JP5038811B2 - Paper feeding device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a sheet feeding device for feeding sheets one by one toward an image forming unit and an image forming apparatus including the sheet feeding device.

  Image forming apparatuses such as copiers, printers, and facsimiles that form images on paper by an electrophotographic system are provided with a paper feeding device that feeds paper one by one to the image forming unit. The paper fed out by the paper device is fed to the registration roller by primary paper feeding and put in a temporary standby state, and then fed to the transfer section by the registration paper at a suitable timing by secondary paper feeding. The toner image on the photosensitive drum is transferred.

  Here, the configuration of the paper feed roller drive system of the conventional paper feed device will be described with reference to FIG.

  FIG. 5 is a front sectional view showing a configuration of a paper feed roller drive system of a conventional paper feed device. In FIG. 5, 134 is a main body side drive shaft, 135 is a paper feed shaft for supporting a paper feed roller (not shown). The main body side drive shaft 134 and the paper feed shaft 135 are coaxially arranged, and both are connected by a cylindrical joint member 136 that engages with the outer periphery thereof.

  The joint member 136 is slidable in the axial direction with respect to the paper feed shaft 135 and the main body side drive shaft 134, and is supplied by a spring 138 that is contracted between a flange 136A and a main body frame 137 formed on the outer periphery thereof. It is biased toward the paper shaft 135 (left side in FIG. 5), and its one axial end surface (left end surface in FIG. 5) is in pressure contact with one axial end surface (right surface in FIG. 5) of the paper feed shaft 135. .

Thus, when the main body side drive shaft 134 is rotationally driven by a motor (not shown) provided on the image forming apparatus main body side, the rotation is transmitted to the paper feed shaft 135 via the joint member 136, and The shaft 135 and the paper feed roller supported by the shaft 135 are driven to rotate, and the paper is primarily fed toward the registration roller pair. When removing the paper feed roller for maintenance, the joint member 135 is slid in the direction of the main body side drive shaft 134 (to the right in FIG. 5) against the biasing force of the spring 138 and By releasing the engagement, the paper feed shaft 135 and the paper feed roller can be easily removed.
JP-A-11-227963 JP-A-11-334904 JP-A-6-144606

  By the way, in the conventional paper feeding apparatus shown in FIG. 5, when the paper supplied to the registration roller pair by the paper feeding roller in the primary paper feeding is conveyed to the transfer unit by the registration roller pair in the secondary paper feeding. Then, the paper feed roller whose drive transmission is stopped is rotated by the paper and idles.

  However, since the joint member 136 urged by the spring 138 abuts against the paper feed shaft 135 and constantly urges it in the axial direction, the thrust load received by the thrust bearing of the paper feed shaft 135 becomes large. There is a problem that the idling torque of the paper feed shaft 135 at the time of the next paper feed increases, the registration roller pair does not pull the paper, and it may adversely affect the jitter, the image magnification, etc. and cause image defects. It was.

  The present invention has been made in view of the above problems, and an object of the present invention is a sheet feeding device capable of suppressing the idling torque of the sheet feeding shaft during secondary sheet feeding and preventing the occurrence of image defects. The present invention provides an image forming apparatus including the above.

In order to achieve the above-mentioned object, the invention according to claim 1 is provided with a joint member that engages with a paper feed shaft for supporting a paper feed roller for feeding paper and a main body side drive shaft and couples them together so as not to be relatively rotatable. In the paper feeding device that holds the paper feed shaft and the main body side drive shaft so as to be movable in the axial direction and urges the joint member in the axial direction by a spring, the joint urged in the axial direction by the spring When the member is at the maximum projecting position, the joint member is configured not to contact either the paper feed shaft or the main body side drive shaft in the axial direction .

  According to a second aspect of the present invention, the image forming apparatus includes the paper feeding device according to the first aspect.

According to the present invention, do not abut in the axial direction to either the joint member when the joint member which is urged axially in the maximum jumping out position of the paper feed shaft and the main body side drive shaft in the axial direction by a spring Therefore, the feed shaft does not receive a thrust load from the joint member, the thrust load acting on the thrust bearing of the feed shaft is suppressed to a small value, and the idling torque of the feed shaft during the secondary feeding is also reduced. It can be suppressed. For this reason, the sheet is reliably pulled by the registration roller, and there is no adverse effect on jitter, image magnification, and the like, the occurrence of image defects is prevented, and high-quality images can be stably obtained.

