JP7744835B2 - Sheet ejection device and image forming apparatus equipped with same - Google Patents

Description

The present invention relates to a sheet discharge device and an image forming apparatus equipped with the same, such as a copying machine, multifunction machine, printer, or facsimile machine.

In a sheet ejection device equipped with a pair of ejection rollers consisting of a drive roller and a driven roller, which ejects sheets such as paper or documents onto an ejection tray, the circumferential contact position of the contact area (nip) between the driven roller and the drive roller has been changed so that the sheets are ejected diagonally upward to ensure stackability of sheets loaded onto the ejection tray. Furthermore, to reduce the transport marks (roller marks) left by the pair of ejection rollers and ensure stackability, the pressure of the driven roller on the drive roller has been reduced. If the circumferential contact position of the driven roller and the drive roller is changed so that the sheets are ejected diagonally upward, for example, when a switchback transport is performed in which the pair of ejection rollers (drive roller and driven roller) transports the sheet in a reverse direction opposite to the ejection direction, as in double-sided printing, the sheet's transport direction does not match the sheet transport path (switchback transport path) (it is diagonal to the sheet transport path), causing the leading edge of the sheet to contact the sheet transport path. Furthermore, because the pressure of the driven roller against the drive roller is reduced, sheet transport delays are likely to occur when switchback transport is performed. This is particularly noticeable with sheets that are small in size in the width direction perpendicular to the transport direction, or sheets that are large in size in the transport direction.

In this regard, Patent Document 1 describes a configuration in which a solenoid is used to change the nip position of the driven roller relative to the drive roller, thereby changing the paper discharge direction, thereby discharging paper in an orderly manner (see Figures 3 and 4 of Patent Document 1).

Patent document 2 also describes a configuration in which the rotation drive shaft is offset relative to the discharge roller, changing the nip position relative to the mating roller and changing the discharge direction relative to the discharge tray, thereby improving the stacking condition of paper in the discharge tray (see Figure 4 of cited document 2).

Japanese Patent Application Laid-Open No. 2007-91358 JP 2013-43738 A

However, the configurations described in Patent Documents 1 and 2 do not reduce sheet delays when conveying sheets in the opposite direction to the discharge direction while simultaneously reducing the marks left by the pair of discharge rollers when discharging sheets and ensuring stackability.

The present invention aims to provide a sheet discharge device and image forming apparatus that includes a pair of discharge rollers consisting of a drive roller and a driven roller, which discharges sheets onto a discharge tray, and that can reduce sheet delays when transporting sheets in the opposite direction to the discharge direction while simultaneously reducing the marks left by the pair of discharge rollers when discharging sheets and ensuring stackability.

In order to solve the above problems, the present invention provides a sheet discharge device and an image forming apparatus according to the following first to third aspects.
(1) Sheet discharge device
(1-1) Sheet Discharge Device of First Aspect
A sheet discharge device according to a first aspect of the present invention is a sheet discharge device that includes a pair of discharge rollers composed of a drive roller and a driven roller, and discharges a sheet onto a discharge tray using the pair of discharge rollers, and further includes a support member that supports the driven roller rotatably about a rotation axis, and the support member rotates about a rotation axis parallel to the rotation axis of the driven roller and is biased toward the drive roller, and when the drive roller rotates to discharge the sheet in a discharge direction onto the discharge tray, a first traveling direction of the sheet at a first contact portion between the driven roller and the drive roller reaches a first contact position where the first traveling direction of the sheet is inclined upward downstream in the discharge direction. When the driven roller is moved and the drive roller rotates to transport the sheet in a reverse direction opposite to the discharge direction, the driven roller is moved to a second contact position where the second traveling direction of the sheet at the second contact point between the driven roller and the drive roller is closer to horizontal or becomes horizontal than the inclination of the first traveling direction, the driven roller is located below the drive roller, the first contact position is downstream and above the second contact position in the discharge direction, and the rotation axis of the support member is located upstream in the discharge direction of the rotation axis of the driven roller .
(1-2) Second Aspect of Sheet Discharge Device
A second aspect of the present invention is a sheet discharge device that includes a pair of discharge rollers composed of a drive roller and a driven roller, and discharges a sheet onto a discharge tray using the pair of discharge rollers. The sheet discharge device further includes a support member that supports the driven roller rotatably about a rotation axis, and the support member rotates about a rotation axis parallel to the rotation axis of the driven roller and is biased toward the drive roller. When the drive roller rotates to discharge the sheet in a discharge direction onto the discharge tray, a first traveling direction of the sheet at a first contact portion between the driven roller and the drive roller is set to the discharge direction. and when the drive roller rotates to transport the sheet in a reverse direction opposite to the discharge direction, the driven roller is moved to a second contact position where the second traveling direction of the sheet at the second contact point between the driven roller and the drive roller is closer to horizontal than the inclination of the first traveling direction or is horizontal, and the support member is provided with a long hole through which the rotation axis of the driven roller moves, and the long hole is formed so that the downstream side in the discharge direction is inclined upward more than the upstream side.
(1-3) Sheet Discharge Device of Third Aspect
A third aspect of the present invention provides a sheet discharge device that includes a pair of discharge rollers each composed of a drive roller and a driven roller, and discharges a sheet onto a discharge tray using the pair of discharge rollers. The sheet discharge device further includes a support member that supports the driven roller so as to be rotatable about a rotation axis, and the support member rotates about a rotation axis parallel to the rotation axis of the driven roller, and is biased toward the drive roller. When the drive roller rotates to discharge the sheet in a discharge direction onto the discharge tray, a first traveling direction of the sheet at a first contact portion between the driven roller and the drive roller is inclined upward downstream in the discharge direction. The driven roller is moved to a contact position, and when the drive roller rotates to transport the sheet in a reverse direction opposite to the discharge direction, the driven roller is moved to a second contact position where the second traveling direction of the sheet at the second contact point between the driven roller and the drive roller is closer to horizontal or becomes horizontal than the inclination of the first traveling direction, and a virtual line connecting the rotation axis of the drive roller and the rotation axis of the driven roller when positioned at the first contact position is inclined so that the rotation axis of the driven roller is located downstream in the discharge direction from the rotation axis of the drive roller.

