JPH10297773A - Paper feeding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly feed paper, and reduce back tension without requiring a complicated structure. SOLUTION: In a paper feeding method in which a paper S is pressed by a hopper 10 to be fed by a paper feeding roller 20 of a D-shaped side view comprising an arc part 20a to get in contact with the paper S and a straight line part 20b without getting incontact with the paper S, and in which pressing to the paper S by the hopper 10 to the paper feeding roller is released before a back end S1b of the paper S passes the paper feeding roller 20, the paper feeding roller is temporarily stopped after it is rotated to set the arc part 20a is to the paper S, the paper S is pressed by the hopper 10 to the arc part 20a of the paper feeding roller in a stopped condition, and after this press contact is detected, the paper feeding roller 20 is rotated to feed the paper. This detection is performed by detecting a position of the paper feeding roller which is moved by press contact to the paper S by the hopper 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a paper feeding method.
The present invention mainly relates to a method of feeding paper to an image forming apparatus that forms an image (including characters) on paper, such as a printer, a copying machine, a facsimile, and the like. As the paper, plain paper, coated paper, OHP (overhead projector) sheets, glossy paper, glossy films, cut sheets such as postcards, envelopes, and the like can be used.

[0002]

2. Description of the Related Art As a conventional paper feeding method, a side view D having an arc portion that comes into contact with a sheet and a linear portion that does not come into contact with a sheet is provided.
After pressing the paper against the rotating paper feed roller with a hopper on which the paper is placed and feeding the paper with the paper feed roller, before the trailing edge of the paper passes through the paper feed roller, There has been known a paper feeding method for releasing the press-contact of the paper by the hopper with respect to a paper feeding roller.

According to such a paper feeding method, before the rear end of the paper fed by the paper feeding roller passes through the paper feeding roller,
The linear state of the paper feed roller is opposed to the paper to release the contact state between the paper feed roller and the paper, and the pressure contact of the paper with the paper feed roller by the hopper is also released, so that the so-called back tension is reduced. be able to.

More specifically, the fed sheet is conveyed by a sheet conveying means of the image forming apparatus, for example, a conveying roller to form an image. At this time, a rear portion of the fed sheet is formed. Is pressed against the paper feed roller by the hopper, and when the paper feed roller is not driven, this pressure contact portion acts as a load on the paper conveyed by the conveyance means, and as a result, The sheet is conveyed in a state where the sheet is pulled backward, that is, in a state where the back tension is applied. In the state where the back tension is applied, there is a possibility that the conveyance accuracy of the paper may be reduced, and as a result, the accuracy of an image formed on the paper may be reduced.

On the other hand, according to the above-described paper feeding method,
Since the back tension can be reduced, as a result, the deterioration of the image accuracy can be reduced.

[0006]

In the above-described conventional paper feeding method, the paper is pressed against the rotating paper feeding roller, so that the following problems have been found.

(1) The sheet to be fed is curled, so that the sheet does not uniformly contact the arc portion of the feed roller, that is, only one side of the sheet is fed first. When the paper feed roller starts to come into contact with the arc portion of the paper roller, the paper feed roller has already been rotated, so that feeding starts from the contact portion, and as a result, the paper may be fed obliquely.

(2) When a large number of sheets are placed in a stacked state on the hopper, the stacked sheets are swelled by air entering between the sheets, and particularly when the sheets are envelopes. However, if this is pressed against the paper feed roller with a hopper, it will take some time until the desired pressure contact force against the paper feed roller is obtained. Since the rollers are rotating, feeding is started in an unstable state, and as a result, the sheet may be fed obliquely.

The above problem can be solved by making the paper feed roller circular instead of D-shaped when viewed from the side, and always pressing the paper against the paper feed roller.

However, if the paper is always kept in pressure contact with the paper feed roller, the above-described problem of back tension occurs.
The paper feed roller must be rotated and driven in synchronization with the paper conveyance means of the image forming apparatus, which complicates the structure of the paper feed device and reduces the durability of the paper feed roller.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, to feed a sheet properly without requiring a complicated structure, and to reduce a back tension. Is to provide.

[0012]

According to a first aspect of the present invention, there is provided a sheet feeding method comprising: a sheet feeding roller having a circular portion contacting a sheet and a straight portion not contacting the sheet; After the paper is pressed by a hopper on which the paper is placed and the paper is fed by a paper feed roller, before the trailing end of the paper passes through the paper feed roller, A paper feeding method for releasing pressure contact of paper,
First, the paper feed roller is temporarily stopped after rotating so that the arc portion thereof corresponds to the paper, and then the paper is pressed against the arc portion of the paper feed roller in a stopped state by a hopper, and After detecting the pressure contact of the paper with the paper feed roller, the paper feed roller is rotated to feed the paper.

