JP2941360B2 - Paper feeder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding device, and more particularly, to a sheet feeding device for conveying a sheet to an image forming unit of an image forming apparatus.

[Conventional technology]

2. Description of the Related Art An image forming apparatus, for example, a copying machine is provided with a paper feeding device for transporting sheets stored in a paper feeding cassette or the like to an image forming unit including a photosensitive drum and a developing device. The paper feeding device is provided between a paper feeding cassette or the like and the image forming unit, and has a conveying roller for conveying the paper, a registration roller for feeding the paper to the image forming unit in synchronization with the image forming operation, and A guide plate provided between the transport roller and the registration roller;

In such a sheet feeding device, a loop is formed by bending the sheet between the registration roller and the conveyance roller in order to correct a so-called oblique sheet feeding in which the sheet is fed while being inclined with respect to the conveyance direction. I am trying to do it. By forming this loop portion, the entire leading edge of the sheet uniformly contacts the registration roller due to the stiffness of the sheet, and the oblique feeding is corrected. Further, the leading end of the sheet is sufficiently engaged with the registration roller, and the sheet is conveyed at an accurate timing.

As a conventional example of a sheet feeding device for forming a loop portion on a sheet, there is a device disclosed in Japanese Patent Application Laid-Open No. 63-154553. In the device disclosed in this publication, an elastic member is attached to a guide plate. The elastic member prevents the paper from being broken even when a loop is formed on a relatively thick paper such as a postcard.

[Problems to be solved by the invention]

The paper feeding device disclosed in the above publication can prevent the paper from being broken when the paper is thick, but when the paper is thin like plain paper, the loop amount of the paper is absorbed by the elastic member. As a result, the force for pushing the leading edge of the sheet toward the registration roller is weakened. Therefore, the leading end of the sheet cannot be sufficiently engaged with the registration roller, and the correction of the oblique sheet feeding cannot be sufficiently performed.

Therefore, it is conceivable to increase the pressing force on the registration roller by increasing the loop amount. However, when the loop amount is increased, when a thick paper such as a postcard is conveyed and the paper is strong, the pressing force on the registration rollers and conveyance rollers becomes excessively strong, and each roller rotates forward or backward. Therefore, there is a problem that the paper cannot be conveyed at an appropriate timing.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sheet feeding device that can ensure an appropriate loop amount regardless of the thickness and size of a sheet, can reliably correct skewed sheet feeding, and can convey a sheet to an image forming unit at an appropriate timing. Is to provide.

[Means for solving the problem]

The sheet feeding device according to the present invention includes a registration roller that feeds a sheet to an image forming unit in synchronization with an image forming operation, a conveyance roller that is disposed upstream of the registration roller in the sheet conveyance direction and conveys the sheet, and the registration roller. Paper feed guide means disposed between the transport rollers.

The paper feed guide unit includes a guide plate and an elastic member. The guide plate has a notch in a part thereof,
It is formed of a member that is not deformed by the pressing of the sheet.
Further, the elastic member is arranged so as to close the notch of the guide plate, and can be deformed by pressing a curved sheet. The notch of the guide plate is formed to have a predetermined width in the width direction of the paper with reference to the reference position in the width direction of the paper, and has a predetermined length in the paper conveyance direction with reference to the end of the guide plate on the conveyance roller side. Is formed.

[Operation] In the present invention, the sheet sent from the sheet cassette or the like is conveyed by the conveying roller and temporarily stopped by the registration roller. Even after the leading edge of the sheet comes into contact with the registration roller, the conveyance roller feeds the sheet for a certain period of time, whereby the sheet curves between the registration roller and the conveyance roller to form a loop.

At this time, when a sheet having a large width and a small thickness such as plain paper is conveyed, the loop portion of the sheet comes into contact with a guide plate which is not deformed by the pressing of the sheet. Although plain paper is generally not stiff, the guide plate is not deformed, and the leading end of the paper is pressed against the registration roller by an appropriate force when the loop portion comes into contact with the guide plate.

