JP2000203737A - Paper feeder and image forming device provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impede returning of paper of an upper layer part in an opposite paper feed direction so as to prevent generation of wedge shape in a tip end of a paper sheaf in the paper upper layer part, by giving return resistance force resisting against press return force acting in the paper in the upper layer part to the paper therein by a lock part. SOLUTION: This paper feeder has a paper feed means calling paper 18 loaded in a prescribed location successively from the uppermost part and friction separating this called paper 18 fed and a saw-shaped lock part 36 integrally provided with a paper retaining member 28 in a condition abutting to a rear end part upper surface of the paper 18 in a layered condition. This lock part 36, when press return force (p) tending to press return the paper 18 in an opposite direction to a paper feed direction acts relating to the paper 18 in an upper layer part fed after the paper 18 in the uppermost part, locks this paper so as to be hooked by a paper rear end in the upper layer part, and return resistance force P resisting against the press return force (p) is given to the paper 18 in the upper layer part by this lock condition, so as to impede returning of the paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a paper feeder for feeding paper and an image forming apparatus having the same.

[0002]

2. Description of the Related Art Conventionally, as a means for picking up sheets loaded on a sheet stacking plate by a pickup roller and separating the called sheets, a device utilizing frictional separation is known.
Specifically, a pad-shaped or roller-shaped friction member is brought into contact with the lower peripheral surface of a paper feed roller for feeding the paper picked up by the pickup roller, and the frictional force acting between the friction member and the paper causes the paper There is something to handle. In image forming apparatuses such as copying machines and printers, cut sheets that can be continuously fed are usually limited to high-quality paper and plain paper specified by the copier maker. Such a sheet has low surface smoothness, so that when the sheets stacked on the sheet stacking plate are sent out, the sheets are in close contact with each other and double feeding is less likely to occur. On the other hand, in recent years, with the diversification of recording media,
In addition to OHP paper, tracing paper, etc., images are formed on smooth paper such as art paper and coated paper that have been coated on the sheet surface to provide whiteness and gloss in response to the market demand for colorization. Demands are growing.
However, with such high-smoothness paper, the adhesion between the papers in a stacked state is high, so that when the paper is fed, the paper is not reliably separated, and there is a problem that multiple feeding or misfeeding occurs frequently.

In order to enhance the paper separating performance, for example, Japanese Patent Application Laid-Open No. Hei 4-23747 discloses a paper feeding apparatus in which paper is fed while being frictionally separated by a paper feed roller and a retard roller (friction member) for separation. As shown in FIGS. 6 and 7, the air outlet 54 of the air blowing means 53 is attached to the end face of the paper 52 stacked on the bottom plate 51.
By blowing more air to form an air layer between the sheets, the upper layer of the sheet 52 is floated in a mountain shape to weaken the adhesion between the sheets, and the floating of the sheet 52 due to the air blowing is controlled by the sheet pressing member 55. There is disclosed a technology in which the air between the sheets is caused to penetrate by controlling the air flow.

[0004]

By the way, the sheets 52 stacked on the bottom plate 51 are called up by a pickup roller in order from the top, and the called out sheet is brought into contact with a sheet feeding roller and a retard roller. Nip). At that time, the technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 4-23747 has the following problems.

That is, when an air layer is formed between the sheets by the air blowing means 53, the resistance between the sheets is reduced. Therefore, when the uppermost sheet is called by the pickup roller, the upper layer sheet is accompanied. Also moves to the vicinity of the contact portion between the feed roller and the retard roller.

On the other hand, in a device in which a sheet is fed while being separated by a sheet feeding roller and a retard roller, as shown in FIG. The sheet 52 sent out by the roller 58 is transferred to a pair of take-away rollers 59 disposed downstream of the sheet 52, and thereafter, the sheet 52 and the sheet feed roller 57 are moved in accordance with the pulling force of the sheet by the take-away roller 59. Retard roller 58
Goes around. In such a situation, as the take-away roller 59 pulls the paper 52, the shaft of the paper feed roller 57 and the rubber material on the roller surface move downstream (in the direction of arrow A in the drawing) in the paper feed direction. It is pulled and deformed.

In this state, as shown in FIG. 8 (b), when the rear end of the paper 52 delivered to the takeaway roller 59 passes through the contact portion between the paper supply roller 57 and the retard roller 58, At a moment, the pulling force of the takeaway roller 59 is released all at once, and
The deformation of the rubber material on the shaft of 7 and the roller surface is also eliminated. Then, as described above, the upper-layer paper 52 that has moved to near the contact portion between the feed roller 57 and the retard roller 58
Is kicked back to the upstream side in the paper feeding direction (the side seen from the arrow B in the drawing).

