JP3611959B2 - Paper feeder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sheet feeding device for feeding out sheets stacked on a hopper, and more particularly to a structure for preventing double sheet feeding.
[0002]
A paper feeding device in an image forming apparatus such as a copying machine, a laser printer, a facsimile, etc., draws sheets stacked on a hopper one by one from the top by a paper feeding roller, and prevents a double feed by a pair of conveying rollers and a separation roller. Although only one sheet is transported to the other side, there is a demand for extending the life of the torque limiter provided on the separation roller, particularly from the viewpoint of improving the reliability of the sheet feeding device.
[0003]
[Prior art]
As shown in the schematic plan view of the roller drive system of the paper feeding device of FIG. 2 (see also FIG. 3), the conventional paper feeding device feeds the paper 2 in pressure contact with the paper 2 stacked on the hopper 1. A paper roller 3, a pair of separation rollers 4 and a first transport roller 5 that are pressed against each other with a predetermined pressure and transport the paper 2, and a paper feed motor 6 that drives these rollers 3, 4, 5, respectively. The drive transmission means 7 (gears 7a to 7d) for transmitting the driving force to the rollers 3, 4 and 5 of the roller, the pulleys 7e and 7f, the belt 7g, the feed roller 3 and the first transport roller 5 are locked. A conveying one-way clutch 8 and a paper feeding one-way clutch 9 that transmit the driving force with the direction set to the sheet conveying direction, and a separating one-way clutch 10 that transmits the driving force with the locking direction set to the separation roller 4 and the anti-paper conveying direction. This separation machine It is composed of a torque limiter 11 which is set to a predetermined limit torque between the-way clutch 10 and the separation roller 4.
[0004]
The gear 7b of the separation roller 4 that meshes with the gear 7a of the paper feed motor 6 meshes with the gear 7d of the first transport roller 5 via the intermediate gear 7c and rotates in the same direction, and the first transport roller 5 transports the paper. The separation roller 4 is driven and rotated in the direction of pulling back the paper 2 and driven and rotated later than the first conveying roller 5.
[0005]
The pulley 7f of the paper feed roller 3 is driven to rotate in the paper transport direction from the pulley 7e of the first transport roller 5 via the belt 7g.
Furthermore, in order to send one sheet 2 sent out from the first transport roller 5 forward, a second transport roller 12 driven and rotated by gears 15 and 16 by another transport motor 13; A paper detection sensor 14 for detecting the paper 2 is provided immediately after the second transport roller 12.
[0006]
Next, a state when the paper 2 is fed out from the paper feed roller 6 will be described with reference to FIGS. FIG. 3 shows the driving state of each roller before feeding. In FIG. 3, the solid-line arc arrow direction indicates the rotation direction by driving, and the dotted-line arc arrow direction indicates the driven direction by rotation.
[0007]
The separation roller 4 before feeding is driven in the anti-paper conveyance direction via the torque limiter 11, but the torque limiter 11 slips due to the frictional rotational force of the separation roller 4 and is rotated in the paper conveyance direction A. . In addition, the solid-line arc arrow direction and the dotted-line arc arrow direction indicate the rotation direction by driving and the driven direction by follow-up through the following drawings.
When the paper 2 is fed out from the hopper 1, the paper feed motor 6 is activated.
Pressure contact force between the separation roller 4 and the first conveying roller 5: 500 g,
Coefficient of dynamic friction between the sheet 2 and the first conveying roller 5: 1.5,
Coefficient of dynamic friction between paper 2a and paper 2b: 0.7,
Outer diameters of the separation roller 4 and the first conveying roller 5: 2.5 cm,
Gear reduction ratio between the paper feed motor 6 and the separation roller 4: 1/4,
Holding torque T when feeding motor 6 is stopped: 70 gcm:
And each is set,
The sheet conveying force of the first conveying roller 5 when feeding one sheet 2 in FIG. 4: F ₁ = 1.5 × 500 g = 750 g (T ₁ = 750 g × 2.5 cm / 2 = 937. 5 gcm),
Friction between the two sheets 2a and 2b in FIG. 5, that is, the sheet conveying force of the first conveying roller 5 when the upper sheet 2a is separated and sent out: F ₃ = 0.7 × 500 g = 350 g (T ₃ = 350 g × 2.5 cm / 2 = 437.5 gcm in terms of torque)
become.
