JPH08310681A - Sheet feeding device and image forming device - Google Patents

Abstract

PURPOSE: To prevent the set condition of the sheets from being disordered when a feed roller is rotated with a retard roller. CONSTITUTION: The drive of a feed roller 2 is transmitted to a retard roller 3 through gears 6, 7, 8, and the retard roller 3 is in the stopped condition before the drive is transmitted from a unidirectional rotary clutch 5 to the feed roller 2, and the feed roller 2 is not rotated with the retard roller 3 before the drive is transmitted from the unidirectional rotary clutch 5 to the feed roller 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding device provided in an image forming apparatus such as a facsimile, a printer and a copying machine.

[0002]

2. Description of the Related Art Image forming apparatuses such as facsimiles, printers and copiers are equipped with a sheet feeding device that separates and feeds stacked sheets one by one.

There are various configurations of this sheet feeding device, and one of them is a separation roller pair 1 shown in FIG.
There are some that use. The separation roller pair 1 includes a feed roller 2 that feeds the stacked sheets S, and a retard roller 3 that pushes back the second and subsequent sheets S fed by the feed roller 2.

The feed roller 2 rotates in a counterclockwise direction (sheet conveying direction) by the drive transmitted from a drive source (not shown), and feeds the stacked sheets S in order from the lowest sheet. The retard roller 3 is rotated in the counterclockwise direction (the direction opposite to the sheet conveying direction) by the drive transmitted from a drive source (not shown) through a route different from that of the feed roller 2, and is fed by the feed roller 2. The sheets S after the first sheet (other than the lowest sheet) are pushed back.

The sheet S sent out by the separation roller pair 1 is conveyed to a target place by the conveyance roller pair 4. In this case, the peripheral speed of the feed roller 2 is set to be smaller than the peripheral speed of the conveying roller pair 4 in order to provide a predetermined interval (sheet interval) between the sheets S sent by the separation roller pair 1. ing. In order to prevent the feed roller 2 from rubbing the sheet S when the sheet S sent out by the separation roller pair 1 starts to be conveyed by the conveyance roller pair 4, the feed roller 2 has a one-way rotation clutch (one-way clutch). ) 5, the drive is transmitted, and the feed roller 2 is rotated along with the sheet S which is being conveyed to the conveying roller pair 4.

However, in the case where the driving force is transmitted to the feed roller 2 via the one-way rotation clutch 5,
The following problems occur.

That is, when the trailing edge of the sheet S, which has started to be conveyed by the conveying roller pair 4, passes through the nip of the separating roller pair 1, the driving force is transmitted to the feed roller 2 again via the one-way rotation clutch 5. Before being transmitted to the feed roller 2, the feed roller 2 rotates along with the retard roller 3 and rotates in the reverse direction, and pushes the waiting sheet S back upstream. In this case, the set state of the sheet S is disturbed, which may cause feeding failure or skew.

Conventionally, as a countermeasure for this, a one-way rotating clutch 5 such as a needle clutch having a small backlash is used. If the backlash of the one-way rotating clutch 5 is small, the amount of rotation of the feed roller 2 by the retard roller 3 is small, and the returning amount of the sheet S in standby can be suppressed to a certain amount or less.

[0009]

However, even if the return amount of the waiting sheet S is suppressed to a certain amount or less by the countermeasure of the above-mentioned conventional example, the set state of the sheet S may be disturbed, and feeding failure or skew feeding may occur. It was not possible to prevent the occurrence of such problems. Further, there is a problem that the cost increases when a needle clutch or the like having a small backlash is used.

Therefore, the present invention has been made in view of the above circumstances, and provides a sheet feeding apparatus which eliminates the disorder of the set state of the sheet and prevents feeding failure and skew. With the goal.

[0011]

SUMMARY OF THE INVENTION According to the present invention, a feed roller that rotates in a sheet conveying direction to feed a stacked sheet, and a sheet that rotates in a direction opposite to the sheet conveying direction and is fed by the feed roller. The present invention relates to a sheet feeding device including a retard roller that pushes back the second and subsequent sheets, and a one-way rotation clutch that transmits driving force to the feed roller.

In order to achieve the above object, the present invention is characterized in that the drive of the feed roller is transmitted to the retard roller through a drive transmission means.

[0013]

According to the sheet feeding apparatus of the present invention having the above structure, the retard roller is driven by the feed roller to rotate in the direction opposite to the sheet conveying direction.

Therefore, when the trailing edge of the sheet, which has started to be conveyed by the conveying roller pair, passes through the nip between the feed roller and the retard roller, the retard roller stops rotating until the drive is transmitted from the one-way rotation clutch to the feed roller. It is in a state of inside.

As a result, the feed roller does not follow the retard roller until the drive is transmitted from the one-way rotation clutch to the feed roller, and the sheet setting state is not disturbed.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 shows the configuration of a sheet feeding apparatus according to Embodiment 1 of the present invention.

In describing the structure of the present sheet feeding apparatus, the same members and the like as those of the conventional sheet feeding apparatus (FIG. 7) are designated by the same reference numerals and are structurally and functionally unchanged. The description of the items is omitted.

In this sheet feeding apparatus, the drive of the feed roller 2 is transmitted to the retard roller 3 via gears (drive transmission means) 6, 7, and 8. The drive of a drive source (not shown) is transmitted to the feed roller 2 via the one-way rotation clutch 5, and the feed roller 2 rotates in the sheet conveying direction. The drive of the feed roller 2 is driven by the gear 6,
It is transmitted to the retard roller 3 via 7 and 8, and the retard roller 3 rotates in the direction opposite to the sheet conveying direction.

In this way, when the drive of the feed roller 2 is transmitted to the retard roller 3, the trailing edge of the sheet S which is started to be conveyed by the conveying roller pair 4 is the feed roller 2.
After passing through the nip of the retard roller 3 and the retard roller 3, the rotation of the retard roller 3 is stopped until the drive is transmitted from the one-way rotation clutch 5 to the feed roller 2.
The feed roller 2 does not follow the retard roller 3 until the drive is transmitted from the one-way rotation clutch 5 to the feed roller 2.

Since the rotation of the retard roller 3 is stopped and the feed roller 2 is not rotated together, it is not necessary to reduce the backlash of the one-way rotation clutch 5. For this reason, in the present sheet feeding device, an inexpensive spring clutch having a large backlash is used as the one-way rotating clutch 5.

Further, in the present sheet feeding apparatus, torque is applied during the power transmission path for transmitting the drive of the feed roller 2 to the retard roller 3 (between the roller shaft 9 of the retard roller 3 and the gear shaft 10 of the gear 8). The limiter 11 is provided.

In the case of such a configuration, when the torque of a predetermined value or more is applied to the retard roller 3, the power of the feed roller 2 is not transmitted to the retard roller 3,
Rubbing does not occur between the retard roller 2 and the feed roller 3 and between the retard roller 3 and the sheet S.

Here, when there is no sheet S between the feed roller 2 and the retard roller 3 (FIG. 2), when there is one sheet S (FIG. 3), there are two sheets S1 and S.
The drive conditions in each case of 2 (FIG. 4) will be examined.

The frictional force and friction coefficient between the feed roller 2 and the retard roller 3 are F1, μRB, and the frictional force and friction coefficient between the feed roller 2 and the sheet S are F2, μ.
PB, the frictional force and the friction coefficient between the retard roller 3 and the sheet S are F3 and μPR, the frictional force and the friction coefficient between the sheet S and the sheet S are F4 and μPP, and the retard roller 3
Of the feed roller 2 is W, the set value of the torque limiter 11 is TR, the reduction ratio η between the feed roller 2 and the retard roller 3 and the radius of the feed roller 2 are r.
B, the radius of the retard roller 3 is rR.

(1) When there is no sheet S between the feed roller 2 and the retard roller 3 (FIG. 2) In this case, the retard roller 3 must rotate so as not to rub against the feed roller 2 and wear. The condition therefor is F1 × rR> TR F1 × rB> TR / η, but since F1 can be the maximum μRB × W, μRB × W × rR> TR (1) μRB × W × rB> TR / η ... Equation (2).

