JP2011236054A - Image forming device and paper feeding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of surely preventing a double feed, and a paper feeding method.SOLUTION: The image forming device includes: a paper feeding part capable of placing two or more paper sheets; a pickup roller which can rotate positively and reversely to send off the paper sheet from the paper feeding part; a pickup roller driving part which drives the pickup roller for positive rotation or reverse rotation; an arm which supports the pickup roller; an arm driving part which drives the arm; and a control part which controls the arm driving part to bring by the arm the pickup roller into contact with the paper sheet placed on the paper feeding part, and controls the pickup roller driving part to rotate the pickup roller in the opposite direction to the feeding direction to make the contacting paper flexed, and to rotate the pickup roller in the paper feeding direction to send out the paper sheet from the paper feeding part, and controls the arm driving part after feeding the paper sheet to detach the pickup roller from the paper sheet by the arm.

Description

  Embodiments described herein relate generally to a paper feeding unit that feeds paper such as recording paper in an image forming apparatus such as a copying machine, a facsimile machine, or a printer.

  2. Description of the Related Art Conventionally, various types have been proposed and implemented in order to prevent double feeding of sheets stacked on a cassette, tray, or the like in a sheet feeding unit of an image forming apparatus. For example, in order to prevent double feeding, there is a technique in which a separation roller is provided below a paper feed roller that feeds paper from a paper feed cassette into the main body.

  Specifically, by providing a paper feed roller and a separation roller downstream of the paper feed cassette, when two sheets are fed, the friction between the paper and the paper is small. The upper sheet is not conveyed anymore, and the upper sheet is conveyed and separated by the sheet feeding roller. When a paper feed command is received, the paper feed roller is driven in reverse to bend the uppermost paper so that it is separated from the second and subsequent papers. There is another paper feeding device that transports the uppermost paper.

  In the double feed prevention configuration using the paper feed roller and the separation roller, complicated settings such as the positioning of the paper feed roller and the separation roller, the friction coefficient of the separation roller, and the pressure contact conveyance force are required. In the other paper feeding device described above, the paper feeding roller rotates forward and backward each time printing is performed, so that it takes some time to transport the paper. In addition, since the above-described paper feed roller is always in contact with the uppermost sheet, the structure is easy to cause double feed due to pressure applied to the second and subsequent sheets.

Japanese Patent Laid-Open No. 5-147752

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and a paper feeding method that can reliably prevent double feeding.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a paper feed unit on which a plurality of papers can be placed, a pickup roller that can rotate forward and backward to feed the paper from the paper feed unit, and the pickup roller. A pickup roller driving unit for driving forward or reverse rotation, an arm for supporting the pickup roller, an arm driving unit for driving the arm, and controlling the arm driving unit to feed the pickup roller by the arm. The pickup roller is controlled to rotate in the direction opposite to the feeding direction to bend the contacting sheet, and then the pickup roller is moved in the feeding direction. Rotate to feed the paper out of the paper feed unit, and after the paper feed is finished, control the arm drive unit to separate the pickup roller from the paper by the arm A control unit that, characterized by comprising a.

FIG. 2 is a block diagram illustrating a configuration example of a control system of the image forming apparatus in the first embodiment. It is a figure which shows the example of an external appearance of the paper feed part in 1st embodiment. It is a figure which shows the example of an external appearance of the paper feed part in 1st embodiment. 6 is a flowchart illustrating an operation of a paper feeding unit in the first embodiment. 10 is a flowchart illustrating an operation of a sheet feeding unit in the second embodiment.

  Hereinafter, a sheet feeding unit of an image forming apparatus according to an embodiment will be described in detail with reference to the accompanying drawings.

