JP4917343B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer.

  2. Description of the Related Art Conventionally, there has been known an image forming apparatus in which a paper transport unit is disposed above a paper feed cassette that is attached to the apparatus main body so as to be able to be pulled out and stored.

  In general, the sheet conveying unit of such an image forming apparatus includes an upper guide unit having a plurality of upper rollers disposed along the sheet conveying direction, and a plurality of correspondingly disposed upper rollers. A flat lower guide portion having a lower roller, and biasing means attached to the lower guide portion and biasing the lower roller toward the upper roller. The upper roller and the lower roller And the paper is sandwiched and conveyed.

For example, in Patent Document 1, a paper transport unit (switchback unit) is arranged at a position directly above a paper feed cassette, and the width of the lower guide part of the paper transport unit is stored in the apparatus main body. An image forming apparatus having a configuration in which the lower surfaces in both directions are supported by the upper surfaces of both ends of the sheet cassette is disclosed.
JP 200531216 A

  However, in the conventional image forming apparatus as described above, the lower roller is urged toward the upper roller by the urging means attached to the lower guide portion and is pressed against the upper roller. By pressing the side roller against the upper roller, the attachment portion is bent downward and deformed by a reaction force acting on the attachment portion of the biasing means of the lower guide portion. In particular, in a model that handles a relatively large size paper of A4 or larger, there is a disadvantage that the vicinity of the center of the lower guide portion is largely deformed downward by its own weight. This makes it difficult for the plurality of lower rollers to contact the corresponding upper rollers with substantially the same contact pressure, so that it is difficult to convey the sheet with the conveying forces of the plurality of roller pairs being substantially equal. As a result, there is a problem that the sheet conveyance performance is deteriorated.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of sufficiently improving sheet conveyance performance.

In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention is provided above a sheet feeding unit including a sheet feeding cassette that can be pulled out and stored in the apparatus main body. An image forming apparatus including a sheet conveyance unit configured to convey a sheet in a substantially horizontal direction, wherein the sheet conveyance unit includes a plurality of upper rollers disposed along the sheet conveyance direction. A lower guide portion having a plurality of lower rollers disposed corresponding to each of the plurality of upper rollers, and being attached to the lower guide portion so that the lower roller faces the upper rollers Biasing means for biasing, and configured to sandwich and transport the sheet between the upper roller and the lower roller, and the sheet feeding cassette includes a cassette body for storing the sheet, and the cassette body To cover from above A restriction portion that is formed on an upper portion of the upper surface cover and restricts deformation of the lower guide portion downward in a state in which the paper feed cassette is housed in the apparatus main body. The lower guide portion supports the flat guide plate and the lower roller in a rotatable manner, and the lower end portion projects downward from the lower surface of the guide plate. And the restricting portion protrudes from an upper portion of the upper surface cover, and is capable of contacting the lower surface of the bearing in a state where the paper feed cassette is housed in the apparatus main body. It includes a contact portion that can be stopped .

  In the image forming apparatus according to the first aspect, as described above, the restricting portion that restricts the downward deformation of the lower guide portion of the sheet conveying portion is provided on the upper portion of the upper surface cover of the sheet feeding cassette. The lower guide portion suppresses the lower guide portion from being deformed downward by the reaction force acting on the attachment portion of the biasing means of the lower guide portion by pressing the lower roller against the upper roller. Therefore, the plurality of lower rollers can be brought into contact with the corresponding upper rollers with substantially the same contact pressure. Accordingly, the sheet can be conveyed in a state where the conveying forces of the plurality of roller pairs are substantially equal, so that the sheet conveying performance can be sufficiently improved.

Further, as described above, the lower roller for transporting paper contacts the upper cover by bringing the abutting portion protruding from the upper portion of the upper cover into contact with the lower surface of the bearing that rotatably supports the lower roller. Since the rotation can be prevented from being obstructed, it is possible to improve the conveyance performance while reliably conveying the paper.

The image forming apparatus according to claim 1, preferably, the abutting portion is provided in the vicinity of the center of the conveying direction and the width direction substantially perpendicular to the sheet of the top cover (claim 2).

In the image forming apparatus according to the second aspect , as described above, the contact portion is provided in the vicinity of the center in the width direction of the top cover, thereby supporting the vicinity of the center in the width direction of the guide plate which is particularly easily deformed. Therefore, downward deformation of the lower guide portion can be efficiently suppressed.

The image forming apparatus according to claim 1 or 2, wherein the contact portion is preferably a rail-shaped ribs extending along the pull-out-housing direction of the paper feed cassette (claim 3) .

