JP6016021B2 - Paper feeding device and image forming apparatus - Google Patents

Description

  The present invention relates to a paper feeding device that feeds paper such as transfer paper, and an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine or a printing machine including the same.

  Conventionally, in an image forming apparatus such as a copying machine, a printer, or a printing machine, a paper feeding mechanism including a feed roller, a pickup roller, and a reverse roller is installed in a paper feeding device that feeds paper such as transfer paper. Techniques are known (see, for example, Patent Documents 1 and 2).

Specifically, a feed roller (paper feed roller), a pickup roller, and a reverse roller (separation roller, separation roller) are installed in the paper feed mechanism of the paper feeder in Patent Documents 1 and 2 and the like.
Then, the uppermost paper placed on the placement portion is fed in the feeding direction by a pickup roller that rotates while contacting the surface of the paper placed on the placement portion (paper feeding portion, paper tray). It is conveyed toward the nip portion between the feed roller and the reverse roller installed on the front end side. The paper that has reached the position of the nip portion is in a state in which the paper is sandwiched between the feed roller that rotates along the paper feeding direction and the paper in the nip portion even when the two papers overlap each other. And a reverse roller that rotates in a direction opposite to the feeding direction of the paper, and only one sheet is separated from the nip portion along the rotation of the feed roller and fed in the feeding direction. Become.

In a conventional paper feeder, when a user sets a bundle of sheets on the loading section, the sheet bundle is pushed in and set so that a plurality of sheets enter the nip portion between the feed roller and the reverse roller. was there. In particular, such a defect is provided with a presser mechanism (for example, a presser filler and an inclined part at the upper end of the paper tray front end fence) that restricts an excessive bundle of papers from entering the nip part. Reference 2 and the like can be referred to).
If the sheet feeding mechanism operates in a state where a plurality of sheets are inserted into the nip portion in this way, there is a problem that a plurality of sheets are continuously fed from the nip portion (multiple feeding). There was a case.

  Further, such a problem is not limited to when a user sets a sheet on the loading unit, but in a sheet feeding device that automatically raises and lowers the sheet loading surface according to the number of sheets in the loading unit. It also occurred during the elevation of the surface. That is, the posture of the sheet with respect to the nip portion changes when the loading surface is raised and lowered, and a plurality of sheets may enter the nip portion.

  The present invention has been made to solve the above-described problems. When a sheet is set on the loading portion, a plurality of sheets are inserted into the nip portion between the feed roller and the reverse roller. Another object of the present invention is to provide a sheet feeding device and an image forming apparatus that are less likely to cause a problem that a plurality of sheets are fed continuously from the nip portion.

The paper feeding device according to the first aspect of the present invention is a paper feeding device that feeds paper, and is installed on the front side in the feeding direction with respect to the paper placed on the placement portion, A feed roller that rotates along the paper feeding direction and conveys the paper, and rotates in contact with the surface of the paper placed on the mounting portion and moves the paper to the position of the feed roller. A nip portion is formed between the feed roller and a pickup roller that is transported and movable to a retraction position that does not contact the paper placed on the placement portion, and the feed roller The sheet is rotated in the direction opposite to the sheet feeding direction while the sheet is nipped in the nip part so that one sheet is fed in the feeding direction from the nip part. And reverse roller Even after the sheet is placed on the mounting section, before the rotation of the feed roller is started, the reverse roller is intended to rotate for a predetermined time so as to extend along the said opposite direction.

  In the present invention, since the reverse roller is rotated before the rotation of the feed roller is started, a plurality of sheets are placed in the nip portion between the feed roller and the reverse roller when the sheet is set on the loading portion. It is possible to provide a paper feeding device and an image forming apparatus that are less likely to cause a problem that a plurality of sheets are continuously fed from the nip portion even if they enter.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. It is the schematic which shows a paper feeder. FIG. 6 is a diagram illustrating an operation of a paper feeding device.