(2) Image forming device
An image forming apparatus according to the present invention is characterized by including the sheet discharge device according to any one of the first to third aspects of the present invention and the discharge tray.

This invention makes it possible to reduce sheet delays when transporting sheets in the opposite direction to the discharge direction, while simultaneously reducing the marks left by a pair of discharge rollers when discharging sheets and ensuring stackability.

1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention, as viewed from the front. 2 is a perspective view of the sheet discharge device in the image forming apparatus shown in FIG. 1 as viewed from below on the front side. FIG. FIG. 4 is a perspective view of a support member that supports a driven roller, viewed obliquely from below on the front side. FIG. 4 is a perspective view of a support member that supports a driven roller, as viewed obliquely from above on the rear side. FIG. 10 is a side view illustrating the positional relationship between the rotation axis of the driven roller located at the first contact position relative to the rotation axis of the support member, the rotation axis of the driven roller located at the second contact position, and the pressure point of the urged support member. 10 is a side view showing a first contact portion between the driven roller and the drive roller located at a first contact position. FIG. FIG. 10 is a side view showing a second contact portion between the driven roller and the drive roller located at a second contact position. 5B is an enlarged side view showing a first contact position portion between the drive roller and the driven roller shown in FIG. 5A. FIG. 5C is an enlarged side view showing a second contact position portion between the drive roller and the driven roller shown in FIG. 5B. FIG. 10 is a table showing example values of the first pressing force and the second pressing force obtained by specific values of the first linear distance, the second linear distance, the third linear distance, and the biasing force.

Embodiments of the present invention will be described below with reference to the drawings. In the following description, identical components are designated by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[Image forming apparatus]
1 is a schematic cross-sectional view of an image forming apparatus 100 according to the present embodiment, viewed from the front. In the figure, the symbol X denotes the left-right direction when viewed from the front, and the symbols X1 and X2 denote the left side (one side) and the right side (the other side), respectively. The symbol Y denotes the depth direction perpendicular to the left-right direction X, and the symbols Y1 and Y2 denote the front side (one side) and the rear side (the other side), respectively. The symbol Z denotes the vertical direction (up-down direction).

The image forming apparatus 100 according to this embodiment is a monochrome image forming apparatus. The image forming apparatus 100 performs image formation processing in accordance with image data read by the image reading device 120 or image data transmitted from an external source. Note that the image forming apparatus 100 may also be a color image forming apparatus that forms multicolor and monochrome images on a sheet P such as paper.

The image forming apparatus 100 includes a document feeder 200 and an image forming apparatus main body 110. The image forming apparatus main body 110 includes an image forming unit 102 and a sheet transport system 103.