In the image forming apparatus according to claim 3 , as described above, the rail-shaped rib extending along the drawing / storage direction of the sheet feeding cassette is provided on the upper surface cover, thereby moving the sheet feeding cassette in the moving direction. The rail-shaped rib extending along the bearing can be brought into contact with the lower surface of the bearing, so that the contact area is reduced, and the frictional force between the members when the paper cassette is pulled out (or stored) with respect to the apparatus main body is reduced. Can be small. Thereby, the drawer / housing operation of the sheet cassette with respect to the apparatus main body can be performed easily and smoothly.

The image forming apparatus according to any one of the preceding claims 1 to 3, preferably, the sheet conveying unit, for performing image formation on both sides of the arranged by said sheet position immediately above the sheet feeding unit a switchback portion (claim 4).

  If comprised in this way, the conveyance performance of the switchback part arrange | positioned in the position right above a paper feed part can fully be improved.

  According to the image forming apparatus of the present invention, the lower guide portion is caused by the stress from the urging means by the restricting portion formed on the upper surface cover by rationally using the existing upper surface cover for the paper feed cassette. By suppressing the deformation of the guide portion in the downward direction around the biasing means, the plurality of lower rollers can be brought into contact with the corresponding upper rollers, respectively, with substantially the same contact pressure. The paper can be conveyed in a state where the conveying forces of the roller pairs are substantially equal. As a result, the paper conveyance performance can be sufficiently improved.

  It should be noted that the above effect can also be obtained by removing the top cover from the cassette body of the existing paper feed cassette and attaching the top cover of this proposal instead.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 and 2 are perspective views showing an overall configuration of a printer according to an embodiment of the present invention, and FIG. 3 is a schematic side view showing an internal configuration of the printer shown in FIG. 4 and 5 are diagrams showing a switchback unit and a paper feed cassette of the printer shown in FIG. First, an overall configuration of a printer 1 according to an embodiment of the present invention will be described with reference to FIGS. In this embodiment, an example in which the image forming apparatus of the present invention is applied to the printer 1 will be described.

  As shown in FIGS. 1 to 3, the printer 1 includes a box-shaped apparatus main body 1a, and conveys paper along a conveyance path L (see FIG. 3) provided in the apparatus main body 1a. An image is formed on the paper based on image data transmitted from a terminal (not shown). The conveyance path L has a horizontal portion L1 that extends substantially horizontally from the front to the rear of the printer 1 and a vertical portion L2 that rises substantially vertically from the rear end of the horizontal portion L1, and is substantially L-shaped in a side view. It is comprised so that it may become a shape.

  The printer 1 stores a sheet and supplies the sheet to the image forming unit 3 described below, an image forming unit 3 that forms an image on the sheet supplied from the sheet feeding unit 2, and image formation And a fixing unit 4 for fixing the toner image transferred to the sheet by the unit 3 to the sheet.

  The paper feed unit 2 includes a paper feed cassette 6 that can stack and store sheets. As shown in FIG. 3, the paper feeding unit 2 takes out the paper in the paper feeding cassette 6 one by one by the pickup roller 22, and removes the paper in the conveying path L by the paper feeding rollers 23, 24, 25 and 26. It is configured to be sent to the horizontal portion L1 and further temporarily held by the registration roller 27, and then supplied to the image forming portion 3 at a predetermined timing.

  The paper feed unit 2 has a manual feed tray 28 attached to the front of the apparatus main body 1a. The paper placed on the manual feed tray 28 is taken out by a pickup roller 29, and the paper is taken out by a paper feed roller 24 and 26, it is possible to feed one sheet at a time to the horizontal portion L1 of the transport path L.

  The image forming unit 3 is configured to transfer a toner image to a sheet after forming the toner image on the drum surface of the photosensitive drum 31. In other words, the image forming unit 3 includes a photosensitive drum 31 disposed substantially at the center in the front-rear direction of the horizontal portion L1 of the conveyance path L, a charging unit 32 disposed above the photosensitive drum 31, and a photosensitive member. The developing unit 33 disposed in front of the photosensitive drum 31, the transfer unit 34 disposed below the photosensitive drum 31, the cleaning unit 35 disposed behind the photosensitive drum 31, and the image formation. And a laser scanner unit (LSU) 36 disposed above the fixing unit 4.

