JPH07172601A - Paper feeding device - Google Patents

Abstract

PURPOSE:To transmit a rotational force gradually to a paper feed roll through an energizing means so as to prevent any paper feed slippage due to abrupt start of the paper feed roll by supporting the paper feed roll of a paper feeding device rotatably within a specified angle range while energizing the paper feed roll in the direction of paper feeding without fixing the paper feed roll of the paper feeding device to the rotary shaft. CONSTITUTION:The paper feed roll 22 of a paper feeding device is supported unfixedly through a torsional spring 34 on a rotary shaft 33 to which a rotational force from a drive gear 31 is transmitted through an electromagnetic clutch 32. Namely, the paper feed roll 22 is supported rotatably on the rotary shaft 33 within a specified angle range, and its both sides are engaged with an E ring 35 and the torsional spring 34. Also the torsional spring 34 is wound around the rotary shaft 33 so that, when the rotary shaft 33 is rotated in a specified direction B corresponding to a paper feeding direction A, an energizing force in the same direction as that direction is added to the paper feed roll 22, and its both ends are engaged with the oval hole 22a of the paper feed roll 22 and the small hole 33a of the rotary shaft 33, respectively. Thus the rotational force of the rotary shaft 33 is transmitted gradually to the paper feed roll 22 through the torsional spring 34.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feeding device applicable to various devices such as printers and copying machines that require paper feeding, and more particularly to feeding paper one by one by a paper feeding roll. Sheet feeding device.

[0002]

2. Description of the Related Art Conventionally, in a sheet feeding device built in an image forming apparatus such as a printer or a copying machine, a sheet is stacked one by one on a sheet stacking means such as a sheet feeding cassette. It is configured such that the sheet is fed by, and the fed sheet is once made to stand by by a waiting roll, and then re-conveyed toward the image forming unit. In addition, a transport roll that transports the paper fed by the paper feed roll to the standby roll is provided in the middle path from the paper feed roll to the standby roll, and the transport roll and the paper feed roll work together to transport the paper. There are also things to do.

As a paper feeding roll used in such a paper feeding device, like a paper feeding roll 1 shown in FIG. 5, rotation from a main body drive system (gear 2 is a gear provided in the final stage thereof). The driving force is fixedly supported by a fixing means such as an E-ring 5 and a spring pin 6 with respect to a rotating shaft 4 which is transmitted through an electromagnetic clutch 3 as a drive transmitting means, and rotation control is performed according to ON / OFF control of the electromagnetic clutch 3. What is done is common. Further, in such a sheet feeding device, in order to separate and feed the sheets stacked and stored in the sheet stacking unit by the sheet feeding roll, for example, as shown in FIG. 7, a sheet stacking plate in the sheet stacking unit is provided. A friction plate 10 is provided on the (bottom plate) 9, or a friction pad 11 for separating and feeding is provided separately from the friction plate 10, and a predetermined pressure F _{1 is} applied to the peripheral surface of the paper feed roll through these friction members via paper. Many are configured to be pressed by F ₂ . In this case, the frictional force between the paper feed roll and the paper is μ ₁ ,
Assuming that the frictional force between the friction member and the paper is μ ₂ and the frictional force between the papers is μ ₃ , the frictional forces are differentiated so that the relationship of μ ₁ > μ ₂ > μ ₃ is satisfied. It is possible to feed each sheet individually.

[0004]

In the conventional paper feeding apparatus shown in FIG. 5, when the paper feeding is started, the electromagnetic clutch 3 is turned on so that the rotational force of the gear 2 is instantaneously passed through the rotary shaft 4. Since it is transmitted to the paper feed roll 1 and the paper feed roll 1 suddenly starts to rotate, there is a problem that a paper feed slip easily occurs between the paper and the paper. With such would temporarily cause feeding slip during feeding start, for switching to a smaller dynamic friction coefficient than this friction coefficient from the static coefficient of friction between the sheet feed roller 1 and the paper, of the mu _1> mu
The relationship of ₂ > μ ₃ is broken, and no matter how much the paper feed roll 1 rotates, the paper is not fed. In particular, as the sheet feeding speed becomes higher, the frictional force between the sheet feeding roll 1 and the sheet becomes smaller than the inertial force of the sheet and the frictional force between the sheet and the next sheet, so that the sheet is more likely to slip.

