JPH09110200A - Paper sheet feed device and image forming device provided with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper sheet feed device which can surely feed a sheet to a separation part and stably feed paper, and an image forming device provided with it. SOLUTION: A sheet bundle PX loaded on a sheet placing base 13 is carried to a separation part C by a delivery roller 4 which is provided under the sheet placing base 13, and formed with a lock part 25 on the circumferential face projecting from the sheet placing base 13 at carrying sheet so as to lock with the lowermost sheet of the sheet bundle PX and carry the lowermost sheet to the separation part C. Further, by forming the extreme end of the lock part 25 of the delivery roller 4 locking with the lowermost sheet into a sharp claw shape, feeding force of the delivery roller 4 is enlarged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding apparatus and an image forming apparatus such as a copying machine and a laser beam printer having the sheet feeding apparatus.

[0002]

2. Description of the Related Art In an automatic document feeder, which is an example of a conventional sheet feeder, a stack of originals (sheets) stacked on a document table is separated by a separating unit and then separated originals are separated. The image is fed to the image reading unit of the image forming apparatus such as a copying machine.

Here, in the automatic document feeder as described above, when feeding a document, first, as shown in FIG. 7, a plurality of document bundles PX are placed on the tray 113, while the shutter 105 is used. Document stack PX by protruding to the position shown by the dotted line
I try to hold. Then, when the start switch of the operation unit (not shown) is pressed in this state, the shutter 105 sinks from the tray 113 as shown by the solid line, and the half-moon roller 104 starts rotating counterclockwise.

At the same time when the shutter 105 descends, the weight plate 106 rotates downward in the direction of arrow A to press the document stack PX, and the half-moon roller 104 is pressed with the document stack PX thus pressed. By rotating the document, the lowermost original (hereinafter referred to as the lowermost sheet) of the original bundle PX can be sequentially fed. It should be noted that the half-moon roller 104 is located at a home position where a business trip is not made from the tray 113, as shown in FIG.

On the other hand, the original bundle PX sent out by the half-moon roller 104 in this way is provided in the separating section C and rotates in the paper feeding direction shown by the arrow B, and the sheet returning direction shown by the arrow D. Separation belt 107 driven by
By the action of, the bottom sheet is separated one by one.

After that, the separated bottom sheet is pulled out by a roller on the downstream side (not shown) and then placed on the image reading section of the image forming apparatus. The separation belt 107 and the paper feed roller 108 are alternately formed in a comb shape in the thrust direction, and the nip portions are arranged so as to slightly overlap each other.

In the figure, reference numeral 109 denotes a separation regulating plate, and the separation regulating plate 109 is formed at the lower end so that a large number of documents of the document stack P that have entered do not enter the separation nip portion C1 at the same time. Document stack P at section 115
It controls X and serves as a guide outside the area of the separation belt 107. Further, in the figure, reference numeral 104a denotes a locking portion which is formed on the peripheral surface of the half-moon roller 104 and which locks the lowermost paper and conveys it to the separating portion C when the original is conveyed.

[0008]

By the way, for example, when the humidity of the outside air is high, the adhesion between the originals of the original bundle PX is increased. In the case of feeding such a document with increased adhesion, in the conventional automatic document feeder, the document is driven by the half-moon roller 104 due to its adhesion and the regulation portion 115 of the separation regulation plate 109 and the tray 113. And between the separation belt pulley 114 that drives the separation belt 107 and the tray 113.

However, in the case where a large amount of the document has entered in this way, the angle θ'of the tip portion of the locking portion 104a of the half-moon roller 104 is an obtuse angle (see FIG. 7), so that the half-moon roller 104 can perform the feeding. Even if the force F reaches the point A where the feeding force F becomes the largest as shown in FIG.
₁ 'can not exceed the minimum supply Okuchikara F ₀ required to separate the high adhesion document. In the figure,
Point B indicates a point where the feeding force F becomes a stable feeding force F ₂ .

Here, when the feeding force F of the half-moon roller 104 cannot exceed the minimum feeding force F ₀ in this way, the document cannot be separated and the document stack PX is locked. If the document stack PX is locked in this way, it becomes impossible to feed the documents into the separation nip portion C1 and there is a problem in that feeding failure occurs.