  The photosensitive drum 31 rotates clockwise in FIG. 3. After the drum surface is uniformly charged by the charging unit 32, the photosensitive drum 31 is converted into image data by the laser scanner unit 36. An electrostatic latent image is formed by irradiating the laser beam based on between the charging unit 32 and the developing unit 33, and toner is supplied from the developing unit 33 to the drum surface on which the electrostatic latent image is formed. As a result, a toner image is formed.

  The paper supplied from the paper supply unit 2 is conveyed while being pressed against the photosensitive drum 31 by the transfer roller 34a of the transfer unit 34, thereby forming the drum surface of the photosensitive drum 31 on the surface of the paper. The toner image is transferred and then sent to the fixing unit 4. Note that the toner and residual charges remaining on the drum surface of the photosensitive drum 31 after the transfer are removed by the cleaning unit 35.

  The fixing unit 4 includes a heat roller 41 and a pressure roller 42, and the toner image is fixed to the paper by heat and pressure by sandwiching the paper on which the toner image is transferred by the rollers 41 and 42. It is supposed to be.

  The sheet on which the toner image is fixed is discharged by a discharge roller 51 to a discharge unit 5 formed on the upper surface of the apparatus main body 1a. Conveying rollers 71 and 72 are arranged between the fixing unit 4 and the discharge roller 51 at appropriate positions.

  In addition, the printer 1 of the present embodiment includes a switchback unit 8 disposed between the horizontal part L1 of the conveyance path L and the paper feeding unit 2, and can perform image forming processing on both sides of the paper. It is like that. In other words, the sheet on which one side has been subjected to image forming processing in the image forming unit 3 is pulled out from the fixing unit 4 by the forward rotation of the transport roller 72 and then the transport direction is switched by the reverse rotation of the transport roller 72. And sent to the switchback unit 8. The sheet sent to the image forming unit 3 through the switchback unit 8 is configured to be subjected to image forming processing on the other side. The switchback unit 8 is an example of the “paper transport unit” in the present invention.

  Specifically, as shown in FIG. 4, the switchback unit 8 is disposed at a position immediately above the sheet feeding unit 2 and is configured to convey the sheet along a conveyance path L ′ extending in a substantially horizontal direction. Has been. The switchback portion 8 includes an upper guide portion 81 and a lower guide portion 83 that constitute the upper and lower portions of the transport path L ′ and guide the paper. The upper guide portion 81 has driving rollers 82 disposed at three locations along the paper conveyance direction (front-rear direction), and the lower guide portions 83 correspond to the driving rollers 82 at three locations. A driven roller 84 is provided. As shown in FIG. 2, these rollers 82 and 84 are provided in the respective guide portions 81 and 83 so as to be located near the center in the width direction (left-right direction) of the transport path L ′. In addition, three leaf springs 85 (see FIG. 4) for urging the driven roller 84 toward the drive roller 82 are attached near the center of the lower guide portion 83 in the left-right direction. The drive roller 82 and the driven roller 84 are examples of the “upper roller” and “lower roller” of the present invention, respectively, and the leaf spring 85 is an example of the “biasing means” of the present invention.

  The lower guide portion 83 includes a flat guide plate 86 and three bearings 87 that rotatably support the driven rollers 84. As shown in FIG. 5, the bearing 87 is provided so as to be swingable in the vertical direction with respect to the guide plate 86 with its lower end projecting downward from the lower surface of the guide plate 86. It is biased upward by a spring 85. The driven roller 84 is configured by connecting two rotating bodies (rollers) with a rod-shaped connecting member (not shown), and a bearing 87 receives the connecting member rotatably.

  Further, as shown in FIG. 4, the lower guide portion 83 is configured to be able to contact and separate from the upper guide portion 81 with a shaft 88 provided at the rear end of the switchback portion 8 as a rotation fulcrum. Yes. That is, the lower guide portion 83 is rotatably attached to the shaft 88 in a state in which the lower guide portion 83 is constantly urged in a direction in pressure contact with the upper guide portion 81 by a torsion coil spring (not shown) attached to the shaft 88. As a result, the switchback unit 8 moves the lower guide unit 83 into the space formed in the lower part of the apparatus main body 1a by pulling out the paper feed cassette 6 from the apparatus main body 1a, and the paper generated in the switchback unit 8 It is possible to perform jam processing.

  In the switchback unit 8 configured as described above, the sheet can be sandwiched and conveyed by the drive roller 82 and the driven roller 84, while the plate spring 85 is attached to the attachment portion of the plate spring 85 of the lower guide unit 83. Since the stress (reaction force generated by pressing the driven roller 84 against the driving roller 82) acts, the guide plate 86 is bent downward and deformed around the mounting portion.