[0013] Here, the linear portion is referred to as:
This is in comparison with the arc portion, and therefore may be slightly curved or bent as long as it is not in contact with the paper.

[0014]

According to the sheet feeding method of the first aspect, before the trailing end of the sheet fed by the arc portion of the sheet feeding roller passes through the sheet feeding roller, the straight portion of the sheet feeding roller is converted to the sheet. The contact state between the paper feed roller and the paper can be released by facing the paper feed roller, and the press contact of the paper with the paper feed roller by the hopper can be released, so that the so-called back tension can be reduced.

According to the paper feeding method of the first aspect, first, the paper feeding roller is temporarily stopped after the arc portion is rotated so as to correspond to the paper, and then the paper feeding roller in the stopped state is stopped. The paper is pressed against the arc of the paper roller by the hopper, and after the paper is pressed against the paper feed roller by the hopper, the paper feed roller rotates and the paper is fed. Even if the paper is curled, the paper feed roller rotates after the paper uniformly contacts the arc portion of the paper feed roller.

Therefore, it is possible to prevent the sheet from being fed obliquely as in the related art.

Further, even if a large number of sheets, especially envelopes, are placed on the hopper in a stacked state, even if the sheets are expanded, the arcs of the paper feed roller in the stopped state are not affected. After it is detected that the paper is pressed by the hopper, the paper feed roller rotates and the paper is fed, so that the paper feed roller rotates after a desired pressing force against the paper feed roller is reliably obtained. It will be.

Therefore, the feeding is not started in an unstable state as in the prior art, and as a result, the sheet is prevented from being fed obliquely.

Further, according to such a paper feeding method, when the hopper presses the paper toward the paper feeding roller, it is only necessary to stop the paper feeding roller, which complicates the paper feeding device. Not at all.

That is, according to the paper feeding method of the first aspect, the paper can be properly fed without requiring a complicated structure, and the back tension can be reduced.

According to the paper feeding method of the present invention, in the paper feeding method of the first aspect, the detection is performed by detecting a position of a paper feed roller that moves by pressing the paper by the hopper. Therefore, it can be reliably detected that the paper is pressed against the paper feed roller with a desired pressing force.

More specifically, as a method for detecting that a sheet is pressed against a sheet feed roller by a hopper,
For example, there may be a method in which the detection is performed by detecting the upper surface of the sheet placed on the hopper.

However, as described above, when a large number of sheets are placed in a stacked state on the hopper, the stacked sheets are swelled by air that has entered between the sheets, and particularly, the sheets are enveloped. In the case of, the swelling becomes large, and if this is pressed against the paper feed roller by the hopper, it takes some time until a desired pressure contact force against the paper feed roller is obtained.

In such a situation, if it is assumed that the paper is pressed against the paper feed roller by detecting the upper surface of the paper placed on the hopper, Even if the paper is not pressed sufficiently, the upper surface of the paper may reach the detected position, and as a result, the paper feed roller may rotate without obtaining the desired pressing force. There is.

On the other hand, according to the paper feeding method of the second aspect, the detection of the pressing of the paper against the paper feeding roller by the hopper is performed by detecting the position of the paper feeding roller moving by the pressing of the paper by the hopper. As long as the paper is not pressed against the paper feed roller with the desired pressing force,
That is, the above-described detection is not performed unless the paper feed roller is pressed against the sheet by a pressure enough to move the sheet feed roller to the detection position. Conversely, when the above-mentioned detection is performed, it means that a pressing force sufficient to move the sheet feeding roller to the detection position, that is, a desired pressing force is obtained.

Therefore, according to the paper feeding method of the second aspect, it is possible to reliably detect that the paper is pressed against the paper feeding roller with a desired pressing force, and as a result, the paper is further layered. It can be fed properly.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 (a) to 1 (d), 2 (e) and 2 (f) are explanatory views showing an embodiment of the paper feeding method according to the present invention.

In the figure, 10 is a hopper, 20 is a paper feed roller, and 30 is a detector.

On the hopper 10, a plurality of sheets S are placed in a stacked state. The hopper 10 can press the paper S against the paper feed roller 20 by an appropriate mechanism (not shown) (see FIG. 1C).

The paper feed roller 20 is formed in a side view D-shape having an arc portion 20a in contact with the sheet and a straight portion 20b not in contact with the sheet.
Is made of a high friction material such as rubber. The paper feed roller 20 is rotatably supported at the tip of a lever 21 by a shaft 22.
It is designed to rotate around two turns.