The present invention has been made in order to solve such a problem, and is provided with a sheet feeding device capable of reliably feeding a sheet to a separating portion to stably feed the sheet, and a sheet feeding device including the sheet feeding device. An object is to provide an image forming apparatus.

[0012]

SUMMARY OF THE INVENTION According to the present invention, a sheet feeding method in which a sheet bundle stacked on a sheet mounting table is conveyed to a separating section, and then the separating section separates and feeds the sheets one by one. In the apparatus, provided below the sheet mounting table,
At the time of sheet transport, a transport rotating body is formed on the peripheral surface, which projects from the sheet mounting table to lock the lowermost sheet of the sheet bundle, and which has a locking portion for transporting the lowermost sheet to the separating section. It is characterized in that the tip of the locking portion for locking the lowermost sheet is formed into a pointed claw shape.

Further, the present invention is characterized in that at least two pawl-shaped engaging portions are formed at symmetrical positions on the conveying rotary member.

Further, according to the present invention, a sheet feeding device that separates and feeds the sheets of the sheet bundle one by one, and an image forming unit that reads the sheets fed by the sheet feeding device and forms an image. And an image forming apparatus comprising:
The sheet feeding device is the sheet feeding device according to claim 1.

And, by configuring in this way,
The sheet bundle stacked on the sheet stacking table is provided below the sheet stacking table, and when the sheets are conveyed on the peripheral surface, the sheet stack protrudes from the sheet stacking table to lock the lowermost sheet of the sheet stack, and the lowermost sheet is It is configured to be transported to the separation unit by a transport rotating body in which a locking unit for transporting to the separation unit is formed. Further, the leading end of the locking portion of the transporting rotary body that locks the lowermost sheet is formed into a pointed claw shape to increase the feeding force of the transporting rotary body.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an internal structure of a copying machine as an example of an image forming apparatus to which an automatic document feeder as an example of a sheet feeding apparatus according to the present invention can be applied.

In FIG. 1, reference numeral 900 denotes a copying machine main body (hereinafter referred to as a main body). The main body 900 includes a platen glass 3 as a document reading section, a light source (reading means) 907,
A lens system 908, a paper feeding unit 909, an image forming unit 902 and the like are provided. It should be noted that the original P is fed to the platen glass 3 one by one by an automatic document feeder 2 having a configuration described later.

Here, the sheet feeding unit 909 is provided with cassettes 910 and 911 for accommodating the sheet material S on which an image is formed and detachable from the apparatus main body 900, and a deck 913 arranged in the pedestal 912. In addition, the image forming unit 9
Reference numeral 02 denotes a developing device 9 having a cylindrical photosensitive drum 914 built therein.
15, a transfer charging device 916, a separation charging device 917, a cleaner 918, a primary charging device 919, and the like are provided.

Incidentally, on the downstream side of the image forming section 902, a conveying device 920, a fixing device 904, a discharge roller 90.
5 and the like are disposed, and the sheet material S ejected by the ejection roller 905 is classified as necessary by the sheet classification device 922 connected to the copying machine main body 900. In the figure, 930 is a copying machine main body 90.
0 controller (CPU) is shown.

By the way, when an image is formed in the copying machine constructed as described above, the cassette 91 is generated in response to a paper feed signal from the control device 930 provided in the main body 900.
The sheet material S is fed from the deck 0, 911 or the deck 913. On the other hand, the light which is applied from the light source 907 to the original P placed on the platen glass 3 and reflected by the optical system 90.
The light is irradiated onto the photosensitive drum 914 via the beam line 8.

Here, the photosensitive drum 914 has been charged in advance by the primary charger 919, and an electrostatic latent image is formed by being irradiated with light, and then the developing unit 9 is formed.
A toner image is formed by 15.

On the other hand, the sheet material P fed from the sheet feeding section 909 is corrected for skewing by the registration rollers 901, and further fed to the image forming section 902 at a timed timing. Here, in the image forming unit 902, the photosensitive drum 9 is applied to the sheet material P sent by the transfer charger 916.
The toner images of 14 are transferred, and the transferred sheet material P is charged by the separation charging device 917 to a polarity opposite to that of the transfer charging device 916 and separated from the photosensitive drum 914.

The separated sheet material P is conveyed to the fixing device 904 by the conveying device 920, the unfixed transferred image is permanently fixed by the fixing device 904, and finally the discharging roller 905 discharges it from the apparatus main body 900. To be done. In this way, the sheet material P fed from the paper feeding unit 909 is formed with an image and discharged.