  Next, the configuration of the paper feed cassette 6 will be described.

  The paper feed cassette 6 is mounted on the paper feed unit 2 so that it can be pulled out and stored in the apparatus main body 1a, and is configured to be positioned directly below the switchback unit 7 in the stored state. The paper feed cassette 6 includes a substantially rectangular parallelepiped cassette body 61 having an open upper surface, and a dust cover 62 that is provided so as to cover the cassette body 61 from above and suppresses entry of dust and the like into the cassette body 61. have. The dust cover 62 is an example of the “top cover” in the present invention.

  Here, in this embodiment, the dust-proof cover 62 has two rail-like ribs 63 protruding from the upper part of the dust-proof cover 62 as shown in FIGS. 1, 4, and 5. The rib 63 is an example of the “restricting portion” and the “contact portion” in the present invention. These ribs 63 extend in parallel in the vicinity of the center of the dustproof cover 62 in the left-right direction along the pull-out / storage direction (front-rear direction) of the paper feed cassette 6, and the paper feed cassette 6 is stored in the apparatus main body 1a. In this state, it is configured to be able to contact the lower surface of the rear end bearing 87 attached to the guide plate 86. As a result, in the printer 1 of the present embodiment, the two ribs 63 protruding from the dust cover 62 of the paper feed cassette 6 hold the bearing 87 that is bent and deformed (displaced) downward together with the guide plate 86, and Deformation of the side guide portion 83 in the downward direction is restricted.

  The rib 63 is set so that the clearance (clearance) between the upper surface of the rib 63 and the lower surface of the bearing 87 is substantially zero when the sheet feeding cassette 6 is stored in the apparatus main body 1a. It is preferable that the bearing 87 is configured to come into contact with the bearing 87 when it is bent downward. Thereby, since it can suppress that the rib 63 and the bearing 87 always contact, it can prevent that a weakly rigid site | part among the dust-proof cover 62 and the lower side guide part 83 deform | transforms with load.

  Further, as shown in FIG. 4, an inclined portion 63a is formed at the rear end portion of the rib 63 so that the sheet feeding cassette 6 can be smoothly accommodated in the apparatus main body 1a.

  In the present embodiment, as described above, the rib 63 that restricts the downward deformation of the lower guide portion 83 of the switchback portion 8 is provided on the upper portion of the dust cover 62 of the paper feed cassette 6, thereby the rib 63 The lower guide portion 83 presses the driven roller 84 against the driving roller 82, thereby suppressing the lower guide portion 83 from being deformed downward around the attachment portion by the reaction force acting on the attachment portion of the leaf spring 85 of the lower guide portion 83. Therefore, the three driven rollers 84 can be brought into contact with the corresponding driving rollers 82 with substantially the same contact pressure. Accordingly, the sheet can be transported in a state where the transport forces of the three roller pairs 82 and 84 are substantially equal, so that the sheet transport performance can be sufficiently improved.

  Further, in the present embodiment, as described above, the rib 63 protruding from the upper portion of the dust cover 62 is brought into contact with the lower surface of the bearing 87 that rotatably supports the driven roller 84 to thereby convey the paper. Since it is possible to prevent 84 from contacting the dust-proof cover 62 and obstructing its rotation, the conveyance performance can be improved while reliably conveying the paper.

  Further, in the present embodiment, as described above, by providing the rib 63 near the center in the left-right direction of the dustproof cover 62, it is possible to support the vicinity of the center in the width direction of the guide plate 86 that is particularly easily deformed. The downward deformation of the lower guide portion 83 can be efficiently suppressed.

  Further, in the present embodiment, as described above, the rail-shaped rib 63 extending along the drawing / storage direction of the paper feed cassette 6 is provided in the dustproof cover 62 so that the paper feed cassette 6 moves in the moving direction. Since the rail-like rib 63 extending along the surface can be brought into contact with the lower surface of the bearing 87, the contact area between the members is reduced and the sheet cassette 6 is pulled out (or stored) with respect to the apparatus main body 1a. The frictional force can be reduced. As a result, the drawer / storage operation of the sheet cassette 6 with respect to the apparatus main body 1a can be performed easily and smoothly. Moreover, since the flat upper surface of the dust-proof cover 62 can be prevented from being damaged by bringing the rib 63 into contact with the bearing 87, the appearance of the dust-proof cover 62 can be prevented from being damaged.