Embodiment.
Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes an apparatus main body (image forming apparatus main body) of a copying machine as an image forming apparatus, 2 an original reading unit that optically reads image information of an original D, and 3 an image information read by the original reading unit 2. An exposure unit that irradiates the photosensitive drum 5 with the exposure light L based on the above, 4 is an image forming unit that forms a toner image (image) on the photosensitive drum 5, and 7 is a toner formed on the photosensitive drum 5. A transfer unit (image forming unit) that transfers an image onto a sheet P (sheet), 10 is a document transport unit (automatic document transport device) that transports a set document D to the document reading unit 2, and 12 to 15 are transfer paper and the like 16 is a paper feed device (manual paper feed unit) that feeds paper P manually set by the user, and 17 is a paper P toward the transfer unit 7. Registration rollers (timing rollers) that convey the paper, 20 is paper A fixing device that fixes a toner image (unfixed image) carried thereon, 21 is a fixing roller installed in the fixing device 20, 22 is a pressure roller installed in the fixing device 20, and 31 is discharged from the apparatus main body 1. A paper discharge tray on which paper P is stacked, 42 to 45 is a mounting plate (mounting surface) configured to be raised and lowered in each of the paper feeding cassettes 12 to 15, and 52 is a paper feeding device 12 to 16. An installed paper feed mechanism is shown.

With reference to FIG. 1, an operation during normal image formation in the image forming apparatus main body 1 will be described.
First, the document D is transported (feeded) from the document table in the direction of the arrow in the drawing by the transport rollers of the document transport unit 10 and passes over the document reading unit 2. At this time, the document reading unit 2 optically reads the image information of the document D passing above.
Then, the optical image information read by the document reading unit 2 is converted into an electric signal and then transmitted to the exposure unit 3 (writing unit). Then, exposure light L such as laser light based on the image information of the electrical signal is emitted from the exposure unit 3 toward the photosensitive drum 5 of the image forming unit 4.

On the other hand, in the image forming unit 4, the photosensitive drum 5 is rotated in the clockwise direction in the drawing, and image information is transferred onto the photosensitive drum 5 through a predetermined image forming process (charging process, exposure process, development process). An image (toner image) corresponding to is formed.
Thereafter, the image formed on the photosensitive drum 5 is transferred onto the paper P conveyed by the registration roller 17 in the transfer unit 7 as an image forming unit.

On the other hand, the sheet P conveyed to the transfer unit 7 (image forming unit) operates as follows.
First, one of the plurality of sheet cassettes 12 to 15 of the image forming apparatus main body 1 is automatically or manually selected (for example, it is assumed that the uppermost sheet cassette 12 is selected). ). Then, the uppermost sheet P of paper P stored in the paper feed cassette 12 is fed by the paper feed mechanism 52 and conveyed toward the conveyance path K. Thereafter, the paper P passes through a conveyance path K in which a plurality of conveyance rollers are arranged, and reaches the position of the registration roller 17.
When the paper feeder 16 (manual paper feeder) installed on the side of the apparatus main body 1 is selected, the user can place it on the placement unit 51 (see FIG. 2) of the paper feeder 16. The loaded paper P (the uppermost paper P when a plurality of papers P are stacked) is fed toward the conveyance path by the paper feeding mechanism 52 (feeding means), and the registration roller The position 17 will be reached.

The sheet P that has reached the position of the registration roller 17 is conveyed toward the transfer unit 7 (image forming unit) at the same timing in order to align with the image formed on the photosensitive drum 5.
Then, after the transfer process, the sheet P passes through the position of the transfer unit 7 and then reaches the fixing device 20 through the conveyance path. The sheet P that has reached the fixing device 20 is fed between the fixing roller 21 and the pressure roller 22, and the toner image is fixed by the heat received from the fixing roller 21 and the pressure received from both members 21 and 22. (This is a fixing process). The paper P after the fixing process on which the toner image has been fixed is delivered from between the fixing roller 21 and the pressure roller 22 (a fixing nip), and then is discharged from the image forming apparatus main body 1 to be an output image. As shown in FIG.
Thus, a series of image forming processes is completed.

