JP2003327341A - Sheet feeder of image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet feeder for an image forming device capable of precluding noise emission from the supporting part of a feed roller and/or a separation roller owing to a varying slip torque of a torque limiter and assuring a stable sheet feed operations. <P>SOLUTION: The separation roller 5 of this sheet feeder is coupled with a drive shaft 7A functioning also as a shaft of a swingable supporting frame 9 by a gear transmitting means 16 through the torque limiter, and a drive torque in the opposite direction to the sheet transporting direction is applied to the separation roller 5 from the drive shaft 7A. The gear transmitting means 16 is constituted so that the torque applied to the drive shaft 7A is directed oppositely to the direction of the moment around the drive shaft 7A owing to the friction force acting from the side with the feed roller 4 to the surface of the separation roller 5. <P>COPYRIGHT: (C)2004,JPO

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 used in a sheet feeding portion of an image forming apparatus such as an electrophotographic copying machine,
In particular, the present invention relates to a paper feeding device having a paper separating mechanism configured such that the contact pressure of the paper separating roller against the paper feeding roller is not affected by the drive torque of the paper separating roller.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic copying machine or a laser printer, sheets taken out from a sheet feeding tray by a pickup roller are separated one by one by a sheet separating mechanism. A sheet feeding device configured to feed a sheet toward a sheet conveying path is used. An example of a paper feeding device provided with the paper separating mechanism is described in
Devices such as those described in JP-A-59-74,841, JP-A-63-139,842, JP-A-3-23,125 and the like are known. In the paper feeding device as described above, as shown in FIG. 6, in the upper part of the paper feeding tray 1 near the end on the paper feeding side,
The paper feed tray 1 is formed by a combination of the pickup roller 3 supported by the support shaft 3A and the paper separating mechanism 17 arranged on the downstream side of the pickup roller 3 in the paper feed direction.
The sheet feeding device 15 has a function of sequentially taking out the sheets 2 accommodated therein from the upper one and feeding them one by one.

The paper separating mechanism 17 of the paper feeding device 15 has a paper feeding roller 4 for conveying the paper 2 in the paper feeding direction and a paper feeding roller 4 for feeding the paper 2 in the direction opposite to the paper feeding direction, that is, in the direction for returning the paper to the paper feeding tray 1. The separating roller 5 to which a driving force is applied is disposed so as to face the separating roller 5, and the separating operation for the sheet 2 is performed. Then, a separating roller gear 6 is attached to the support shaft 5A so that the driving force is transmitted by the drive gear 7 provided on the drive shaft 7A, and between the drive shaft 7A and the drive gear 7, A torque limiter 13 is arranged. The support shaft 5A provided with the separating roller 5 is attached to a support frame 9 which is swingably supported around a drive shaft 7A, and the support frame 9 is on the downstream side in the paper feeding direction. A coil spring 10 stretched between a bracket 9A provided at the lower part of the sheet and a coil spring fixing portion 12 on the image forming apparatus main body side is urged in a direction in which the separation roller 5 is pressed against the sheet feeding roller 4. .

As shown in FIG. 7, the sheet separating mechanism 17 in the sheet feeding device 15 having the conventional structure as described above is driven by rotating the drive shaft 7A clockwise by a drive source (not shown). Gear 7 and separating roller gear 6
A torque is generated via and to drive the separating roller 5 counterclockwise. Therefore, the paper sorting mechanism
On the other hand, when two sheets of paper are intruded in a state of being overlapped with each other, a slip occurs between the upper and lower sheets and the lower sheet in contact with the separating roller 5 moves in the counterclockwise direction of the separating roller 5. It is returned to the paper feed tray 1 side by rotation, and the paper feed roller 4
Only the upper sheet in contact with the lower surface of the sheet is sent out toward the sheet conveying path 11.