  Note that the above-described effects can be easily obtained by removing the dustproof cover from the cassette body of the existing paper feed cassette and attaching the dustproof cover 62 of the present invention instead.

  In the above-described embodiment, the present invention is applied to a printer as an example of an image forming apparatus. However, the present invention is not limited to this, and the present invention can be applied to a copying machine other than a printer, a facsimile machine, or a multifunction machine thereof. .

  In the above embodiment, rail-shaped ribs 63 extending in parallel along the direction in which the paper feed cassette 6 is pulled out and stored are provided in the dustproof cover 62, and the paper feed cassette 6 is stored in the apparatus main body 1a. Although an example in which the guide plate 86 is brought into contact with the lower surface of the bearing 87 at the rear end in the state is not limited to this, a protrusion protruding upward is provided on the dust-proof cover 62 of the paper feed cassette 6, and the protrusion is The sheet feeding cassette 6 may be brought into contact with the lower surface of the bearing 87 at the rear end of the guide plate 86 in a state where the sheet feeding cassette 6 is housed in the apparatus main body 1a. Further, the protruding portion may be brought into contact with the guide plate 86.

  In addition, a protrusion protruding downward may be provided on the guide plate 86 of the lower guide portion 83, and the protrusion may be in contact with the upper surface of the dust cover 62 of the paper feed cassette 6. In this case, the dust cover 62 of the paper feed cassette 6 corresponds to the “regulator” of the present invention.

  In the above embodiment, an example in which the paper transport unit of the present invention is applied to the switchback unit 8 of the printer 1 has been described. For example, the present invention can be applied to a sheet conveying unit other than the switchback unit 8.

1 is a perspective view illustrating an overall configuration of a printer according to an embodiment of the present invention. FIG. 2 is a perspective view illustrating a state where the printer illustrated in FIG. 1 is viewed from different directions. FIG. 2 is a schematic side view showing an internal configuration of the printer shown in FIG. 1. FIG. 4 is an enlarged side sectional view showing a switchback portion and a paper feed cassette of the printer shown in FIG. 3. FIG. 5 is an enlarged view showing a state in which the switchback unit and the paper feed cassette shown in FIG. 4 are viewed from the direction of arrow A.

Explanation of symbols

1 Printer (image forming device)
1a Device body 2 Paper feed unit 6 Paper feed cassette 8 Switchback unit (paper transport unit)
61 Cassette body 62 Dust-proof cover (top cover)
63 Ribs (abutment and restriction)
81 Upper guide portion 82 Driving roller (upper roller)
83 Lower guide 84 Driven roller (lower roller)
85 Leaf spring (biasing means)
86 Guide plate 87 Bearing

Claims (4)

The image forming apparatus includes a paper feed unit including a paper feed cassette that can be pulled out and stored in the apparatus main body, and a paper transport unit that is provided above the paper feed unit and transports paper in a substantially horizontal direction. And
The paper transport unit includes an upper guide portion having a plurality of upper rollers disposed along the paper transport direction, and a plurality of lower rollers disposed to correspond to the plurality of upper rollers, respectively. A lower guide portion and biasing means attached to the lower guide portion and biasing the lower roller toward the upper roller, and sandwiching the sheet between the upper roller and the lower roller Configured to be transported by
The paper feed cassette includes a cassette main body that accommodates the paper, and an upper surface cover that is provided so as to cover the cassette main body from above.
The upper surface cover is formed on an upper surface of the upper surface cover, and has a restricting portion for restricting the lower guide portion from being deformed in a state where the sheet feeding cassette is housed in the apparatus main body .
The lower guide part is
A flat guide plate;
The lower roller is rotatably supported, and has a bearing provided on the guide plate in a state where the lower end protrudes downward from the lower surface of the guide plate.
The restricting portion includes an abutting portion that protrudes from an upper portion of the upper surface cover and that can contact the lower surface of the bearing and can hold the bearing in a state in which the sheet feeding cassette is housed in the apparatus main body. An image forming apparatus. The image forming apparatus according to claim 1, wherein the contact portion is provided in the vicinity of a center of the upper surface cover in a width direction substantially orthogonal to the sheet conveyance direction . 3. The image forming apparatus according to claim 1 , wherein the contact portion is a rail-shaped rib extending along a drawing / storage direction of the sheet feeding cassette . The said paper conveyance part is a switchback part for performing image formation on both surfaces of the said paper arrange | positioned in the position right above the said paper feeding part, The any one of Claims 1-3 characterized by the above-mentioned. The image forming apparatus described.

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