JPH02127330A - Sheet supply device - Google Patents

Abstract

PURPOSE:To prevent trouble of overlappingly sending of the last two sheets by composing a frictional separation member of a first frictional separation member opposed to a supply roller and a second frictional separation member opposed to an auxiliary roller and an auxiliary cam, and setting the frictional coefficient of the first member higher than that of the second one. CONSTITUTION:When the number of remaining sheets loaded on the plate of a sheet housing unit is two and a sheet just on the last sheet is sent, high frictional force is applied to the last sheet by means of a first frictional separation member 12a of a high frictional coefficient provided on a loading plate 9. Overlapped sending of the last two sheets is thus prevented. The last sheet is supplied to a relay transfer means and then transferred downstream being sandwiched by an auxiliary roller 5 and second frictional separation member 12b of a low frictional coefficient. As a result, the shock applied to the rear end of the last sheet is reduced when it passes through the second frictional member 12b, so that the image blurring is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is applicable to image forming apparatuses such as copying machines, facsimile machines, laser beam printers, word processors, and other apparatuses that handle sheets. Separates and feeds paper, photosensitive paper, recording paper, printing paper, etc. (cut sheets) one by one to a sheet receiving section such as an image transfer section or exposure section of a main unit such as an image forming apparatus. The present invention relates to a sheet feeding device.

More specifically, it includes a sheet storage section having a sheet stacking plate that is lifted and biased by a biasing means, and a top sheet of the stacked sheets that is in contact with the upper surface of the leading edge side in the sheet feeding direction of the stacked sheets on the stacking plate. It has a sheet feeding means for feeding, and a friction separation member that presses into contact with the sheet feeding means at a predetermined pressure, and these means and members work together to feed the stacked sheets in the sheet storage section one sheet from the top. The present invention relates to a sheet feeding device that separates and feeds sheets one by one.

(Prior Art) Figures 4a to 4e show an example of this type of sheet feeding device, in which (a) is an exploded perspective view of the sheet feeding means, and (b) to (e) is a diagram showing the process of separating and feeding one sheet.

100 is a sheet feeding means that feeds the sheet;
An unillustrated 1 wheel is supported between the left and right side plates (not shown) of the device.
(b) A one-rotation drive shaft 3 that is driven one rotation clockwise in the figure by a drive system including a rotary clutch mechanism, etc. each time a feeding start signal is received, and an occluded-circle-shaped feeding roller 1 that rotates integrally with this shaft. And, with this roller l inside, there are shafts 3 coaxially on the left and right sides respectively.
Alternatively, it has a pair of left and right auxiliary cams integrally supported by the roller 1, and a pair of left and right auxiliary rollers 5, 5 coaxially and rotatably supported on the shaft 3 further outside the left and right auxiliary cams. There is.

Reference numerals 6 and 7 are upper and lower sheet guide plates that constitute a conveyance path for sheets that are separated and fed, and the front end of the lower guide plate 7 on the side of the sheet feeding means 100 is connected to the sheet feeding means! 00, and a sheet feeding means 100 is provided on the upper surface of the extended portion.
The feeding roller 1, the left and right auxiliary cams 4, and the left and right auxiliary rollers 5, 5 are supported by a friction separation member 2 (hereinafter referred to as a separation pad) that faces in series. The lower guide plate 7 is supported to be able to swing freely around supports 11iIII7a, and is biased to rotate counterclockwise in the drawing by a pull-up spring 8, and the above-mentioned separation pad 2 is pulled out of the sheet by the rotational biasing force. It is in contact with the lower surface of the feeding means 100 with a predetermined pressing force.

Reference numeral 10 denotes a sheet cassette loaded into a cassette receiver (not shown) of the sheet feeding means 100, and only the leading end side thereof is shown in the figure. Reference numeral 9 denotes an intermediate plate serving as a sheet stacking plate disposed within the cassette 10, and sheets S are stacked on the intermediate plate 9 and stored within the cassette 10.

Reference numeral 11 denotes a middle plate lifting mechanism, and when the cassette 10 is fully loaded into the cassette receiver, a lifting arm flb is inserted between the bottom plate of the cassette 10 and the middle plate 9 from the tip side of the cassette 10.
enters the plunged state, and the arm llb is biased to rotate counterclockwise in the drawing by the spring lla about the support shaft 11C, thereby lifting and biasing the tip side of the middle plate 9. As a result, the upper surface portion of the leading edge side in the sheet feeding direction of the stacked sheets S on the intermediate plate 9 comes into contact with the lower surface side of the sheet feeding means 100 with a predetermined pressing force.

Reference numeral 13 denotes a pair of registration rollers as a sheet relay conveying means provided on the downstream side in the sheet feeding direction of the sheet path composed of the upper and lower sheet guide plates 6 and 7.