As a result, in the upper layer portion of the sheets stacked on the bottom plate 51, the leading end portion 52a of the sheet bundle becomes wedge-shaped, and when the next sheet 52 is called by the pickup roller 56, as shown in FIG. In addition, three or more sheets 52 are fed with a feed roller 57 and a retard roller 58.
Into the contact area of Then, the retard roller 58
Although the sending out of the paper 52 in contact with is stopped,
Since the other two or more sheets 52 are sent out as they are, multiple running occurs. Such a problem occurs even in a case where the air blowing means 53 is not provided, that is, in a case where the paper is separated only by frictional separation, but is particularly remarkable in a case where the adhesion between the papers is released by blowing the air.

[0009]

In a paper feeder according to the present invention, paper loaded in a predetermined portion is sequentially called from a top, and the called paper is frictionally separated and fed. When the paper is fed by the paper feeding means, the sheet acts on the upper-layer paper fed after the uppermost sheet, and is pushed back in a direction opposite to the paper feeding direction by the paper feeding means. And an anti-return means for applying a return resistance force to the upper layer paper.

In the paper feeder having the above structure, when paper is fed by the paper feeding means, a push-back force acts on the upper layer paper in a direction opposite to the paper feeding direction. Then, the return resistance force against this is applied to the upper sheet by the return prevention means. This prevents the upper sheet from returning during paper feeding, so that the leading end of the sheet bundle does not become wedge-shaped at the upper layer of the sheet.

[0011]

FIG. 1 is a schematic side view showing a configuration example of an image forming apparatus to which the present invention is applied. The illustrated image forming apparatus 1 is based on an image reading device 2, a receiving unit 5 connected to an external device 3 such as a partner computer (PC) via a communication line 4, and image information from the receiving unit 5. An image recording control unit 7 for controlling the image writing device 6, a cylindrical image carrier 8 on which an electrostatic latent image is written by the image writing device 6, and a circumferentially extending image carrier 8. Charging device 9, developing device 10 and cleaner 11, transfer roller 12 for transferring an image formed on image carrier 8 to a sheet, fixing device 13 for fixing the image transferred to the sheet, and this fixing device A discharge roller 14 for discharging the paper from the discharge roller 13, a discharge tray 15 on which the paper discharged by the discharge roller 14 is stacked, and an image carrier 8
And a multi-stage (four-stage in the illustrated example) paper feed device 17 that supplies paper to the transfer roller 12 via the paper transport unit 16.

FIG. 2 shows a schematic configuration of the sheet feeding device.
(A) is a top view and (b) is a side view. As shown in the drawing, the paper feeding device 17 is provided with a paper feeding tray 19 serving as a stacking portion of the paper 18. The paper feed tray 19 has a bottom plate (paper stacking plate) 20 that moves up and down by driving a motor (not shown), and has a configuration in which a plurality of sheets 18 can be stacked on the bottom plate 20. Further, a paper feeding unit 21 is provided above the paper feeding tray 19. The paper feed means 21 is provided with a pickup roller 22 which can swing freely via a support arm (not shown). The pickup roller 22 swings in contact with the upper surface of the rising paper 18. A height detection sensor (not shown) is provided near the support arm, and the height detection sensor can detect the swing of the support arm so that the height of the sheet 18 can be detected.

The paper feed tray 19 has a movable end guide 23 for regulating an end (paper rear end) of the paper 18 opposite to the paper feeding direction, and a paper 18 in a direction orthogonal to the paper feeding direction.
And a movable side guide 25 that regulates the other side of the sheet 18 at a position facing the fixed side guide 24 and is movable according to the sheet size. It is provided.

The fixed type side guide 24 is provided with air blowing means 26 in a state of facing one side end of the paper 18 stacked on the bottom plate 20. The air blowing means 26 includes, for example, an axial fan, a sirocco fan, a cross flow fan, and the like. The air blowing means 26 can blow air to the side end of the sheet 18.

The movable end guide 23 is provided with a paper pressing member 28 which comes into contact with the upper surface of the paper 18 stacked on the bottom plate 20. A predetermined load (for example, the paper pressing member 28) is applied by the paper pressing member 28. Paper 1 with own weight)
By holding down 8, the air is prevented from leaking more than necessary from the side regulated by the movable end guide 23, and the air between the sheets is completely penetrated.

