JPH07309466A - Sheet feeder and automatic document feeder having the sheet feeder and image forming device - Google Patents

Abstract

PURPOSE:To secure the separating-carrying operation of a separating-carrying part composed of carrier rollers to rotate in the sheet carrying direction and separating rollers to rotate in the return direction. CONSTITUTION:A sheet D is separated and carried by carrier rollers 3 to rotate in the sheet carrying direction and first and second separating rollers. The first separating roller 13 is set almost in the same with a friction coefficient of the carrier rollers 3, and the second separating roller 12a is set smaller than a friction coefficient of the first separating roller 13. Thereby, though the first separating roller 13 and the carrier rollers 3 are formed of a material having almost the same friction coefficient, carrying force of the carrier rollers 3 can be made larger than carrying force of the first and the second separating rollers, and the sheet can be reliably separated and carried, and selectivity of a construction material of the carrier rollers 3 and the first separating roller 13 can be widened.

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 for separating sheets one by one from a sheet stacking table such as an image forming apparatus such as a facsimile machine, a copying machine, an LBP and the like and conveying the sheets.

[0002]

2. Description of the Related Art Conventionally, as in an original feeding device such as an electrophotographic copying machine as an image forming apparatus and a refeeding unit of a duplex unit in a copying machine, the type and state of a sheet such as an original or a recording sheet is As a sheet feeding device used in a wide variety of places, a latitude for sheet separation and conveyance is widely required. It is generally known that the comb tooth separation method is effective as a paper feeding method therefor. A conventional sheet feeding apparatus using the comb tooth separation method will be described with reference to FIG. 4 by taking an automatic document feeding apparatus DF of a copying apparatus as an example.

In FIG. 4, reference numeral 101 denotes a document placing table (sheet stacking table) on which a document D as a sheet for copying is stacked with a face UP (upward facing the document). 10
Reference numeral 2 denotes a pickup roller that rotates in a direction of contacting the document D and rotates to rotate to feed the document D to the downstream side. Reference numeral 103 denotes a shutter that stops the document D with its leading end aligned.

The sheet feeding device DF is arranged on a copying machine main body 900 as an image forming apparatus main body. As will be described later with reference to FIG. 3, the copying machine main body 900 includes a solenoid 20 that drives the shutter 103 and a separating / separating unit to be described later.
The control unit 93 includes a drive unit 21 that drives the transport unit.
It is controlled by 0.

When the image forming start signal is issued from the copying machine main body 900, the shutter 103 is closed.
It is attracted by the solenoid 20 controlled by the control unit 930 of 0 and retracts to below the document table 101. Then, the pickup roller 102 rotates on its axis while falling on the upper surface of the document D, and conveys the uppermost document in the lower left direction in the drawing.

Reference numeral 104 denotes a comb-like conveying roller, and 105.
Is a separating roller having a comb-like shape and arranged alternately with the conveying roller 104. Both transport rollers 1
04104 and the separation roller 105 form a comb tooth separation portion. The detailed relationship between the two rollers 104 and 105 will be described with reference to FIG. 5, which is a sectional view.

FIG. 5 shows the separation / conveyance unit 104 shown in FIG.
FIG. 10 is a plan view of 105 viewed from the roller nip portion direction.
In the figure, reference numeral 120 is a conveyance drive shaft of the conveyance roller 104, 121 is a separation drive shaft of the separation roller 105,
It is supported by the main body of the automatic document feeder DF. Also,
The transport drive shaft 120 is driven by the drive unit in the direction in which the document D is transported (clockwise in FIG. 4), and the separation drive shaft in the direction in which the document D is returned (clockwise in FIG. 4).

The carrying roller 104 is a resin collar 10.
Four rollers 104a made of annular EPDM (ethylene / propylene terpolymer) are press-fitted into 4b. Then, the transport roller 104 is
It is fixed to the transport drive shaft 120 and integrally rotates in the sheet feeding direction. The separating roller 105 includes a resin collar 105b and an annular urethane rubber roller 105b.
It is configured by press-fitting three a's. Then, the separation roller 105 is fixed to the separation drive shaft 121 and integrally rotates in the direction of returning the sheet.