The shape of the feeding roller 1, the auxiliary cam 4, and the auxiliary roller 5, which are coaxially supported on the shaft 3 of the sheet feeding means 100, is that from point A to point B, the feeding roller is the auxiliary roller 5 when viewed from the side.
- The auxiliary cam 4 is formed in the order of decreasing size, and from the fork point B to the point C, the auxiliary cam 4 and the feeding roller auxiliary roller 5 are formed in the order of decreasing size, and from the point to the point E, the auxiliary roller 5 is formed.
From point E to point F, in order of auxiliary cam 4, feeding roller 1, point F
From to point A, the auxiliary cam 4 and feed roller auxiliary roller 5
They are formed in order of decreasing size.

The figure (b) shows the rotational angle posture state of the feeding means 100 when the feeding means 100 is waiting for rotation to stop before starting feeding. The cutout portion of the feeding roller 1 faces downward and is not in contact with the upper surface of the stacked sheets S. The auxiliary cams 4, 4 are also not in contact with the upper surface of the stacked sheet S.

The separation pad 2 is in pressure contact with the lower surface of the auxiliary rollers 5.

The feed start signal drives the shaft 3 of the sheet feeding means 100 one rotation, that is, the occluded circular feeding roller 1 and the left and right auxiliary cams 4.
- When the rotation (clockwise rotation) of step 4 is started, the uppermost sheet S of the stacked sheets S on the middle plate 9 of the cassette 10, which is the sheet storage section, is moved by the feeding roller 1 as shown in the figure (C).
Feeding starts from point A of .

At this time, the leading edge of the stacked sheets S is pressed by the auxiliary cam 4 and the friction between the stacked sheets increases, so that the sheets are not fed in duplicate due to the frictional force between the sheets and the frictional force of the separation pad 2. Only the uppermost sheet S is separated and fed, and the uppermost sheet S passes between the separation pad 2 and the feeding roller 1 as shown in FIG. Furthermore, this uppermost sheet S is fed by the portion of the feeding roller 1 from point A to point B, and is fed toward the registration roller pair 13 through the upper and lower guide plates 6 and 7.

During this process, the registration roller pair 13 is in a rotationally stopped state, and the tip of the sheet S fed by the feeding roller 1 is in contact with the registration roller pair 13 in the rotationally stopped state.
The registration roller pair 13 and the feeding means 1 are fed by feeding the sheet S, which is received in contact with and is received by the feeding roller by the continuous rotation of the feeding roller.
00, a sheet loop is formed as shown in (e). By forming this sheet loop, the entire length of the leading edge of the sheet S1 is pressed along the length of the nip between the pair of registration rollers 13, and the sheet is skewed somewhere.

Near the end of one rotation of the feed roller 1, point B is the sheet S.
At a predetermined timing after the sheet S1 leaves the surface of the sheet S1, the rotational drive of the pair of registration rollers 13 is started, and the sheet S1 obtains an input force to the pair of loop rollers 13 and enters the nip portion of the pair of rollers ( f) As shown in the figure, the sheet is sandwiched and conveyed by the rotational conveying force of the pair of rollers to a sheet receiving section (image forming section, etc., not shown) of a main body device such as an image forming apparatus.

The feeding roller 1 stops rotating when it completes one rotation. In this state, the cutout portion of the feeding roller 1 faces downward and does not make contact with the sheet S1, so that the feeding roller 1 no longer feeds the sheet S1, but the leading end of the sheet S is generally used as an intermediate conveying means. Registration roller pair 13
Since the paper is held between the rollers 13, feeding is continued by the group roller pair 13. The sheet S1 is sandwiched between the auxiliary rollers 5, 5 of the feeding means 100 and the separation pad 2, and since the auxiliary rollers 5, 5 are rollers that rotate freely relative to the shaft 3, the roller pair of the sheet S, The sheet S rotates as a result of feeding by the sheet S, and stops rotating when the rear end of the sheet S passes between the auxiliary rollers 5 and the separation pad 2. As a result, the feeding means 100 returns to the rotational posture state shown in FIG. 3B when the rotation is stopped and stands by before the feeding starts.

In this way, each time the shaft 3 of the feeding means 100 is driven once in response to the feeding start signal, the operation process cycle shown in FIGS.
The sheets are separated and fed sequentially starting from the number 81.

When the stacked sheets S on the middle plate 9 are sequentially separated and fed one by one and the stacked sheets are consumed and only two sheets remain on the middle plate 9, the last sheet Sn (stacked sheet S
If there is no friction between the sheet (the lowest sheet) and the middle plate 9, the last sheet Sn and the sheet Sn-1 above it will be fed simultaneously, causing so-called last sheet double feeding.
A frictional separation member 12 (hereinafter referred to as separation sheet) is attached to the upper surface of the leading end of the intermediate plate 9 in the sheet feeding direction.
This applies a frictional force between the last sheet Sn and the intermediate plate 9 to prevent double feeding of the last sheet.

