JPH08217288A - Sheet conveying device and image forming device - Google Patents

Abstract

PURPOSE: To decrease the difference of conveying resistance to be generated by the size of the sheets, by providing a first guide member for sucking and guiding a sheet by static electric force and a second guide member arranged on the first guide member into a comb shape, and providing many openings on both sides in the sheet width direction of the first guide member. CONSTITUTION: Ribs 3g for holding the gap between them and a sheet 2 are provided into a comb shape on a conveyance guide plate 3e for conveying and guiding the sheet 2 on which a toner image is transferred. A plurality of round holes 3e2 are approximately symmetrically provided on the outer side from the center part in the sheet width direction on the conveyance guide plate 3e. Since the conveyance guide plate 3e is grounded to a frame 13 of a device main body 13 and the electric potential is 0V, the potential difference is generated between it and the charged sheet 2, the sheet 2 is to be attracted to the conveyance guide plate 3e, however, the wide sheet 2 is held by the constant attraction force and conveyed to the next process by the presence of the round holes 3e2.

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 for electrostatically adsorbing and conveying a sheet, and more particularly to a sheet conveying device used in an image forming apparatus such as a laser beam printer, a copying machine, a facsimile machine or the like.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a laser beam printer provided with a sheet conveying device for electrostatically adsorbing and conveying a sheet, a conveying portion for guiding and conveying a sheet on which an image is transferred to a fixing portion is used. , Was configured as follows.

FIG. 4 is a schematic perspective view showing a schematic structure in the vicinity of the sheet conveying portion in the conventional image forming apparatus. In the figure, 52 is a registration unit that conveys the sheet 51 at a predetermined timing after adjusting the registration of the sheet 51, and 53 is integrally provided with a photosensitive drum 53a and process means (not shown) that acts on the photosensitive drum 53a. 53a is a process unit for forming an image on the sheet 51 by electrophotography, 54 is a transfer device for transferring the image on the drum 53a in the process unit 53 onto the sheet 51, and 55 is the transfer image on the sheet 51 fixed onto the sheet 51. The fixing device 56 is a conveying device for guiding and conveying the sheet 51 on which the image is transferred by the transfer device 54 to the fixing device 55.

The transport device 56 has a sheet metal (conductor) 57 partially grounded to the main body of the image forming apparatus, and a predetermined amount of space between the sheet 51 and the sheet metal 57 arranged in a comb-like shape on the sheet metal 57. It is composed of a plurality of ribs (insulators) 58 for holding the gap.

A sheet conveying operation in the above conventional apparatus will be described. First, one sheet 51 separated and fed by a sheet feeding unit (not shown) has its leading end formed a predetermined loop by the nip portion of the roller pair of the registration unit 52 to perform registration adjustment, and at a predetermined timing. It is conveyed to the transfer device 54. At the same time, an image is formed on the drum surface in the process unit 53 by a well-known electrophotographic technique. Then, the transfer device 54 sequentially transfers the toner image on the drum surface in the process unit 53 onto the sheet 51 by electrostatic force. At this time, the sheet 51 is a transfer device.
It is charged by the transfer voltage of 54 and is sent to the carrying device 56 while holding the toner image. The sheet metal 57 in the transfer device 56
Has a potential of 0 V because it is grounded to the main body of the image forming apparatus. Therefore, the sheet 51 charged by the transfer device 54 is subjected to the electrostatic force due to the potential difference between the sheet 51 and the sheet metal 57.
Attracted to 57. However, the sheet 51 is conveyed to the fixing device 55 while receiving a suction force by the sheet metal 57 because a predetermined amount of gap is held between the sheet 51 and the sheet metal 57 by the plurality of ribs 58. Since the sheet 51 is conveyed while receiving the suction force by the sheet metal 57, the sheet 51 is conveyed without being exposed and the toner image on the sheet 51 is not disturbed.

[0006]

However, recently, a wide variety of sheets tend to be used in image forming apparatuses, and in the above-described conventional sheet conveying apparatus, in the sheet width direction orthogonal to the sheet conveying direction, As the sheet size increases (the sheet width increases), the sheet resistance increases due to the increase in the sheet area. Conversely, when the sheet size decreases, the sheet area decreases. However, there is a problem that the transport resistance due to the above-mentioned suction force is reduced by that much, that is, the suction force is changed depending on the size of the sheet, resulting in a difference in transport resistance.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to make it possible to carry out stable sheet conveyance by reducing the difference in conveyance resistance depending on the size of the sheet. It is intended to provide a carrier.