The document feeder 200 includes a sheet loading tray 210 (document loading tray), a sheet supply unit 220 (document supply unit), a sheet transport unit 230 (document transport unit), a sheet discharge device 240 (document discharge device), and a discharge tray 250 (document discharge tray). The sheet loading tray 210 loads documents G. The sheet supply unit 220 supplies the documents G loaded on the sheet loading tray 210 one by one to the sheet transport unit 230. The sheet transport unit 230 transports the documents G supplied by the sheet supply unit 220. The sheet discharge device 240 discharges the documents G transported by the sheet transport unit 230 toward the discharge tray 250. The sheet discharge device 240 includes a pair of discharge rollers 241 (see Figure 1). The discharge tray 250 holds documents G to G discharged by the sheet discharge device 240. In the document feeder 200, the sheet loading tray 210 and the discharge tray 250 are arranged so that they overlap in the vertical direction.

The image forming unit 102 includes an exposure unit 1, a development unit 2, a photosensitive drum 3 that functions as an image carrier, a cleaning unit 4, a charging device 5, and a fixing unit 7. The sheet transport system 103 also includes a paper feed tray 81, a manual paper feed tray 82, a sheet discharge device 300, and a discharge tray 14.

An image reading device 120 for reading an image of an original G is provided on top of the image forming apparatus main body 110. The image reading device 120 has an original placement table 221 on which the original G is placed. In addition, an original feeding device 200 is provided above the original placement table 221. In the image forming apparatus 100, the image of the original G read by the image reading device 120 is sent to the image forming apparatus main body 110 as image data, and the image is recorded on a sheet P.

The image forming apparatus main body 110 is provided with a sheet transport path S1. A paper feed tray 81 or manual feed tray 82 supplies a sheet P to the sheet transport path S1. The sheet transport path S1 guides the sheet P to the discharge tray 14 via a transfer roller 10 and a fixing unit 7. The fixing unit 7 heats and fixes the toner image formed on the sheet P to the sheet P. Arranged near the sheet transport path S1 are pickup rollers 11a and 11b, a conveyance roller 12a, a registration roller 13, a transfer roller 10, a fixing roller 71 and a pressure roller 72 in the fixing unit 7, and a discharge roller 310 of the sheet discharge device 300. The sheet discharge device 300 discharges the sheet P toward the discharge tray 250, centered in the width direction H, which is perpendicular to the discharge direction D1.

When double-sided printing is performed on sheet P, sheet discharge device 300 conveys sheet P in reverse direction D2. That is, when double-sided printing is performed on sheet P, image forming apparatus 100 rotates a pair of discharge rollers 310 in the forward direction, and then rotates the pair of discharge rollers 310 in the reverse direction to perform switchback conveyance, conveying sheet P in reverse direction D2, opposite discharge direction D1. Image forming apparatus main body 110 is provided with a reverse sheet conveyance path S2 that leads from branch point S1a on sheet conveyance path S1 to the upstream side (switchback conveyance path) of sheet conveyance path S1 relative to registration rollers 13.

A branching claw T is provided near the branching point S1a between the sheet transport path S1 and the reverse sheet transport path S2. The branching claw T takes a first switching position (the position shown by the solid lines in Figure 1) in which it guides the sheet P from the branching point S1a to a pair of discharge rollers 310, and a second switching position (the position shown by the imaginary lines in Figure 1) in which it guides the sheet P that switches back from the pair of discharge rollers 310 to the reverse sheet transport path S2. Reverse transport rollers 12b are arranged near the reverse sheet transport path S2.

In the image forming apparatus 100, first, the branch claw T is set to the first position, and the sheet P supplied from the paper feed tray 81 or manual feed tray 82 is conveyed to the registration rollers 13. Next, the sheet P is conveyed to the transfer rollers 10 by the registration rollers 13 at a timing that aligns the sheet P with the toner image on the photosensitive drum 3. Next, the toner image on the photosensitive drum 3 is transferred onto the sheet P by the transfer rollers 10. The sheet P then passes through the fixing rollers 71 and pressure roller 72 in the fixing unit 7, and is discharged in the discharge direction D1 toward the discharge tray 14 via the conveyance rollers 12a, the branch claw T, and the discharge rollers 310. If an image is to be formed on both the front and back sides of the sheet P, the branch claw T is set to the second position, and the sheet P is conveyed in the reverse direction D2 from the discharge rollers 310 toward the reverse sheet conveyance path S2. Next, the sheet P passes through the reverse conveyance rollers 12b and is inverted, and is guided again to the registration rollers 13. Then, the branch claw T is placed in the first position, and a toner image is formed and fixed on the back side of the sheet P in the same manner as on the front side, and the sheet is then discharged toward the discharge tray 14.