Therefore, after the last sheet Sn is fed to the registration roller pair 13 by the feeding roller 1, its rear end is held between the auxiliary roller 5, the separation pad 2, and the separation sheet 12, and then conveyed downstream.

(Problem to be Solved by the Invention) However, as the separation sheet 12 is used, the friction coefficient gradually decreases due to wear, adhesion of paper dust, dirt, etc., and the frictional force acting on the last sheet becomes small. This may cause double feeding of the last paper, and this tendency is particularly noticeable in low temperature and low humidity conditions as the coefficient of friction further decreases.

On the other hand, if a separation sheet with a high coefficient of friction is used in the initial state, the shock when the last sheet passes through the separation sheet 12 will be large, making it easier for image blurring to occur.
The large frictional force causes paper feeding failures, especially under high temperature and high humidity conditions.

The present invention solves this problem, that is, it is possible to feed sheets without causing the last sheet to be double fed, and it also prevents image blurring and paper feeding errors when the last sheet passes through the separation sheet. The present invention provides a seed sheet feeding device.

(Means for Solving the Interval Point) The present invention provides a sheet storage section having a sheet stacking plate that is lifted and biased by a biasing means, and a leading edge side of the stacked sheets on the stacking plate in the sheet feeding direction. It has a sheet feeding means that feeds the uppermost sheet of the stacked sheets in contact with the upper surface, and a friction separation member that presses into contact with the sheet feeding means with a predetermined pressure, and these means and members work together to feed the sheet. This is a sheet feeding device that separates and feeds stacked sheets in a storage section one by one from the top, and the sheet feeding means is integrally supported by a rotary drive shaft and supported in the same direction. a portion of the top surface of the sheet stacking plate on the leading end side in the sheet feeding direction that faces the sheet feeding means; is provided with a frictional separation member, and the frictional separation member includes a first frictional separation member facing the feeding roller of the sheet feeding means and a second frictional separation member facing the auxiliary roller and the auxiliary cam. A sheet feeding device characterized in that the friction coefficient of the first friction separation member is higher than that of the second friction separation member.

It is.

Further, in the sheet feeding device configured as described above, the upper surface portion of the front end side of the sheet stacking plate facing the auxiliary cam is a portion where neither the first nor the second friction separation member is present. It is.

(Function) When there are two remaining sheets stacked on the stacking plate of the sheet storage section and the sheet above the last sheet is fed, the first F'J with a high friction coefficient provided on the stacking plate is attached to the last sheet. Since a strong frictional force is applied to the medical layer separation member, double feeding of the last paper will not occur.

Furthermore, after the last sheet is fed to the intermediate conveying means, it is conveyed downstream while being held between an auxiliary roller and a second friction separation member with a low friction coefficient, so that the rear end of the last sheet is conveyed downstream. The shock when the image passes through the second frictional separation member is small, and image blur does not occur.

In addition, by not having a frictional separation member on the surface of the sheet stacking plate facing the auxiliary cam, the shock when the rear end of the last sheet passes through the second frictional separation member is further reduced, thereby reducing image blur. It is more effective in preventing

(Embodiment) FIG. 1 shows an exploded perspective view of the sheet feeding means portion of the apparatus of the present invention. Components and portions common to those of the apparatus shown in FIG. 4 are given the same reference numerals and will not be described again.

12a, 12b, 12b are seat storage parts (cassette 1
0) is a separation pad as a frictional separation member provided on the upper surface of the leading end side in the sheet feeding direction of the sheet stacking plate 9 (middle plate) in the portion facing the sheet feeding means 100. A first separating bat 12a facing the feeding roller 1 of the feeding means 100, and a second separating bat 12b facing the auxiliary rollers and auxiliary cams 5, 4, 5, and 4 on the left and right sides of the feeding roller 1. 12b, and the coefficient of friction of the first separating bat 12a is higher than that of the second separating bats 12b. The coefficient of friction of the first separation bat f2a depends on the paper type and environment of the sheet S, but for example, it is about 0.8 to 1, and the coefficient of friction of the second separation bat f2a is about 0.8 to 1.
Similarly, it is, for example, about 0.4 to 0.6.

The stacked sheets on the stacking plate 9 are fed by feeding means 1 for each feeding start signal.
When the shaft 3 of 00 is driven by one revolution, one sheet is separated and fed from the top sheet in the same feeding process as in the apparatus shown in FIG. However, since the frictional force of the first layered sheet 12a that the feeding roller 1 comes into contact with is large, the last sheet Sn and the sheet S above it
n-1 is separated, and due to durability, the first separation sheet 12a
Even if the 1'ffl coefficient decreases, double feeding of the last paper will not occur.