[0008]

A typical constitution of the present invention for achieving the above object is to guide a sheet while attracting the sheet by electrostatic force in a sheet conveying apparatus that conveys the sheet while attracting the sheet by electrostatic force. A first guide member, and a second guide member arranged in a comb-like shape on the first guide member to maintain a predetermined distance between the first guide member and the sheet, It is characterized in that a large number of openings are provided on both sides of the guide member in the sheet width direction orthogonal to the sheet conveying direction.

[0009]

In the above structure, a large number of openings are provided on both sides in the sheet width direction orthogonal to the sheet conveying direction of the first guide member that guides the sheet while electrostatically attracting it.
Since the area of the first guide member is adjusted, even if the size of the sheet is changed, the difference in electrostatic force for attracting the sheet can be suppressed to be small, and the difference in conveyance resistance due to the size of the sheet can be suppressed to be small. it can.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the sheet conveying apparatus to which the present invention is applied will be concretely described with reference to the drawings. In the following embodiments, an image forming apparatus provided with the above-described sheet conveying device will be described as an example.

First Embodiment First, an image forming apparatus equipped with a sheet conveying device according to the first embodiment will be described with reference to FIGS. 1 and 2. 1 is a schematic configuration diagram of a sheet conveying device according to the present invention, and FIG. 2 is a schematic configuration explanatory diagram of an image forming apparatus provided with the sheet conveying device according to the present invention.

As an order of description, the overall structure of an image forming apparatus having a sheet conveying device will be described first, and then the sheet conveying device which is a feature of the present invention will be described.

This electrophotographic image forming apparatus (laser beam printer) A, as shown in FIG. 2, irradiates a drum-shaped electrophotographic photosensitive member with information light based on image information from an optical system 1 to form the photosensitive member. A latent image is formed on the toner image, and the latent image is developed to form a toner image. Then, in synchronism with the formation of the toner image, the sheet 2 is conveyed from the cassette 3a by a conveying means 3 including a pickup roller 3b, a pair of registration rollers 3c1 and 3c2, and the toner image formed on the electrophotographic photosensitive member is transferred. A voltage is applied to the transfer roller 4 as a unit to transfer the sheet 2 to the sheet 2, and the sheet 2 is conveyed to the fixing unit 5 by the intermediate conveyance roller 3d and the conveyance guide plate 3e. The fixing unit 5 includes a driving roller 5a and a fixing roller 5c having a heater 5b built therein, and applies heat and pressure to the passing sheet 2 to fix the transferred toner image.
Then, the sheet 2 is conveyed by the discharge roller pair 3f, and is discharged to the discharge section 6 through the reverse conveyance path.

On the other hand, the process cartridge B comprises an electrophotographic photosensitive member and at least one process means. Here, as the process means, for example, a charging means for charging the electrophotographic photoreceptor, a developing means for developing the latent image formed on the electrophotographic photoreceptor, and a cleaning means for cleaning the toner remaining on the surface of the electrophotographic photoreceptor Etc. The process cartridge B of this embodiment is
As shown in FIG. 2, a photosensitive drum 7 having a photosensitive layer which is an electrophotographic photosensitive member is rotated, and its surface is uniformly charged by applying a voltage to a charging roller 8 which is a charging means. Information light from the photosensitive drum 7 is exposed to the photosensitive drum 7 through the exposure unit 9 to form a latent image, and the developing device 10 transfers toner to the photosensitive drum 7 according to the latent image to form a toner image. The latent image is visualized (developed). Then, a voltage having a polarity opposite to that of the toner image is applied to the transfer roller 4 to transfer the toner image onto the sheet 2, and thereafter, the toner remaining on the photosensitive drum 7 is removed by the cleaning means 11. Each component such as the photosensitive drum 7 is housed in a housing 12 to form a cartridge, which is detachably attached to a cartridge attaching means provided in the apparatus main body 13.

Next, the sheet conveying apparatus (conveying means 3) to which the present invention is applied will be specifically described with reference to the drawings. In FIG. 1, reference numeral 3e is a conveyance guide plate for guiding the sheet 2 on which the toner image has been transferred to the next step, and ribs 3g for maintaining a predetermined gap between the sheet 2 and the sheet 2 are provided in a comb-like shape. The notch 3e1 is provided. The transport guide plate 3e is a member having conductivity, and a sheet metal is used in this embodiment. A part of the transport guide plate 3e is fixed to the frame 13a of the apparatus main body 13 by screws (not shown).
It is fixed to and is electrically connected to the device body 13. The rib 3g is provided on the sheet 2 similarly to the conveyance guide plate 3e.
Is a guide rib for guiding the
And a conveyance guide plate 3e have a height for maintaining a predetermined gap. The rib 3g is an electrically insulating member, and the rib in this embodiment is made of ABS resin. Further, the conveyance guide plate 3e is provided with a plurality of round holes 3e2, which are substantially symmetrical to the outside of the center in the sheet width direction orthogonal to the sheet conveyance direction. Further, the ribs 3g provided in the conveyance guide plate 3e in the shape of comb blades are arranged such that the pitch between the ribs becomes narrower toward the outside of the center in the sheet width direction orthogonal to the sheet conveyance direction. .