[Sheet ejection device]
(First embodiment)
FIG. 2 is a perspective view of the sheet discharge device 300 in the image forming apparatus 100 shown in FIG. 1, viewed obliquely from below on the front side.

The sheet discharge device 300 is equipped with a pair of discharge rollers 310 consisting of a drive roller 311 and a driven roller 312, and discharges the sheet P onto the discharge tray 14 using the pair of discharge rollers 310.

More specifically, the drive roller 311 includes a rotation shaft 311a and one or more (two in this example) drive roller units 311b, 311b fixed to the rotation shaft 311a. The sheet ejection device 300 includes a drive transmission mechanism 320. The drive transmission mechanism 320 includes a first transmission gear 321 (3211, 3212), a second transmission gear 322, and an intermediate gear 323. The outer first transmission gear 321 (3211) is meshed with the drive gear of a rotation drive unit (drive motor) not shown. The inner first transmission gear 321 (3212) is meshed with the second transmission gear 322. The second transmission gear 322 is fixed to the rotation shaft 311a of the drive roller 311. The intermediate gear 323 meshes with the inner first transmission gear 321 (3212) and also meshes with the second transmission gear 322. The first transmission gear 321 (3211, 3212) and the intermediate gear 323 are rotatably supported by fixed shafts 321a and 323a, respectively, fixed to the sheet discharge device main body 301. The rotation shaft 311a is rotatably supported by the sheet discharge device main body 301 (main body frame). This allows the drive roller 311 to be rotated by the rotation drive unit via the drive transmission mechanism 320.

The sheet ejection device 300 includes a support member 330 that supports the driven roller 312 so that it can rotate freely around a rotation axis α (rotation axis 312a). The driven roller 312 includes a rotation axis 312a and one or more (two in this example) driven roller portions 312b, 312b fixed to the rotation axis 312a. The support member 330 supports the rotation axis 312a around the rotation axis α.

Figures 3A and 3B are perspective views of the support member 330 supporting the driven roller 312, viewed obliquely from below on the front side and from above on the rear side, respectively.

The support member 330 rotates around a rotation axis β (rotation axis 330a) that is parallel to the rotation axis α of the driven roller 312.

More specifically, the support member 330 has a box-like shape that is open at the top and on the sheet P discharge side. A rotation shaft 330a protrudes from both side surfaces 331, 332 of the support member 330 in the width direction H. The rotation shaft 330a of the support member 330 is rotatably supported by the sheet discharge device main body 301 (main body frame).

Figure 4 is a side view illustrating the positional relationship between the rotation axis α (α1) of the driven roller 312 located at the first contact position relative to the rotation axis β of the support member 330, the rotation axis α (α2) of the driven roller 312 located at the second contact position, and the pressure point Q of the biased support member 330. In Figure 4, the solid line indicates the driven roller 312 located at the first contact position, and the dashed line indicates the driven roller 312 located at the second contact position.

Furthermore, Figures 5A and 5B are side views showing the first contact portion N1 and the second contact portion N2 between the driven roller 312 and the drive roller 311, respectively, when they are located at the first contact position and the second contact position.

When the support member 330 is biased toward the drive roller 311 and the drive roller 311 rotates in the forward direction R1 to discharge the sheet P in the discharge direction D1 onto the discharge tray 14, the support member 330 moves the driven roller 312 to a first contact position (solid line in FIG. 4, see FIG. 5A) where the first travel direction W1 of the sheet P at the first contact portion N1 (first nip portion) between the driven roller 312 and the drive roller 311 is tilted upward downstream in the discharge direction D1; and when the drive roller 311 rotates in the reverse direction R2 to transport the sheet P in the reverse direction D2 opposite the discharge direction D1, the support member 330 moves the driven roller 312 to a second contact position (dashed line in FIG. 4, see FIG. 5B) where the second travel direction W2 of the sheet P at the second contact portion N2 (second nip portion) between the driven roller 312 and the drive roller 311 is closer to horizontal than the inclination of the first travel direction W1 or is horizontal.

More specifically, in the sheet discharge device 300, the first and second contact positions are such that the imaginary straight line La passing through the rotation axis α (α1) of the driven roller 312 located at the first contact position and the rotation axis α (α2) of the driven roller 312 located at the second contact position is inclined upward downstream in the discharge direction D1.