[0008]
Furthermore, when the limiting torque of the torque limiter 11 is set to, for example, 600 gcm within a range satisfying the condition of F ₁ > F ₂ > F ₃ , the maximum pulling force F ₂ of the separation roller 4 is 600 gcm ÷ 2.5 cm / 2 = 480 g. Thus, when a further force in the sheet conveyance direction is applied to the separation roller 4, the torque limiter 11 acts (slips). In the case of FIG. 4, the first transport roller 5 feeds the paper 2 forward in the paper transport direction (solid arrow direction), but the torque limiter 11 is driven and rotated in the anti-paper transport direction ( solid arrow direction ). In spite of this, the slipping of the torque limiter 11 causes the separation roller 4 to be forcibly rotated in the paper transport direction (indicated by the dotted arrow) due to the relationship of F ₁ > F ₂ . In the case of FIG. 5, the first transport roller 5 is driven and rotated in the sheet transport direction (solid arrow direction) from the relationship of F ₂ > F ₃ to pull the upper sheet 2a away from the lower sheet 2b. Since the separation roller 4 is driven and rotated slower than the first conveyance roller 5 in the counter-sheet conveyance direction, the lower sheet 2b is stopped to prevent double feed.
[0009]
Further, as shown in FIG. 6 and FIG. 7, a second sheet of paper 2a is fed from the first conveying roller 5 and is driven and rotated by another driving motor (see FIG. 2). When the paper is detected by the paper detection sensor 14, the paper feed motor 6 is stopped by the output.
[0010]
At this time, since the paper feed motor 6 is stopped, the paper feed roller 3 and the first transport roller 5 are the same as the second transport roller 12 (the same as the first transport roller 5) until the paper 2a is removed. are the pressure contact force of the mutually 600 g.) are rotated together in the sheet conveying direction by the sheet 2 conveyed by the force of _{F 4 (F 4 = F 1} = 937.5gcm) by. The separation roller 4 varies depending on the number of sheets at the position of the first conveyance roller 5. That is, when there is only one sheet 2 in FIG. 6, F ₄ has a relationship of F ₄ > F ₂ with F _{2 in} FIG. 4, and the separation roller 4 is driven and rotated by the sheet feeding motor 6. Therefore, the separation roller 4 is rotated in the sheet conveying direction by the locking of the separation one-way clutch 10.
[0011]
However, when there are two or more sheets 2 in FIG. 7, F ₃ has a relationship of F ₂ > F ₃ with F _{2 in} FIG. 5, and the separation roller 4 is driven and rotated by the sheet feeding motor 6. Since the separation one-way clutch 10 is locked, the separation roller 4 is held without being rotated and double feed is prevented.
[0012]
[Problems to be solved by the invention]
As described above, although the movement of the separation roller varies depending on whether the paper feed motor is driven and whether the sheet at the position of the first transport roller is one sheet or two or more, normally one sheet is sent out. Normal paper transport. Therefore, the state in which the torque limiter slips continues for a long time regardless of the driving of the paper feed motor.
[0013]
For this reason, the conventional roller driving system of the paper feeding device has a problem that the life of the torque limiter is shortened and the change with time of the set limit torque is increased.
In view of the above problems, an object of the present invention is to extend the life of a torque limiter provided on a separation roller.
[0014]
[Means for Solving the Problems]
The present invention, in order to achieve the above object, a first conveying roller and the separation roller which is pressed against the each other physician via the drive transmission means and rotated by a common feed motor, and the first conveying roller In the paper feeding device that transports the paper in the paper transport direction with the paper sandwiched between the separation roller and prevents the double feed of the paper by rotation of the separation roller in the anti-paper transport direction, the first transport a second conveying roller that is rotationally driven by a separate drive motor and the paper feed mora to deliver the sheet fed from the roller to the other party, it is provided between the separation roller and said drive transmitting means and a torque limiter, the paper feed motor is driven is stopped after the leading edge of the first said sheet fed from the conveying roller has passed the second conveying roller, the paper feed motor Value holding torque when driving stop was converted to the torque limiter shaft of smaller than the limit torque of the torque limiter, and is set larger than the value of the frictional force in terms of the torque limiter shaft between the sheets Provided is a sheet feeding device characterized by being a thing.
[0015]
With this configuration, the holding torque when driving of the paper feed motor is stopped is set smaller than the torque limiter limit torque in terms of the torque limiter shaft. The holding torque of the paper motor rotates without being able to support the load torque in the paper conveyance direction generated by F ₄ (= F ₁ ) applied to the separation roller.