Next, the image forming apparatus 1 thus configured
Will be described. First, the paper 1 is placed in the paper feed tray 19.
8 is supplied or replenished and the paper feed tray 19 is inserted, and when the bottom plate 20 is driven by a motor (not shown), the uppermost sheet 18 is moved to the pickup roller 22 waiting above it. Abut At this time, the height of the sheet 18 accompanying the rise of the bottom plate 20 is detected based on a detection signal of a height detection sensor (not shown), and when the detected height reaches a predetermined height, the driving of the motor is stopped. Is done.

Next, when a paper feed command is issued, the air blowing means 26 is driven, whereby air is blown to the side end of the paper 18. The air blown in this way is blown between each sheet to form an air layer there. As a result, the sheets 18 are separated and sorted one by one. Thereafter, the pickup roller 22 pressed by a solenoid (not shown) comes into contact with the sheet 18,
Paper feed is started by the rotation of the pickup roller 22. The blowing of air at the time of paper feeding may be performed all the time or may be performed intermittently.

On the downstream side of the pickup roller 22, a paper feed roller 29 that rotates in a direction for feeding the paper 18 (counterclockwise direction in FIG. 2B) and a direction opposite thereto (in FIG. 2B). While a certain limit of torque is applied in the clockwise direction (not shown) by a torque limiter (not shown), the retard roller 30 rotatable in both directions comes into contact with a predetermined pressure, and the interaction causes the paper 18 to be frictionally separated and fed. . Incidentally, the retard roller 30 is connected to the sheet feeding roller 2.
When there is only one sheet at the contact portion with the sheet 9, the sheet rotates in the direction of feeding the sheet, and when there are two or more sheets, the sheet rotates in the direction opposite to the direction of feeding the sheet. Thereby, the retard roller 30
The paper 18 other than the uppermost sheet in contact with the retard roller 3
The sheet is pushed back in the direction opposite to the sheet feeding direction due to frictional resistance with zero.

The sheet 18 sent out in the sheet feeding direction is conveyed by the sheet feeding roller 29 until a predetermined time elapses after the sheet 18 is detected by the feed-out sensor 35. Thereafter, the sheet 18 is delivered to the takeaway roller 31 and is transported further downstream. When the paper is being conveyed by the takeaway roller 31, the driving of the paper supply roller 29 is stopped, and during that time, the paper supply roller 29 is rotated by a one-way clutch (not shown) built in the drive system.

When the paper feed proceeds in this manner, the uppermost sheet 18
Of the pickup roller 22 at the time of pressing down also gradually decreases. As a result, the support arm (not shown) of the pickup roller 22 operates the height sensor to raise the minute amount bottom plate 20,
Continue the paper feeding operation. By repeating the above operation, the sheets 18 on the bottom plate 20 are sequentially sent out.

Here, as described in the above-mentioned subject, separation / separation by the feed roller 29 and the retard roller 30 is performed.
After the fed paper 18 is delivered to the takeaway roller 31, the trailing end of the delivered paper 18 is
When the sheet 18 passes through the contact portion between the retard roller 30 and the retard roller 30, at that moment, a force acts to push the sheet 18 in the upper layer part back in the direction opposite to the sheet feeding direction. Then, in the upper layer of the sheet, the leading end of the sheet bundle becomes wedge-shaped, and due to this, the double running occurs. Therefore, the paper feeder according to the present invention employs the following configuration.

FIG. 3 is a schematic side view showing a first embodiment of the paper feeding apparatus according to the present invention. In the figure, the rear end E of the paper 18 stacked on the bottom plate 20 is regulated by a movable end guide 23. Further, a paper pressing member 28 is disposed near the movable end guide 23. The leading end of the sheet holding member 28 is arranged in a state of extending from the movable end guide 23 to the sheet stacking area (the area where the sheets 18 are actually stacked), and the extended portion is, for example, a sheet holding member 28. Is held in contact with the upper surface of the sheet 18 by its own weight.

Further, the lower surface of the leading end of the sheet pressing member 28, that is, the contact portion with the sheet 18 is in contact with the rear end of the sheet 18 located on the upstream side (left side in the drawing) in the sheet feeding direction. Is provided with a lock portion 36 which can be locked.

The locking portion 36 corresponds to a return preventing means in the present invention, and is formed integrally with the sheet pressing member 28 (for example, resin molding). In addition, the locking portion 36
It is formed in a sawtooth shape having a regular order in the sheet feeding direction, and has a structure in which each sawtooth portion (uneven portion) can be locked to the rear end of the sheet.

In the paper feeding device provided with such a locking portion 36, when the paper is fed by the paper feeding means 21, the upper layer paper 1 fed after the uppermost paper 18 is fed.
When a force (hereinafter referred to as a push-back force) p is applied to push back the sheet 8 in a direction opposite to the sheet feeding direction (hereinafter referred to as a counter-feeding direction), the sawtooth portion of the locking portion 36 which comes into contact with the upper surface of the sheet And the rear end of the paper in the upper layer portion is hooked.