Here, the separation roller 105 and the transport roller 1
04 are opposite to each other as shown in FIG.
It is arranged so as to have a predetermined overlap amount l (0.3 to 0.7 mm).

In FIG. 4, a separation / conveyance roller pair 10 is provided.
A pair of guide plates 106a and 106b are provided downstream of 4, 105.
Is provided. The document D is the guide plate pair 106.
The registration roller pair 107 is guided by a and 106b.
It is conveyed again by the pair of registration rollers 107a and 107b which collide with the main body 900 of the copying machine and stop again after hitting the nip of a and 107b.

The original D is fed from the separating / conveying unit to the platen glass (reading unit) 11 by the front end of the original placing table 101, the guide plate pairs 106a and 106b, the guide plate 108, and the like.
A sheet conveying path (original conveying path) 10 that leads to the sheet 2 is configured.

Thereafter, the document D is printed on the guide plates 108 and 10.
It is guided by 6 and guided onto the platen glass 112 of the main body. Reference numeral 111 denotes a wide belt for conveying a document, which is stretched around a driving roller 110 and a driven roller 109, and conveys the document D while pressing it against a platen glass 112. After the reading of the document D by the optical system of the copying machine main body 900 is completed, the conveyance belt 111 is driven in the direction of the arrow in the drawing to convey the document D in the right direction in the drawing, and the document D is conveyed through the paper discharge roller 113. The sheet is discharged to the sheet discharge tray 114.

The above is the general operation of the automatic document feeder DF. Here, the conveying roller 104 and the separating roller 105 are described.
The method for separating the sheet according to will be further described. The basic principle of this separation method is to convey only the uppermost paper by using upper and lower rollers made of materials having different friction coefficients.

FIG. 6 shows the conveying roller 104 and the separating roller 1.
The state in which the document D is sandwiched by 05 is shown.

Here, the rollers 104 and 105 and the original D
As shown in the enlarged view of FIG.
They are in contact with each other at the corners of 4, 105. Then, the document D is bent into a wavy shape as illustrated by the conveying roller 104a and the separating roller 105a which are arranged in a staggered shape and staggered from each other. Then, the corners of the transport roller 104a and the separation roller 105a apply a vertical reaction force N ₁ to the document D, and the component force perpendicular to the transport direction acts on the document D in the transport direction N with respect to the transport direction. Is.

Due to this vertical reaction force N, the document D receives a frictional force from the rollers 104a and 105a, and this frictional force acts as a conveying force or a returning force F to the document D.

Here, the apparent friction coefficient μ acting has a relationship of F = Nμ (F is a conveying force and a returning force). This friction coefficient μ is a value that depends on the material of the roller, and is the following for the material in this example.

[0018]

[Table 1] Further, FIG. 7 shows a conveyance roller 104104 and a separation roller 1.
In the case of one original D entering during 05, 2
When the originals D are fed by double feeding, the originals D are sandwiched by the nip between the separation roller 105a and the conveying roller 104a, and the vertical drag force N acts in the vertical direction.

A friction force of 0.5.times.N is generated between the original document D and the original document D due to the adhesion force N (the friction coefficient between the paper sheets is 0.5).

The acting force on the document D when one document D is sandwiched between the rollers is Then, the document D is conveyed with a force of 3.6 N.

Next, the conveying roller 104 and the separating roller 10
When two originals are sandwiched between 5 and 5, the force balance of original D ₁ (the upper original is D ₁ and the lower original is D ₂ ) is Thus, the document D ₁ is conveyed with a force of 7.8N.

The balance of the force of the manuscript D ₂ is Then, the document D ₂ is returned and separated by a force of 4.2N.

Conventionally, such comb tooth separation system has been used to reliably separate and convey stacked sheets.

[0024]

However, in the above-mentioned conventional example, since the original document D is separated by the difference in the friction coefficient of the separating / conveying section, the material of the conveying roller 104 is the friction between the original documents (sheets). Those with a higher coefficient of friction than the coefficient, such as EPDM (ethylene propylene
Since the terpolymer) etc. were required, there were the following drawbacks.

(1) Conveying roller (conveying rotating means) 104
However, when it rubs against an image on an original (sheet) (a pencil writing document, a toner image by electrophotography), the conveyance roller 104
Is a member having a high friction coefficient, the image on the document D (document image) may be scraped off.

