JP2014214013A - Recording medium feeder, and image forming apparatus including the same - Google Patents

Abstract

There is provided a recording medium feeding device capable of suppressing bending of a recording medium, suppressing wear of a pickup roller, and suppressing vibration and impact. The recording medium feeding device is in pressure contact with a pickup roller 29 for feeding a sheet 26 from a sheet feeding cassette 10, a feed roller 30a for conveying the sheet 26 fed from the pickup roller 29, and the feed roller 30a. A conveyance roller pair 30 including a retard roller 30b. The peripheral speed of the pickup roller 29 is smaller than the peripheral speed of the feed roller 30a and is larger than the peripheral speed of the retard roller 30b. [Selection] Figure 2

Description

  The present invention relates to a recording medium feeding apparatus and an image forming apparatus including the recording medium feeding apparatus, and in particular, a pickup roller that feeds a recording medium from a recording medium stacking unit, a feed roller that conveys the recording medium fed from the pickup roller, and a feed BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium feeding device including a retard roller that is in pressure contact with a roller and an image forming apparatus including the recording medium feeding device.

  Conventionally, a pickup roller that feeds paper from a paper feed cassette (recording medium stacking unit) that stores sheet-like paper (recording medium), a feed roller that transports the paper fed from the pickup roller, and a retarder that presses against the feed roller An image forming apparatus including a roller is known.

  The feed roller and the retard roller are configured to convey the sheet fed from the pickup roller one by one. Specifically, the feed roller is configured to rotate by a driving force from a driving motor. The retard roller is configured to be driven to rotate while being pressed against the feed roller, and has a built-in torque limiter. Accordingly, when a plurality of sheets are simultaneously fed by the pickup roller, the retard roller stops rotating, the sheet is rolled by the feed roller and the retard roller, and only the topmost sheet is conveyed.

  Further, a driving force transmission gear for transmitting the driving force from the driving motor to the pickup roller and the feed roller is provided. The pickup roller is provided with a pickup roller gear with which a driving force transmission gear is engaged, and the feed roller is provided with a feed roller gear with which the driving force transmission gear is engaged. Usually, the number of teeth of the pickup roller gear is formed to be the same as the number of teeth of the feed roller gear, and the diameter of the pickup roller is formed to be the same as the diameter of the feed roller. That is, the peripheral speed of the pickup roller is set to the same magnitude as the peripheral speed of the feed roller.

  On the other hand, since the retard roller has a built-in torque limiter and a rotational load is generated, the peripheral speed of the retard roller is reduced by about 10% to 15% with respect to the peripheral speed of the feed roller. Normally, the paper that has passed through the nip portion between the feed roller and the retard roller is conveyed at the peripheral speed of the retard roller. For this reason, the paper conveyance speed by the pickup roller is usually higher than the paper conveyance speed by the nip portion. Therefore, the paper is bent in the region between the pickup roller and the feed roller, or the paper is bent due to the paper bending. A jam may occur.

  In view of this, a method has been proposed in which the sheet is prevented from being bent in the region between the pickup roller and the feed roller (see, for example, Patent Document 1). In Patent Document 1, the peripheral speed of the pickup roller is made smaller than the peripheral speed of the separation roller and separation roller (feed roller and retard roller), and the paper is always transported while being pulled backward (upstream in the paper transport direction). A paper feeding device (recording medium feeding device) is disclosed.

JP-A-5-147754

  However, in the structure of Patent Document 1, the peripheral speed of the pickup roller is smaller than the peripheral speed of the separation roller and the separation roller (feed roller and retard roller), and the pickup roller is used when the paper (recording medium) is conveyed by the separation roller and separation roller. Is pulling the paper backward. For this reason, the pickup roller slides on the paper when the paper is conveyed by the separation roller and the separation roller. As a result, there is a problem that the pick-up roller is worn and the life is shortened.

  Further, since the paper is pulled downstream by the feed roller and pulled upstream by the pickup roller, the paper is tensioned. Then, when the trailing edge of the paper passes through (removes from) the pickup roller, the tension applied to the paper is released, thereby causing vibration and impact. For this reason, there is a problem that due to the vibration and impact, a streak occurs in the image and the image quality is deteriorated.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to suppress the bending of the recording medium, suppress wear of the pickup roller, and suppress vibration and impact. It is an object to provide a recording medium feeding apparatus capable of performing the above and an image forming apparatus including the recording medium feeding apparatus.