(First embodiment)
As an image forming apparatus 1 according to the first embodiment of the present invention, for example, a block configuration of an MFP is shown in FIG. The image forming apparatus 1 has a paper feed cassette 2 (see FIG. 2) inside. The image forming apparatus 1 includes a combination of a CPU 3 as a control unit that controls the overall operation, and nonvolatile and volatile storage devices such as a RAM 4, a ROM 5, and an HDD. The CPU 3 performs operations, signal processing, and the like based on programs, data, input signals, and the like, and controls the operation of each unit. The image forming apparatus 1 includes a paper feeding unit 6 including the paper feeding cassette 2, an image forming unit 7, a document reading unit 8, a transfer unit 9, a fixing unit 10, a communication interface 11, a display unit 12, and a clock that measures various times. Unit 13, paper input unit 14 used when using manual paper, an operation unit 15 for a user to input an operation, a paper feed roller 16 for conveying paper into the image forming apparatus 1, a pair of conveyance rollers (not shown), and the like The above-mentioned respective parts are connected by a bus line 18 or the like.

  Hereinafter, an outline from reading of an original image to printing on paper with the above configuration will be described.

  The document reading unit 8 is a so-called scanner, which reads a document and outputs it as image data. The image forming unit 7 includes an image carrier (for example, a photosensitive drum), a charger, a developing unit, and the like. The image forming unit 7 is formed on the photosensitive drum by a laser beam modulated by image data from the document reading unit 8. The electrostatic latent image is developed with toner to obtain a toner image. The toner image is transferred by a transfer roller onto a sheet fed from the sheet feeding unit 6 via a transfer body such as a transfer belt included in the transfer unit 9. The sheet onto which the toner image has been transferred is conveyed to the fixing unit 10 where heat and pressure are applied by, for example, a fixing roller, and the toner image is fixed. Finally, the paper on which the toner image is fixed is discharged to, for example, a paper discharge tray.

  Next, the configuration of the paper feeding unit 6 will be described. The sheet feeding unit 6 starts a sheet feeding operation in response to an instruction from a user terminal or the like (for example, a PC) via the operation unit 15 or the communication interface 11 of the image forming apparatus 1.

  The drive unit connected to the paper feed unit 6 includes a lift motor 19, a pickup roller drive unit 20, and an arm drive unit 21. The lift motor 19 is a drive source that raises and lowers the paper placing plate 22 (see FIG. 2) on which the paper P is stacked. The pickup roller driving unit 20 is a driving source that rotationally drives a pickup roller 23 that conveys the uppermost sheet P1 of the sheets P loaded in the sheet feeding cassette 2 into the image forming apparatus 1. Controlled to allow reverse rotation. The arm drive unit 21 is a drive source that drives the arm 24, and is controlled by the CPU 3 so that the pickup roller 23 can be moved up and down so that the pickup roller 23 can contact and separate from the paper P.

  Next, the configuration of the sheet feeding unit 6 will be described with reference to FIG. The paper feed unit 6 includes a pickup roller 23 that conveys the paper P stacked in the paper feed cassette 2 to the inside (for example, the transfer unit 9). On the main body side, there are a paper feed roller 16 and a separation roller 25 provided downstream of the pickup roller 23. The pickup roller 23 has a roller shaft 26 supported by the arm 24, and the arm 24 is moved by a shaft 27. For example, when the shaft 27 is rotated clockwise, the arm 24 is raised, and when the shaft 27 is rotated counterclockwise, the arm 24 is lowered. The pickup roller 23 is formed of a rubber resin having a high frictional resistance. At the bottom of the paper feed cassette 2 is provided a paper placement plate 22 on which paper is placed. The paper placement plate 22 is moved upward by a lift motor 19 as the paper is fed by a pickup roller 23. . A paper rear end guide 28 for aligning a bundle of the loaded paper P is provided at the upstream rear end of the paper feed cassette 2.

  FIG. 2A is a diagram of a state before feeding and conveying. Before the sheet feeding conveyance, the pickup roller 23 is not in contact with the uppermost sheet of the sheet P placed on the sheet feeding cassette 2. The arm 24 is rotated by the print signal from the image forming apparatus 1 (CPU 3) to push down the pickup roller 23. Thereafter, at the timing when the pickup roller 23 comes into contact with the uppermost paper P1, the pickup roller 23 is reversely rotated by a predetermined number (for example, 1/2 to 3/4 rotation) in a direction opposite to the sheet conveyance direction.