When only one sheet of paper enters the sheet separating mechanism 17, the frictional force between the sheet and the separating roller 5 becomes larger than the transmission force of the torque limiter 13. The torque limiter 13 that transmits torque to the drive shaft 7A slips on the drive shaft 7A, the separating roller 5 is rotated clockwise by the frictional force received from the lower surface of the sheet, and the sheet is rotated by the frictional force from the sheet feeding roller 4. , And is delivered to the side of the paper transport path 11. The paper feeding device shown in FIG. 6 is provided with a paper separating mechanism conventionally called a friction retard system, which is arranged in a paper supplying portion of an image forming apparatus, and includes a paper supplying roller 4 and a separating roller. The drive of the pickup roller 5 and the pickup roller 3 is performed by a single drive source.

When the sheet separating mechanism 17 is used as described above, the drive gear 7 provided on the drive shaft 7A meshes with the separating roller gear 6 provided on the support shaft 5A to transmit the drive force. Therefore, as shown in FIG. 7, the drive gear 7 is
An upward force X acts on the separating roller gear 6, and the separating roller 5 receives a horizontal frictional force F from the sheet feeding roller 4. Therefore, the pressing force of the separating roller 5 against the paper feeding roller 4 is the urging force Y by the coil spring 10 and the frictional force F acting on the outer periphery of the separating roller 5.
And the force X acting between the drive gear 7 and the separating roller gear 6, of which the forces F and X are proportional to the slip torque of the torque limiter 13. But in general,
Since the slip torque of the torque limiter 13 tends to change periodically, the forces F and X change, and the pressing force of the separating roller 5 on the sheet feeding roller 4 also changes. As a result, there arise problems that the member holding the paper feed roller 4 and the support frame 9 vibrate, noise becomes large, and the paper feed operation is disturbed.

[0007]

SUMMARY OF THE INVENTION The present invention solves the problems of the sheet feeding device in the prior art as described above, and the variation of the slip torque of the torque limiter causes the sheet feeding roller and the separating roller to be different. An object of the present invention is to provide a sheet feeding device of an image forming apparatus capable of preventing noise generated in a supporting portion and performing a stable sheet feeding operation.

[0008]

To achieve the above object, according to the present invention, a separating roller is arranged so as to face a sheet feeding roller which is driven to rotate in the sheet conveying direction, and the separating roller is provided with respect to the sheet feeding roller. And is rotatably supported by a supporting frame which is swingably supported in the contacting / separating direction, and an urging means is connected to the supporting frame so that the separating roller is urged so as to come into pressure contact with the sheet feeding roller. The separating roller is configured such that a drive torque in a direction opposite to the sheet conveying direction is applied to the separating roller from a support shaft of a support frame or a drive shaft on a coaxial center by gear transmission means via a torque limiter. In the paper feeding device of the image forming apparatus, the torque applied to the drive shaft and the moment around the support shaft due to the frictional force acting on the surface of the separating roller from the paper feeding roller side have opposite directions. To so that is obtained by forming the gear transmission unit. In particular, it is preferable to configure the gear transmission means so that the torque and the moment have the same magnitude and opposite directions.

The rotational driving force of the drive shaft is transmitted to the separating roller via the gear transmission means, and the separating roller is given a drive torque in the direction opposite to the sheet conveying direction. that time,
The torque limiter interposed in the gear transmission means drivingly connected to the drive shaft limits the transmission torque to the separating roller side. The drive torque applied to the drive shaft tends to rotate the support frame provided so as to be swingable around the support shaft. Since the gear transmission means is configured so that the moment is in the opposite direction to the torque applied to the drive shaft, the moment due to the frictional force from the side of the paper feed roller applied to the surface of the separating roller and the moment are driven. The torque applied to the shaft will cancel each other out. As a result, the judgment roller
Even if the transfer torque of the torque limiter changes periodically due to the constant biasing force of the biasing means connected to the support frame, the fluctuation of the pressure contact force of the separating roller against the paper feeding roller is reduced. To be done. In the above case, in particular, by configuring the gear transmission means so that the moment and the torque are equal in magnitude and opposite in direction, the influence of fluctuations in the torque transmitted by the torque limiter can be completely eliminated.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the sheet feeding device of the image forming apparatus of the present invention, and the same numbers are given to the members having the same functions as those of the conventional example shown in FIG. I am doing it. In FIG. 1, as in the conventional example, the paper feeding device 15 feeds out the paper 2 stored in the paper feeding tray 1 from the paper feeding side thereof, and a pickup roller 3 which is rotationally driven around a support shaft 3A, It is configured by combining with a sheet separating mechanism 17 located in the downstream portion thereof, and is provided so as to send out the sheets 2 one by one toward the sheet conveying path 11. The paper separating mechanism 17 includes a paper feeding roller 4 arranged at a fixed position on the downstream side of the pickup roller 3.
And a separating roller 5 facing the paper feeding roller 4, and is in contact with the upper surface of the paper 2 in the paper feeding direction.
The separating roller 5 is configured to contact the lower surface of the sheet 2 with respect to the sheet feeding roller 4 which is rotatably driven about the axis, and a driving torque is applied in a direction of returning the sheet 2 around the support shaft 5A. There is.