Therefore, the leading end of the sheet can be sufficiently bitten by the registration roller, and the oblique sheet feeding can be reliably corrected.

On the other hand, when a sheet having a small width and a large sheet thickness is conveyed, such as a postcard, a loop portion is formed in the same manner as the above-described plain paper. However, a loop portion of a sheet such as a postcard having a small width abuts on an elastic member that closes a notch of the guide plate, and the elastic member is deformed by the loop portion of the sheet.

Therefore, when a sheet such as a postcard is conveyed, the loop amount is absorbed by the elastic member, and the registration roller and the conveyance roller do not rotate forward or reverse due to the stiffness of the sheet, and at an appropriate timing. Paper can be fed.

〔Example〕

FIG. 1 is an overall configuration diagram of a copying machine to which an embodiment of the present invention is applied.

The copying machine main body 1 is mounted on a mounting table 2. A document table 3 is fixed on the upper surface of the copying machine body 1, and a document holder 4 is mounted on the document table 3 so as to be freely opened and closed.
On the left side of the copying machine 1, a paper discharge tray 5 for discharging copied paper is mounted.

Inside the copier main body 1, an optical system 6 for reading image information of a document is provided at an upper portion thereof. The optical system 6 includes a light source, a mirror, a lens, and the like. A photoconductor drum 7 on which an electrostatic latent image is formed is disposed substantially at the center of the copying machine main body 1. Around the photosensitive drum 7, a charging device 8 for charging the photosensitive drum 7 to a predetermined charge, a developing device 9 for developing an electrostatic latent image, a transfer device 10 for transferring a toner image to paper, and a photosensitive drum 7 Paper separation device 11 for separating paper from paper
And a cleaning device 12 for removing toner on the photosensitive drum 7 are arranged in order.

A paper discharge path 13 is provided downstream of the image forming unit including the photosensitive drum 7 and the developing device 9 in the paper transport direction. A fixing device 14 for fixing the toner image on the conveyed paper is provided between the paper discharge conveyance path 13 and the paper discharge tray 5.
And a paper discharge roller 15 are provided.

A plurality of paper cassettes 16 are detachably mounted inside the mounting table 2 on which the copying machine body 1 is mounted. These sheet cassettes 16 can store sheets of different sizes. Above the leading end side (right side in the figure) of the paper feed cassette 16, a paper feed roller 17 for feeding out paper from the paper feed cassette 16 is provided. In addition, each paper cassette 16
A transport path 18 for transporting the paper from the paper feed cassette 16 to the copying machine main body 1 is provided on the right side of the mounting table 2 in front of the printer 1. At the front end of each paper feed cassette 16, a feed roller 19 for feeding the paper sent out by the feed roller 17 to an upper portion of the feed path 18 is provided at a portion of the feed path 18.

On the other hand, at the bottom of the copying machine main body 1, a paper feeding device 20 for feeding the sheet sent from the conveyance path 18 on the mounting table 2 side to the image forming unit is provided. FIG. 2 shows the details of the paper feeding device 20. FIG. 2 is an enlarged view of the sheet feeding device portion of FIG. 1, and FIG. 3 is a perspective view of the sheet feeding portion.

In these figures, a registration roller 21 is provided in the vicinity of an image forming unit including the photosensitive drum 7 and the like. The registration roller 21 is for supplying a sheet to the image forming unit at a predetermined timing. Registration roller 21
A transport roller 22 is disposed upstream of the paper transport direction. The transport roller 22 includes an upper roller 22a and a lower roller 22b.
It is composed of Registration roller 21 and transport roller
Between 22, a paper feed guide means including an upper guide plate 23 and a lower guide plate 24 is arranged. Under the lower guide plate 24 and immediately before the registration roller 21, the paper is
Is provided with a registration switch 25 for detecting that the vehicle has reached.