  FIG. 2B is a diagram in which the uppermost paper P1 of the paper P placed in the paper feed cassette 2 is bent when the pickup roller 23 rotates in the reverse direction. After the pickup roller 23 rotates reversely a predetermined number of times, the rear end of the uppermost paper P1 stops at the paper rear end guide 28 and bends upward to be separated from the second sheet. The pickup roller 23 once stops and then rotates forward. Immediately after the forward rotation of the pickup roller 23, the paper feed roller 16 is rotated. By the rotation of the paper feed roller 16, the separation roller 25 is passively rotated, and the uppermost paper P1 is conveyed into the main body of the image forming apparatus 1. . This operation is repeated until the print signal is completed. Upon completion of the print signal, the arm 24 is moved up so as to separate the pickup roller 23 from the uppermost sheet P1, and waits for the next print signal.

  In such a configuration, the user performs a print start operation using a terminal such as a PC held by the user via the communication interface 11, or the user visits the image forming apparatus 1, and the original to be printed is printed by the paper reading unit 8. Read and start printing.

  In response to a print start operation from the operation unit 15, a print signal (paper feed command) of the image forming apparatus 1 is output. In response to this print signal, the arm 24 rotates, and the pickup roller 23 for feeding the paper P placed on the paper feed cassette 2 to the transfer unit 9 contacts the uppermost paper P1. Then, the pick-up roller 23 makes a half turn (counterclockwise in FIG. 2) in the direction opposite to the sheet conveyance direction, and the uppermost sheet P1 moves away from the second sheet. Thereafter, the pickup roller 23 is rotated forward, and the uppermost paper P1 is conveyed into the main body by the paper feed roller 16, and is reliably separated from the second paper to prevent double feeding. Thereafter, when the printing signal ends, the arm 24 moves up with the rotation of the shaft 27, whereby the uppermost paper P1 and the pickup roller 23 are separated from each other, and the next print job is prepared. These controls are performed by a control unit including the CPU 3.

  FIG. 3 shows a flowchart of the paper feed process in the first embodiment. In the following, detailed processing modes will be described in the order of flowcharts.

  First, at ST11, the presence or absence of a print signal is detected. When a print signal is detected (YES at ST11), the shaft 27 is rotated by the arm drive unit 21 and the arm 24 is moved downward at ST12. Then, when the pickup roller 23 rotatably supported by the arm 24 in ST13 comes into contact with the uppermost paper P1 in the paper feed cassette 2, the pickup roller driving unit 20 sets the pickup roller 23 in a predetermined number (step 14). Approx. 1/2 rotation) Reverse rotation. Then, since the rear end of the uppermost paper P1 is positioned by the paper rear end guide 28, it bends upward and separates from the second sheet (see FIG. 2B). Thereafter, the rotation of the pickup roller 23 is stopped in ST15.

  Next, in ST16, the pickup roller 23 is rotated forward by the pickup roller driving unit 20 so that the bent uppermost sheet P1 is conveyed to the transfer unit 9. By the forward rotation of the pickup roller 23, the leading edge of the uppermost paper P1 is sent to the nip portion between the paper feeding roller 16 and the separation roller 25, and the paper feeding roller 16 rotates to convey the uppermost paper P1 into the main body. When a plurality of sheets are fed in one print job, the process of ST16 is repeated for the second and subsequent sheets until the print signal ends (NO in ST17).

  Upon completion of the print signal (YES in ST17), the rotational driving of the pickup roller 23 and the paper feed roller 16 is stopped in ST18. Thereafter, in ST19, the shaft 24 is rotated by the arm driving unit 21 to raise the arm 24, the pickup roller 23 is separated from the paper P1, and the paper feeding process is finished.