A supporting shaft 5A of the separating roller 5 is attached to a supporting frame 9 which is swingably supported about a driving shaft 7A as a supporting shaft, and a driving gear 7 provided on the driving shaft 7A,
The idle gear 8 rotatably supported on the support frame 9 by the idle gear shaft 8A, and the gear transmission means 16 constituted by the separating roller gear 6 provided on the support shaft 5A together with the separating roller 5 and the drive shaft 7A. The driving torque applied to the separating roller 5 is transmitted to the separating roller 5. Further, a bracket 9A is formed on the support frame 9 so as to project from a lower portion of the support frame 9 opposite to the separating roller 5 side with respect to the drive shaft 7A. The bracket 9A and the image forming apparatus main body side are provided. A coil spring 10 as a biasing means is stretched between the coil spring fixing portion 12 and the coil spring fixing portion 12.
As shown in FIG. 2, the gear transmission means 16 has a torque limiter 13 interposed between the drive shaft 7A and the drive gear 7, and slips when the drive torque applied to the drive shaft 7A exceeds a certain value. Is configured.

FIG. 3 shows a direction in which a force applied to each part of the sheet separating mechanism 17 having the above-described structure acts, and the drive torque applied from the outside to the drive shaft 7A is as follows. The torque is limited to a size less than or equal to the value set by the torque limiter 13 and transmitted to the drive gear 7, and at the meshing portion between the drive gear 7 and the idle gear 8, as shown in FIG. A force X acts on the separating roller gear 6 via the idle gear 8 to rotate the separating roller 5 rotated integrally with the separating roller gear 6 in the counterclockwise direction. Try to. On the other hand, the separating roller gear 6 receives the tangential frictional force F at the contact position P with the paper feeding roller 4 rotating counterclockwise. Further, the support frame 9 receives an urging force Y from a coil spring 10 connected between the bracket 9A and the coil spring fixing portion 12.

As shown in FIG. 4, the center O2 of the drive shaft 7A, which is the swinging fulcrum of the support frame 9, is the vertical distance a of the contact position P between the sheet feeding roller 4 and the separating roller 5 with respect to the tangential direction. , Are provided at positions shifted downward. Further, the relationship between the radius R from the center O1 of the support shaft 5A on the outer peripheral surface of the separating roller 5, the radius r1 of the pitch circle of the separating roller gear 6, and the radius r2 of the pitch circle of the drive gear 7 is r2.
It is set so that / r1 = a / R. The force X is transmitted by the idle gear 8 and acts on the meshing position between the idle gear 8 and the separating roller gear 6, and the radius r1 of the pitch circle of the separating roller gear 6 and the radius R of the separating roller 5 are transmitted. Due to the relationship with
, A force of magnitude X · (r1 / R) is applied from the separating roller gear 6 to the side of the paper feeding roller 4 in the direction opposite to the paper feeding direction. As a reaction force of the force, the separating roller 5 is A force F in the paper feed direction is received from the paper feed roller 4 side. Therefore, the magnitude of the force F is equal to X · (r1 / R), and the force F causes the support frame 9 to generate a clockwise moment a · F = aX · (r1) with respect to the swing fulcrum O2. /
R). In addition, the support frame 9 is around O2,
It receives the counterclockwise drive torque from the drive gear 7,
Since the pitch circle radius of the drive gear 7 is r2, the size thereof is r2 · X. From the above relationship, since r2 = r1 · (a / R), the magnitude of the driving torque that the support frame 9 receives from the driving gear 7 is aX · (r1 / R), and the moment is The moment that acts on the support frame 9 by canceling out the drive torque applied to the drive gear 7 from the drive shaft 7A is only due to the biasing force of the coil spring 10. The above relationship holds regardless of the magnitude of the drive torque applied to the drive shaft 7A. Therefore, even if the transmission torque of the torque limiter 13 fluctuates periodically, the moment acting on the support frame 9 does not reach the coil spring 10. Only due to the power, the influence due to the change in the transmission torque can be eliminated.

