JP3618994B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, and more particularly to a sheet feeding unit that is provided in an image forming apparatus and separates a plurality of stacked sheets one by one and conveys them to an image forming unit.
[0002]
[Prior art]
A conventional image forming apparatus such as a copying machine includes a sheet feeding unit that separates a plurality of stacked sheets one by one and conveys them to an image forming unit. FIG. 3 is a diagram showing the configuration of the sheet feeding unit in such a conventional image forming apparatus. The uppermost sheet of the sheet bundle P stacked on the sheet storage unit 30 by the feeding roller 31 serving as the feeding unit. After feeding out P1 (hereinafter referred to as the uppermost sheet), the uppermost sheet P1 is separated one by one by the conveying roller 32 and the separating roller 33 of the separating / conveying means 35 and conveyed to the image forming unit. ing.
[0003]
Here, the transport roller 32 is rotatably supported, and the separation roller 33 is rotatably supported by a support member 27 as shown in FIG. The support member 27 is rotatably held by a rotation shaft 27a and is urged in a direction in which the separation roller 33 is pressed against the conveying roller 32 by a pressure spring 28 as an urging means.
[0004]
Then, the uppermost sheet P1 fed by the feeding roller 31 is in a nip portion between the conveyance roller 32 and a separation roller 33 provided to the conveyance roller 32 through a pressure spring 28 and a support member 27 so as to be able to contact and separate. When entering, the separation roller 33 moves in a direction away from the conveying roller 32 as shown in FIG. 3 while resisting the spring force of the pressure spring 28 by the pressing force from the uppermost sheet P1. As a result, the uppermost sheet P1 can pass through the nip portion N, and when another sheet has been fed in a multiple manner, the uppermost sheet P1 and the other sheet can be separated.
[0005]
Incidentally, the uppermost sheet P1 fed by the feeding roller 31 is guided to the conveying roller 32 and the separation roller 33 on the downstream side in the conveying direction of the sheet storage unit 30, that is, between the feeding roller 31 and the separation / conveying unit 35. In addition, an upper guide 36 and a lower guide 34 are provided as a pair of upper and lower guide means for forming a guide passage R for guiding the separated sheet P1 to the image forming unit.
[0006]
In the figure, t ₁ is the gap between the conveying roller 32 and the lower guide 34, even when the sheet is fed in a bundle by the feeding roller 31, when the thickness of the sheet bundle is t ₁ following When the separation roller 33 moves below the lower guide 34, the uppermost sheet P1 can be separated.
[0007]
[Problems to be solved by the invention]
However, in such a conventional image forming apparatus, when a sheet bundle having a bundle thickness t _P larger than the gap t ₁ between the conveying roller 32 and the lower guide 34 is fed as shown in FIG. Even if the sheet is retracted from the lower guide 34, the sheet bundle becomes wedge-shaped and the sheet conveyance resistance increases, so that the sheet cannot be separated and conveyed by the conveyance roller 32 and the separation roller 33.
[0008]
Here, for example, when the position of the lower guide 34 is set so that the value of the gap t ₁ is sufficiently larger than the assumed maximum sheet bundle thickness t _P , the fed uppermost sheet P 1 is conveyed to the transport roller. 32 and the separation roller 33 cannot be surely guided, and problems such as breakage of the tip occur.
[0009]
Therefore, conventionally, a gap t ₁ was mounted to adjust the position of the lower guide 34 to a predetermined value, this adjustment must be performed in accordance with the sheet to be conveyed, time-consuming that problem There was a point.
[0010]
Accordingly, the present invention has been made to solve such a conventional problem, and provides an image forming apparatus capable of reliably separating and conveying a sheet without adjusting a guide unit. With the goal.
[0011]
[Means for Solving the Problems]
The present invention provides an image forming apparatus including a sheet feeding unit that feeds the sheets stacked and stored in the sheet storage unit by the feeding unit and then separates the sheets one by one and conveys them to the image forming unit. A separation roller that is arranged on the downstream side in the conveyance direction and that separates and conveys the fed sheets one by one and a separation / conveyance unit that is capable of contacting and separating the conveyance rollers, and the separation and conveyance of the fed sheets. A pair of upper and lower guide means forming a guide path for guiding the conveying means, and one of the separation roller or the conveying roller is urged to be brought into pressure contact with the other roller, and the sheet bundle is fed by the feeding means. In this case, an urging unit that retracts the one roller from the guide path by a distance corresponding to a sheet bundle thickness by a pressing force from the sheet bundle; The pair of upper and lower guide means are provided on the side of the separation roller and the conveyance roller and from the upstream side to the downstream side of the separation roller and the conveyance roller, and the guide means on the side where the one roller is retracted A part is composed of a flexible member.