Here, the conveying force by the feeding roller is F, the frictional force between the separating pad 2 and the feeding roller 1 and the auxiliary rollers 5 and 5 is R,
R', the frictional force caused by the first and second separation sheets 12a and 12b is respectively Ta-Tb, and the frictional force between the sheets is N, as shown in FIG. 2(a), F≧R+N, N ≦
It is expressed as R+Tb.

After the last sheet Sn reaches the pair of registration rollers (13), its trailing end is held between the auxiliary roller 5, the separation pad 2, and the second separation sheets 12b and 12b, and the last sheet Sn is conveyed. Since the frictional force between the sheets 12b and 12b is small, this second separating sheet 12b-12b
The shock when passing through is small, so there is no image blurring, and there are no adverse effects such as poor feeding.

At this time, the relationship among the conveyance force F by the feed roller 1, the friction force R' between the separation pad 2 and the auxiliary rollers 5, and the friction force Ta caused by the second separation sheets 12b is shown in FIG.
), it is expressed as F≧R'+Ta.

FIG. 3 is an exploded perspective view of a sheet feeding means 100 portion of another embodiment of the apparatus. In this example, the second separation sheet 12
b and 12b are auxiliary rollers 5 and 5 of the sheet feeding means 100.
The auxiliary cams 4 and 4 are not provided with a separation sheet. As a result, the second separation sheet 12
b.12b, the frictional force acting on the last sheet is further reduced, and the rear end of the last sheet is connected to the second separation sheet 12b.1.
The shock when passing through the 2b portion is reduced, which is further advantageous in preventing image blur.

Furthermore, this does not impair the functionality of this configuration.

(Effects of the Invention) As described above, according to the sheet feeding device configuration of the present invention, one of the sheets set to be stacked on the stacking plate of the sheet storage section is
This simple configuration prevents the trouble of double feeding of the last sheet that occurs when sheets are separated and fed sequentially and only two sheets remain, and the rear end of the last sheet is located at the friction separation member on the stacking plate side. The shock that occurs when the paper comes out against the frictional force with the member is also reduced, and image blurring and paper feeding failures that are likely to occur due to a large shock are prevented, and the intended purpose is well achieved.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of the sheet feeding means of an embodiment of the apparatus, and FIGS. 2(a) and 2(b) show friction during feeding of sheets above the last sheet and during feeding of the last sheet, respectively. 3 is a perspective view of the sheet feeding means portion of another embodiment of the apparatus, FIG. 4(a) is a perspective view of the sheet feeding means portion of the conventional apparatus, and FIG. f) is a cycle diagram of the process of separating and feeding one sheet. 100 is a sheet feeding means, 2 is a friction separation member (separation pad), 3 is a one-rotation drive shaft, 1 is an occluded circular feeding roller, 4.
4 is an auxiliary cam, 5 and 5 are auxiliary rollers, 10 is a sheet cassette, 9 is a sheet stacking plate (middle plate), 11 is a middle plate lifting and urging means, 12, 12a, and 12b are friction separation members (separation sheets), S is Ma sheet, SL is top sheet, 6/7
13 is a sheet relay conveying means (a pair of registration rollers).

Claims (2)

[Claims] (1) A sheet storage section having a sheet stacking plate that is lifted and biased by a biasing means, and feeding the topmost sheet of the stacked sheets in contact with the upper surface of the leading edge side in the sheet feeding direction of the stacked sheets on the stacking plate. It has a sheet feeding means for applying pressure, and a friction separation member that presses into contact with the sheet feeding means at a predetermined pressure, and these means and members work together to feed the stacked sheets in the sheet storage section one by one from the top. The sheet feeding device is a separate feeding type sheet feeding device, and the sheet feeding means includes a semicircular feeding roller and an auxiliary cam that are coaxially supported by a rotary drive shaft and rotate integrally with the shaft. and a freely rotating auxiliary roller on the shaft, and a frictional separation member is provided on the upper surface of the leading end side of the sheet stacking plate in the sheet feeding direction at a portion facing the sheet feeding means, and the frictional separation member The member consists of a first frictional separation member that faces the feeding roller of the sheet feeding means, and a second frictional separation member that faces the auxiliary roller and the auxiliary cam, and the first frictional separation member has a friction coefficient of A sheet feeding device characterized in that the frictional separation member is higher than that of the frictional separation member of No. 2. (2) The sheet feeding device according to claim 1, wherein the upper surface portion of the sheet stacking plate on the leading end side facing the auxiliary cam is a portion where neither the first nor the second frictional separation member is present.