(2) Paper powder or the like is heavily adhered to the conveying roller 104, so that the performance of the paper feeding device is not stable.

(3) The material of the conveying roller 104 is EPDM
In this case, since its tensile strength is low, EPDM is not suitable for a method of applying tension such as a belt shape.

Further, as the material of the separating roller (separating means) 105, it is necessary to lower the friction coefficient than that of the conveying roller 104, and it is necessary to use urethane rubber or the like having a low friction coefficient. There was a flaw.

(1) Urethane rubber has a low friction coefficient at low temperatures (about 5 ° C. or lower), and is not suitable for a sheet feeding device used in such an environment.

The present invention relates to a sheet feeding apparatus provided with a separating / conveying unit comprising a conveying rotating means rotating in the sheet conveying direction and a separating means rotating in the sheet returning direction to separate the sheet. The separating means and the separating means are members having substantially the same friction coefficient, but the return force of the separating means is smaller than the conveying force of the conveying / rotating means to ensure the separation and conveyance of the sheet. It is an object of the present invention to provide a sheet feeding device having the above structure.

[0031]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and separates the sheet (D) from the separating means (3.
In the sheet feeding apparatus for separating and feeding the sheets one by one by means of 13, 12a, 12b), the separating means (3, 1)
3, 12a, 12b) are arranged in plural at intervals in the direction orthogonal to the direction in which the sheet (D) is transported, and the transport rotation means (3) that rotates in the transport direction of the sheet (D) and the sheet (D). ) Are arranged at intervals in a direction orthogonal to the feeding direction of the sheet (D) and are rotated in a direction in which the sheet (D) is returned in the direction opposite to the conveying direction of the sheet (D).
3) and the second separating / rotating means (1) arranged coaxially with the first separating / rotating means (13) and having a friction coefficient lower than that of the first separating / rotating means (13). 12
a, 12b), and the transport rotating body (3) and the first and second separating / rotating means (13, 12a, 12b).
And (3) are alternately arranged so that the sheet (D) is sandwiched and separated / conveyed between the conveyance rotating body (3) and the first and second separating / rotating means (13, 12a, 12b). Configure and
It is characterized in that the coefficient of friction of the carrier rotating body (3) and the coefficient of friction of the first separating and rotating means (13, 213) are set to be substantially the same.

Further, the conveyance rotating means (3) and the first
The separating and rotating means (13) is made of a low friction coefficient member.

Further, the transport rotation means (3) and the first
The separating / rotating means (13) is composed of a high friction coefficient member.

[0034]

According to the above construction, when the sheets (D) are separated one by one by the separating means (3, 13, 12a, 12b) and conveyed, the sheets (D) are conveyed by the conveying rotating body (3). Direction, and the first and second separating means (13, 12a, 12b) receive a sheet conveying direction opposite to the sheet conveying direction.

The friction coefficient of the second separating / rotating means (12) is set smaller than that of the friction coefficient of the first separating / rotating means (13), so that the conveying / rotating means for the sheet (D) ( The conveying force of the first and second (13, 12a, 12b) can be made smaller than the conveying force of 3) and the conveying rotating means (3) and the first and second separating rotating means (13, It is possible to ensure the separating action of the sheet (D) by 12a, 12b). Then, by setting the friction coefficient of the transport rotating body (3) and the friction coefficient of the first separating / rotating means (13) substantially equal to each other, the transport rotating body (3) and the first separating / rotating means (13). ) And the degree of freedom of material selection is expanded.

Further, since the conveying rotating means (3) and the first separating rotating means (13) are constituted by members having a low coefficient of friction of the material thereof, for example, a sheet feeding device is automatically fed by an original document. Even if a document (sheet) of pencil writing or a document composed of a fixed toner image is fed in the case of the feeding device, the document rotation image is written by the conveyance rotation unit like the conveyance rotation unit of the high friction coefficient member. It does not happen to drop it.