In FIG. 1, 3h is a pre-conveying guide for guiding the sheet 2 onto the transfer roller 4, and 3i is an entrance guide for guiding the sheet 2 to the fixing means 5.

In the sheet conveying apparatus having the above-described structure, when one sheet 2 is separated and fed, the leading end thereof strikes the nip portion of the registration roller pair 3c1 and 3c2 to form a predetermined loop to correct skew feeding. Is done. After that, the pair of registration rollers 3c1 and 3c2 are rotationally driven at a predetermined timing, and the sheet 2 is fed onto the transfer roller 4 (between the photosensitive drum 7). At the same time, a toner image is formed on the photosensitive drum 7 in the process cartridge B shown in FIG. 2 by the electrophotographic process described above. When the sheet 2 passes between the nip between the photosensitive drum 7 and the transfer roller 4, a voltage is applied to the transfer roller 4 and the toner images on the photosensitive drum 7 are sequentially transferred onto the sheet 2. At this time, the sheet 2 is charged by the voltage applied to the transfer roller 4. Then, the transferred sheet 2 is guided and conveyed to the fixing means 5 by a conveyance guide plate 3e provided with ribs 3g having a comb blade shape and a large number of round holes 3e2.

Since the transport guide plate 3e is grounded to the frame 13a of the apparatus main body 13 and has a potential of 0V, a potential difference is generated between the transport guide plate 3e and the charged sheet 2 after transfer, and the sheet 2 is An attraction force is generated to try to attract the carrier guide plate 3e. However, the ribs 3 for maintaining a predetermined gap with the sheet 2 are provided on the transport guide plate 3e.
Since a large number of g are provided, the sheet 2 having a narrow width is stably conveyed in the sheet width direction to the fixing unit 5 in the next step while being held with a constant suction force. Then, the fixing unit 5 fixes the toner image on the sheet 2.

When the sheet 2 wider than the above-mentioned sheet is conveyed to the conveying guide plate 3e, the central portion of the sheet is conveyed in a stable state while being held by the same suction force as that of the narrow sheet. . Further, since the conveying guide plate 3e is provided with a large number of round holes 3e2 toward the outer side in the sheet width direction and the area is smaller, the above-mentioned suction force is reduced, and the ribs 3g on the outer side in the sheet width direction are ribs. Since the pitch between them is narrow, the suction force is further reduced. Therefore, compared to a narrow sheet, a wide sheet can suppress the increase in suction force to be smaller than the ratio of the wider width (the larger size), that is, the sheet size It is possible to suppress the change in the adsorption force due to. Therefore, it is possible to suppress an increase in the conveyance resistance due to the widening of the sheet, and it is possible to prevent a jam due to a poor conveyance force of the sheet and a conveyance failure due to only the stiffness of the sheet.

In this embodiment, the round hole 3e2 provided in the transport guide plate 3e is not provided near the fixing means 5. This is because the sheet 2 is the entrance guide 3i of the fixing means 5.
This is because the leading edge of the sheet can stably enter when entering the sheet, and the state of the sheet 2 in the vicinity of the fixing unit 5 is stabilized by the attraction force due to the potential difference.

[Second Embodiment] Next, a second embodiment of the sheet conveying apparatus to which the present invention is applied will be described with reference to the drawings. FIG. 3 is a schematic configuration diagram of the sheet conveying apparatus according to the present embodiment.

In addition to the structure of the above-described embodiment, the sheet conveying apparatus according to this embodiment is configured so that the height of the guide portion of the rib 3g has a height difference in the sheet width direction orthogonal to the sheet conveying direction. are doing. Specifically, rib 3
The rib 3g2 is configured so that the guide portion is higher than the g1 by about 1 mm, and the ribs 3g2 are alternately arranged in a comb-like shape on the transport guide plate 3e.