As a result, a force P (hereinafter referred to as "return resistance") that resists the push-back force p is applied to the upper layer paper 18 from the locking portion 36, and the return resistance P causes the sheet to be fed back. The return (reverse feed) of the sheet 18 in the direction is prevented. As a result, the leading end of the sheet bundle does not become wedge-shaped in the upper layer portion of the sheet, so that it is possible to prevent double running due to this. Further, in the image forming apparatus provided with such a sheet feeding device, the number of stoppages of the processing operation due to the occurrence of double running during the sheet feeding is reduced, so that the processing efficiency of image formation is improved.

In the first embodiment, the locking portion 3
6 is formed in a saw-like shape having a smooth line in the paper feeding direction,
Compared with the sheet feeding resistance applied to the uppermost sheet 18 fed by the sheet feeding means 21, a significantly larger return resistance is applied to the upper layer sheet 18, so that the uppermost sheet 18 is provided. The return of the upper sheet 18 can be reliably prevented without hindering the feeding of the sheet 18.

In the first embodiment, the locking portion 36 is provided integrally with the paper pressing member 28. However, the present invention is not limited to this, and the locking portion 36 is provided separately from the paper pressing member 28. The locking portion 36 may be provided by a body. However, when the paper pressing member 28 and the locking portion 36 are integrated, the configuration is simplified, and this is more preferable. Further, the arrangement range of the locking portion 36 may be such that it is arranged not only in a part of the paper width but also in the entire width thereof in the direction orthogonal to the paper feeding direction. further,
The number of the locking portions 36 may be one or more.

FIG. 4 is a schematic side view showing a second embodiment of the sheet feeding apparatus according to the present invention. In the second embodiment, a brush-like (including an artificial grass-like) engaging portion 3 having a straight line in the paper feeding direction is provided on the lower surface of the leading end of the paper pressing member 28.
7 are provided. The lower surface of the leading end of the sheet pressing member 28 is inclined obliquely upward from the trailing end of the sheet toward the leading end of the sheet (from the upstream side to the downstream side in the sheet feeding direction), and the inclined surface has a brush-like inclined portion 37. Is attached using an adhesive or the like. Further, the locking portion 37 has a structure in which the brush portion has flexibility.

In the paper feeding device provided with such a locking portion 37, when the paper is fed by the paper feeding means 21, the upper layer paper 1 fed after the uppermost paper 18 is fed.
When a push-back force p is applied to push back the sheet 8 in the direction opposite to the sheet feeding direction, the rear end of the sheet in the upper layer portion is engaged with the brush portion of the engaging portion 37 which comes into contact with the upper surface of the sheet.

As a result, a return resistance P that resists the push-back force p is applied from the locking portion 37 to the upper sheet 18, and the return resistance P causes the sheet 18 to move in the opposite sheet feeding direction. (Return) is prevented. Further, since the locking portion 37 is formed in the shape of a brush having an order in the paper feeding direction, the paper feeding resistance applied to the uppermost paper 18 fed by the paper feeding means 21 is lower than that. Also, a remarkably large return resistance is applied to the upper sheet 18.
As a result, similarly to the first embodiment, the uppermost sheet 1
8 without disturbing the feeding of the upper sheet 18.
Can be reliably prevented from returning.

In the second embodiment, the lower surface of the leading end of the paper pressing member 28 is inclined, and a flexible and brush-shaped locking portion 37 is provided on the inclined surface. The tip of the brush can be brought into contact with the trailing end of the paper in accordance with the floating shape (angle shape) of the paper by the air blowing means 26. Thereby, the floating of the paper is not excessively hindered, and even if the floating state of the paper varies, the leading end of the brush of the locking portion 39 is stably brought into contact with the rear end of the paper, and the return of the paper as described above is performed. Can be prevented.

FIG. 5 is a schematic side view showing a third embodiment of the paper feeding apparatus according to the present invention. In the figure, a swing bracket 41 that swings around a support shaft 40 is attached to the upper end of the movable end guide 23. Further, a roller 42 made of a high friction material such as a rubber material is attached to the tip (free end) of the swing bracket 41.
A clutch (one-way clutch) that regulates the rotation direction of the roller 42 in one direction is provided on the rotation axis of the roller 42.
43 are incorporated.