Next, with reference to FIGS. 2 and 3, the sheet feeding device 16 that is characteristic in the present embodiment will be described in detail.
Referring to FIGS. 2 and 3, the paper feeding device 16 is provided with a placement portion 51 (base portion) on which the paper P is placed, and for feeding the paper P placed on the placement portion 51. The paper feed mechanism 52, the paper detection sensor 60 for detecting the leading edge of the paper P fed by the paper feeding mechanism 52 (the leading edge in the feeding direction), and the state where the paper P is placed on the placement portion 51. A set detection sensor (not shown) for detection is installed.
The paper feed mechanism 52 includes a feed roller 53, a pickup roller 54, a backup roller 54, a drive motor 71, an electromagnetic clutch 72, a moving mechanism 73, and the like.

  The feed roller 53 is installed on the leading end side in the feeding direction with respect to the paper P placed on the placement unit 51, and rotates so as to contact the upper surface of the paper P and follow the feeding direction of the paper P ( This is the clockwise rotation in FIG. 2). The shaft portion of the feed roller 53 is connected to the drive motor 71 via an electromagnetic clutch 72 (switching means for switching between a drive state and a drive stop state of the feed roller 53). The feed roller 53 is rotationally driven in a state where both the drive roller 71 and the electromagnetic clutch 72 are turned on.

The pickup roller 54 rotates in contact with the surface (upper surface) of the paper P placed on the placement unit 51 and conveys the paper P to the position of the feed roller 53. The pickup roller 54 has a timing belt 58 wound between the shaft portion and the shaft portion of the feed roller 53, and is configured to rotate together with the feed roller 53 in the direction of the arrow in FIG.
Further, the pickup roller 54 is formed to be movable to a retracted position where it does not contact the paper P placed on the placement portion 51. Specifically, the pickup roller 54 is moved (rotated) by the moving mechanism 73 so as to be able to contact with and separate from the paper P in the double arrow direction (vertical direction) in FIG. 2 with the shaft portion of the feed roller 53 as the rotation center. It is configured to be able to. In the present embodiment, the moving mechanism 73 is mounted so as to resist the urging force of the spring (the urging member) that urges the pickup roller 54 to move to the retracted position. The cam member is configured to push toward the paper P placed on the portion 51.

The reverse roller 55 is installed so as to form a nip portion with the feed roller 53. The reverse roller 55 feeds the paper P in a state where the paper P is nipped at the nip portion so that one paper P is fed in the feeding direction from the nip portion along the rotation of the feed roller 53. Rotate along the opposite direction to the direction (clockwise rotation in FIG. 2).
Specifically, the shaft portion of the reverse roller 55 is connected to the drive motor 71 via a gear train (not shown). Further, a torque limiter (not shown) is installed at the shaft portion of the reverse roller 55, and the reverse roller 55 is configured to idle when a rotational load exceeding a predetermined value is applied to the reverse roller 55. . With such a configuration, the sheet P is fed in the feeding direction (conveying direction) without being fed from the nip portion between the feed roller 53 and the reverse roller 55.

  In this embodiment, each of the feed roller 53, the pickup roller 54, and the reverse roller 55 has a roller portion (roller portion) formed of a rubber material (or resin material) on the shaft portion in the axial direction. It is formed by dividing into a plurality of parts. Further, the feed roller 53, the pickup roller 54, and the reverse roller 55 are formed so that the roller portion can be attached to and detached from the shaft portion (replaceable), and the maintenance of the roller portion can be facilitated. Yes.

Here, in the paper feeding device 16 (paper feeding mechanism 52) in the present embodiment, the reverse roller 55 is in the reverse direction (the reverse direction to the paper feeding direction) before the rotation of the feed roller 53 is started. It is controlled so as to rotate for a predetermined time along.
By performing such control, when the user sets a bundle of a plurality of sheets P on the loading unit 51, the plurality of sheets P enters the nip portion between the feed roller 53 and the reverse roller 55. Even if the paper is set, the paper P that has entered the nip portion by rotating the reverse roller 55 clockwise in FIG. 2 with the feed roller 53 (and the pickup roller 55) stopped rotating before the paper feeding operation. Since the sheet is conveyed from the nip portion to the placement portion 351 side, it is possible to reduce a problem that a plurality of sheets P are continuously fed from the nip portion.