By the way, FIG. 2 is a diagram showing the internal structure of an automatic document feeder 2 for feeding a document to the platen glass 3 for forming such an image. In FIG.
Is a transport belt (endless belt) which is disposed on the platen glass 3 and is wound around the driving roller 11 and the driven roller 15 so as to freely rotate forward and backward.

A bundle of originals is placed on the original placing table 13, and these bundles of originals are aligned in a width direction by a pair of width regulating plates 20 (only one is shown in the drawing). Has been done. Further, a recycle lever 21 is placed on the original stack of the original placing table 13, and the original not yet fed by the recycling lever 21 and the fed originals discharged onto the original placing table 13 after being fed. And are being distinguished.

On the other hand, in the figure, reference numeral 4 denotes a document placing table 13
The lowermost sheet of the document bundle is provided under the sheet and is fed out to feed the lowermost sheet of the document bundle. A shutter (moving means) retracted below the table 1 is a weight plate.

A separating portion C composed of a conveying roller 8 rotating in the document feeding direction and a separating belt 7 rotating in the document returning direction is disposed downstream of the sending roller 4. In the section C, the documents fed by the feeding roller 4 are separated and conveyed one by one.

A registration roller pair consisting of a reversing roller (driving roller) 9 and a driven roller 10 which is in contact with the reversing roller (driving roller) is disposed on the downstream side of the separating section C. The original is fed onto the platen glass 3 at a predetermined timing. The platen glass 3 is rotated by the rotation of the conveyor belt 12.
A document that has been conveyed to the upper position and stopped at a predetermined position has a light source 90.
By manipulating 7 in the direction of the arrow, the original image is fixedly read.

In the figure, reference numeral 22 is a conveying path including the separating section C and a pair of registration rollers, and the original is conveyed to the reading position by switchback by the conveying path 22, the conveying belt 12 and the discharging path 23. A switchback path for discharging is formed.

On the other hand, the original after the fixed reading is finished, the conveyance belt 12 is rotated in the reverse direction so that the discharge path 23 is provided outside the reversing roller 9.
And is conveyed to the flapper 24. Here, the flapper 24 reverses and guides the document to the platen glass 3 when reading both sides of the document, and guides the document to the discharge roller pair 19 when reading on one side. After that, the document discharged by the discharge roller pair 19 is placed on the document not yet fed on the document mounting table 13, and is partitioned by the recycling lever 21 to be distinguished.

By the way, as shown in FIG. 3, the tip of the locking portion 25 for locking the lowermost sheet of the feed roller 4 rotating counterclockwise for feeding the document on the document table 13 has a cross section thereof as shown in FIG. It is formed in a sharp claw shape with an acute angle θ. By forming the tip of the locking portion 25 in such a shape, the contact portion with the bottom sheet can be made closer to the point, and the weight of the original stack PX can be concentrated on the contact portion. .

Here, by concentrating the self-weight of the document stack PX on the contact portion in this way, the tip of the locking portion 25 can be strongly locked to the bottom sheet, and the feeding roller 4
The feeding force F can be increased.

FIG. 4 is a view showing how the document bundle PX is conveyed by the delivery roller 4, and when the delivery roller 4 rotates, the locking portion 2 of the delivery roller 4 is provided.
5 strongly locks the lowermost sheet, whereby the document stack PX is transported in a wedge shape and approaches the separating portion C.

Here, the conveying roller 8 and the separating belt 7 are rotated counterclockwise, respectively, and the conveying roller 8 and the separating belt 7 sequentially move from the bottom sheet of the original stack PX to 1
It is designed to be delivered downstream one by one. In addition,
At the same time when the delivery roller 4 rotates, the weight plate 6
As shown by the dotted line in FIG. 4, the document stack PX is configured to be tapped several times in succession, so that the document stack PX can be reliably separated.

By thus forming the tip of the engaging portion 25 into a pointed claw shape, the feeding force F can be increased. For example, when the environmental condition is high temperature and high humidity, or the sheet is used. Even if the μ of itself is high, the document stack PX can be shifted like a wedge, and stable separation and feeding can be performed.