The upper guide plate 23 has two bent portions 23a and 23b, and includes a downstream portion 23c, a center portion 23d, and an upstream portion 23e with these bent portions 23a and 23b as boundaries. Upstream section 23
At both ends in the paper width direction of e, the upper guide plate 23 is
It is bent upward to attach it to the subframe.

As shown in FIG. 3, a trapezoidal notch 26 is formed at the center of the upstream portion 23e of the upper guide plate 23 in the sheet width direction. The dimension of the notch 26 in the width direction corresponds to the postcard width size (the size indicated by the two-dot chain line P2 in FIG. 3) at its narrowest part. An elastic member 27 formed of a polyethylene terephthalate film or the like is provided so as to cover the notch 26. In this apparatus, the paper is fed with the center in the width direction as a reference position.

The elastic member 27 is formed in a substantially rectangular shape, and a protruding portion 27 is provided at both ends in the sheet width direction on the upstream side in the sheet conveying direction.
a, 27b are provided. The elastic member 27 has four notches 28a to 28d formed in the paper width direction. The notch grooves 28a to 28d are formed from the end on the downstream side in the paper transport direction.
It is formed along the paper transport direction. Notch groove 28a
And 28d are formed at positions corresponding to the protruding portions 27a and 27b of the elastic member 27, and the notch grooves 28b and 28c are formed on the upper guide plate.
It is formed corresponding to the 23 notches 26.

The elastic member 27 has a central end (a portion indicated by a hatched broken line in FIG. 3) between the notches 28b and 28c, which is attached to the lower surface of the upper guide member 23. Also, the notch groove 28
The upstream portion 23e of the upper guide plate 23 is engaged with the
a and 27b are in contact with the rotating shaft of the upper roller 22a.

The elastic member 27 has a thickness of 180 μm to 250 μm.
A PET biaxially stretched film of about μm is desirable. Also, TALPA, PSu, polyarylate (U polymer), PI (KAPTON), PEI (ULTEM), etc., manufactured by Mitsui Toatsu Chemicals, Inc. can be used.

 Next, the operation will be described.

When the copy start key is pressed, one of the paper feed cassettes 16 is selected, and the paper in the cassette 16 is fed into the transport path 18 by the rotation of the paper feed roller 17. The paper fed into the conveyance path 18 is
The paper is fed upward by 19 and is
Transported to the part.

In the sheet feeding device 20, the sheet fed from below by the feed roller 19 is sent downstream by the transport roller 22. The sheet fed by the transport roller 22 is guided by the upper guide plate 23 and the lower guide plate 24 and
To reach. At this time, since the registration roller 21 is not rotating, the fed paper is
At 21, the operation is temporarily stopped and the apparatus enters a standby state. The arrival of the sheet at the registration roller 21 is detected by the registration switch 25.

After the registration switch 25 detects that the sheet has been transported, the rotation of the transport roller 22 is stopped after a predetermined time. As described above, since the transport roller 22 is rotated for a certain period of time even after the paper arrives at the registration roller 21, the paper bends between the registration roller 21 and the transport roller 22, and the second
As shown by a chain line in the figure, loop portions are formed at a plurality of places.

If the conveyed paper is plain paper, as indicated by the alternate long and short dash line P1 in FIG. 3, the width size is larger than the notch 26 of the upper guide plate 23, and the paper thickness is relatively thin. In this case, the loop shape of the sheet is regulated by the upper guide plates 23 and 24 and the elastic member 27. That is, the loop amount of the paper is mainly the upper guide plate 23 which is not deformed by the pressing of the paper.
Is determined by Therefore, the leading edge of the sheet is pushed to the extent that it is sufficiently engaged with the registration roller 21, and the entire leading edge of the sheet is uniformly nipped by the registration roller 21. Thereby, the inclination of the sheet is corrected even when the oblique sheet feeding is performed.