Specifically, after the paper P is placed on the placement portion 51 and before the rotation of the feed roller 53 is started, the reverse roller 55 rotates for a predetermined time so as to follow the reverse direction. In addition, when the reverse roller 55 rotates in the reverse direction for a predetermined time as described above, the pickup roller 54 is moved to the retracted position (the upper position that does not contact the paper P). Then, after the reverse roller 55 rotates for a predetermined time so as to follow the reverse direction, the pickup roller 54 is a contact position (a position where the pickup roller 54 contacts the surface of the paper P placed on the placement unit 51 from the retracted position). ) And the paper P is conveyed to the position of the feed roller 53 by the rotation.
In particular, in the present embodiment, after the reverse roller 55 rotates for a predetermined time so as to follow the reverse direction, the reverse roller 55 continuously rotates so as to follow the reverse direction without stopping the rotation, The rotation (feed operation) of the feed roller 53 is started. In other words, the rotation of the reverse roller 55 is started a predetermined time before the rotation of the feed roller 53 (and the pickup roller 54) is started. Further, the rotation of the reverse roller 55 is continuously performed without stopping the rotation before and after the rotation of the feed roller 53 (and the pickup roller 54).

Hereinafter, the operation of the sheet feeding device 16 controlled as described above will be described with reference to FIG.
First, as illustrated in FIG. 3A, when a bundle of a plurality of sheets P is set on the placement unit 51 of the sheet feeding device 16 in a state where the pickup roller 54 has moved to the retracted position, the placement unit 51. The state is detected by a set detection sensor (not shown) installed in the. At this time, it is assumed that a plurality of sheets P have been set by the user so as to enter the nip portion between the feed roller 53 and the reverse roller 55.

  Thereafter, as shown in FIG. 3B, when the state where the paper P is placed on the placement portion 51 is detected by the set detection sensor, the reverse roller 55 starts to rotate in the clockwise direction in the drawing. At this time, the feed roller 53 and the pickup roller 54 (in a state where the feed roller 53 and the pickup roller 54 are moved to the retracted position) are in a state where the rotation is stopped. Specifically, the drive motor 71 is operated in a state where the electromagnetic clutch 72 is turned off by the control unit 70 (a state where transmission of the drive force by the drive motor 71 to the feed roller 53 is blocked). Thus, the rotation of the reverse roller 55 is started. As a result, the paper P that has entered the nip portion between the feed roller 53 and the reverse roller 55 is sent out from the nip portion in the direction of the white arrow in FIG. 3B (conveyed to the placement portion 51 side). )

  Thereafter, after the rotation of only the reverse roller 55 is performed for a predetermined time, the pickup roller 54 moves to the contact position as shown in FIG. 3C, and in addition to the rotation of the reverse roller 55, the feed roller 53 and The rotation with the pickup roller 54 is started. Specifically, the drive motor 71 is operated and the reverse roller 55 in a state where the electromagnetic clutch 72 is turned on by the control unit 70 (a state in which the driving force by the drive motor 71 is transmitted to the feed roller 53). In addition to this rotation, the rotation of the feed roller 53 and the pickup roller 54 is started. As a result, the uppermost sheet P of the sheet bundle placed on the placing portion 51 by the pickup roller 54 is conveyed toward the nip portion between the feed roller 53 and the reverse roller 55 and further from the nip portion. One sheet P is separated and conveyed toward the image forming unit. At this time, the leading edge of the paper P sent out from the nip portion is detected by the paper detection sensor 60, and the subsequent image forming process is controlled based on the detection timing.

Here, in the present embodiment, the time (predetermined time) during which only the reverse roller 55 rotates after the paper P is set on the placement unit 51 is configured to be arbitrarily variable.
Specifically, referring to FIG. 2, only the reverse roller 55 is set after the paper P is set on the placement portion 51 by the user operating the operation panel 77 (operation means) installed on the exterior portion of the apparatus main body 1. The time required for rotation (predetermined time) can be varied arbitrarily. That is, by operating the operation panel 77, the timing at which the electromagnetic clutch 72 is switched from the off state to the on state after the paper P is set on the placement unit 51 can be adjusted.
As a result, when the type of paper P used by the user is easy to cause double feeding (for example, thin paper), the time during which only the reverse roller 55 rotates (predetermined time) is adjusted to be longer, When the double feed is difficult to occur (for example, thick paper), the time for which only the reverse roller 55 rotates (predetermined time) is adjusted to be short, and the above-described effects of the present invention can be efficiently exhibited. Can be done. In addition, when the paper P is set, the time (predetermined time) during which only the reverse roller 55 rotates is adjusted to be longer in response to a user who has a particularly strong tendency to set the paper P in the nip portion. it can.