The lever 21 has a central portion supported by a frame on a shaft 23 and is rotatable about the shaft 23. A tension spring 24 is provided between the lever 21 and the frame F as an urging means.
The lever 21 is always urged clockwise in the drawing by the action of the above, but its rotation is regulated by the rear end 25 of the lever 21 abutting on the frame.

A piece 26 to be detected to be detected by the detector 30 is provided near the paper feed roller (in this case, the leading end) of the lever 21.

The detector 30 is an optical sensor, and detects when the detected piece 26 enters the recess 31. The detector 30 is attached to the frame F such that the recess 31 is located on the rotation track of the non-detection piece 26.

FIG. 1A shows a standby state.

In the standby state, the hopper 10 is located below, and the paper S is not pressed against the paper feed roller 20. The lever 21 is rotated clockwise so that the rear end 25 contacts the frame F, and the detected piece 26 is not detected by the detector 30. The paper feed roller 20 is stopped, and its linear portion 20b is
Facing.

In the paper feeding method of this embodiment, the paper is fed as follows.

First, from the state shown in FIG.
As shown in (b), the paper feed roller 20 is
After rotation is performed so that 0a corresponds to the sheet S, the sheet is temporarily stopped.

Next, from the state shown in FIG.
As shown in (c), the hopper 10 is moved upward with respect to the arc portion 20a of the paper feed roller 20 in the stopped state, and the paper S is pressed against the arc portion 20a of the paper feed roller 20. On this occasion,
With the upward movement of the hopper 10, the paper S
When the paper feed roller 20 comes into contact with the circular arc portion 20a, the paper feed roller 20 is pushed up, and the lever 21 rotates counterclockwise against the urging force of the spring 24. Therefore, the upward movement of the hopper 10 is performed until the detection target piece 26 of the lever 21 is detected by the detector 30, that is, until the sheet feeding roller 20 is pushed up to a predetermined position (detection position). The lever 2
Due to the rotation of 1 in the counterclockwise direction, the rear end 25 is separated from the frame F, and as a result, the paper feed roller 20 is pressed against the sheet S by the urging force of the spring 24.

Thereafter, as shown in FIG. 1D, the sheet feeding roller 20 is rotated to feed the top sheet S1.

After the paper feed roller 20 is rotated once as shown in FIG. 2E, the hopper 10 is rotated as shown in FIG.
Is moved downward to release the pressure contact between the sheet feeding roller 20 and the sheet S. The paper feed roller 20 is stopped. Therefore,
This state is the same as the above-described standby state except for the sheet S1.

The paper S1 fed by one rotation of the paper feed roller 20 reaches the paper transport means of the image forming apparatus (not shown), and is transported by the transport means. At this point, that is, when the feed roller 20
At the time when the paper S1 is rotated and the feeding of the paper S1 is completed (at the time shown in FIG. 2F), the rear end S1b of the fed paper S1 is
As shown in FIG. 2F, the sheet has not passed through the sheet feeding roller 20 yet.

Thereafter, the fed sheet S1 is further conveyed by the sheet conveying means of the image forming apparatus, and the rear end S1b passes through the sheet feeding roller 20, so that the state shown in FIG.

According to the above-described paper feeding method, the following operational effects can be obtained.

(I) Before the trailing end S1b of the paper S1 fed by the arc portion 20a of the paper feed roller 20 passes through the paper feed roller 20, the linear portion 20b of the paper feed roller 20 is made to face the paper S1. As a result, the contact state between the paper feed roller 20 and the paper S1 can be released, and the pressing of the paper S1 by the hopper 10 against the paper feed roller 20 is released, so that the so-called back tension can be reduced (FIG. 2).
(F)).

According to the paper feeding method of this embodiment, first, the paper feeding roller 20 is rotated so that its arc portion 20a corresponds to the paper S, as shown in FIG. After that, the sheet S is temporarily stopped, and then, as shown in FIG. 1C, the sheet S is pressed against the arc portion 20a of the sheet feeding roller 20 in the stopped state by the hopper 10, and the sheet feeding roller 20 by the hopper 10 is pressed. After the pressure contact of the sheet S to the sheet S is detected by the detector 30, the sheet feeding roller 20 rotates as shown in FIGS. Even if S1 is curled, the paper feed roller 20 will rotate after it has uniformly contacted the arc portion 20a of the paper feed roller 20.

Therefore, it is possible to prevent the sheet S1 from being fed obliquely as in the related art.