The rotation restricting direction (Lock direction) of the roller 42 by the clutch 43 is set clockwise in the drawing. Thus, when the paper 18 in contact with the roller 42 moves in the paper feeding direction, the rotation of the roller 42 is free (Unloc
k), and the rotation of the roller 42 is prevented (locked) when it is attempted to move in the counterclockwise direction.

The roller 42 and the clutch 43 work together with a sheet holding member for controlling the floating of the sheet 18 due to the air blowing by the air blowing means 26 (see FIG. 2), and return the sheet 18 in the direction opposite to the sheet feeding direction. A return prevention means for preventing is provided.

That is, when the uppermost sheet 18 is fed, the roller 42 comes into contact with the upper surface of the rear end portion of the stacked sheets due to the swing of the swing bracket 41 due to its own weight or the like. While suppressing the floating of the sheet, the roller 42 rotates (is idle) in accordance with the feeding of the uppermost sheet 18. On the other hand, when a push-back force p is applied to the upper layer sheet 18 fed after the uppermost sheet 18 in a direction opposite to the sheet feeding direction, the rollers 42 are pressed to resist the push-back force p. The rotation is blocked (locked) by the clutch 43. As a result, the return resistance force P against the push-back force p is exerted on the upper layer paper 18 due to the frictional resistance between the paper 18 and the roller 42 contacting the rear end of the paper 18.
, Which prevents return of the upper sheet 18. As a result, as in the first embodiment, it is possible to reliably prevent the upper-layer paper 18 from returning, without hindering the feeding of the uppermost paper 18.

In the third embodiment, when the uppermost sheet 18 is fed, the roller 42 is rotated (idle) while contacting the sheet 18, so that the sheet feeding resistance is reduced. The desired return prevention effect can be obtained without substantially increasing the value.

[0038]

As described above, according to the present invention, when the paper is fed by the paper feeding means, the return resistance force against the push-back force acting on the paper in the upper layer is prevented by the return preventing means. , It is possible to prevent the upper-layer sheet from returning in the direction opposite to the sheet feeding direction. As a result, the leading end of the sheet bundle does not become wedge-shaped in the upper layer of the sheet, so that double running due to this can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic side view illustrating a configuration example of an image forming apparatus to which the present invention is applied.

FIG. 2 is a schematic configuration diagram of a sheet feeding device to which the present invention is applied.

FIG. 3 is a schematic side view showing a first embodiment of the sheet feeding device according to the present invention.

FIG. 4 is a schematic side view showing a sheet feeder according to a fourth embodiment of the present invention.

FIG. 5 is a schematic side view showing a third embodiment of the paper feeding device according to the present invention.

FIG. 6 is a diagram (part 1) for explaining a conventional technique.

FIG. 7 is a diagram (part 2) for explaining a conventional technique;

FIG. 8 is a diagram for explaining a problem of the related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 17 ... Paper feeder, 18 ... Paper, 21
... sheet feeding means, 26 ... air blowing means, 36, 37 ...
Locking part, 42 ... roller, 43 ... clutch

Claims (9)

[Claims] 1. A sheet feeding means for sequentially calling sheets stacked on a predetermined portion from the uppermost part and frictionally separating and feeding the called sheet, and feeding a sheet by the sheet feeding means. A return resistance force acting on an upper layer sheet fed after the uppermost sheet and resisting a push-back force in a direction opposite to the sheet feeding direction by the sheet feeding means, And a return preventing means for applying the sheet to the sheet. 2. The sheet feeding device according to claim 1, further comprising an air blowing unit that blows air to an end surface of the sheets stacked on the predetermined portion. 3. The method according to claim 1, wherein the return preventing unit is arranged in a state of contacting a rear end of the sheet located on an upper surface of the sheet stacked on the predetermined portion and upstream of the sheet feeding direction. The sheet feeding device according to claim 1 or 2, wherein 4. The return prevention unit applies a return resistance greater than that to the uppermost sheet fed to the uppermost sheet fed by the sheet feeder to the upper layer sheet. 4. The paper feeding device according to claim 1, wherein the paper feeding device is provided. 5. The sheet feeding device according to claim 3, wherein the return preventing unit has a locking portion that can be locked to a rear end of the sheet at a contact portion with the sheet. 6. The sheet feeding device according to claim 3, wherein the return preventing unit includes a roller that contacts the sheet and a clutch that restricts a rotation direction of the roller in one direction. 7. The sheet feeding device according to claim 5, wherein the locking portion is formed in a saw-like shape or a brush-like shape having a regular pattern in the sheet feeding direction. 8. The paper feeding device according to claim 7, wherein the locking portion is formed in a brush shape, and the brush portion has flexibility. 9. An image forming apparatus comprising the sheet feeding device according to claim 1. Description: