JPH069079A - Sheet feed device and image forming device - Google Patents

Abstract

PURPOSE:To attain simplification and miniaturization of a separation type construction by means of a retard roller. CONSTITUTION:By providing a cassette 22 to loadingly support sheets, a semicircular feed roller 27 to feed the sheet from the cassette, and a separating means consisting of a normally driven roller 28 to rotate in the feeding direction and a retard roller 29 to reversely rotate against the feeding direction, a moving mechanism and the like to move paper feed rollers up and down in a customary device is dispensable, and hence simplification and miniaturization of the construction can be attained.

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 such as a copying machine and a printer, and particularly to a retard sheet feeding device having a low cost and a simple structure and excellent in sheet feeding and separating performance. It is a thing.

[0002]

2. Description of the Related Art Conventionally, three types of rollers, namely, a feeding roller, a forward drive roller, and a reversible retard roller are used.
In the so-called retard roller method, in which sheets stacked in a paper cassette or the like are separated and fed one by one, and the sheets are conveyed to the image forming unit, the height of the uppermost surface of the stacked sheets is kept substantially constant. However, in this method, the contact pressure between the feeding roller and the sheet can be easily kept constant by utilizing the self-weight of the roller regardless of the sheet loading amount. It is an effective means not only for the retard roller type sheet feeding apparatus but also for other feeding methods.

Here, a conventional example will be described with reference to FIG.

Reference numeral 1 is a main body of an image forming apparatus such as a copying machine or printer, 2 is a paper cassette, 3 is an intermediate plate rotatable around a shaft 2a fixed to the cassette 2, and S is a sheet such as transfer paper. Is.

A height detecting sensor 4 measures the height of the uppermost surface of the sheet, and detects the movement of a lever made of resin such as polycarbonate by a photo interrupter.

Reference numeral 5 is a lifter plate which raises the intermediate plate 3, and is fixed to a lifter shaft 6 which is rotated by a lifter drive motor 6a. A paper feed roller 7 is configured to rotate in the direction of the arrow and move vertically.

Reference numeral 8 is a forward rotation driving roller, and 9 is a retard roller, which has a torque limiter in the middle of the driving system. 1
0 and 11 are conveying roller pairs.

Next, the operation will be briefly described.

In response to a paper feed signal from the main body, the feeding roller 7 descends and presses against the uppermost sheet to rotate to feed the sheet. Next, the leading edge of the sheet enters the forward drive roller 8 and the retard roller 9. At this time, if there is only one sheet that has entered, the retard roller 9 rotates in the sheet advancing direction, and if more than two sheets have entered, the retard roller 9 reverses the action by the action of the torque limiter and returns the lower sheet in the cassette direction. To prevent double feed.

Further, the feeding roller 7 is controlled so as to move upward after a lapse of a certain time after the leading edge of the sheet has entered the retard roller pair, so that the above-mentioned double-feeding-prevented sheet is smoothly returned to the cassette direction.

As described above, by sequentially feeding the sheets from the uppermost sheet, the height of the uppermost sheet of the sheet is gradually reduced, and it is detected by the height detection sensor 4 that the height of the sheet falls below a certain height. Then, the lifter drive motor 6a is rotated for a certain minute time to raise the middle plate 3 and raise the uppermost surface level to a specified height.

By repeating the above operation, the sheets are sequentially fed one by one.

[0013]

However, in the conventional retard roller system, as described above, the lifter mechanisms 5, 6, 6a of the middle plate 3, the paper height detection sensor 4, and the feeding roller 7 are moved up and down. Since it requires a mechanism, etc., it is much more expensive than the claw separation method and the duplo method, the mechanism is complicated, and it is also disadvantageous in terms of space, so it is easily adopted for small copying machines and small printers. It was hard to be done.

[0014]

Means (and Action) for Solving the Problems
This is done in order to solve the drawbacks of the above-mentioned conventional example, that is, the cost increase and the space increase due to the complicated structure.

The structure of the present invention for achieving the above object is a sheet stacking means such as a paper cassette, and a sheet feeding means by one rotation control of a feeding roller having a half-moon shape in cross section, which is fixed in an axial position and does not need to be moved vertically. A sheet feeding apparatus having a separating and conveying unit downstream of the so-called retard roller pair for the purpose of preventing double feeding and a conveying unit further downstream of the conveying roller pair.

Further, the rotation driving control of the forward rotation driving roller of the retard roller pair is performed by one of the half-moon type feeding rollers.
It is synchronized with rotation.

By adopting these structures, the mechanism is greatly simplified and the cost is reduced as compared with the conventional retard roller system, and the sheet feeding means which is very effective for space saving is provided. It has become possible.

[0018]

1 to 3 show a first embodiment of the present invention, in which FIG. 1 is a main cross section thereof, and FIG. 2 is a plan view from above. FIG. 3 is a view of the drive transmission system as viewed in the direction of arrow E in FIG.

Reference numeral 22 is a paper cassette made of ABS resin or the like, and 23 is an intermediate plate serving as a sheet stacking base, which is rotatable around a fulcrum (not shown) behind the cassette.
Pressure is applied upward by the compression coil spring 24.

Reference numeral 25 denotes an auxiliary separating claw, which is adapted to be hooked to the front end and the right and left of the sheet similarly to the known separating claw method, but it is desirable that the hooking amount is slightly reduced. This is because the regulation of the upper surface of the stacked sheets is the primary purpose, the retard roller pair as the original separating means is provided downstream, and it is easy to deal with thick paper.

A feeding roller 27 has a substantially half-moon shape as shown in the drawing.

Reference numeral 28 is a forward rotation driving roller, which has a one-way clutch 32, and 29 is a retard roller,
Drive is transmitted via a torque limiter. 30, 3
Reference numeral 1 denotes a pair of conveyance rollers, and the sheet S is conveyed to the image forming section after passing through the pair.

Explaining the drive transmission system, the motor 3
By rotation of 4, the feeding clutch gear 36, the retard roller gear 39, and the transport roller gear 40 rotate via the idler gear 34 '.

Further, on the feeding roller shaft 44, a one-rotation transmission gear 37 is integrated on the side opposite to the feeding clutch gear 36 by a spinning pin or the like.
It is also connected to the forward rotation drive roller drive gear 38 via ′.

The feeding clutch gear 36 is usually idle around the shaft, but when the solenoid 41 is turned on (sucked) in response to a sheet feed start signal from the main body, the known spring clutch 35 acts. The feeding roller 27 is configured to rotate once by being integrated with the shaft.

The process from sheet feeding to separation and conveyance will be described in detail.

As described above, when the solenoid 41 is turned on by the feeding start signal and the feeding roller 27 makes one rotation, the leading end of the sheet comes off the auxiliary separating claw 25 and enters the retard roller pair 28, 29. To do.

As described above, the retard roller 29 is connected to the drive source via a so-called torque limiter 33, which is a power transmission mechanism that idles when a torque of a predetermined value or more is applied as a load. Therefore, when one sheet is fed, the load torque applied to the torque limiter 33 from the sheet via the retard roller 29 exceeds a predetermined value,
The torque limiter 33 idles and the retard roller 29 rotates.
Is driven to rotate by the sheet conveyed by the normal rotation driving roller 28. In addition, the auxiliary separation claw 25 cannot be completely separated.
When more than one sheet is sent, the frictional force between the sheets is applied as a load torque to the torque limiter 33 via the retard roller 29. Since this value is less than a predetermined value, the torque limiter 33 should be idle. Instead, the retard roller 29 rotates in the direction of returning the sheet to the cassette.

That is, if the sheet entering the retard roller pair 28, 29 is not double-fed, it is directly fed to the image forming section through the pair of conveying rollers 30, 31.
In the case of double feeding, the retard roller 29 is rotated in the reverse direction to separate the lower sheet, and only one sheet is fed to the image forming unit via the pair of conveying rollers 30 and 31. .

On the other hand, the forward rotation driving roller 28 is driven in synchronization with one rotation of the feeding roller 27 as described above, and the sheet is conveyed to the conveying roller pair 30, 31 by the completion of one rotation of the feeding roller 27. . Here, the normal rotation driving roller 28 is drive-transmitted through a known one-way clutch, and after the completion of one rotation of the feeding roller 27, the pair of conveying rollers 30 and 31.
It is configured to be driven to rotate by the sheet conveyed to.

As described above, as compared with the conventional retard roller system, the mechanism for vertically moving the feeding roller 27 and the device for detecting the paper surface height are not required, and a special lifter mechanism is not required, and the structure is greatly simplified. However, another feature of the present invention is that the arrangement of the roller pair and the like must satisfy the following conditions.

This will be described with reference to FIG.

From the cassette tip to the retard roller pair 28,
The distance to 29 is A, and the retard roller pair 28, 29
The distance from the transport roller pair 30 and 31 to B is B, and the distance that the sheet is fed and transported by one rotation of the feeding roller 27 (the length where the sheet and the surface of the feeding roller 27 are in contact) is C
Then, it is necessary to satisfy A <C <B. It goes without saying that the relationship of A <C will not be described, and if this is not established, the leading edge of the sheet does not reach the retard roller pair 28, 29. The relationship of C <B will be described with reference to FIG.

For example, as shown in FIG. 4, assuming that two sheets are fed in an overlapping manner just before the nip of the retard roller pair 28, 29, the retard roller 29 moves in the cassette direction in order to separate the double feeding. Although the sheet is rotated in the reverse direction, the feeding roller 27 is still in pressure contact with the upper sheet, so that the lower sheet may not return to the cassette direction and may advance to the pair of conveying rollers 30 and 31 while being double fed.

At this time, in the worst case, if C <B is not satisfied, the two sheets will enter the pair of conveying rollers 30 and 31 in a state of being overlapped with each other, and the separation will be impossible. .

FIG. 5 shows a second embodiment of the present invention, which is an electrophotographic printer to which the present invention is applied. A mounting plate 102 for stacking the sheets P is provided on the cassette 101 that can be pulled out in the front direction (the direction perpendicular to the paper feeding direction) in FIG.
The mounting plate 102 is lifted together with the sheet P at the lower part of the mounting plate 102 and substantially in the center of the paper width to generate a sheet feeding pressure with the feeding roller 103 for half a month. A rotatable pressure plate 104 is provided.

This pressure plate 104 is fixed to the rotary shaft 105, and the rotary power is transmitted to the front side in the direction of the cutting direction to rotate the rotary shaft 10.
A pressure arm 106 is fixed on the front side of the No. 5. The pressure arm 106 has one end of a pressure spring (tensile spring) 107 for generating a pressure corresponding to the sheet feeding pressure, and the other end has a pressure control arm 108 for controlling the pressure. There is.

The pressure control arm 108 rotates about the support shaft 108a and is provided with a member 108b such as POM having a high slip property at the end opposite to the end on which the pressure spring (tensile spring) 107 is applied. .

When the cassette is inserted from the front side of the apparatus, the cassette 1 is inserted in the width direction of the apparatus body into which the cassette 101 is inserted.
Rail portions 109, 109 'as means for suspending 01
Is provided, and by engaging with the rail portion 101a of the cassette 101, the insertion can be smoothly performed.

A cam portion 109a that engages with the pressure control arm 108 described above on one side 109 of the rail portion of the main body.
The pressure control arm 108 is rotated by the cam portion 109a immediately before the end of the cassette inserting operation, and the pressure spring 107 is pulled up, so that the spring force is applied to the pressure arm 106, The sheet P is transmitted to the pressure plate 104 via the rotation shaft 105, and the sheet P on the mounting plate 102 is lifted upward with a predetermined pressure. Lifted sheet P
The upper position is restricted by separation claws 110 provided at both ends of the leading end in the sheet feeding direction.

The separating claw 110 of the upper regulating member may have a performance of separating the sheets one by one when the paper is fed from the cassette as in the conventional case, but it is originally a retard roller as a separating mechanism on the downstream side. Since the pair 111 and 112 are provided, the main purpose is to regulate upwards. Therefore, as shown in FIG. Easy direction (L
By setting 1 and L2 in a direction of increasing θ), it is possible to feed 105 g / m ² paper, 128 g / m ² paper, etc., which could be fed by the conventional separating claws.

In this case, it is conceivable to double feed 60 g / m ^{2 of} thin paper or the like, but since usually several sheets are mostly fed, it is possible to sufficiently separate them with the next retard roller pair 111, 112. .

Outside the main body, no pressure is applied to the mounting plate 102 so that the paper can be loaded easily, and no pressure is applied even during insertion into the main body, so that the sheet can be smoothly removed. It is possible to prevent the upper sheet from catching on the main body. Then, the pressing force works in the vicinity of the end of loading the cassette 101, so that the paper can be stored well.

Further, as shown in FIG. 9, an inclined surface 109b is formed so that the pressing control arm 108 and the cam portion 109a exert a force for pulling the entire cassette to the inner side. There is also an effect that the cassette 101 can be used, and the cassette 101 is attached to the inner side reference.

As described above, the cut sheet P in the cassette 101, which has been loaded into the main body, is turned on by the feed solenoid in response to the feed start signal, whereby the control ring of the one-rotation control spring clutch is opened. The driving force from the motor is transmitted to 103. At that time, the driving force is transmitted to the forward rotation driving roller 111 of the retard roller pair 111 and 112 together with the feeding roller 103 on the driving downstream side of the spring clutch. Therefore, the rotation of the feeding roller 103 by one rotation control also rotates the forward rotation driving roller 111 at the same time, and the speed of the feeding roller 103 and the forward rotation driving roller 1
The speed of 11 is almost the same or the speed of the forward rotation driving roller 111 is made a little faster, so that the retard roller pair 11
There is no slack in the paper between 1 and 112 and no damage to the sheet.

The other retard roller 112 of the pair of retard rollers 111, 112 is constantly rotated by a torque limiter, and separates the double-fed sheets.

A paper path of a U-turn path is provided downstream of the retard roller pair 111 and 112, and the drive roller 11
3 and an idler roller 114 that follows it.

The idler roller 114 is located on the inner peripheral side of the U-turn portion and has a curvature which is the same as or slightly smaller than the curvature of the paper path. The drive roller 113 and the idler roller 114 cooperate with each other to form a pair of retard roller pairs 111 and 112. The forward rotation drive roller 111 that conveys the sheet P that has been conveyed from
At the same time, the drive transmission is turned off by controlling one rotation, and the sheet P is pulled by the drive roller 113. At that time, since the idler roller 114 is provided, the sheet is smoothly pulled along the curvature, and the retard roller pair 111, 1
Even if the back tension of 12 is received, the load on the drive roller 113 is reduced, the durability of the drive roller 113 is increased, and the required torque is small.

This drive roller 113 and idler roller 11
The number of pairs of conveying rollers can be reduced by guiding the sheet P conveyed from the other sheet feeding port to the nip portion of No. 4, and the separation pad 115 and the feeding roller 1 as in the present embodiment.
Sheets from the multi-sheet feeding unit 16 and a transport path 117 from an optional cassette removably disposed below the apparatus main body (not shown) are collected in the same transport unit, and the control downstream from that portion is the same. The method is adopted.

The driving roller 113 has a pair of registration rollers 117 and 118 next to the registration roller 11.
The sheet leading edge detection sensor 119 located immediately before 7, 118 detects the sheet leading edge, and temporarily stops after a predetermined timing. As a result, a skew of about 3 to 10 mm is formed between the pair of register rollers 117 and 118 and the driving roller 113 to correct skew and align the ends.

Next, according to the image, the pair of register rollers 11
7, 118 and the driving roller 113 are started at the same time, and the register roller pair 117, 118 and the driving roller 11 are started.
By transporting while keeping the loop with 3, the speed of the register roller pair 117, 118 can be stably maintained.

A laser optical system 120, an electrophotographic cartridge 121, a biased transfer roller 122, a conveyance guide 123, a heating and pressurizing fixing roller portion 124, and an ejecting device are provided on the downstream side of the register roller pair 117 and 118 as image forming means. It has rollers 125 and a discharge tray unit 126 and functions as an image forming apparatus.

In this embodiment as well, the paper feed amount C of the paper feed roller 103 is determined from the paper path length A from the leading edge of the paper inside the cassette 101 to the pair of retard rollers 111 and 112 and the retard roller nip in the same manner as in the previous embodiments. The gear drive system arrangement and the half-moon angle of the feeding roller are set so as to have a relationship of A <C <B with the paper path length B to the next drive roller nip portion.

11 and 12 show the third embodiment, in which the sheet feeding pressure spring 130 below the sheet placing plate 102 is pressed by the feeding roller 131 even if the sheet stacking amount increases. The spring constant is determined so that the paper pressure is always constant.

For example, if the distance l ₁ from the center of rotation of the mounting plate 102 to the tip is l ₁ = 220 mm and the paper width is 210 mm for A4 vertical feed size, 220 × 210 mm ² for 80 g / m ² paper, 1 Sheet weight 3.7g, 80g /
The thickness of one sheet of m ² paper is about 0.1 mm, so the thickness is 1 m
When m, that is, 37 sheets, 37 g is Wp as the weight of the paper.

Therefore, if a spring 130 is placed immediately below the feeding roller 131 in order to make the pressure of the feeding roller 131 constant regardless of the amount of stacked sheets, the spring constant is

[0057]

[Outer 1] become. Normally, the pressure with the feeding roller 131 is about 200 g, and therefore the amount of pushing of the spring at the point A is l ₄ =
It becomes 200 / 21.4 = 9.3 mm.

Therefore, by setting the interval l ₃ when the feeding roller 131 comes into contact with the paper and when it separates from the value l _{4 obtained} from the relationship between the spring constant and the sheet feeding pressure, there is no upper regulating means. In both cases, the present invention can be implemented.

In addition, in the first embodiment, the auxiliary upper claw (height) regulating member, which is similar to the conventional separating claw, is used as the auxiliary separating claw. Since it has a pair of retard rollers as a separating mechanism, it basically needs only to regulate the upper surface (height) of the sheet as a sheet feeding section, so that the shape, the contact position with the sheet, etc. are limited to those in the above embodiment. is not. That is, when the half-month feeding roller is not rotating, there is no problem if a gap is guaranteed between the half-month feeding roller and the uppermost sheet and it can be maintained at a certain height.

[0060]

As described above, the sheet feeding means using the substantially half-month feeding roller, the separating means including the retard roller pair located downstream of the sheet feeding means, and the sheet conveying means including the conveying roller pair located further downstream thereof are provided. By synchronizing the rotation driving of the sheet feeding device and further the normal rotation driving roller of the retard roller pair with one rotation of the feeding roller and satisfying the conditions A <C <B such as the roller arrangement described above, A great simplification of the mechanism is achieved as compared with the conventional retard roller method.

In other words, the number of parts is reduced, the reliability of the device is improved, and the cost and space are saved.

By applying the present invention, it has become possible to provide a sheet feeding device having excellent paper feeding and separating performance even for a small copying machine, a small printer, and the like.

In particular, the type in which the paper feed cassette is attached and detached at right angles to the conveying direction is very effective for downsizing.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a sheet feeding device according to a first embodiment of the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a diagram showing a gear train shown in FIG.

FIG. 4 is a diagram showing a two-sheet feeding state in the apparatus of FIG.

FIG. 5 is a vertical sectional view of an image forming apparatus according to a second embodiment of the present invention.

6 is a perspective view of the cassette shown in FIG.

7 is a vertical cross-sectional view showing the pressure plate shown in FIG.

8 is a sectional view showing a pressure mechanism of the pressure plate of FIG.

9 is a sectional view showing a pressure mechanism of the pressure plate of FIG.

10 is a diagram showing a dimensional relationship of the separation claw portion shown in FIG.

FIG. 11 is a view showing the dimensional relationship of the cassette of the third embodiment of the present invention.

12 is a view showing a usage state of the cassette shown in FIG.

FIG. 13 is a cross-sectional view of a conventional sheet material feeding device.

[Explanation of symbols]

 22 and 101 cassette (sheet stacking means) 27 and 103 feeding roller 28 and 111 forward rotation driving roller (feeding rotating body) 29 and 112 retard roller (reverse rotating body) 30 and 31 conveying roller (conveying means) 114 driving roller (Transportation means)

Claims (10)

[Claims] 1. A sheet stacking unit for stacking and supporting sheets, a feeding roller for feeding the sheet from the sheet stacking unit, the shape having different radial dimensions along the entire circumference, and a feeding unit that rotates in the feeding direction. A sheet feeding device including a rotating body and a reverse rotating body that rotates in a direction opposite to the feeding direction, and a reverse separating unit for separating the sheets sent by the feeding roller one by one. Sending device. 2. The sheet feeding apparatus according to claim 1, wherein the feeding roller presses the uppermost sheet stacked on the sheet stacking unit and sends it out. 3. The sheet stacking means comprises a spring for urging the stacked sheets toward the feeding roller, and a regulating member for maintaining the uppermost sheet at a constant position against the urging force of the spring. The sheet feeding device according to claim 2, further comprising: 4. The sheet feeding apparatus according to claim 1, wherein the feeding rollers having different shapes in the radial direction along the entire circumference are half-moon rollers. 5. A sheet stacking unit for stacking and supporting the sheet, a feeding roller for feeding the sheet from the sheet stacking unit, the size of which is different in radial direction along the entire circumference, and a feeding unit which rotates in the feeding direction. A rotating body and a reverse rotating body that rotates in a direction opposite to the feeding direction, and a reverse separating means for separating the sheets sent by the feeding roller one by one, and a sheet separated by the reverse separating means. Transporting means for transporting, the distance A between the sheet leading end stacked on the sheet stacking means and the reverse rotation separating means, the distance B between the reverse rotation separating means and the transporting means, and the feeding roller. A sheet feeding device characterized in that a dimensional relationship with a length C for sliding a sheet to feed the sheet satisfies A <C <B. 6. A sheet stacking means for stacking and supporting sheets, a feeding roller for feeding a sheet from the sheet stacking means, the dimension of which is different in the radial direction along the entire circumference, and a feeding roller which rotates in the feeding direction. A reverse rotation separating unit configured to include a rotating body and a reverse rotating body that rotates in a direction opposite to the feeding direction, for separating the sheets sent by the feeding roller one by one, and a rotational drive of the feeding rotating body. A sheet feeding device comprising: a synchronizing mechanism that synchronizes with one rotation of the feeding roller. 7. The sheet feeding apparatus according to claim 5, wherein the synchronization mechanism is a gear train for transmitting the rotation of the feeding roller to the feeding rotating body. 8. A sheet stacking means for stacking and supporting sheets, a feeding roller for feeding a sheet from the sheet stacking means, the dimension of which is different in the radial direction along the entire circumference, and a feeding roller which rotates in the feeding direction. A rotating body and a reverse rotating body that rotates in the opposite direction to the feeding direction, and a reverse separating means for separating the sheets sent by the feeding roller one by one, and one sheet by the reverse separating means. An image forming unit for forming an image on the formed sheet. 9. A sheet stacking unit for stacking and supporting the sheet, a feeding roller for feeding the sheet from the sheet stacking unit, the shape having different radial dimensions along the entire circumference, and a feeding unit that rotates in the feeding direction. A rotating body and a reverse rotating body that rotates in a direction opposite to the feeding direction, and a reverse separating means for separating the sheets sent by the feeding roller one by one, and a sheet separated by the reverse separating means. A conveyance unit configured to convey the sheet, and an image forming unit configured to form an image on the sheet conveyed by the conveyance unit, and a distance A between the sheet leading end stacked on the sheet stacking unit and the reverse separation unit; An image forming apparatus, wherein a dimensional relationship between a distance B between the reverse rotation separating means and the conveying means and a length C for feeding the sheet by sliding contact with the feeding roller satisfies A <C <B. 10. A sheet stacking unit for stacking and supporting the sheet, a feeding roller for feeding the sheet from the sheet stacking unit, the dimension of which is different in the radial direction along the entire circumference, and a feeding unit that rotates in the feeding direction. A reverse rotation separating unit configured to include a rotating body and a reverse rotating body that rotates in a direction opposite to the feeding direction, for separating the sheets sent by the feeding roller one by one, and a rotational drive of the feeding rotating body. An image forming apparatus comprising: a synchronization mechanism that synchronizes with one rotation of the feeding roller; and an image forming unit that forms an image on each sheet separated by the reverse separation unit.