  In order to achieve the above object, a recording medium feeding device of the present invention includes a pickup roller that feeds a recording medium by rotating while being pressed against the uppermost surface of a bundle of recording media stacked on a recording medium stacking unit, A feed roller that feeds and conveys the recording medium fed from the pickup roller, and a transport roller pair that is driven to rotate while being pressed against the feed roller, and the retard roller is provided on the surface of the feed roller. In contrast, the peripheral speed of the pickup roller is smaller than the peripheral speed of the feed roller in a state where only one sheet of the recording medium is nipped in the nip portion of the transport roller pair. It is larger than the peripheral speed of the retard roller.

  According to the present invention, the peripheral speed of the pickup roller is smaller than the peripheral speed of the feed roller. As a result, the recording medium bends in the region between the pickup roller and the feed roller compared to the case where the peripheral speed of the pickup roller is the same as the peripheral speed of the feed roller. Occasional jams can be suppressed.

  In the state where only one recording medium is nipped in the nip portion of the transport roller pair, the peripheral speed of the pickup roller is greater than or equal to the peripheral speed of the retard roller. As a result, the feed roller and the retard roller can pull the recording medium forward (downstream in the recording medium conveyance direction) and can prevent the pickup roller from sliding relative to the recording medium. For this reason, it can suppress that a pick-up roller wears and a lifetime becomes short.

  Further, since it is possible to suppress the recording medium from being pulled backward by the pickup roller, the tension of the recording medium is released when the rear end of the recording medium passes through (removes from) the pickup medium, and vibration or impact occurs. Can be suppressed. As a result, it is possible to prevent the image quality from being deteriorated due to the occurrence of streaks in the image due to the vibration or impact.

1 is a cross-sectional view illustrating the overall structure of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a structure of a recording medium feeding device of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a structure around one end of a pickup roller of a recording medium feeding device of an image forming apparatus according to an embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  An image forming apparatus 100 according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the image forming apparatus 100 is a tandem type color copying machine, and in the main body of the image forming apparatus 100, four image forming portions Pa, Pb, Pc, and Pd are arranged in order from the left side in FIG. It is installed. The image forming units Pa to Pd are provided corresponding to images of four different colors (yellow, magenta, cyan, and black), and yellow, magenta, cyan, and black are respectively performed by charging, exposure, development, and transfer processes. Are sequentially formed.

  These image forming portions Pa to Pd are provided with photosensitive drums 1a, 1b, 1c and 1d which carry visible images (toner images) of the respective colors, and further rotate counterclockwise in FIG. An intermediate transfer belt 8 is provided adjacent to each of the image forming portions Pa to Pd. The toner images formed on the photosensitive drums 1 a to 1 d are sequentially transferred and superimposed on the intermediate transfer belt 8 that moves while contacting the photosensitive drums 1 a to 1 d, and then the secondary transfer roller 9. Is transferred onto a sheet 26 as an example of a recording medium, and further fixed on the sheet 26 in the fixing device 7 and then discharged from the apparatus main body. An image forming process for each of the photosensitive drums 1a to 1d is executed while rotating the photosensitive drums 1a to 1d clockwise in FIG.

  The paper 26 onto which the toner image is transferred is accommodated in a paper feed cassette (recording medium stacking unit) 10 at the lower part of the apparatus. The paper 26 is stacked on a paper stacking plate 28 of the paper feed cassette 10, and the paper 26 is fed by rotating the pickup roller 29 with the upper surface of the paper 26 being pressed against the pickup roller 29 with a predetermined pressure. Is started. Then, only the uppermost one of the plurality of sheets 26 is separated by the conveyance roller pair 30 and conveyed toward the sheet conveyance path 11. The sheet 26 that has passed through the sheet conveying path 11 reaches the registration roller pair 14 and is conveyed to a nip portion between the secondary transfer roller 9 and the driving roller 13 of the intermediate transfer belt 8 in accordance with the image forming timing.

  A sheet made of dielectric resin is used for the intermediate transfer belt 8, and a (seamless) belt having no seam is mainly used. A cleaning blade 17 for removing the toner remaining on the surface of the intermediate transfer belt 8 is disposed on the downstream side in the moving direction of the intermediate transfer belt 8 when viewed from the secondary transfer roller 9.