(2) When there is one sheet S between the feed roller 2 and the retard roller 3 (FIG. 3) In this case, the retard roller 3 is not rotated with the sheet S so as not to damage the sheet S. I have to do it. The conditions therefor are: F2> F3 F3 × rR> TR F2 × rB> TR / η, but F2 can be the maximum μPB × W, F3 can be the maximum μPR × W, and when the torque limiter 11 slips. Force F3 is TR / rR, so μPB × W> TR / rR ... Equation (3) μPR × W × rR> TR Equation (4) μPB × W × rB> TR / Η ··· Equation (5)

(3) When there are two sheets S1 and S2 between the feed roller 2 and the retard roller 3 (FIG. 4) In this case, the retard roller 3 must push back the second sheet S2. . The conditions therefor are: TR> F4 × rR F3> F4 F2> F4, but F2 can be maximum μPB × W, F3 can be maximum μPR × W, and the sheets S1 and S2 are slippery. Since F4 = μPP × W, TR> μPP × W × rR ... Equation (6) μPR × W> μPP × W ... Equation (7) μPB × W> μPP × W ... ... becomes equation (8).

The driving conditions in the cases of (1), (2), and (3) are summarized as follows: Equations (1), (3), (4), (6), (7), (8)
From min [μRB, μPB, μPR]> TR / W × rR> μPP ... Equation (9) Equations (2) and (5) From min [μRB, μPB]> TR / W × rB × η・ ・ ・ Each of the equations (10) can be obtained, and these equations (9) and (10) are the separate feeding conditions in this sheet feeding device.

In this embodiment, μRB = 3, μPB
= 1.5, μPR = 1.5, μPP = 0.7, TR = 2
95gf · cm, W = 261gf, rR = 10mm, r
B = 15 mm and η = 1 are set. Therefore, equation (9)
Is 1.5>1.13> 0.7, and the formula (10) is 1.5>
It became 0.75, and all satisfied the conditions.

When the peripheral velocities of the feed roller 2 and the retard roller 3 are SB and SR, there is a relation of SR = SB × 1 / η × rR / rB. In the case of this embodiment, SR = 1/1 × 10/15 × SB = (2/3) × SB. Therefore, good separation and feeding performance can be obtained. <Embodiment 2> FIG. 5 shows another configuration example of the drive transmission means for transmitting the drive of the feed roller 2 to the retard roller 3.

The drive of the feed roller 2 is first transmitted to the pulley 14 on the support shaft 13 by the belt 12, and the drive transmitted to the pulley 14 is transmitted to the retard roller 3 by the belt 15.

Further, the retard roller 3 is swingable in the vertical direction about the support shaft 13. The retard roller 3 is normally in contact with the feed roller 2 at a predetermined pressure due to its own weight, but can be separated from the feed roller 2 by lifting it upward. Therefore,
Jam removal and cleaning of the rollers 2 and 3 are easy.

Reference numeral 16 in the drawing is a motor as a drive source for driving the feed roller 2.

FIG. 6 shows an example of the overall configuration of a facsimile apparatus (image forming apparatus) equipped with the sheet feeding apparatus of the present invention.

A document P set on the document table 17
Are fed one by one by the sheet feeding apparatus of the present invention using the pair of separation rollers 1. Then, the fed original P is conveyed by the conveying roller pair 4 to the contact image sensor 1
8 and information is read while passing through the image sensor 18. The information read by the image sensor 18 is temporarily stored in the storage means. In the transmission mode, the stored information is transmitted from the control unit to the facsimile machine of the other party. The document P that has passed through the image sensor 18 is discharged onto a discharge tray 20 outside the apparatus by a discharge roller pair 19.

In the copy mode, the document information read by the image sensor 18 is sent from the control section to the laser scanner 21, and the laser scanner 21 emits a laser beam L based on the document information. In the reception mode, the information transmitted from the facsimile machine of the other party is sent from the control section to the laser scanner 21, and the laser scanner 21 emits a laser beam L based on the received information.