Further, in the present embodiment, referring to FIG. 2, only reverse roller 55 rotates after paper P is set on placement unit 51 according to the type of paper P placed on placement unit 51. The time (predetermined time) is configured to be variable.
Specifically, referring to FIG. 2, a paper thickness sensor 78 (which detects the thickness of the paper P optically and can use a known one) installed in the placement unit 51. Based on the detection result, the control unit 70 automatically adjusts the time (predetermined time) during which only the reverse roller 55 rotates after the paper P is set on the placement unit 51. Specifically, when the paper P set on the loading unit 51 is a thin paper that is likely to be double-fed, the time (predetermined time) during which only the reverse roller 55 rotates is adjusted to be longer, and double-fed occurs. When it is difficult to use thick paper, the time for rotating only the reverse roller 55 (predetermined time) is adjusted to be short. Thereby, the effect of the present invention described above is efficiently exhibited.

In the sheet feeding device 16 according to the present embodiment, a one-way clutch may be installed as a restricting unit that restricts the feed roller 53 from rotating along the direction opposite to the sheet P feeding direction. Specifically, a one-way clutch (regulating means) is installed on the shaft portion of the feed roller 53 where the electromagnetic clutch 72 is installed.
As a result, the feed roller 53 rotates only in the clockwise direction in FIG. 2 without rotating in the counterclockwise direction in FIG. Therefore, even when a load that causes the feed roller 53 to rotate in the reverse direction is generated, only one sheet P is separated from the nip portion and conveyed by the rotation of the feed roller 53 and the reverse roller 55. The conveyance function can be exhibited reliably, and the conveyance load at that time can be reduced.

  As described above, in the present embodiment, since the reverse roller 55 is rotated before the rotation of the feed roller 53 is started, the feed roller 53 is set when the paper P is set on the placement unit 51. Even if a plurality of sheets P enters the nip portion between the nip portion and the reverse roller 55, it is possible to make it difficult to cause a problem that the plurality of sheets P are continuously fed from the nip portion.

In the present embodiment, the present invention is applied to the paper feeding device 16 installed in the monochrome image forming apparatus 1. However, the present invention is naturally applied to the paper feeding device installed in the color image forming apparatus. The present invention can be applied.
Further, in the present embodiment, the present invention is applied to the paper feeding device 16 installed in the electrophotographic image forming apparatus 1, but the application of the present invention is not limited to this, and other methods are applied. The present invention can also be applied to a paper feeding device installed in an image forming apparatus (for example, an inkjet image forming apparatus or a stencil printing machine).
Even in those cases, the same effects as in the present embodiment can be obtained.

  In the present exemplary embodiment, the present invention is applied to the manual sheet feeding unit 16 serving as a sheet feeding device in the image forming apparatus 1, but naturally also to the sheet feeding cassettes 12 to 15 serving as sheet feeding devices. The present invention can be applied, and naturally, the present invention can also be applied to the document conveying section 10 (automatic document conveying device) as a paper feeding device. In particular, the paper feed cassettes 12 to 15 in the present embodiment automatically raise and lower the placement plates 42 to 45 (mounting surface) according to the number of sheets P (remaining number) in the loading section. Since the posture of the paper P with respect to the nip portion changes when the placement plates 42 to 45 (mounting surfaces) are moved up and down, there may be a problem that a plurality of paper P enters the nip portion. It is useful to apply the present invention to the paper cassettes 12 to 15 (paper feeders). That is, in the paper feed mechanism 52 of the paper feed cassettes 12 to 15, after the mounting plates 42 to 45 (mounting surfaces) are raised and lowered, before the rotation of the feed roller 53 is started, Similarly to the embodiment, by rotating the reverse roller 55 for a predetermined time, it is possible to reliably reduce double feeding from the nip portion.