In the sheet conveying apparatus having the above-mentioned structure, the sheet 2 transferred in the same manner as in the above-mentioned embodiment is electrostatically transferred to the conveying guide plate 3e in the process of being guided to the entrance guide 3i of the fixing means 5 in the next step. Guided while being adsorbed. At this time, since the ribs 3g1 and 3g2 have the above-mentioned height difference, the sheet 2 is guided while being adsorbed in a wavy shape in the sheet width direction following the height difference between the ribs. As a result, the sheet 2 has a stronger waist than its own in the sheet conveying direction. Therefore, according to the present embodiment, even a sheet having a weak waist (thinness) can be stably conveyed. In addition, it is possible to prevent a conveyance failure due to only a wide sheet being stiff.

In the above-described embodiment, the laser beam printer has been described as an example of the image forming apparatus provided with the sheet conveying apparatus to which the present invention is applied, but the present invention is not limited to this. For example, the same effect can be obtained by applying the present invention to a sheet conveying system of a copying machine or a facsimile machine.

[0025]

As described above, according to the present invention,
Since the area of the first guide member is adjusted by providing a large number of openings on both sides in the sheet width direction orthogonal to the sheet conveying direction of the first guide member that guides the sheet while electrostatically adsorbing the sheet, Even if the size is changed, the difference in electrostatic force for attracting the sheet can be suppressed to a small value, and the difference in conveyance resistance due to the size of the sheet can be suppressed to a small value. Therefore, stable sheet conveyance can be performed.

Further, since the height of the guide portion of the second guide member has a height difference in the sheet width direction orthogonal to the sheet conveying direction, the guided sheet is corrugated in the sheet conveying direction. Therefore, it is possible to obtain a waist stronger than that of the user's own, it is possible to prevent a conveyance failure due to only a thin sheet being bent, and it is possible to carry the sheet in a stable state.

Further, the second guide members are arranged such that the pitch between the guide members becomes narrower toward the outside in the sheet width direction orthogonal to the sheet conveying direction. It is possible to reduce the suction force of the sheet toward the outside, and to suppress the change in the suction force due to the size of the sheet. Therefore, even if the size of the sheet changes, the difference in conveyance resistance can be suppressed to a small value, and stable sheet conveyance can be performed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a sheet conveying apparatus according to a first embodiment.

FIG. 2 is a schematic diagram illustrating a configuration of an image forming apparatus including the sheet conveying device.

FIG. 3 is a schematic configuration diagram of a sheet conveying device according to a second embodiment.

FIG. 4 is an explanatory diagram of a conventional sheet conveying device.

[Explanation of symbols]

 A ... Image forming apparatus B ... Process cartridge 1 ... Optical system 2 ... Sheet 3 ... Conveying means 3a ... Cassette 3b ... Pickup rollers 3c1, 3c2 ... Registration roller pair 3d ... Intermediate conveying roller 3e ... Conveyance guide plate 3e1 ... Notch 3e2 ... Round Hole 3f ... Ejection roller pair 3g, 3g1, 3g2 ... Rib 3h ... Pre-conveying guide 3i ... Entrance guide 4 ... Transfer roller 5 ... Fixing means 5a ... Driving roller 5b ... Heater 5c ... Fixing roller 6 ... Ejection section 7 ... Photosensitive drum 8 ... Charging roller 9 ... Exposure part 10 ... Developing means 11 ... Cleaning means 12 ... Housing 13 ... Device body 13a ... Frame

Claims (5)

[Claims] 1. A sheet transporting device for transporting a sheet while attracting the sheet by electrostatic force, wherein a first guide member for guiding the sheet while attracting the sheet by electrostatic force, and a predetermined interval between the first guide member and the sheet. A second guide member arranged in a comb-like shape on the first guide member to hold the sheet, and a large number of openings are provided on both sides in the sheet width direction orthogonal to the sheet conveying direction of the first guide member. A sheet conveying device characterized in that 2. The first guide member is a conductor configured to have a potential difference from the sheet, and the second guide member is an insulator that maintains a predetermined distance between the sheet and the conductor. The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a sheet conveying apparatus. 3. The second guide member according to claim 1, wherein a height of a guide portion of the second guide member has a height difference in a sheet width direction orthogonal to a sheet conveying direction. The sheet conveying device described. 4. The second guide member is arranged such that the arrangement position of the second guide member becomes narrower toward the outer side in the sheet width direction orthogonal to the sheet conveying direction. Alternatively, the sheet conveying device according to claim 2. 5. A sheet conveying device that conveys a sheet while attracting the sheet by electrostatic force, and a first guide member that guides the sheet while attracting the sheet by electrostatic force, and a predetermined gap between the first guide member and the sheet. A second guide member arranged in a comb-like shape on the first guide member in order to maintain the distance between the first guide member and a large number of openings on both sides in the sheet width direction orthogonal to the sheet conveying direction of the first guide member. An image forming apparatus having a sheet conveying device provided with.