[0016]
At this time, the torque limiter does not act (slip), and neither the paper feed roller nor the first transport roller is rotated by the idling of the paper feed one-way clutch and the transport one-way clutch.
[0017]
Further, when two sheets of paper in Figure 7, the holding force of the feed motor, since it is possible to support the paper load torque in the conveying direction caused by the F ₃ applied to the separation roller, retaining the conventional similar separation roller It is possible to prevent double feed.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the gist of the present invention will be described in detail based on the embodiments shown in the drawings.
As shown in the schematic plan view of the roller drive system of the paper feeding device according to the present invention in FIG. 1, the roller drive system is configured by removing the one-way clutch 10 for separation from the conventional roller drive system shown in FIG. The paper feed motor (pulse motor) 17 is configured by converting the holding torque when the drive is stopped to the shaft of the torque limiter 11 and setting it smaller than the limit torque set in the torque limiter 11. In addition, the part demonstrated in the prior art figure uses the same code | symbol, and abbreviate | omits the description.
[0019]
The paper feed motor 17 when the drive is stopped has a holding torque of 70 gcm generated by the magnetic force of the permanent magnet of the stator.
In this embodiment, the gear reduction ratio of the paper feed motor 17 and the separation roller 4 is set to 3/20, and the holding torque 70 gcm of the paper feed motor 17 when driving is stopped is converted into the shaft of the torque limiter 11 to the torque limiter 11. It is set to 467 gcm which is smaller than the set limit torque of 600 gcm. In this case, it is necessary to satisfy the condition of F ₁ > F ₂ > F ₃ as in the conventional case.
[0020]
With this configuration, in the case of one sheet of FIG. 6 shown above, the load torque applied to the separation roller 4 by F ₄ (= F ₁ ) is the holding torque of the paper feed motor 17 (see FIG. 1). On the contrary, the paper feed motor 17 is rotated without being supported. However, since the revolving direction is the anti-paper conveying direction, the feeding roller 3 and the first conveying roller are operated by the action of the conveying one-way clutch 8 (see FIG. 1) and the feeding one-way clutch 9 (see FIG. 1). 5 is not transmitted.
[0021]
Further, when two sheets of FIG. 7, it is possible to support the load torque applied to the separation roller 4 by F ₃ by the holding torque of the paper feed motor 17 (see FIG. 1), was left to hold the separation roller 4 Double feed can be prevented.
[0022]
【The invention's effect】
As described above in detail, according to the present invention, since the slipping time of the torque limiter can be shortened while maintaining the sheet feeding separation function, the life of the torque limiter can be extended, and the reliability of the sheet feeding device can be increased. It exhibits extremely useful effects in the industry, such as increasing the degree.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of a roller driving system of a paper feeding device according to an embodiment of the present invention. FIG. 2 is a schematic plan view of a roller driving system of a paper feeding device according to the prior art. FIG. 4 is a diagram showing the rotation state of each roller during paper. FIG. 4 is a diagram showing the rotation state of each roller when one sheet of FIG. 3 is fed out. FIG. 5 is a diagram showing two sheets of FIG. FIG. 6 is a view showing the rotation state of each roller when the paper is moved. FIG. 6 is a view showing the rotation state of each roller when the paper in FIG. 4 reaches the paper detection sensor. Showing the rotation state of each roller at the time of operation [Explanation of symbols]
2: Paper 4: Separation roller 5: First transport roller 11: Torque limiter 17: Paper feed motor (pulse motor)

Claims (1)

Together with the first conveying roller to be pressed against the separation roller through a drive transmission means is rotated by a common feed motor, the paper across the paper between the separation roller and the first conveyance roller In a paper feeding device that transports the paper in the paper transport direction and prevents double feed of the paper by rotation of the separation roller in the anti-paper transport direction,
A second transport roller that is driven and rotated by a drive motor different from the paper feed mora in order to send the paper fed from the first transport roller forward;
And a torque limiter provided between the separating roller and the drive transmission means,
The paper feed motor, the first distal end of the sheet fed from the conveying rollers are driven stopped after passing through the second conveyance roller, said torque limiter holding torque when the drive stop of the paper feed motor value converted to the axis is smaller than the limit torque of the torque limiter, and the sheet feeding apparatus, characterized in that it is the frictional force between the sheets that is set larger than the value in terms of the torque limiter shaft .

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