Further, since a large number of sheets, especially envelopes, are placed on the hopper 10 in a stacked state, even if the sheets are swelled, the circular arc portion 20a of the sheet feed roller 20 in the stopped state. Paper S with the hopper 10
Is detected, the paper feed roller 20 rotates and the sheet S1 is fed, so that the paper feed roller 20 rotates after a desired pressure contact force is obtained against the paper feed roller 20. Becomes

Therefore, the feeding is not started in an unstable state as in the related art, and as a result, the paper is prevented from being fed obliquely.

In addition, according to such a paper feeding method, when the hopper 10 presses the paper S toward the paper feeding roller 20, it is only necessary to stop the paper feeding roller 20.
The paper feeding device does not become complicated.

That is, according to the paper feeding method of this embodiment, the paper can be properly fed without requiring a complicated structure, and the back tension can be reduced.

(Ii) Paper feed roller 20 by hopper 10
Is detected by detecting the position of the paper feed roller 20 that is moved by the pressing of the paper S by the hopper 10 (see FIG. 1C). It is possible to reliably detect that S is pressed with a desired pressing force.

More specifically, as a method of detecting that the paper S is pressed against the paper feed roller 20 by the hopper 10, for example, as shown by a virtual line in FIG.
There is also a method of detecting the upper surface Sa of the sheet S placed on the hopper 10 by detecting the upper surface Sa with the detector 33.

However, as described above, the hopper 1
When a large number of sheets S are placed in a stacked state on the sheet 0, the stacked sheets S are inflated by air entering between the sheets, and especially when the sheet S is an envelope, When the hopper 10 is pressed against the paper feed roller 20 by the hopper 10, it takes some time until a desired pressure contact force against the paper feed roller 20 is obtained.

In such a situation, if the paper S is pressed against the paper feed roller 20, it is determined that the hopper 10
If the detection is performed by detecting the upper surface Sa of the paper S placed on the upper surface with the detector 33, the stacked paper is compressed at the portion pressed against the paper feed roller 20 to reduce the height. On the other hand, since the other portions remain expanded, the upper surface Sa of the sheet S reaches the detected position and is detected by the detector 33 even though the sheet S is not sufficiently pressed against the sheet feeding roller 20. May be detected. Therefore, there is a possibility that the paper feed roller may rotate in a state where a desired pressure contact force cannot be obtained.

On the other hand, according to the paper feeding method of this embodiment, the detection of the pressing of the paper S against the paper feeding roller 20 by the hopper 10 is performed by the paper feeding roller 20 moving by the pressing of the paper S by the hopper 20. Since the detection is performed by detecting the position, unless the paper S is pressed against the paper feed roller 20 with a desired pressing force, that is, the pressure contact sufficient to move the paper feed roller 20 to a predetermined position (detection position). Unless pressed by force, the above detection will not be performed. Conversely, when the above detection is performed, it means that a pressing force sufficient to move the sheet feeding roller 20 to a predetermined position, that is, a desired pressing force is obtained.

Therefore, according to this paper feeding method, it is possible to reliably detect that the paper S has been pressed against the paper feed roller 20 with a desired pressing force.
Can be more appropriately fed.

As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of the present invention.

[0059]

According to any of the paper feeding methods of the first and second aspects, the paper can be properly fed without requiring a complicated structure, and the back tension can be reduced.

Further, according to the paper feeding method of the present invention, it is possible to reliably detect that the paper has been pressed against the paper feeding roller with a desired pressing force, and as a result, the paper can be more appropriately adjusted. Can be sent to

[0061]

[Brief description of the drawings]

FIGS. 1A to 1D are explanatory views showing an embodiment of a sheet feeding method according to the present invention.

FIGS. 2E and 2F are explanatory views showing an embodiment of a sheet feeding method according to the present invention.

[Explanation of symbols]

 S paper S1b rear end 10 hopper 20 paper feed roller 20a arc portion 20b linear portion 26 non-detection piece 30 detector

Claims (2)

[Claims] A paper is fed by pressing the paper with a hopper on which the paper is placed against a D-shaped paper feed roller having a circular portion that comes into contact with the paper and a linear portion that does not come into contact with the paper. After feeding by rollers, before the trailing edge of the paper passes through the paper feed roller, a paper feeding method for releasing the press of the paper by the hopper to the paper feed roller, first, the paper feed roller, After the arc is rotated so as to correspond to the sheet, the sheet is stopped once, and then the sheet is pressed against the arc of the sheet feed roller in a stopped state by a hopper, and the sheet is pressed against the sheet feed roller by the hopper. A paper feeding method characterized in that the paper is fed by rotating a paper feed roller after the detection. 2. The sheet feeding method according to claim 1, wherein the detection is performed by detecting a position of a sheet feeding roller that moves when the sheet is pressed by the hopper.