In the present embodiment, the reverse roller 55 is continuously rotated without stopping the rotation before and after the feed roller 53 (and the pickup roller 54) starts rotating. On the other hand, after rotating the reverse roller 55 for a predetermined time after setting the paper P, the rotation of the reverse roller 55 is temporarily stopped until the rotation of the feed roller 53 and the pickup roller 55 is started, and then the feed roller The rotation of the reverse roller 55 may be restarted with the start of rotation of the pickup roller 55 and the pickup roller 55.
Even in this case, the same effect as that of the present embodiment can be obtained.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

  In the present application, “paper” includes all sheet-like recording media such as OHP in addition to transfer paper, and also includes documents fed by an automatic document feeder as a paper feeder. It is defined as

1 image forming apparatus body (apparatus body),
16 paper feeder,
51 placement section,
52 paper feed mechanism,
53 Feed roller,
54 Pickup roller,
55 Reverse roller,
60 Paper detection sensor,
P paper.

JP 2011-236054 A JP 7-315608 A

Claims (9)

A paper feeding device for feeding paper,
A feed roller that is installed on the leading end side in the feeding direction with respect to the paper placed on the placement unit and rotates along the paper feeding direction to convey the paper;
It rotates while contacting the surface of the paper placed on the placement section and conveys the paper to the position of the feed roller, and does not contact the paper placed on the placement section. A pick-up roller formed to be movable to a retracted position;
A nip portion is formed between the nip portion and the feed roller, and a sheet is sandwiched in the nip portion so that one sheet is fed in the feeding direction from the nip portion along the rotation of the feed roller. A reverse roller that rotates in the opposite direction to the paper feeding direction in the state;
With
The reverse roller is rotated for a predetermined time so as to follow the reverse direction after the paper is placed on the placement unit and before the rotation of the feed roller is started. Paper device. After the reverse roller rotates for the predetermined time so as to follow the reverse direction, the pick-up roller moves from the retracted position to a position where it contacts the surface of the paper placed on the placement unit, and the paper is moved. The sheet feeding device according to claim 1, wherein the sheet feeding device is transported to a position of the feed roller. A paper feeding device for feeding paper,
A feed roller that is installed on the leading end side in the feeding direction with respect to the paper placed on the placement unit and rotates along the paper feeding direction to convey the paper;
It rotates while contacting the surface of the paper placed on the placement section and conveys the paper to the position of the feed roller, and does not contact the paper placed on the placement section. A pick-up roller formed to be movable to a retracted position;
A nip portion is formed between the nip portion and the feed roller, and a sheet is sandwiched in the nip portion so that one sheet is fed in the feeding direction from the nip portion along the rotation of the feed roller. A reverse roller that rotates in the opposite direction to the paper feeding direction in the state;
With
Before the feed roller starts rotating, the reverse roller rotates for a predetermined time so as to follow the reverse direction,
After the reverse roller rotates for the predetermined time so as to follow the reverse direction, the pick-up roller moves from the retracted position to a position where it contacts the surface of the paper placed on the placement unit, and the paper is moved. A sheet feeding device that conveys to a position of the feed roller. 4. The pickup roller moves to the retracted position when the reverse roller rotates for the predetermined time so as to follow the reverse direction. 5. Paper feeder.   After the reverse roller rotates for the predetermined time so as to follow the reverse direction, the reverse roller continuously rotates along the reverse direction without stopping the rotation, and the feed roller rotates. The sheet feeding device according to claim 1, wherein the feeding is started.   6. The sheet feeding device according to claim 1, wherein the predetermined time can be arbitrarily changed.   The paper feeding device according to any one of claims 1 to 6, wherein the predetermined time is varied in accordance with a type of paper placed on the placement unit.   The sheet feeding device according to claim 1, further comprising a regulating unit that regulates the feed roller so as not to rotate along a direction opposite to a sheet feeding direction.   An image forming apparatus comprising the paper feeding device according to claim 1.

Images