In order to solve such a problem, it is conceivable to set the friction coefficient of the paper feed roll 1 or the pressing force of the friction pad to a high value. An abnormal sound (squeaking) may occur between the friction pad and its setting, which is difficult to set.

Further, at the start of paper feeding, as described above, the gear 2
When the rotational force of is transmitted to the paper feed roll 1 through the electromagnetic clutch 3 instantaneously, the inertial load at that moment is so large that if the electromagnetic clutch 3 does not have a sufficient margin, the electromagnetic clutch 3 itself There was also a problem that it was easy to cause slip.

On the other hand, for example, as shown in FIG.
Standby roll (or transport roll) for the paper fed in 1
And then re-convey to the image forming unit 8.
In this device, the paper feed roll 1 is fed by this.
Rotate by itself until the cut paper reaches the standby roll 7.
However, after that, it will be transported by the standby roll 7.
Just follow the paper. For such devices
When there is enough paper on the paper stacking plate 9,
Between the friction plate 10 and the paper feed roll 1 and the friction pad 11
Between the paper feed roll 1 and the paper feed roll 1, as shown in FIG.
Since there are always two or more sheets of paper in between, it is for carrying
The friction force between the next paper and the paper μ₃Only this happens
Force F that resists the conveyance of paper generated by the frictional force of_A(=
μ₃(F ₁+ F₂)) Is only a few. By the way
Is the last sheet (final sheet) P on the sheet stacking plate 9._LPaper feed
At the time of printing, as shown in FIG._L
Directly rub against the friction plate 10 and the friction pad 11,
Last paper P_LAnd a friction plate 10 and a friction pad 11 at the lower end of the
Large friction force between₂Caused by this frictional force
As shown in 6, the final paper P_LForce against paper transport
F_A′ (= Μ₂(F₁+ F ₂)) Occurs and this F_A′
Is the above F_AMuch bigger than As a result,
As shown, the final paper P being conveyed by the standby roll 7_L
Has a conveyance force F by the standby roll 7 at its tip._BWorks
On the other hand, the transfer force F is applied to the rear end._BForce F against_A′ Works
The end paper P_LExcessive tension T is applied to
Wow

Then, at the moment when the trailing edge of the final paper P _L passes between the paper feed roll 1 and the friction plate 10 and the friction pad 11, the excessive tension T suddenly disappears. Abrupt tension fluctuations applied to such last sheet P _L is, if occurred midst of image formation by the image forming unit 8 on the final paper P _L, the image blurring problem can not be avoided of course.

In view of the above-mentioned conventional problems, it is an object of the present invention to provide a paper feeding device which can improve the paper feeding performance of a paper feeding roll and effectively prevent problems such as paper feeding slip and clutch slip. To do.

[0010]

In order to achieve the above-mentioned object, a sheet feeding device of the present invention has a stacking unit for stacking and storing sheets, and a peripheral surface of the sheet to be stacked on the stacking unit. A paper feed roll that feeds a sheet, a rotating shaft that rotatably supports the paper feed roll at a predetermined angle, and a driving force from the main body drive system that is transmitted and not transmitted to the rotating shaft as a rotational force in the paper feeding direction. Drive transmission means that is controlled to be switched to transmission, and urging means that engages the paper feed roll and the rotation shaft to urge the paper feed roll in a rotation direction of the paper feed direction with respect to the rotation shaft,
It is characterized by including.

[0011]

In the present invention, the paper feed roll is not fixed to the rotary shaft but is rotatably supported within a predetermined angle range while receiving the urging force in the paper feed direction by the urging means. Therefore,
When the drive force from the main body drive system is transmitted to the rotary shaft by the switching control of the drive transmission means, the rotation force is not instantaneously transmitted to the paper feed roll, but is applied to the biasing force via the biasing means. It is gradually transmitted in response. As a result, the paper feeding power of the paper feeding roll is increased smoothly,
As the sheet begins to slip relative to the next sheet, the paper feed rate will continue to accelerate. That is, in the present invention,
Fast static feed is always possible.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of the paper feeding device and its vicinity in an image forming apparatus such as a printer device to which the paper feeding device according to an embodiment of the present invention is applied.