Further, since the material of the transport rotation means (3) and the first separation rotation means (13) is made of a material having a high friction coefficient, for example, the sheet feeding device is not installed in the image forming apparatus. When the recording sheet (S) for recording is applied to the sheet feeding unit that separates and conveys the recording sheet (S), even if the environment in which the image forming apparatus is used is low (5 ° C. or less), the friction coefficient of the conveyance rotation unit of the high friction coefficient member is high. The recording sheet (S) can be stably separated and conveyed without change at low temperatures.

The reference numerals in parentheses are shown for reference to the drawings and do not limit the configuration of the present invention.

[0039]

【Example】

<First Embodiment> An embodiment of the present invention will be described below with reference to the drawings.

An image forming apparatus main body (copier main body) to which the sheet feeding apparatus according to the present invention can be applied will be described first with reference to FIG.

In FIG. 3, an image forming apparatus main body (copier main body) 900 includes a platen glass (reading section) 112 as a document placing table, a light source 907, a lens system 908, a sheet feeding section 909, an image forming section 902 and the like. Is provided. The document D separated and conveyed from the sheet feeding device is fed to a predetermined position on the platen glass 902.

The paper feeding unit 909 accommodates recording sheets and is detachably attached to the apparatus main body 900.
1 and deck 911 located in pedestal 912
have. The image forming unit 902 includes a cylindrical photosensitive drum (image forming unit) 914 and a developing unit 915 around the photosensitive drum.
Transfer charger 916, separation charger 917, cleaner 91
8, a primary charger 919 and the like are provided, respectively. A conveying device 920, a fixing device 904, a pair of discharge rollers 905, and the like are arranged on the downstream side of the image forming unit 902.

Reference numeral 930 denotes a control unit of the copying machine main body 900, and 2
Reference numeral 0 denotes a solenoid for driving the shutter 103 (FIG. 4) of the sheet feeding device, and 21 denotes a driving unit for driving the separating / conveying unit of the sheet feeding device.

The operation of the image forming apparatus main body will be described.

When a paper feed signal is output from the control unit 930 provided on the apparatus main body side 900, the cassette 910,
The sheet S is fed from the 911 or the deck 913.
On the other hand, the document D placed on the platen glass 112
In addition, the light reflected by the light source 907 is applied to the photosensitive drum 914 via the lens system 908. The photosensitive drum 914 is previously charged by the primary charging device 919, and an electrostatic latent image is formed by irradiating light, and then the developing device 915 develops the electrostatic latent image to form a toner image. .

The sheet S fed from the paper feeding unit 909 is
The skew feeding is corrected by the registration roller 910, and the timing is adjusted to send the image to the image forming unit 902. In the image forming unit 902, the toner image on the photosensitive drum 914 is transferred to the sent sheet S by the transfer charger 916, and the sheet S onto which the toner image is transferred is separated by the separation charger 91.
7 is charged to the opposite polarity to the transfer charger 916,
Separated from the photosensitive drum 914.

Then, the separated sheet S is conveyed to the fixing device 904 by the conveying device 920, and the sheet S is fixed.
The transfer image is permanently fixed to the sheet S by 04. The sheet S having the image fixed thereon is ejected from the apparatus main body 900 by the ejection roller pair 905. In this way, an image is formed and discharged on the sheet S fed from the sheet feeding unit 909.

Next, an example in which the sheet feeding apparatus of the present invention is used as an automatic document feeding apparatus DF provided in a copying machine as an image forming apparatus will be described. In this case, the sheet feeding device according to the present invention is different from the sheet feeding device described with reference to FIG. 4 only in the separating / conveying units 104 and 105, and the other configurations are the same, so that the present invention is related. The separation / conveyance part will be described, and the other parts will be omitted by referring to the above description of FIG. 4.

FIG. 1 shows a main part of a sheet feeding device of the comb tooth separation type according to the present invention, and shows an improved type of the separating part of the automatic document feeding device of the conventional example (FIG. 4).

In the figure, 1 is a conveyance drive shaft, 2 is a conveyance collar, and 3 is an annular conveyance roller (conveyance rotation means) made of urethane rubber having a low friction coefficient with respect to a document (sheet) D. A plurality of transport rollers 3 are provided in a direction perpendicular to the sheet transport direction and are press-fitted into the transport collar 2. The transport collars 2 are further press-fitted into the transport drive shaft 1 so that they can rotate as an integral roller. Has become.