In this embodiment, when the drive roller 311 rotates in the forward direction R1, the driven roller 312 rotates in conjunction with the rotation of the drive roller 311 in the forward direction R1 and moves to the first contact position due to the rotational force of the drive roller 311. On the other hand, when the drive roller 311 rotates in the reverse direction R2, the driven roller 312 rotates in conjunction with the rotation of the drive roller 311 in the reverse direction R2 and moves to the second contact position due to the rotational force of the drive roller 311. At this time, when the driven roller 312 is located at the first contact position, the first travel direction W1 of the sheet P at the first contact portion N1 is inclined upward, and when the driven roller 312 is located at the second contact position, the second travel direction W2 of the sheet P at the second contact portion N2 is closer to horizontal than the inclination of the first travel direction W1 or is horizontal.

In other words, the first tangent δ1 (see Figure 5A) (first traveling direction W1) at the circumferential center of the first contact portion N1 is inclined so that the downstream side in the discharge direction D1 (the side on which the sheet P advances toward the discharge tray 14) is higher than the downstream side in the discharge direction D1 of the second tangent δ2 (see Figure 5B) (second traveling direction W2) at the circumferential center of the second contact portion N2.

As a result, the sheet P can be discharged diagonally upward, thereby ensuring stackability. Furthermore, the first pressing force F1 applied to the drive roller 311 by the driven roller 312 positioned at the first contact position (see FIG. 5A) can be made smaller than the second pressing force F2 applied to the drive roller 311 by the driven roller 312 positioned at the second contact position (see FIG. 5B). This reduces the marks left on the sheet P by the pair of discharge rollers 310 when the sheet P is discharged.

The first pressing force F1 and the second pressing force F2 will now be explained with reference to Figures 6A and 6B.

Figure 6A is an enlarged side view showing the first contact position between the drive roller 311 and the driven roller 312 shown in Figure 5A. In Figure 6A, f1 is the first moving force that the drive roller 311 applies to move the driven roller 312 in the discharge direction D1, f1a is the component force of the first radial component of the first moving force f1 in the radial direction K1 about the rotation axis β of the support member 330, and f1b is the component force of the first orthogonal component of the first moving force f1 in the orthogonal direction K2 that is orthogonal to the radial direction K1.

Figure 6B is an enlarged side view showing the second contact position between the drive roller 311 and the driven roller 312 shown in Figure 5B. In Figure 6B, f2 is the second moving force that causes the drive roller 311 to move the driven roller 312 in the reverse direction D2, f2a is the second radial component of the second moving force f2 in the radial direction K1 about the rotation axis β of the support member 330, and f2b is the second orthogonal component of the second moving force f2 in the orthogonal direction K2 that is orthogonal to the radial direction K1.

In Figures 6A and 6B, F3 is the biasing force of the driven roller 312, which is supported by the biased support member 330, on the drive roller 311.

As shown in FIG. 6A , when a first angle formed by the first moving force f1 and the first orthogonal direction component force f1b is defined as θ1,
f1b=f1×cosθ1
This becomes:

In this case, the first pressing force F1 of the driven roller 312 positioned at the first contact position against the driving roller 311 is expressed as follows:
F1=F3-f1b=F3-f1×cosθ1
This becomes:

On the other hand, as shown in FIG. 6B, if the second angle formed by the second moving force f2 and the second radial component force f2a is θ2, then:
f2b=f2×sinθ2
This becomes:

In this case, the second pressing force F2 of the driven roller 312 positioned at the second contact position against the driving roller 311 is expressed as follows:
F2=F3+f2b=F3+f2×sinθ2
This becomes:

Therefore, the first pressing force F1 applied to the drive roller 311 by the driven roller 312 positioned at the first contact position is smaller than the second pressing force F2 applied to the drive roller 311 by the driven roller 312 positioned at the second contact position.

As shown in FIG. 4, the position of the rotation axis β of the support member 330 may be any position other than the rotation axis α of the driven roller 312, preferably on the side opposite to the side along which the driven roller 312 moves. In this example, as shown in FIG. 4, the first linear distance between the rotation axis β of the support member 330 and the rotation axis α of the driven roller 312 positioned at the first contact position is L1, the second linear distance between the rotation axis α of the driven roller 312 positioned at the second contact position is L2, and the third linear distance between the rotation axis β of the support member 330 and the pressing point Q of the support member pressed by the pressing member 340 is L3. Here, the pressing point Q is the center point of the pressing area of the support member 330 pressed by the pressing member 340. However, this positional relationship is merely an example, and the positional relationship shown in FIG. 4 is not limited to that shown in FIG. 4, as long as the first pressing force F1 can be made smaller than the second pressing force F2.