This image forming apparatus is detachable from the apparatus main body M, and is a sheet feeding cassette 21 as a stacking means for stacking and storing sheets P for image formation, and the sheets P stacked therein.
A paper feed roll 22 that feeds the paper P by bringing the peripheral surface into contact with the paper
And is pressed against the peripheral surface of the paper feed roll 22 with a predetermined pressure,
It is provided with a friction pad 23 for separating and feeding the sheets P in the sheet feed cassette 21 one by one from the topmost sheet in order when the sheet is fed by the sheet feed roll 22. Further, in the paper feed cassette 21, a paper stacking plate 24 that can move up and down while stacking the paper P, and by pushing up the paper stacking plate 24, the front end of the paper P above the paper stacking plate 24 is moved around the paper feed roll 22. A push-up member 25 that presses the surface with a predetermined pressure, and a friction plate 26 that is provided at the front end of the upper surface of the sheet stacking plate 24 and that prevents double feeding of the sheets P are provided. In addition, the paper feed roll 22
In the downstream side of the paper feeding direction (direction of arrow A), the paper feeding roll 22
A reversing guide 27 that reverses and guides the sheet fed from the front, a slip roll 28 that further conveys the reversed sheet, a leading edge detection sensor 29 that detects the leading edge of the conveyed sheet, A standby roll 30 or the like is provided for temporarily waiting the conveyed sheet and then re-conveying it toward an image forming unit (not shown) at a predetermined timing. After a predetermined image forming process by, the sheet is discharged outside the apparatus.

Further, the paper feed roll 22 is shown in FIG.
As shown in FIG. 5, the urging means is applied to the rotary shaft 33 to which the rotational drive force from the main body drive system (the gear 31 is a gear provided at the final stage of the main body) is transmitted via the electromagnetic clutch 32 as the drive transmission means. It is non-fixedly supported via a torsion spring 34 as. That is, the paper feed roll 22 is supported rotatably within a predetermined angle range with respect to the rotation shaft 33, and the paper feed roll 22 is attached to the E ring 35 fitted to the rotation shaft 33 as a retaining member. One side surface of the rotary shaft 33 is in contact with the other side surface of the paper feed roll 22.
Is engaged with a torsion spring 34 wound around. Here, in the torsion spring 34, the rotary shaft 33 has a sheet feeding direction (arrow A).
Direction), when it is driven to rotate in the direction of arrow B, which is the direction of rotation corresponding to the (direction), it is wound around the rotary shaft 33 so as to apply a biasing force to the paper feed roll 22 in the same direction as the direction of arrow B. , One end of the torsion spring 34 is shown in FIG.
As shown in (b), it engages with a long hole 22a provided on the other side surface portion of the paper feed roll 22 with a certain amount of play,
The other end is engaged with a small hole 33a provided in the rotary shaft 33.

In the above structure, the paper feed roll 22 operates as shown in FIG. 3 when the paper feed is started. First, since the electromagnetic clutch 32 (FIG. 2) is turned off before paper feeding,
As shown in (a), the rotating shaft 33 is twisted to the torsion spring 34.
It is completely free up to the paper feed roll 22 via (FIG. 2). When a predetermined feeding start signal (start signal) is output and the electromagnetic clutch 32 is turned on, the gear 31 (FIG. 2)
The rotational driving force of the
As shown in (b), the rotating shaft 33 suddenly starts to rotate, but at this point, the rotating force of the rotating shaft 33 is equal to that of the torsion spring 34.
It is absorbed by and is not transmitted to the paper feed roll 22.

After that, when the rotating shaft 33 further rotates, the torsion spring 34 gradually deforms accordingly, and the urging force to the paper feed roll 22 gradually increases. Along with this, the paper feed force by the paper feed roll 22 is also increased. Going up. Then, when the sheet feeding force is increased to the extent that the sheet feeding roll 22 can feed the uppermost sheet of the sheet P against the frictional force between the sheets, FIG.
At the same time that the topmost sheet slips with respect to the sheet below it, the paper feed roll 22 starts rotating, as shown in FIG.