Reference numeral 11 is a separation drive shaft, 12 is a separation collar made of polyacetal resin, and 13 is an annular first separation roller (first separation rotation means) made of urethane rubber having a low friction coefficient with the original D. is there. Then, the first separation roller 13
Are provided in the sheet conveying direction and are press-fitted into the separation collar 12, and the separation collars 12 are further press-fitted into the separation drive shaft 11 so that they can rotate as an integral roller.

The conveying roller 3 and the first separating roller 13
Are opposed to each other with a predetermined overlap amount (l 'in the figure) in a cross section orthogonal to the transport drive shaft 1 and the separation drive shaft 11. In addition, the drive unit 21 (FIG. 3) drives the transport drive shaft 1 in the sheet transport direction and the separation drive shaft 11 in the sheet return direction.

First, in the present embodiment, as the material of the conveying roller 3 and the separating roller 13, urethane rubber having a low friction coefficient is used. Here, the coefficient of friction of the urethane rubber with the original document D is about 1.2 at the maximum, and the lower limit of the coefficient of friction when it is used stably as a conveying member is about 0.9.
Under these circumstances, the coefficient of friction of the conveyance roller 1 with the document D is 1.2, and the coefficient of friction of the separation roller 11 with the document D is 1.
0 material is used.

The reason why EPDM is not used for both the conveying roller 3 and the first separating roller 13 is that the sheet feeding apparatus having the separating / conveying rotating means according to this embodiment is applied automatically. This is with respect to the document feeding device DF, and this automatic document feeding device DF has a case of conveying a document written in pencil. Since the friction coefficient of EPDM (ethylene / propylene terpolymer) is a high coefficient of friction, there is a problem that the conveying roller 3 scrapes off the pencil image on the document D, which is improved. Therefore, urethane rubber is used.

In this embodiment, as shown in FIG. 1, a vertical reaction force of N is applied from the corner of each roller to the document D in the direction orthogonal to the conveying direction. This vertical reaction force N generates a frictional force between the document D and the roller, which acts as a conveying force and a returning force. This conveyance force and return force are F
And the apparent frictional force is μ, then there is a relationship of F = μN, and the frictional coefficient μ is a value that differs depending on the roller material. The value of μ is as follows.

[0056]

[Table 2] Further, in the case where two originals D have entered between the conveyance roller 3 and the first separation roller 13, each part of the conveyance roller 3 is
In the portion sandwiched by the respective portions of the separation roller 13, the adhesive force N acts between the documents D. Since the coefficient of friction between the sheets of the document D is 0.5, the frictional force between the documents D is 0.5 N.

Here, the principle of conveyance / separation in this embodiment will be described.

In this structure, the conveying roller 3 and the separating roller 1
Since the difference in the friction coefficient from 3 is small, it is difficult for the document D to obtain a large conveyance force [(friction force received from the conveyance roller 3)-(friction force received from the separation roller 13)].

Therefore, the number of separating rollers 13 is reduced,
Instead, the second separation roller (pseudo roller) 12 made of polyacetal, which has the same shape as the first separation roller 13 and has an extremely low friction coefficient, presses the document D against the conveyance roller 3.
It is replaced by a and 12b.

As a result, a measure is taken to reduce the carrying force of the document D in the returning direction. The second separation rollers 12a and 12b are the same as the second separation roller 12 as shown in FIG.
It may be formed integrally with or may be separately formed and fixedly or rotatably attached to the separation collar 12.

The force acting on the document D is as follows.

(N: vertical force applied to each original by each roller)
First, when one document D enters between the rollers, the force received by the document D is Then, the document D is conveyed with a force of 4.4 N.

Next, when two originals D ₁ and D ₂ are inserted between the rollers, the upper original D ₁ is The document D is conveyed by a force of 7N. The lower document D ₂ is Then, the document D ₂ is returned with a force of 2.6.