In the case of plain paper, the upper guide plate 23 is not deformed, so the loop amount of the paper is not absorbed by the upper guide plate 23.However, since the stiffness of the paper is weak, the registration roller 21 is rotated forward by the loop portion, Alternatively, the sheet can be sent to the image forming unit at an appropriate timing without rotating the transport roller 22 in the reverse direction.

On the other hand, when the width size is small, such as a postcard, and enters the notch 26 of the upper guide plate 23 as shown by the two-dot chain line P2 in FIG. Is formed, the loop shape is determined only by the elastic member 27. Therefore, when a sheet having a small width and a large sheet thickness is fed, such as a postcard, the elastic member 27 bends upward as shown by a dashed line in FIG. Absorb the amount to some extent. Therefore, even in the case of a stiff sheet such as a postcard, the loop does not excessively push the registration roller 21 or the conveyance roller 22, and the rotation of the rollers 21, 22 can be prevented. Therefore, the paper can be sent out at an appropriate timing during image formation.

When the central portion of the elastic member 27 is largely bent as shown in FIG. 4, the notch grooves 28b and 28c are formed, so that the elastic member 27 bends smoothly along the loop shape of the sheet. further,
Since the notch grooves 28a and 28d are mounted so as to sandwich the upstream portion 23e of the upper guide plate 23, and the protruding portions 27a and 27b are locked on the rotation axis of the upper roller 22a of the transport roller 22,
Even when the elastic member 27 is largely bent, both ends in the width direction do not droop greatly and do not hinder the sheet conveyance.

Further, since the elastic member 27 covers the left and right sides of the cutout portion 26 of the upper guide plate 23 from below, it is possible to prevent the paper from being caught on the end of the cutout portion 26 and to prevent the paper from being broken or broken. Can be prevented.

[Other embodiments]

(A) In the above embodiment, the paper feeding apparatus of the present invention is applied to a front loading type in which a copying machine main body is mounted on a mounting table in which a paper feeding cassette is stored, and paper is fed from below. The present invention can be similarly applied to a type in which a sheet cassette is attached to a side portion of a copying machine main body.

(B) In the above embodiment, as shown in FIG. 3, the elastic member has a substantially rectangular shape, and the protrusions 27a, 27a,
Although the elastic member 27b is formed, the shape and the like of the elastic member 27 are not limited to the above embodiment.

〔The invention's effect〕

As described above, in the present invention, the notch is provided in a part of the width direction of the guide plate, and the elastic member is arranged so as to close the notch, so that an appropriate loop amount is always obtained regardless of the size and thickness of the paper. It is possible to secure the sheet and perform good sheet feeding.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a copying machine employing a paper feeding device according to an embodiment of the present invention, FIG. 2 is a partially enlarged view showing the paper feeding unit, FIG. FIG. 4 is a front view of the paper feeding unit. 7 photoreceptor drum, 9 developing device, 10 transfer device, 20 paper feed device, 21 registration roller, 22 transport roller, 23 upper guide plate, 23c downstream portion , 23d ……
Central part, 23e ... upstream part, 24 ... lower guide plate, 26 ... notch part, 27 ... elastic member.

Claims (1)

(57) [Claims] A registration roller for feeding a sheet to an image forming section in synchronization with an image forming operation; and a registration roller disposed upstream of the registration roller in a sheet conveyance direction.
A transport roller for transporting the paper; and paper feed guide means disposed between the registration roller and the transport roller. The paper feed guide means has a notch in a part thereof, and is provided by pressing the paper. A guide plate formed of a member that is not deformed, and an elastic member that is disposed so as to cover the cutout portion of the guide plate and that can be deformed by pressing a curved sheet, the cutout of the guide plate is It is formed to have a predetermined width in the width direction of the paper with reference to the reference position in the width direction, and is formed to have a predetermined length in the paper transport direction with reference to the guide plate end on the transport roller side. , Paper feeder.