When the paper is fed in this way and the leading edge of the fed paper reaches the standby roll 30 (FIG. 1),
When the electromagnetic clutch 32 is turned off, the rotating shaft 33
To the paper feed roll 22 via the torsion spring 34. After that, when the re-conveyance by the standby roll 30 is started, as shown in FIG. 3D, from the paper feed roll 22 in the free state to the rotating shaft 33 is dragged by the paper conveyed by the standby roll 30. To go around. When the trailing edge of the paper being conveyed is separated from the paper feed roll 30,
Return to the state of (a).

As described above, according to this embodiment,
At the start of paper feeding, the rotational force of the rotary shaft 33 is applied to the paper feeding roll 22.
Is not transmitted instantaneously to the sheet feeding roller 22, but is gradually transmitted via the torsion spring 34. Therefore, the sheet feeding force of the sheet feeding roll 22 is gradually increased, and the uppermost sheet contacting the sheet feeding roll 22 is The paper feeding speed is accelerated when it starts to slide with the paper underneath. Here, the expression “paper feeding power gradually increases” is adopted, but the paper feeding power does not slowly rise, but rather the rotary shaft 33.
It takes only a short time from the start of rotation to the time when the paper feed roll 22 is accelerated and rotated, which means that the paper feed force rises smoothly during that time. Therefore, according to the present embodiment, a paper feeding slip is not caused at the time of starting the paper feeding, and as a result, a quick paper feeding by static friction can always be performed instead of a conventional paper feeding by dynamic friction. Is significantly improved. Moreover, since the inertial load at the moment when the electromagnetic clutch 32 is turned on is only the rotating shaft 33 (there is no load on the paper feed roll 22 or paper feed), clutch slip can also be effectively prevented.

It should be noted that although the torsion spring 34 having a certain weakness can support high-speed paper feeding, the frictional force between the paper being fed and the paper therebelow immediately before reaching the standby roll 30. Since the amount of bending of the paper also varies due to the variation of (μ ₃ ), it is necessary to set the strength of the torsion spring 34 in consideration of this. For example, the frictional force μ ₃ before the standby of the paper is 20 gf, and the diameter of the paper feed roll 22 is 40
In the case of mm, when it is desired to suppress the amount of paper deflection to ± 3 mm, the spring constant k of the torsion spring 34 is k = 20 / (2π × 3 /
A strength of 40π) = 10 / (3/20) ≈67 [gf / rad] or more is required.

Further, in the present embodiment, not only is the means for solving the above-mentioned problem of the paper feed slip at the start of the paper feeding, but also the excessive tension T ( Means for preventing (see FIGS. 6 and 7) are also provided. This means is to perform drive control of the paper feed roll 22 (that is, ON / OFF control of the electromagnetic clutch 32) and the like, and a specific control example thereof is shown in FIG. In addition,
The figure shows an example of control when three sheets are present on the sheet stacking plate 24 and the three sheets are fed.

First, when the paper feed start signal (start signal) is output, the paper feed clutch (electromagnetic clutch 32) is turned on to start the paper feed by the paper feed roll 22 as described above, and at the same time, the slip occurs. Roll 28 (FIG. 1) also begins to rotate. Then, the leading edge of the sheet is detected by the leading edge detection sensor 29.
(FIG. 1), after the time t ₁ required for the leading edge of the paper to reach the standby roll 30 from the time of detection, the paper feed clutch is turned off and the transmission of the rotational force to the paper feed roll 22 is stopped. To be done. Then, after the time t ₂ (> t ₁ ) synchronized with the image forming timing has elapsed from the time when the leading edge was detected, a re-feeding signal is output, and the standby clutch is turned on by this signal to direct the standby roll 30 to the image forming unit. Refeeding is started. Here, after the paper is re-fed, the paper feed roll 22 rotates along with the paper until the trailing edge of the paper passes through the paper feed position of the paper feed roll 22. After the trailing edge of the sheet passes the standby roll 30, the standby clutch is turned off, and the rotation of the standby roll 30 is stopped. After the first sheet is fed in this way, the second sheet is also fed at a predetermined timing.