  The image reading unit 20 includes a scanner lamp that illuminates the document during copying, a scanning optical system equipped with a mirror that changes the optical path of reflected light from the document, and a condensing lens that focuses the reflected light from the document to form an image. And a CCD sensor or the like (both not shown) that converts the imaged image light into an electrical signal, and reads a document image and converts it into image data.

  Next, the image forming units Pa to Pd will be described. There are charging devices 2a, 2b, 2c and 2d for charging the photosensitive drums 1a to 1d and image information on the photosensitive drums 1a to 1d around and below the photosensitive drums 1a to 1d, which are rotatably arranged. The exposure device 4 for exposing the toner, the developing devices 3a, 3b, 3c and 3d for forming toner images on the photosensitive drums 1a to 1d, and the developer (toner) remaining on the photosensitive drums 1a to 1d are removed. Cleaning devices 5a, 5b, 5c and 5d are provided.

  When image data is input from the image reading unit 20, first, the surfaces of the photosensitive drums 1 a to 1 d are uniformly charged by the charging devices 2 a to 2 d, and then a light beam is irradiated according to the image data by the exposure device 4. Then, electrostatic latent images corresponding to the image data from the image reading unit 20 are formed on the photosensitive drums 1a to 1d. Each of the developing devices 3a to 3d includes a developing roller (developer carrying member) disposed so as to be opposed to the photosensitive drums 1a to 1d, and a predetermined amount of two-component developer containing toners of yellow, magenta, cyan, and black, respectively. Filled. This toner is supplied onto the photosensitive drums 1a to 1d by the developing rollers of the developing devices 3a to 3d, and electrostatically adheres to the electrostatic latent image formed by exposure from the exposure device 4. A toner image is formed.

  Then, the primary transfer rollers 6a to 6d apply an electric field at a predetermined transfer voltage between the primary transfer rollers 6a to 6d and the photosensitive drums 1a to 1d, and yellow, magenta, cyan, and cyan on the photosensitive drums 1a to 1d. A black toner image is primarily transferred onto the intermediate transfer belt 8. These four color images are formed with a predetermined positional relationship predetermined for forming a predetermined full-color image. Thereafter, the toner remaining on the surfaces of the photosensitive drums 1a to 1d is removed by the cleaning devices 5a to 5d in preparation for the subsequent formation of a new electrostatic latent image.

  The intermediate transfer belt 8 is stretched over the driven roller 12 and the drive roller 13, and when the intermediate transfer belt 8 starts to rotate counterclockwise as the drive roller 13 is rotated by a belt drive motor (not shown), The sheet 26 is conveyed from the registration roller pair 14 to the nip portion (secondary transfer nip portion) between the secondary transfer roller 9 and the intermediate transfer belt 8 provided close to the intermediate transfer belt 8 at a predetermined timing. A full color image is secondarily transferred onto the paper 26. The paper 26 onto which the toner image has been transferred is conveyed to the fixing device 7.

  The paper 26 conveyed to the fixing device 7 is heated and pressurized when passing through the nip portion (fixing nip portion) of the fixing roller pair 15 to fix the toner image on the surface of the paper 26, and a predetermined full-color image is formed. It is formed. The sheet 26 on which the full-color image is formed is distributed in the conveyance direction by the conveyance guide member 21 arranged at the branching portion of the sheet conveyance path 19 through the conveyance roller pair 16 and is sent as it is (or sent to the double-side conveyance path 23). After duplex copying, the paper is discharged to the discharge tray 18 via the discharge roller pair 24.

  Specifically, the sheet conveyance path 19 is bifurcated into the left and right forks on the downstream side of the conveyance roller pair 16, and one path (the path branched in the left direction in FIG. 1) communicates with the discharge tray 18. ing. The other path (the path branched in the right direction in FIG. 1) is configured to communicate with the double-sided conveyance path 23.

  Next, the configuration of the pickup roller 29 and the transport roller pair 30 will be described.

