a fourth embodiment of the present invention.

[Explanation of symbols]

4 sheet conveyance device, 41 conveyance belt, 42 conveyance guide, 43 suction fan, 44 idler, 45 drive roll, 46 suction hole, 47 motor, 48 suction hole, 49 shielding plate, 49a suction opening.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Norio Ogawara 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Masataka Konishi 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd.

Claims (3)

[Claims] An image forming apparatus is provided on a path for conveying a sheet from a transfer unit to a fixing unit of an image forming apparatus, and includes a suction conveyance unit for conveying the toner image-transferred sheet while suctioning the sheet. 2. A sheet conveying device according to claim 1, wherein the surface of the sheet conveying device on which the sheet is adsorbed is curved upward in a direction perpendicular to the sheet conveying direction. 2. The sheet conveyance device according to claim 1, wherein the suction conveyance means sets the sheet suction force at both ends in a direction orthogonal to the sheet conveyance direction so as to be stronger than that at a center portion. apparatus. 3. After the leading end of the sheet conveyed by the suction conveyance unit is nipped by a fixing device disposed in a fixing unit of the image forming apparatus, the suction unit of the suction conveyance unit is shut off to adsorb the sheet. The sheet according to claim 1, wherein the sheet is stopped, the sheet is fed by the conveying force of the fixing device, and the next sheet is conveyed after the trailing end of the sheet has left the suction conveying unit and suction is performed again. Transport device.