Further, when the sheets have a high adhesion, a large number of originals simultaneously enter between the regulating portion 9a of the regulating plate 9 and the mounting table 13 as described above, and the bundle of originals is locked to cause a sheet feeding failure. However, by increasing the feeding force F in this way, it is possible to transfer only the bottom sheet before a large number of documents enter between the regulation section 9a and the mounting table 13, and the movement of the bottom sheet. With this, the document bundle also becomes wedge-shaped, so locking can be prevented, and stable separation and feeding can be performed.

By the way, FIG. 5 is a graph showing the relationship between the feeding force F of the feeding roller 4 and the time t in the present invention. In the figure, t ₀ indicates the time when the feed roller 4 starts to rotate, after which the locking portion 4a of the feed roller 4 comes into contact with the bottom sheet, so that F gradually rises. Has become.

Further, t ₁ indicates the time when the feed roller 4 is at the position shown in FIG. 4 and reaches the position (A) where the feeding force F becomes the largest, and the feeding force F ₁ at this time is Minimum feeding force F, which is the minimum feeding force required when adhesion is high
_It exceeds ₀ . It should be noted that at this time t ₁ , the document has already been divided into a wedge shape.

On the other hand, t ₂ indicates the time when the delivery roller 4 subsequently rotates and reaches the position (B) in which the delivery roller 4 enters the stable region. At this time t ₂ , the bottom sheet is placed on the curved surface of the delivery roller 4. Are in contact with. Here, the feeding force F ₂ in this stable region is smaller than the minimum feeding force F _0, but the document bundle PX has already been
Since the document bundle PX has a wedge shape, and once it has a wedge shape, the original bundle PX is fed along with the bottommost sheet even if the feeding force is low, there is no problem. It should be noted that t ₃ is a time when the delivery roller 4 reaches a position hidden under the mounting table 13.

By the way, in the above description, the locking portion 4a has been described as being formed at one location on the peripheral surface of the feeding roller 4, but the present invention is not limited to this.
As shown in FIG. 6, the locking portions 31 and 32 are fed out to the roller 3
You may make it form at least 2 opposite to the peripheral surface of 0. As a result, when the delivery roller 4 makes one rotation, a feeding force F ₁ that exceeds the minimum required feeding force F ₀ is generated twice,
Stable separation and feeding can be performed without locking the document stack PX.

[0042]

As described above, according to the present invention,
By forming the tip of the locking part of the feeding roller that feeds the sheet bundle into a sharp claw shape, it is possible to increase the feeding force, which allows the sheet bundle to be separated, and double feeding or defective feeding can be prevented. Stable feeding can be performed without waking.

[Brief description of the drawings]

FIG. 1 is a diagram showing an internal configuration of a copying machine including an automatic document feeder according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an internal configuration of the automatic document feeder.

FIG. 3 is a detailed view of a separation unit of the automatic document feeder.

FIG. 4 is a diagram showing a separating operation in a separating unit of the automatic document feeder.

FIG. 5 is a graph showing the feeding force of a feed roller of the automatic document feeder.

FIG. 6 is a detailed view of a separating portion of the automatic document feeder according to the second embodiment of the present invention.

FIG. 7 is a detailed view of a separation unit of a conventional automatic document feeder.

FIG. 8 is a graph showing the feeding force of a feed roller of a conventional automatic document feeder.

[Explanation of symbols]

 2 Automatic document feeder 4,30 Sending rollers 25, 31, 32 Locking part 13 Sheet placing table 900 Copier body C Separation part PX Document bundle

Claims (3)

[Claims] 1. A sheet feeding device that conveys a sheet bundle stacked on a sheet placing table to a separating section and then separates and feeds the sheets one by one at the separating section. An engaging portion is provided on the lower side of the peripheral surface, the engaging portion protruding from the sheet placing table to engage the lowermost sheet of the sheet bundle and convey the lowermost sheet to the separating portion when the sheet is conveyed. A sheet feeding device, comprising: a conveying rotating body, wherein a tip of the locking portion that locks the lowermost sheet is formed into a sharp claw shape. 2. The sheet feeding device according to claim 2, wherein at least two pawl-shaped engaging portions are formed at symmetrical positions on the conveying rotary member. 3. A sheet feeding device that separates and feeds the sheets of a sheet bundle one by one, and an image forming unit that reads the sheets fed by the sheet feeding device and forms an image. An image forming apparatus comprising the image forming apparatus, wherein the sheet feeding apparatus is the sheet feeding apparatus according to claim 1 or 2.