  As described above, in the first embodiment, the first sheet when one print job is started can be bent to be peeled off from the second sheet. Sending can be reliably prevented. In the present embodiment, the reverse rotation operation of the pickup roller is performed only on the first sheet of one print job, but it goes without saying that the processing from ST14 to ST17 may be repeated each time printing is performed. .

  Further, the pickup roller 23 is reversely rotated at a predetermined rotation speed (one rotation) set in advance, but is reversely rotated for a time (for example, 1.5 seconds) that is set in advance by the setting in the clock unit 13. By doing so, it is possible to prevent double feeding as described above.

(Second embodiment)
Next, a second embodiment will be described. A detailed description of common parts with the first embodiment is omitted. The difference between the second embodiment and the first embodiment is that a dedicated pickup roller driving unit for driving the pickup roller 23 is not provided, and the rotational drive of the up pickup roller 23 is forward rotation. It is a structure (one way clutch) which is only a direction and does not rotate reversely. That is, the drive source of the paper feed roller 16 and the drive source of the pickup roller 23 are performed by the same paper conveyance drive unit 17.

In such a configuration, after the printing signal is output from the image forming apparatus 1, the arm 24 is lowered by the rotation of the shaft 27 connected to the arm driving unit 21. Then, the pickup roller 23 for feeding the sheet bundle P placed in the sheet feeding cassette 2 to the inside one by one contacts the uppermost sheet P1. Then, the arm 24 connected to the pickup roller 23 is moved in the upstream direction opposite to the sheet conveying direction by the arm driving unit 21. Then, since the pickup roller 23 also moves in the upstream direction, the uppermost paper P1 that has come into contact with the pickup roller 23 bends in the upstream direction and separates from the second sheet. Thereafter, the pickup roller 23 and the paper feed roller 16 are rotated forward by the paper conveyance drive unit 17, whereby the uppermost paper P <b> 1 is conveyed into the main body. Therefore, it is possible to prevent double feed by reliably separating it from the second sheet. Thereafter, the arm 24 is moved by the rotation of the shaft 27 from the arm driving unit 21 upon completion of the print signal, so that the uppermost paper P1 and the pickup roller 23 are separated from each other and prepare for the next print job.

  Next, a second embodiment will be described using the flowchart of FIG.

  First, in ST21, the presence / absence of a print signal is detected. When a print signal is detected (YES in ST21), the arm 24 is moved downward by the arm drive unit 21 in ST22. In ST23, the pickup roller 23 rotatably supported by the arm 24 comes into contact with the uppermost paper P1. Next, in ST24, the shaft 27 connected to the arm drive unit 21 is rotated so as to move the pickup roller 23 in the upstream direction. At this time, since the pickup roller 23 is configured to rotate (forward rotation) in the paper conveyance direction but not in the reverse direction, when the arm 24 moves in the upstream direction by a predetermined distance (approximately 3 cm), The pickup roller 23 and the uppermost paper P1 are pressed by the paper rear end guide 28 of the paper feed cassette 2 and bent upward. After the arm 24 is driven, the arm 24 stops at the moving position in ST25.

  Next, in ST26, the pickup roller 23 and the paper feed roller 16 are rotated by driving the paper transport driving unit 17 so as to transport the bent uppermost paper P1 to the inside. The uppermost paper P1 is conveyed into the main body by the rotation of the pickup roller 23 and the rotation of the paper feed roller 16, and the process of ST26 is repeated until the print signal is finished (NO in ST27).

  Upon completion of the print signal (YES in ST27), the rotational driving of the pickup roller 23 and the paper feed roller 15 is stopped in ST28. Thereafter, the arm 24 is raised by the rotation of the shaft 27 connected to the arm drive unit 21 in ST29, and the pickup roller 23 is separated from the uppermost sheet, and the process is finished.