[0012]
Further, as in the present invention, the sheets fed by the feeding means are arranged one by one by the separating / conveying means that is arranged on the downstream side in the conveying direction of the sheet storing means and that can be contacted and separated. While separating and transporting, the guided sheet formed by the pair of upper and lower guide means guides the fed sheet to the separation / conveyance means and guides the sheet separated by the separation / conveyance means to the image forming unit. To. Further, the urging means urges one of the separation roller or the conveying roller to be in pressure contact with the other roller, and when the sheet bundle is fed out by the feeding means, the pressing force from the sheet bundle causes The rollers are retracted from the guide path by a distance corresponding to the sheet bundle thickness. When a sheet bundle having a bundle thickness larger than the retraction distance range of one roller is fed out by configuring a part of the guide means on the side where the one roller is retracted with a flexible member, The flexible member is bent by the pressing force from the sheet bundle, and the sheet bundle is guided to the separating / conveying means.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention are described below.
[0014]
FIG. 1 is a diagram showing a configuration of a copying machine as an example of an image forming apparatus according to an embodiment of the present invention.
[0015]
In the figure, 1 is a copying machine, 3 is a platen glass disposed on the upper surface of a copying machine main body (hereinafter referred to as a main body) 2, 4 is an automatic document feeder installed in the main body 2, and 5 is automatic document feeding. An optical system that scans a document (not shown) fed onto the platen glass by the apparatus 4, 6 is an image forming unit, and 8 is a photosensitive drum that is rotatably supported by a drum unit 7 of the image forming unit 6.
[0016]
Further, 9a, 9b, 9c, 9d are first to fourth sheet storage units capable of storing a large number of sheets, and 10a, 10b, 10c, 10d are first to fourth sheet feeding units provided inside the main body. , 12 is a pre-registration unit, 13 is a registration roller pair, 14 is a pre-transfer guide, 15 is a transfer / separation charger, 16 is a conveying member, 17 is a fixing unit, and 18 is a paper discharge unit.
[0017]
Next, an image forming operation of the copying machine having such a configuration will be described.
[0018]
When a document is automatically fed to the platen glass 3 on the apparatus main body 2 by the automatic document feeder 4, the document is scanned by the optical system 5 and is rotatably supported on the drum unit 7 of the image forming unit 6. A latent image is formed on the photosensitive drum 8. Then, a toner image is formed on the photosensitive drum 8 by developing the latent image.
[0019]
On the other hand, the sheets stored in the first to fourth storage portions 9a, 9b, 9c, and 9d are fed to the first to fourth feeding portions 10a, 10b, 10c, and 10d, respectively, as shown in FIG. After being fed out by the roller 31, the uppermost sheet P1 is separated and fed one by one by the separation roller 33 and the conveying roller 32. After this, the separated and fed sheet P1 passes through the vertical path portion 11 and is conveyed to the pre-registration unit 12, and after being skewed by the registration roller pair 13 of the pre-registration unit 12, the pre-transfer guide. 14 is introduced into the image forming unit 6.
[0020]
In the image forming section 6, the toner image formed on the photosensitive drum 8 is transferred onto the sheet P 1 by the transfer / separation charger 15 provided in the pre-registration unit 12. Thereafter, the sheet P1 separated from the photosensitive drum 8 is conveyed to the fixing unit 17 by the conveying unit 16, and the toner image on the sheet P1 is fixed and discharged from the paper discharge unit 18 to the outside of the apparatus.
[0021]
In FIG. 2, reference numeral 40 denotes a lower guide, and a portion facing the conveyance roller 32 which is a part of the lower guide 40 is configured by a sheet-like flexible member 41. In the present embodiment, the flexible member 41 is fixed to the front lower guide 40 a that constitutes the front portion of the lower guide 40.