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

[Image forming apparatus]
FIG. 1 is a side sectional view of a laser beam printer as an embodiment of an image forming apparatus according to the present invention. The illustrated laser beam printer 1 includes a box-shaped apparatus main body 1a, and an upper surface of the apparatus main body 1a. An inclined concave discharge tray 32 is provided at the center of the sheet. In addition, an openable and closable manual feed tray 8 is provided at the upper part of the front surface of the apparatus main body 1a (the right side in FIG. 1 is the front), and a paper supply cassette constituting the paper supply apparatus 2 according to the present invention is provided at the lower part of the apparatus main body 1a. 7 is provided, and the paper feed cassette 7 can be pulled out to the front side.

  Thus, the laser beam printer 1 according to the present embodiment is based on image data transmitted from a terminal (not shown) while transporting the paper along the transport path L provided in the apparatus main body 1a. An image is formed on a sheet, and the conveyance path L includes a horizontal portion L1 extending substantially horizontally from the front to the rear (right to left in FIG. 1) in the apparatus main body 1a, and the horizontal portion L1. The vertical portion L2 that rises substantially vertically from the end portion is configured in a substantially L shape in side view.

  The laser beam printer 1 includes the paper feeding device 2 provided in the lower part of the apparatus main body 1a, an image forming unit 3 provided in a substantially central part in the apparatus main body 1a above the paper feeding apparatus 2, The fixing unit 4 disposed behind the image forming unit 3, the concave paper discharge unit 5 provided on the upper surface of the apparatus main body 1 a above the fixing unit 4, the horizontal unit L 1 of the conveyance path L, and the A re-feed conveyance unit 6 provided between the sheet cassette 7 and the paper cassette 7 is provided.

  The paper feeding device 2 stores paper and feeds the paper toward the image forming unit 3 and includes the paper feeding cassette 7 and the manual feed tray 8.

  Here, the paper feed cassette 7 has a rectangular box shape with an open upper surface, and has a function of feeding sheets (not shown) stacked and accommodated therein one by one, as shown in the figure. In the state where it is mounted in the apparatus main body 1a, it is located below the horizontal portion L1 of the transport path L.

  The paper feed cassette 7 includes a lift plate 9 that contacts and separates from the inner bottom surface, a paper stacking plate 10 that moves up and down in conjunction with the contact and separation of the lift plate 9, and a front end (paper) of the lift plate 9. 1 is attached in the vicinity of the downstream end of the paper feed direction) and rotates around the lift drive shaft 11 that rotates the lift plate 9 in the direction of the arrow in FIG. 1 and the rear end of the paper stacking plate 10 (upstream end in the paper feed direction). A shaft 12 is provided which is pivotally supported.

  Further, in the paper feeding device 2, a pickup roller 13 that picks up the paper stacked on the paper stacking plate 10 in the paper feeding cassette 7 one by one, and the picked up paper is sent to the horizontal portion L 1 of the transport path L. In addition to the paper feed rollers 14 to 18 and the registration roller pair 19 that supplies the fed paper to the transfer unit of the image forming unit 3 at a predetermined timing after temporarily waiting the fed paper, the paper placed on the manual feed tray 8 A pick-up roller 20 is provided.

  The image forming unit 3 forms an image on a sheet supplied from the sheet feeding device 2, and is an image carrier that is rotatably disposed at a substantially central portion in the front-rear direction of the horizontal portion L 1 of the transport path L. A photosensitive drum 21, a charger 22 disposed around the photosensitive drum 21, a developing device 23, a transfer roller 24 and a cleaning device 25, a laser scanner unit (LSU) 26 disposed above them, a toner hopper 27, and the like. .

  The fixing unit 4 is for fixing the toner image transferred onto the paper in the image forming unit 3 to the paper, and includes a heating roller 28 and a pressure roller 29 that rotate while being pressed against each other. Yes.

  Further, the paper discharge unit 5 is for discharging the paper on which the toner image has been fixed in the fixing unit 4 to the outside of the apparatus main body 1a, and is provided in the middle of the vertical portion L2 of the transport path L. A pair of conveying rollers 30 and a pair of paper discharge rollers 31 provided at the end of the vertical portion L2 and the paper discharge tray 32 for stacking sheets discharged to the outside of the apparatus main body 1a.

The re-feed conveyance unit 6 is used when images are formed on both sides of a sheet. The re-feed conveyance unit 6 is arranged at another conveyance path L ′ arranged below the horizontal portion L1 of the conveyance path L and its proper position. A plurality of conveyance roller pairs 33 are provided.

  Next, an image forming operation of the laser beam printer 1 having the above configuration will be described.

  For example, when a print start signal is transmitted to the laser beam printer 1 from a terminal such as a personal computer (personal computer), in the image forming unit 3, the photosensitive drum 21 is driven in the direction indicated by the arrow (clockwise) in FIG. ) And the surface thereof is uniformly charged to a predetermined potential by the charger 22. When a laser beam based on the image data transmitted from the terminal is output from the laser scanner unit 26 and irradiated onto the photosensitive drum 21, an electrostatic latent image is formed on the photosensitive drum 21. Then, the electrostatic latent image formed on the photosensitive drum 21 is developed by the developing device 23 using toner as a developer to be visualized as a toner image.