  As shown in FIG. 2, a recording medium feeding device is configured by a pickup roller 29, a conveyance roller pair 30, a driving motor and a driving force transmission gear 31, which will be described later. The pickup roller 29 sends out the paper 26 from the paper feed cassette 10. The transport roller pair 30 is disposed opposite to the feed roller 30a that transports the paper 26 fed from the pickup roller 29 and the feed roller 30a, and is a nip portion N for transporting the paper 26 in pressure contact with the feed roller 30a. And a retard roller 30b.

  The feed roller 30a and the retard roller 30b are configured to convey the paper 26 fed from the pickup roller 29 one by one. Specifically, the feed roller 30a is attached to a shaft (not shown) connected to a drive motor (not shown), and is configured to rotate by a driving force from the drive motor. The retard roller 30b is configured to be in pressure contact with the feed roller 30a and to be driven to rotate, and has a built-in torque limiter. Further, a driving force transmission gear 31 that transmits the rotation of the feed roller 30 a to the pickup roller 29 is disposed between the feed roller 30 a and the pickup roller 29. Thus, the feeding of the paper 26 is started by rotating the pickup roller 29 in a state of being pressed against the paper 26. When a plurality of sheets 26 are fed simultaneously by the pickup roller 29, the sheet 26 is rolled by the feed roller 30a and the retard roller 30b, and only the topmost sheet is fed toward the sheet transport path 11.

  As shown in FIG. 3, a driving force transmission gear 31 for transmitting a driving force from a driving motor (not shown) to the pickup roller 29 and the feed roller 30a is provided at one end of the recording medium feeding device. . At one end of the pickup roller 29, a pickup roller gear 29a with which the driving force transmission gear 31 is engaged is provided. A feed roller gear 30c with which the driving force transmission gear 31 is engaged is provided at one end of the feed roller 30a.

  The peripheral speed of the pickup roller 29 is set to be smaller than the peripheral speed of the feed roller 30a. Specifically, as shown in FIG. 2, the diameter of the pickup roller 29 is smaller than the diameter of the feed roller 30a. Alternatively, the pickup roller gear 29a has a larger number of teeth than the feed roller gear 30c. The diameter of the pickup roller 29 may be smaller than the diameter of the feed roller 30a, and the number of teeth of the pickup roller gear 29a may be larger than the number of teeth of the feed roller gear 30c.

  Further, the peripheral speed of the pickup roller 29 is set to be greater than or equal to the peripheral speed of the retard roller 30b. Specifically, since the retard roller 30b has a built-in torque limiter and a rotational load is generated, the retard roller 30b rotates following the sliding with respect to the surface of the feed roller 30a. For this reason, the circumferential speed of the retard roller 30b is smaller than the circumferential speed of the feed roller 30a. For example, the peripheral speed of the retard roller 30b in a state where only one sheet 26 is nipped at the nip portion N between the feed roller 30a and the retard roller 30b is reduced by about 15% with respect to the peripheral speed of the feed roller 30a. Further, in the state where a plurality of sheets 26 are nipped at the nip portion N, the retard roller 30b is substantially stopped.

  The peripheral speed of the pickup roller 29 is set to be greater than or equal to the peripheral speed of the retard roller 30b in a state where only one sheet is nipped in the nip portion N. The peripheral speed of the pickup roller 29 is substantially the same as the peripheral speed of the retard roller 30b when only one sheet is nipped in the nip portion N (for example, a difference of 3% or less with respect to the peripheral speed of the retard roller 30b). Preferably there is.

  In the state where only one sheet 26 is nipped at the nip portion N, the sheet 26 slides with respect to the surface of the feed roller 30a, and the conveying speed of the sheet 26 is substantially the same as the peripheral speed of the retard roller 30b. In a state where a plurality of sheets 26 are nipped at the nip portion N, the uppermost sheet 26 slides with respect to the lower sheet 26, and the conveying speed of the sheet 26 is substantially the same as the peripheral speed of the feed roller 30a.

  The operation of the image forming apparatus 100 (each roller, the drive motor, the image forming units Pa to Pd, the fixing device 7 and the like) is controlled by a control unit (not shown).

  In the present embodiment, as described above, the peripheral speed of the pickup roller 29 is smaller than the peripheral speed of the feed roller 30a. As a result, compared to the case where the peripheral speed of the pickup roller 29 is the same as the peripheral speed of the feed roller 30a, the paper 26 bends in the region between the pickup roller 29 and the feed roller 30a, or the paper 26 It is possible to suppress the occurrence of a jam at the time of paper feeding due to the bending.