Next, FIG. 5 shows a second embodiment of the present invention, in which the position of the drive shaft 7A is
It is located upstream of the separating roller 5 in the paper transport direction. The support frame 9 is provided with a bracket 9A at the lower part on the side of the paper feed tray 1,
The coil spring 10 is horizontally mounted between the bracket 9A and the coil spring fixing portion 12 fixed to the image forming apparatus main body side. The coil spring 10 has a support frame 9 swingably supported by a drive shaft 7A as a support shaft.
Is urged to rotate counterclockwise in FIG. 5, and the urging force presses the separating roller 5 against the sheet feeding roller 4. Drive shaft 7A and drive gear 7
A torque limiter 13 is interposed between the drive gear 7 and the drive gear 7 as in the first embodiment. When a load torque of a certain magnitude or more is applied, the drive gear 7 side slips with respect to the drive shaft 7A. Is configured.

Further, in the present embodiment, contrary to the case of the above-mentioned first embodiment, by the drive torque applied from the drive shaft 7A to the drive gear 7, the support frame 9 is
A counterclockwise rotational force, which is a direction in which the separating roller 5 is pressed against the sheet feeding roller 4, acts, and a frictional force acting on the supporting frame 9 from the sheet feeding roller 4 side causes the supporting frame 9 to move. , Acting to rotate clockwise. Also in the case of this embodiment, as in the case of the above-described first embodiment, driving by the drive torque applied to the drive shaft 7A and the frictional force acting on the surface of the separating roller 5 from the paper feed roller 4 side. By configuring the gear transmission so that the moment about the shaft 7A is equal in magnitude and opposite in direction, fluctuations in the drive torque of the torque limiter 13 can be eliminated.

In each of the above-described embodiments, the torque limiter 13 is interposed between the drive shaft 7A and the drive gear 7, but the position at which the torque limiter 13 is provided is determined by the gear transmission means 16. It may be provided between the separating roller 5 and the drive shaft 7A. Further, in each of the above-mentioned embodiments, one idle gear 8 is used in the gear transmission means 16, but the invention is not limited to this, and the drive shaft 7A
If the gear transmission is configured such that the drive torque applied to the drive roller 7 and the moment around the drive shaft 7A due to the frictional force acting on the surface of the separating roller 5 from the paper feed roller 4 side are opposite in direction. Good. Further, in the above-mentioned embodiment, the drive shaft 7A also serves as the support shaft of the support frame, but the support shaft and the drive shaft 7A may be separately configured on the same axis. Furthermore, in each of the above-described embodiments, the gear transmission means 16 is set so that the drive torque applied to the drive shaft 7A and the moment acting on the support frame 9 around the drive shaft 7A are equal in magnitude and opposite in direction. However, even if the sizes are not made equal, if the directions are opposite, the effect of reducing the torque fluctuation acting on the support frame 9 can be obtained.