  As described above, in the second embodiment, the pickup roller 23 can rotate only in the forward rotation direction (paper feeding direction), and therefore a special drive source such as reverse rotation control of the pickup roller 23 is provided. Instead, double feeding can be prevented by bending the uppermost paper by driving the arm 24.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper feed cassette 3 CPU (control part)
6 Paper Feed Unit 13 Clock Unit 16 Paper Feed Roller 17 Paper Transport Drive Unit 20 Pickup Roller Drive Unit 21 Arm Drive Unit 23 Pickup Roller 24 Arm

Claims (9)

A paper feed unit on which a plurality of sheets can be placed;
A pickup roller capable of rotating forward and reverse to feed the paper from the paper feeding unit;
A pickup roller driving unit for driving the pickup roller to rotate forward or backward, and
An arm for supporting the pickup roller;
An arm drive unit for driving the arm;
The arm driving unit is controlled to bring the pickup roller into contact with the paper placed on the paper feeding unit by the arm, and the pickup roller driving unit is controlled to rotate the pickup roller in the direction opposite to the paper feeding direction. Bending the paper being fed, then rotating the pickup roller in the paper feed direction to feed the paper out of the paper feed unit, and controlling the arm drive unit after the paper feed is completed so that the arm separates the pickup roller from the paper An image forming apparatus.   The image forming apparatus according to claim 1, wherein the control unit controls the pickup roller driving unit to rotate the pickup roller in the reverse direction for a predetermined time. A paper feed unit on which a plurality of sheets can be placed;
A pickup roller rotatable in a paper feeding direction for feeding the paper from the paper feeding unit;
A paper transport drive unit that rotationally drives the pickup roller in the paper feed direction to transport the paper;
An arm for supporting the pickup roller;
An arm drive unit for driving the arm;
By controlling the arm driving unit, the arm causes the pickup roller to contact the sheet of the sheet feeding unit, and the arm causes the pickup roller to move in the direction opposite to the sheet feeding direction to bend the sheet. The paper conveyance driving unit is controlled to rotate the pickup roller in the paper feeding direction to feed the paper out of the paper feeding unit. After the paper feeding is completed, the arm driving unit is controlled to separate the pickup roller from the paper by the arm. An image forming apparatus comprising: a control unit.   The control unit feeds the pickup roller in one print job after the first sheet is fed by the pickup roller without bending the sheet in the reverse direction with the pickup roller in contact with the sheet. The image forming apparatus according to claim 1, wherein the image forming apparatus feeds the sheet by sequentially rotating the sheet in the direction and sequentially feeding the sheet from the sheet feeding unit.   A pair of transport rollers for transporting paper from the paper feed unit; the control unit controls the paper transport drive unit to drive a pickup roller to feed the paper to the pair of transport rollers; 4. The image forming apparatus according to claim 3, wherein the pair of conveying rollers are driven to convey the sheet.   The control unit controls the arm driving unit in one print job, and after the sheet first touched by the pickup roller is sent out from the sheet feeding unit, the pickup roller is separated from the sheet via the arm. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. Bring the pickup roller into contact with the paper in the paper feed section,
Rotate the pickup roller in the direction opposite to the paper feeding direction to bend the paper,
Next, rotate the pickup roller in the paper feed direction to feed the paper out of the paper feed unit,
A paper feeding method, wherein the pickup roller is separated from the paper after the paper feeding is completed. Bring the pickup roller into contact with the paper in the paper feed section,
With the pickup roller in contact with the paper, move the paper in the direction opposite to the paper feed direction to deflect the paper.
Next, rotate the pickup roller in the paper feed direction to feed the paper out of the paper feed unit,
A paper feeding method, wherein the pickup roller is separated from the paper after the paper feeding is completed. In one print job, after the first paper is sent out by the pickup roller, the pickup roller is rotated in the paper feeding direction without bending the paper in the reverse direction with the pickup roller in contact with the paper. 9. The paper feeding method according to claim 7, wherein the paper is sequentially sent out from the paper feeding unit.

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