[0022]
By configuring the flexible member 41 to face the conveying roller 32 of the lower guide 40 in this way, the sheet bundle having a thick bundle thickness t _P than the gap t ₁ between the conveying roller 32 and the lower guide 40 Even when the sheet is fed by the feeding roller 31, the flexible member 41 bends, so that the sheet can be separated and conveyed without giving resistance to the sheet.
[0023]
Next, the sheet separating and conveying operation of each feeding unit configured as described above will be described.
[0024]
When the feeding roller 31 is rotated by a rotation driving means (not shown), the uppermost sheet P1 is fed by the feeding roller 31 and then guided to the conveying roller 32 and the separation roller 33 by the lower guide 40 and the upper guide 36 . Here, when the fed sheet P1 is one sheet, it is conveyed as it is by the conveying roller 32 and the separation roller 33, and when it is a plurality of sheets, only one sheet is separated and conveyed by the conveying roller 32 and the separation roller 33.
[0025]
On the other hand, when a sheet bundle having a bundle thickness t _P thicker than the gap t ₁ between the conveying roller 32 and the lower guide 40 is fed out by the feeding roller 31 as shown in the figure, the flexible member 41 of the lower guide 40 is The sheet is bent and retracted, so that the sheet can be separated and conveyed without giving resistance to the conveyance of the sheet.
[0026]
In the above description, the separation roller 33 is in pressure contact with the conveyance roller 32. Conversely, the portion of the upper guide 36 that faces the separation roller 33 in the configuration in which the conveyance roller 32 is in pressure contact with the separation roller 33. The same effect can be obtained even if the sheet is formed of a sheet-like flexible member.
[0027]
In the above description, the upper separation system that separates and conveys the stacked sheets one by one from the top is described, but the lower separation that separates and conveys the stacked sheets one by one from the bottom. The same effect can be obtained even if the present invention is implemented in a system apparatus.
[0028]
【The invention's effect】
As described above, according to the present invention, a part of one guide means of the pair of upper and lower guide means for guiding the sheet fed by the feeding means to the separating / conveying means is constituted by a flexible member. When a sheet bundle having a bundle thickness larger than the retraction distance range of the roller is fed out, the flexible member of one guide means is bent by the pressing force from the sheet bundle to separate and convey the sheet bundle Can be guided to. As a result, it is possible to reliably separate and convey the sheet without adjusting the guide means and without being affected by poor adjustment or accuracy of parts.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a copying machine as an example of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is an enlarged view of a main part of each feeding unit of the copying machine.
FIG. 3 is an enlarged view of a main part of each feeding unit of a conventional copying machine.
FIG. 4 is a diagram illustrating a structure of a conventional feeding unit.
[Tax of the sign]
1 Copier 2 Copier body 9a, 9b, 9c, 9d
1st-4th sheet storage part 10a, 10b, 10c, 10d
First to fourth sheet feeding unit 28 Pressure spring 30 Sheet storing means 31 Feeding roller 32 Conveying roller 33 Separating rollers 34, 40 Lower guide 35 Separating / conveying means 36 Upper guide 41 Flexible member P Sheet bundle R Guide path t ₁ Gap between transport roller and lower guide t _P sheet bundle thickness

Claims (2)

In an image forming apparatus including a sheet feeding unit that feeds sheets stacked and stored in a sheet storage unit by a feeding unit and then separates the sheets one by one and conveys them to an image forming unit.
A separating / conveying means that is arranged downstream of the sheet storing means in the conveying direction, and that separates and conveys the fed sheets one by one and a conveying roller so as to be able to contact and separate;
A pair of upper and lower guide means forming a guide passage for guiding the fed sheet to the separating / conveying means;
The one roller of the separation roller or the conveying roller is urged to be brought into pressure contact with the other roller, and when the sheet bundle is fed out by the feeding means, the one roller is pressed by the pressing force from the sheet bundle. Urging means adapted to retract from the guide passage by a distance corresponding to the sheet bundle thickness;
With
The pair of upper and lower guide means are provided on the side of the separation roller and the conveyance roller and from the upstream side to the downstream side of the separation roller and the conveyance roller, and a part of the guide means on the side where the one roller is retracted An image forming apparatus comprising: a flexible member. When a sheet bundle having a bundle thickness larger than the retraction distance range of the one roller is fed out, the flexible member is bent by a pressing force from the sheet bundle to separate and convey the sheet bundle. Claims are guided to the means. 1 The image forming apparatus described.

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