In this way, in this embodiment, the document D is pressed against the conveying roller 3 by the second separating rollers 12a and 12b as pseudo rollers, so that both the conveying roller 3 and the first separating roller 13 are made of urethane rubber. Even when using, the conveyance force on the side of the conveyance roller 3 is always larger than the conveyance force on the side of the first and second separation rollers 3 and 13, and therefore the conveyance of the document D by the conveyance roller 3 Make sure,
The document D can be separated and conveyed. As a result, it is possible to prevent the document D from being damaged when the document D is transported by the transport roller 3.

Further, as with EPDM having a high friction coefficient, paper dust is less likely to be generated, and it is possible to feed paper with excellent durability.

In this embodiment, as the conveying / separating means, both the conveying roller 3 and the first separating roller 13 have a roller shape, but the present invention is not limited to this, and a belt-belt combination, Alternatively, the same comb tooth separation performance can be obtained by a belt-roller combination.

Further, in this embodiment, the conveying roller 3 and the first
The material of the separation roller 13 and the separation roller 13 has a small difference in friction coefficient, and both are made of urethane. However, the material is not limited to this, and one material of the conveyance roller and the first separation roller may be used. May be urethane and the other may have substantially the same or the same friction coefficient as the urethane. <Second Embodiment> FIG. 2 is a plan view of a separation / conveyance section of a sheet feeding apparatus according to a second embodiment of the present invention. This sheet feeding device is intended to stabilize the separation / conveyance performance in a low temperature environment (5 ° C. or lower).

In the present embodiment, the friction coefficient of the separating / conveying rotating means in a low temperature environment is set by using EPDM as a material having a high friction coefficient for both the conveying roller of the separating / conveying section and the first separating roller. A stable value that does not change makes it possible to stabilize the separation and conveyance. In addition,
In the case of urethane rubber of a low friction coefficient member, at 5 ° C. or lower, the friction coefficient of the urethane rubber may decrease, and the separation / conveyance performance of the separation / conveyance unit may be reduced.

Further, as the material of the conveying roller, EPDM
Is used because the recording sheet to be separated / conveyed by the separating / conveying unit is a sheet on which image information has not been recorded. This is because there is no image such as writing and there is no need to worry about the image being smeared by the transport roller.

The sheet feeding apparatus according to the present embodiment has, for example, cassettes 910, 9 as sheet stacking means shown in FIG.
11 or the deck 913 is disposed on the downstream side (not shown) of the paper feeding means (paper feeding roller or paper feeding belt). Sheet material S fed from the above-mentioned cassette or a paper feed unit such as a deck
Are separated one by one by a separating / conveying unit, which will be described later, and are conveyed on a recording sheet conveying path (sheet conveying path) to the registration roller pair 901.

In the separation / conveyance unit shown in FIG.
Is a conveying drive shaft, 202 is a conveying collar, and 203 is an annular conveying roller (conveying rotating means) made of EPDM whose material is a high friction coefficient. A plurality of conveying rollers 203 are provided in a direction orthogonal to the sheet conveying direction and are press-fitted into the conveying collar 202.
It is press-fitted onto the conveyance drive shaft 201 and is conveyed by the conveyance roller 203.
Is rotatable as a roller integrated with the transport drive shaft 201.

Reference numeral 211 is a separation driving shaft, 212 is a separation collar made of fluorocarbon resin having a low friction coefficient, and 213 is a conveying roller 2.
This is a circular ring-shaped first separation roller (first separation rotation means) made of EPDM, which is the same as the reference numeral 03.

A plurality of the above-mentioned first separating rollers 213 are provided in the direction orthogonal to the sheet conveying direction and are press-fitted into the separating collar 212. The separation collar 212 is press-fitted onto the separation driving shaft 211, and the first separation roller 21
3 is rotatable as a roller integrated with the separation drive shaft 211.

The transport roller 203 and the first separating roller 213 are opposed to each other with a predetermined overlap amount l ″ as shown in FIG.
The drive unit 21 (see FIG. 3) drives the transport drive shaft 201 in the sheet transport direction and the separation drive shaft 211 in the sheet return direction.

The cassette 910, 911 or the deck 9
The sheet material S sent out from the sheet 13 is conveyed by the conveying roller 203.
2 and the first and second separation rollers 213, 212a are supported by being curved in a corrugated shape as shown in FIG.
The corner portion 3a applies a normal force N to the sheet S in a direction orthogonal to the conveying direction. Friction force F between the rollers 203, 213, 212a and the sheet due to this normal force N
Acts as a conveying force and a returning force to the sheet S.