  At the same time, in the paper feeding device 2, for example, the sheets stored in the paper feeding cassette 7 are picked up one by one from the uppermost one by the pickup roller 13, and are fed to the registration roller pair 19 by the plurality of paper feeding rollers 14 to 18. First, the paper is fed in the primary direction, and is temporarily put into a standby state by the registration roller pair 19. Thereafter, the registration roller pair 19 is rotationally driven at a predetermined timing synchronized with the toner image on the photosensitive drum 21, and the sheet is transferred to the transfer portion which is a contact portion between the photosensitive drum 21 and the transfer roller 24 of the image forming portion 3. The paper is fed secondary. When an image is formed on the paper stacked on the manual feed tray 8, the paper is taken out one by one by the pickup roller 20 and sent out to the horizontal portion L 1 of the transport path L by the paper feeding rollers 16 and 18. .

  In the image forming unit 3, the sheet fed from the registration roller pair 19 to the transfer unit between the photosensitive drum 21 and the transfer roller 24 by the secondary paper feeding is conveyed while being pressed against the photosensitive drum 21 by the transfer roller 24. As a result, the toner image on the photosensitive drum 21 is transferred to the surface (transfer surface). The sheet on which the toner image has been transferred is conveyed to the fixing unit 4, and is heated and pressed in the process of being sandwiched and conveyed by the heating roller 28 and the pressure roller 29 in the fixing unit 4. Get fixed. Note that the toner remaining on the surface of the photosensitive drum 21 (transfer residual toner) after the transfer of the toner image onto the paper is removed by the cleaning device 25.

  Thus, the sheet on which the toner image is fixed on the surface by the fixing unit 4 is conveyed upward through the vertical portion L2 of the conveying path L by the conveying roller pair 30, and the upper portion of the apparatus main body 1a by the discharge roller pair 31. The paper is discharged and stacked on a paper discharge tray 32 provided in the front.

  The above is a series of operations when an image is formed on one side of a sheet. When an image is formed on both sides of a sheet, a sheet having a toner image fixed on one side by a fixing unit 4 is transported to a pair of conveying rollers 30. Then, the sheet is fed to the vertical portion L2 of the conveyance path L, and then the sheet is switched back by reversing the conveyance roller pair 30 and fed to another conveyance path L ′. Then, the paper is transported forward (to the right in FIG. 1) along the transport path L ′ by the plurality of transport roller pairs 33 provided in the transport path L ′, and the paper is transported by the paper feed rollers 16 to 18. If the paper is fed again to the horizontal portion L1 of the path L, the front and back sides of the paper are reversed, and thereafter, the toner image on the photosensitive drum 21 is transferred to the surface of the paper (the other surface on which no image is formed) by the same operation as described above. And the toner image is fixed on the paper in the fixing unit 4, images are formed on both sides of the paper. The paper on which images are formed on both sides in this way is transported upward along the vertical portion L2 of the transport path L by the transport roller pair 30 and is discharged to the paper discharge tray 32 by the paper discharge roller pair 31 as described above. The

[Paper Feeder]
Next, the configuration of the drive system of the paper feed roller 14 in the paper feed device 2 according to the present invention will be described with reference to FIGS.

  2 is a partial perspective view showing the structure of the drive system of the paper feed roller of the paper feed device according to the present invention, FIG. 3 is a front sectional view showing the structure of the drive system, and FIG. 4 is a joint member portion of the drive system. It is a perspective view.

  2 and 3, 34 is a main body side drive shaft, 35 is a paper feed shaft that supports the paper feed roller 14, and the main body side drive shaft 34 and the paper feed shaft 35 are arranged coaxially. Both are connected by a cylindrical joint member 36 engaged with the outer periphery thereof. Here, as shown in FIG. 4, a D-cut portion 36a is formed on the inner periphery of one end in the axial direction of the joint member 36, and the outer periphery of one end in the axial direction of the paper feed shaft 35 is made non-rotatable in this D-cut portion 36a. Is engaged. Although not shown, a D-cut portion is also formed at the inner peripheral portion of the other end of the joint member 36, and one axial outer periphery of the main body side drive shaft 34 is engaged with the D-cut portion so as not to rotate. .

  The joint member 36 is slidable in the axial direction (left and right direction in FIG. 3) with respect to the paper feed shaft 35 and the main body side drive shaft 34, and is contracted between a flange 36A formed on the outer periphery thereof and the main body frame 37. The spring 38, which is a mounted elastic member, is urged toward the paper feed shaft 35 (left side in FIG. 3).