[0017]

As described above, according to the present invention,
Since the gear transmission is configured so that the torque applied to the drive shaft and the moment around the support shaft of the support frame due to the frictional force acting on the surface of the separation roller from the paper feed roller side are opposite in direction, the separation roller Moments acting on the support frame that supports the parts other than the biasing means are reduced. As a result, the influence of torque fluctuation due to the torque limiter interposed in the drive transmission system that drives the separating roller is reduced, and the holding portion of the sheet feeding roller and the support frame supporting the separating roller are affected by the torque fluctuation. Vibration and noise are prevented, and fluctuations in the contact force of the separation roller with respect to the paper feed roller are reduced,
A stable paper feeding operation can be performed. In particular, when the gear transmission means is configured such that the torque and the moment have the same magnitude and opposite directions, the influence of the torque fluctuation can be completely eliminated. Optimum sheet feeding operation can be performed by a constant moment of only.

[Brief description of drawings]

FIG. 1 is a side view showing a first embodiment of a paper feeding device of the present invention.

FIG. 2 is a plan view showing a configuration of a drive system of a paper separating roller of the paper feeding device shown in FIG.

FIG. 3 is a diagram showing an action direction of a force applied to each part of a paper separating mechanism in the paper feeding device of FIG.

FIG. 4 is a diagram showing a positional relationship of respective members of a paper separating mechanism in the paper feeding device of FIG.

FIG. 5 is a side view showing a second embodiment of the paper feeding device of the present invention.

FIG. 6 is a side view showing an example of a conventional paper feeding device.

FIG. 7 is a diagram showing an action direction of a force applied to each part of the paper separating mechanism in the paper feeding device shown in FIG.

[Explanation of symbols]

1 ... paper feed tray, 2 ... paper, 3 ... pickup roller,
4 ... Paper feeding roller, 5 ... Separation roller, 6 ... Separation roller gear, 7 ... Drive gear, 8 ... Idle gear, 9 ... Support frame, 10 ... Coil spring, 11 ... Paper transport path, 12 ... Coil spring fixing portion, 13 ... Torque limiter, 15 ... Paper feeder, 16 ... Gear transmission means, 17 ... Paper separating mechanism.

Claims (6)

[Claims] 1. A paper feeding roller which is driven to rotate in a paper conveying direction, a support frame which is swingably supported in the contacting and separating direction with respect to the paper feeding roller, and a shaft supported by the support frame. A separating roller, which is arranged so as to face the paper roller and is pressed against the paper feeding roller 4 by a biasing means acting on the supporting frame, is connected to a drive shaft, and a driving force is applied to the separating roller via a torque limiter. And a gear transmission means for transmitting the force, the force around the support shaft of the support frame generated by the transmission of the driving force from the drive shaft to the gear transmission means, and the frictional force between the paper feed roller and the separation roller. A force is generated around the support shaft of the supporting frame is a paper feeding device configured to be in opposite directions, the supporting frame, facing each other at a distance,
A wall portion that supports the drive shaft is provided, and an action portion on which one end of the separating roller, the gear transmission unit, the torque limiter, and the urging unit acts is disposed between the wall portions. A sheet feeding device of an image forming apparatus, wherein a supporting shaft of the separating roller is supported by the wall portion on both sides of the separating roller. 2. The support frame according to claim 1, wherein the support frame has a substantially rectangular bottom wall portion, and wall portions facing each other with a space therebetween are provided upright from both side edge portions of the bottom wall portion. A sheet feeding device of the image forming apparatus described. 3. The sheet feeding device of the image forming apparatus according to claim 1, wherein the support frame is supported by a drive shaft as a support shaft. 4. The separating roller is provided on a support shaft which is substantially parallel to the drive shaft and which is axially supported between the wall parts at a predetermined distance from the drive shaft. The sheet feeding device of the image forming apparatus according to any one of 1. 5. The sheet feeding device of the image forming apparatus according to claim 1, wherein the torque limiter is directly connected to the drive shaft. 6. The gear transmission means is provided between a drive gear provided on the drive shaft, a separation roller gear provided on a support shaft of the separation roller, and the drive gear and the separation roller gear. 6. The image forming apparatus according to claim 1, further comprising an idle gear, and a rotation center of the idle gear is arranged below a straight line connecting between rotation centers of the drive gear and the separating roller gear. Paper feeder.