  In the state where only one sheet 26 is nipped in the nip portion N of the transport roller pair 30, the peripheral speed of the pickup roller 29 is greater than or equal to the peripheral speed of the retard roller 30b. Accordingly, the feed roller 30a and the retard roller 30b can pull the paper 26 forward (downstream in the paper conveyance direction) and can prevent the pickup roller 29 from sliding with respect to the paper 26. For this reason, it can suppress that the pick-up roller 29 wears out and a lifetime becomes short.

  In addition, since the paper 26 can be prevented from being pulled backward by the pickup roller 29, the tension of the paper 26 is released when the rear end of the paper 26 passes through the pick-up roller 29, and vibration or impact occurs. Can be suppressed. As a result, it is possible to prevent the image quality from being deteriorated due to the occurrence of streaks in the image due to the vibration or impact.

  Further, as described above, the peripheral speed of the pickup roller 29 may be approximately the same as the peripheral speed of the retard roller 30b. With this configuration, it is possible to effectively suppress the sheet 26 from being bent in the region between the pickup roller 29 and the feed roller 30a, and the occurrence of a jam during sheet feeding due to the bending of the sheet 26. it can.

  Further, as described above, the diameter of the pickup roller 29 may be smaller than the diameter of the feed roller 30a. If comprised in this way, the circumferential speed of the pick-up roller 29 can be easily made smaller than the circumferential speed of the feed roller 30a.

  Further, as described above, the number of teeth of the pickup roller gear 29a may be larger than the number of teeth of the feed roller gear 30c. If comprised in this way, the circumferential speed of the pick-up roller 29 can be easily made smaller than the circumferential speed of the feed roller 30a.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, although an example in which the present invention is applied to a tandem type color image forming apparatus as shown in FIG. 1 is shown, the present invention is not limited to this. Needless to say, the present invention can be applied to various image forming apparatuses including a feeding unit and a conveying unit, such as a monochrome copying machine, a monochrome printer, a digital multifunction peripheral, and a facsimile machine.

  In the above-described embodiment, an example in which the recording medium feeding device of the present invention is used in an image forming apparatus has been described. However, the recording medium feeding device of the present invention may be used in apparatuses other than the image forming apparatus.

  In the above-described embodiment, an example in which a paper feed cassette that stores paper (recording medium) is used as the recording medium stacking unit has been described. However, the recording medium is not stored, and the recording medium is simply stacked. A paper tray may be used.

10 Paper cassette (recording medium stacking unit)
26 Paper (Recording medium)
DESCRIPTION OF SYMBOLS 29 Pickup roller 29a Pickup roller gear 30 Conveyance roller pair 30a Feed roller 30b Retard roller 30c Feed roller gear 31 Driving force transmission gear 100 Image forming apparatus N Nip part

Claims (5)

A pick-up roller for feeding out the recording medium by being pressed against and rotated on the uppermost surface of the bundle-shaped recording medium stacked on the recording medium stacking unit;
A feed roller pair configured to include a feed roller that feeds and conveys the recording medium fed from the pickup roller, and a retard roller that rotates in contact with the feed roller, and
With
The retard roller slides on the surface of the feed roller and has a lower peripheral speed than the feed roller,
In a state where only one sheet of the recording medium is nipped in the nip portion of the transport roller pair, the peripheral speed of the pickup roller is smaller than the peripheral speed of the feed roller, and larger than the peripheral speed of the retard roller. There is provided a recording medium feeding device.   The recording medium feeding apparatus according to claim 1, wherein a peripheral speed of the pickup roller is substantially the same as a peripheral speed of the retard roller.   The recording medium feeding apparatus according to claim 1, wherein a diameter of the pickup roller is smaller than a diameter of the feed roller. A driving force transmission gear provided between the pickup roller and the feed roller;
The pickup roller is provided with a pickup roller gear with which the driving force transmission gear is engaged,
The feed roller is provided with a feed roller gear with which the driving force transmission gear is engaged,
The recording medium feeding device according to claim 1, wherein the number of teeth of the pickup roller gear is larger than the number of teeth of the feed roller gear.   An image forming apparatus comprising the recording medium feeding device according to claim 1.