In the present embodiment, as shown in FIG. 3, when the joint member 36 urged in the axial direction by the spring 38 is in the maximum protruding position, the joint member 36 is in the axial direction in the feed shaft and the main body side. The drive shaft 34 is configured not to contact any of the drive shafts 34, and an axial gap δ is formed between the joint member 36 and the paper feed shaft 35.

  Thus, when the main body side drive shaft 34 is rotationally driven by a motor (not shown) provided on the image forming apparatus main body 1 a side, the rotation is transmitted to the paper feed shaft 35 via the joint member 36, and The paper shaft 35 and the paper feed roller 14 supported by the paper shaft 35 are rotationally driven so that the paper is primarily fed toward the registration roller pair 19 shown in FIG. When the paper feed roller 14 is removed for maintenance, the joint member 36 is slid in the direction of the main body side drive shaft 34 (to the right in FIG. 1) against the biasing force of the spring 38 and By releasing the engagement, the paper feed shaft 35 and the paper feed roller 14 can be easily removed.

  Thereafter, the paper that is primarily fed to the registration roller pair 19 is temporarily put into a standby state, and then the registration roller pair 19 is driven to rotate at a timing synchronized with the toner image on the photosensitive drum 21 to form an image. Secondary feeding is performed toward the transfer section between the photosensitive drum 21 and the transfer roller 24 of the section 3, but during this secondary feeding, drive transmission to the feed roller 14 is not performed, and the registration roller pair 19. The sheet feeding roller 14 is rotated by the sheet conveyed by the above and idles.

Thus, in the present embodiment, as described above, when the joint member 36 biased in the axial direction by the spring 38 is in the maximum protruding position, the joint member 36 is axially fed in the sheet feeding shaft and the main body side drive shaft. 34, the sheet feeding shaft 35 is not subjected to a thrust load from the joint member 36, and the thrust load acting on a thrust bearing (not shown) of the sheet feeding shaft 35 is suppressed to a small level. The idling torque of the paper feed shaft 35 at the time of secondary paper feeding is also kept small. For this reason, the sheet is reliably pulled by the registration roller pair 19 without adversely affecting the jitter, the image magnification, and the like, and the occurrence of image defects can be prevented and a high-quality image can be stably obtained.

  In the above, the embodiment in which the present invention is applied to a laser beam printer has been described. However, the present invention is not limited to a printer, and any other image forming apparatus such as a copying machine, a facsimile machine, or a multifunction machine thereof. Of course, the present invention can be similarly applied to the provided sheet feeding device.

1 is a side sectional view of an image forming apparatus (laser beam printer) according to the present invention. It is a fragmentary perspective view which shows the structure of the drive system of the paper feed roller of the paper feeder which concerns on this invention. It is a front sectional view showing the configuration of the drive system of the paper feed roller of the paper feed device according to the present invention. It is a perspective view of the joint member part of the drive system of the paper feed roller of the paper feeder according to the present invention. It is a front sectional view showing the configuration of a drive system of a paper feed roller of a conventional paper feed device.

Explanation of symbols

1 Laser beam printer (image forming device)
DESCRIPTION OF SYMBOLS 1a Image forming apparatus main body 2 Paper feeding device 3 Image forming part 4 Fixing part 5 Paper discharge part 6 Refeed conveyance part 7 Paper feed cassette 8 Manual feed tray 9 Lift plate 10 Paper stacking plate 11 Lift drive shaft 12 Shaft 13 Pickup roller 14 Feed roller 15 Retard roller 16-18 Feed roller 19 Registration roller pair 20 Pickup roller 21 Photosensitive drum 22 Charger 23 Developing device 24 Transfer roller 25 Cleaning device 26 Laser scanner unit (LSU)
27 Toner hopper 28 Heating roller 29 Pressure roller 30 Conveying roller pair 31 Discharging roller pair 32 Discharging tray 33 Conveying roller pair 34 Main body side drive shaft 35 Feeding shaft 36 Joint member 36A Joint member flange 36a Joint member D-cut Part 37 Main body frame 38 Spring L, L 'Transport path L1 Transport path horizontal part L2 Transport path vertical part

Claims (2)

A joint member that engages the paper feed shaft that supports the paper feed roller that feeds the paper and the main body side drive shaft and connects them together so that they can not be rotated relative to each other is movable in the axial direction of the paper feed shaft and the main body side drive shaft In the paper feeding device configured to hold and urge the joint member in the axial direction by a spring,
When the joint member biased in the axial direction by the spring is in the maximum protruding position, the joint member is configured not to contact either the paper feed shaft or the main body side drive shaft in the axial direction. Characteristic paper feeder.
An image forming apparatus comprising the sheet feeding device according to claim 1.

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