The laser light L emitted from the laser scanner 21 is applied to the photosensitive drum 23 rotating in the clockwise direction via the reflection mirror 22. This allows
An electrostatic latent image is sequentially formed on the photosensitive drum 23. Then, the electrostatic latent image is visualized (toner image) by the toner supplied from the developing device 24 and is sent to the transfer portion between the photosensitive drum 23 and the transfer roller 25.

In the reception mode and the copy mode, one of the sheets S stacked and stored in the paper feed cassette 26 or 27 is fed to the paper feed roller 28 or 29 one by one and sent to the transfer unit. While the fed sheet S is passing between the photosensitive drum 23 and the transfer roller 25, the toner images on the photosensitive drum 23 are sequentially transferred onto the sheet surface by the transfer roller 25.

The sheet S after the transfer of the toner image is sent to the fixing roller pair 30, and is heated and pressed while passing through the nip of the identification fixing roller pair 30, so that the transferred toner image is fixed on the sheet surface. Then, the sheet S for which the fixing process of the transfer toner image has been completed is ejected by the ejection roller pair 31 to the ejection tray 3 outside the apparatus.
2 is ejected to the top.

In the present embodiment, an example in which the present invention is applied to a document reading section in a facsimile apparatus is shown, but the present invention is not limited to this, and for example, an image forming section on which an image is formed. 1 recording sheet to send to
It may be applied to a paper feeding unit for feeding sheets one by one.

[0041]

As described above, in the sheet feeding apparatus of the present invention, the drive of the feed roller is transmitted to the retard roller, so that the trailing edge of the sheet fed by the pair of feeding rollers is fed. After passing through the nip between the roller and the retard roller, the rotation of the retard roller is stopped until the drive is transmitted from the one-way rotation clutch to the feed roller. To this end, 1
The feed roller is not entrained by the retard roller before the drive is transmitted from the directional rotation clutch to the feed roller.

Therefore, when the waiting sheet is pushed back to the feed roller, the sheet set state is not disturbed, and feeding failure or skewing does not occur.

Further, since the present invention is not affected by the magnitude of the backlash of the one-way rotary clutch,
An inexpensive spring clutch with a large backlash can be used as the directional rotation clutch.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a sheet feeding device according to a first embodiment of the invention.

FIG. 2 is a schematic diagram illustrating drive conditions when there is no sheet between a feed roller and a retard roller.

FIG. 3 is a schematic diagram illustrating drive conditions when there is one sheet between a feed roller and a retard roller.

FIG. 4 is a schematic diagram illustrating drive conditions when two sheets are provided between a feed roller and a retard roller.

FIG. 5 is a vertical cross-sectional side view showing another configuration example (Example 2) of the drive transmission means for transmitting the drive of the feed roller to the retard roller.

FIG. 6 is a vertical sectional side view showing an example of the overall configuration of a facsimile apparatus (image forming apparatus) including the sheet feeding apparatus of the present invention.

FIG. 7 is a perspective view showing a configuration of a conventional sheet feeding device.

[Explanation of symbols]

 2 feed roller 3 retard roller 5 one-way rotation clutch 6, 7, 8 gear (drive transmission means) 11 torque limiter 12, 15 belt (drive transmission means) 18 contact image sensor (image reading means)

Claims (4)

[Claims] 1. A feed roller that rotates in a sheet conveying direction to feed out stacked sheets and a feed roller that rotates in a direction opposite to the sheet conveying direction and pushes back the second and subsequent sheets fed out by the feed roller. In a sheet feeding device including a retard roller and a one-way rotation clutch that transmits drive to the feed roller, the drive of the feed roller is transmitted to the retard roller via drive transmission means. A characteristic sheet feeding device. 2. The sheet feeding device according to claim 1, wherein a spring clutch is used as the one-way rotation clutch. 3. The sheet feeding device according to claim 1, wherein a torque limiter is provided in a drive transmission path for transmitting the drive of the feed roller to the retard roller. 4. A sheet feeding device according to claim 1, and image reading means for reading an image of a document fed by the sheet feeding device. An image forming apparatus characterized by.