Here, there is a relationship of F = μN (μ is an apparent friction coefficient), and the value of μ is as shown in the figure below.

[0077]

[Table 3] Then, in the case where two sheets S enter between the conveying / separating rollers, the sheet is stuck by the force of N in the vertical direction by the action of the vertical reaction force N at the portion sandwiched between the conveying roller 203 and the separating roller 213. . Since the coefficient of friction between the sheets is 0.5, the frictional force acting on the sheet material S is 0.
It becomes 5N. Reference numeral 212a denotes a second separation roller (pseudo roller) having a low friction coefficient formed integrally with the separation collar 212, and has the same shape as the first separation roller 213 and is provided on the same shaft. . The second separating roller 212a has a function of pressing the sheet S toward the conveying roller 203.

The material of the second separating roller 212a is fluororesin, and the second separating roller 212a is
And the friction coefficient between the sheet S and the sheet S is 0.4, the EPD
Compared with the roller made of M, it has a very small conveying force.

As a result, the frictional force applied to the sheet by the conveying roller 203 and the first and second separating rollers 213, 2
Since the frictional force applied to the sheet by 12b is different, the separation and conveyance of the sheet S can be reliably performed even in a low temperature environment.

The force acting on the sheet S is as follows. (N in FIG. 2 is a vertical drag force, and the friction coefficient between the sheets is 0.5.) First, when one sheet S enters between the rollers, the force acting on the sheet S is Then, the sheet S is conveyed by the conveying force of 3.4 N.

Further, two sheets S ₁ and S ₂ are interposed between the rollers.
If there is, the upper sheet S ₁ Therefore, the sheet S ₁ is conveyed by the conveying force of 7.2N.

Next, the lower sheet S ₂ is Separated by.

With the above-described structure, the material of both the conveying roller 203 and the first separating roller 213 of the separating / conveying section is EPDM having a high friction coefficient, and the second separating roller has a low friction coefficient. By using fluororesin,
Although the conveying roller 203 and the first separating roller 213 are made of substantially the same (or the same) material, the conveying force between the conveying roller and the separating roller can be made different, and the comb teeth of the sheet S can be formed. It became possible to separate.

As a result, it is possible to realize a sheet feeding apparatus having a separating / conveying unit with stable separation / conveying performance of stacked sheets even in a low temperature environment.

The second separating roller 212 of this embodiment is used.
a is not a function of being driven integrally with the separation roller as in each of the embodiments, and even if it is configured to idle as an idler roller, the conveyance force transmitted to the sheet S is a. The sheet S can be lowered, and the separation / conveyance performance of the sheet S can be similarly stabilized.

[0086]

As described above, according to the present invention,
A plurality of separating means for separating / conveying the sheets one by one are arranged in a direction orthogonal to the sheet conveying direction at intervals and a conveying rotating means, and a plurality of separating means are arranged in a direction orthogonal to the sheet conveying direction to return the sheets. The rotating first separating and rotating means and the second separating and rotating means arranged coaxially with the first separating and rotating means and having a friction coefficient lower than that of the first separating and rotating means.
Separating rotation means, the transport rotating means and the first and second separating rotating means are alternately arranged, and the friction coefficient of the transport rotating means and the friction coefficient of the first separating rotating means are Are set to be substantially the same, the separating / conveying unit composed of the conveying / rotating means rotating in the sheet conveying direction and the conveying / rotating means rotating in the sheet returning direction separates the sheets one by one.
In the sheet feeding apparatus for transporting, the separating means is composed of a member having a friction coefficient substantially the same as the friction coefficient of the transport rotating means.
And the second separating and rotating means composed of a member having a friction coefficient smaller than that of the first separating and rotating means, the friction coefficient of the first separating and rotating means with respect to the sheet is equal to that of the conveying rotating means. Although the friction coefficient with respect to the sheet is substantially the same, the conveying force of the sheet in the sheet returning direction by the second separating and rotating means is extremely small, so that the conveying force of the sheet by the conveying and rotating means is made into the first and second separating rotations. It can be greater than the carrying force of the means,
It is possible to reliably separate and convey sheets.