After that, feeding of the third sheet (final sheet) is started in the same manner, but the fact that there is no sheet left on the sheet stacking plate 24 (FIG. 1) indicates that there is no sheet sensor (Fig. (Not shown in FIG. 1), the standby roll 30 starts to rotate by the re-feed signal output thereafter, and at the same time, the paper feed clutch is turned on to feed the paper by the paper feed roll 22. To be controlled. That is, for the final sheet, the feeding by the standby roll 30 and the forced feeding by the sheet feed roll 22 are simultaneously performed. The forced paper feeding by the paper feeding roll 22 is performed until the trailing edge of the final paper passes the paper feeding position by the paper feeding roll 22.

According to the present embodiment, the following effects can be obtained by performing the above control on the final paper. That is, even if a large frictional force is generated by the friction plate 26 and the friction pad 23 on the final paper as described above with reference to FIGS. 6 and 7, the paper is not forcibly fed by the paper feed roll 22 as described above. In order to execute, the large resistance force F _A ′ in the direction opposite to the paper transport direction, which has been conventionally generated, is applied to the final paper.
(FIG. 6) does not occur, so that it is possible to reliably prevent an excessive tension T from being applied to the final sheet. As a result, the problem of image blur that has occurred in the past can be solved satisfactorily.

If the linear velocity of the paper feed roll 22 is set higher than the linear velocity of the standby roll 30, the above resistance force F _A ′ is obtained.
Is more reliably eliminated, which is preferable. The above embodiments have been described by taking an image forming apparatus such as a printer or a copying machine as an example, but the present invention is not limited to the image forming apparatus, and the sheets are fed one by one by a paper feed roll. The present invention can be applied to various types of equipment that employ a sheet feeding device.

[0025]

According to the present invention, since the rotational force is transmitted from the rotary shaft to the sheet feeding roll at the start of sheet feeding through the biasing means such as a torsion spring, the sheet feeding roll is used. The paper force rises smoothly, so there is no paper feed slip due to a sudden rise as in the past, and as a result, it is possible to always feed quickly with static friction instead of dynamic friction as in the past. A significant improvement in paper feeding performance is realized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the sheet feeding device and its vicinity in an image forming apparatus to which a sheet feeding device according to an exemplary embodiment of the present invention is applied.

FIG. 2 is a diagram illustrating a paper feed roll 2 for a rotating shaft 33 according to the embodiment.
It is a figure which shows the attachment structure of No. 2, (a) is a front view,
(B) is a side view.

FIG. 3 is a diagram for explaining a rotating operation of a rotary shaft 33 and a paper feed roll 22, in which (a) is a state before the start of paper feed,
(B) shows the state when the rotation of the rotating shaft 33 is started, (c) shows the state when the sheet is fed by the sheet feeding roll 22, and (d) shows the state when the sheet is re-conveyed by the standby roll 30.

FIG. 4 is a time chart showing an example of sheet feeding control for the last sheet in the embodiment.

FIG. 5 is a perspective view showing a mounting structure of a paper feed roll with respect to a rotation shaft in a conventional paper feeder.

FIG. 6 is a diagram for explaining an excessive tension T applied to the final sheet, which is a conventional problem.

FIG. 7 is a diagram for explaining a sheet feeding state,
(A) shows a paper feed state of paper other than the last paper, and (b) shows a paper feed state of the last paper.

[Explanation of symbols]

 21 Paper Feed Cassette 22 Paper Feed Roll 23 Friction Pad 24 Paper Loading Plate 26 Friction Plate 29 Tip Detection Sensor 30 Standby Roll 32 Electromagnetic Clutch 33 Rotating Shaft 34 Torsion Spring

Claims (1)

[Claims] 1. A stacking unit for stacking and storing sheets, a sheet feeding roll for feeding the sheets by bringing a peripheral surface into contact with the sheets stacked on the stacking unit, and rotating the sheet feeding roll at a predetermined angle. A freely supporting rotary shaft; drive transmitting means for controlling the drive force from the main body drive system to be transmitted or not transmitted to the rotary shaft as a rotational force in the paper feeding direction; the paper feeding roll and the rotary shaft. And a biasing unit that biases the paper feed roll in the rotation direction of the paper feed direction with respect to the rotation shaft.