Further, by using a low friction coefficient member such as urethane rubber for the conveyance rotation means and the first separation rotation means, the original of the pencil writing or the toner image in the automatic original feeding apparatus is imaged. Separation without disturbing
Can be transported.

Further, by using a low friction coefficient member such as an ethylene / propylene terpolymer as the conveying rotation means and the first separation rotation means, the unrecorded recording paper in the image forming apparatus can be It can be stably separated and transported even in a low temperature environment.

[Brief description of drawings]

FIG. 1 is a plan view of a separating / feeding unit of a sheet feeding apparatus according to a first embodiment of the present invention.

FIG. 2 is a plan view of a separation / conveyance unit of a sheet feeding device according to a second embodiment of the present invention.

FIG. 3 is a vertical cross-sectional side view of an image forming apparatus main body to which the sheet feeding apparatus of the present invention can be applied.

FIG. 4 is a vertical sectional side view of an automatic document feeder as a sheet feeder using a conventional separating / conveying unit.

FIG. 5 is a plan view of the separating / conveying unit.

[Fig. 6] Similarly, an operation diagram of the separation / conveyance unit

FIG. 7 is an enlarged view of FIG.

[Explanation of symbols]

DF automatic document feeder D document (sheet) S sheet 1 transport drive shaft 2 transport collar 3 transport roller (transport rotating means) 10 sheet transport path (document transport path, recording sheet transport path) 11 separation drive shaft 12 separation collar 12a , 12b Second separation roller (second separation rotation means) 13 First separation roller (first separation rotation means) 20 Solenoid 21 Drive section 101 Sheet stacking table 201 Conveyance drive shaft 202 Conveyance color 203 Conveyance roller (conveyance) Rotating means) 211 Separation drive shaft 212 Separation collar 212a Second separation roller (second separation rotation means) 213 First separation roller (first separation rotation means) 900 Copier main body (image forming apparatus main body) 901 Registration Roller pair 902 Image forming unit 909 Paper feeding unit 910, 911 Cassette 913 Paper feeding deck 930 Control unit

Claims (8)

[Claims] 1. A sheet feeding device for separating and feeding sheets one by one by a separating means, wherein a plurality of the separating means are arranged at intervals in a direction orthogonal to a sheet conveying direction. A conveyance rotation unit that rotates in the conveyance direction, and a plurality of first separation rotation units that are arranged at intervals in a direction orthogonal to the sheet conveyance direction and that rotate in a direction that returns the sheet in the opposite direction to the sheet conveyance direction. A second separating / rotating means arranged coaxially with the first separating / rotating means and having a friction coefficient lower than a friction coefficient of the first separating / rotating means; The first and second separating / rotating means are alternately arranged, and a sheet is sandwiched between the conveying rotating body and the first and second separating / rotating means to separate / convey. The coefficient of friction of the transport rotating body and Sheet feeding apparatus characterized by comprising setting the friction coefficient between the first separation rotary means about the same. 2. The transport rotating means is a comb tooth-shaped roller arranged at a plurality of intervals, and the first and second separation rotating means are opposed to the transport rotating means and are arranged at a plurality of intervals. The sheet feeding device according to claim 1, wherein the sheet feeding roller is a comb-shaped roller. 3. The sheet feeding apparatus according to claim 1, wherein the transport rotation means and the first separation rotation means are members having a low friction coefficient. 4. The sheet feeding apparatus according to claim 3, wherein at least one of the conveyance rotating unit and the first separating rotating unit is made of urethane rubber. 5. The sheet feeding device of the sheet feeding device according to claim 1, wherein the conveyance rotating means and the first separation rotating means are made of high friction coefficient members. 6. The sheet feeding apparatus according to claim 5, wherein at least one of the transport rotation means and the first separation rotation means is made of an ethylene / propylene terpolymer. 7. An automatic document feeder comprising the sheet feeding device according to claim 1 and a reading unit for reading an image of a sheet fed from the sheet feeding device. apparatus. 8. A sheet feeding device according to claim 1, and an image forming unit for forming an image on a sheet fed from the sheet feeding device. An image forming apparatus characterized by the above.