[Example]
FIG. 7 is a table showing example values of the first pressing force F1 and the second pressing force F2 obtained from specific values of the first linear distance L1, the second linear distance L2, the third linear distance L3, and the biasing force F3.

As shown in Figure 7, when the first linear distance L1 is 24.2 mm, the second linear distance L2 is 21.5 mm, the third linear distance L3 is 20.4 mm, and the spring force F3 is 29,419.84 Pa (300.00 gf/ ^cm2 ), the first pressing force F1 is 24,800.20 Pa (252.89 gf/ ^cm2 ), while the second pressing force F2 is 27,914.64 Pa (284.65 gf/ ^cm2 ), and the first pressing force F1 is smaller than the second pressing force F2.

However, bringing the second travel direction W2 of the sheet P closer to the direction of the sheet transport path S1 (e.g., horizontal direction) when the driven roller 312 is positioned at the second contact position makes it easier to prevent the leading edge of the sheet P from contacting the sheet transport path S1.

In this regard, in this embodiment, the second traveling direction W2 is closer to horizontal than the inclination of the first traveling direction W1, or is horizontal.

By doing this, when the driven roller 312 is positioned at the second contact position, the second travel direction W2 of the sheet P, which transports the sheet P in the reverse direction D2, can be brought closer to the direction of the sheet transport path S1 (e.g., horizontal), thereby preventing the leading edge of the sheet P from contacting the sheet transport path S1. Furthermore, the second pressing force F2 of the driven roller 312 on the drive roller 311 when positioned at the second contact position can be made greater than the first pressing force F1 of the driven roller 312 on the drive roller 311 when positioned at the first contact position. This effectively prevents delays in the transport of the sheet P when switchback transport is performed. These are particularly effective for sheets P that are small in size in the width direction H perpendicular to the discharge direction D1, or sheets P that are large in size in the discharge direction D1.

In this embodiment, the driven roller 312 is located below the drive roller 311. The first contact position is located downstream and above the second contact position in the discharge direction D1. The rotation axis β of the support member 330 is located upstream of the rotation axis α of the driven roller 312 in the discharge direction D1.

In this way, by having the first contact position be downstream and above the second contact position in the discharge direction D1, and the rotation axis β of the support member 330 be located upstream of the rotation axis α of the driven roller 312 in the discharge direction D1, it is possible to easily realize a configuration in which the driven roller 312 is located below the drive roller 311, and the second pressing force F2 is greater than the first pressing force F1.

Second Embodiment
In this embodiment, the support member 330 is provided with an elongated hole 330b through which the rotation shaft 312a of the driven roller 312 moves. The elongated hole 330b is formed so that the downstream side in the discharge direction D1 is inclined upward more than the upstream side.

In this way, by providing the support member 330 with a long hole 330b through which the rotation shaft 312a of the driven roller 312 moves, the driven roller 312 can be reliably moved between the first contact position and the second contact position despite the simple configuration.

In this embodiment, the elongated hole 330b is formed in an arc shape centered on the rotation axis λ of the drive roller 311.

In this way, by forming the elongated hole 330b in an arc shape centered on the rotation axis λ of the drive roller 311, the driven roller 312 can be reliably and smoothly moved between the first contact position and the second contact position.

(Third embodiment)
In this embodiment, the angle φ (φ1, φ2) between the imaginary line Lb (Lb1, Lb2) passing through the rotation axis λ of the drive roller 311 and the rotation axis α (α1, α2) of the driven roller 312 and the imaginary line Lc passing through the rotation axis α (α1, α2) of the driven roller 312 and the pivot axis β of the support member 330 is greater than 90 degrees and less than 180 degrees (approximately 110 degrees in this example).

In this way, by setting the angle θ between the virtual line Lb (Lb1, Lb2) and the virtual line Lc to be greater than 90 degrees and less than 180 degrees, the biasing force F3 of the driven roller 312, supported by the biased support member 330, acting on the drive roller 311 can be effectively used as the first pressing force F1 and second pressing force F2 of the driven roller 312 acting on the drive roller 311.

In this embodiment, the angle φ may be the angle φ1 when the driven roller 312 is located at the first contact position, or the angle φ2 when the driven roller 312 is located at the second contact position. By setting the angle φ to the angle φ2 when the driven roller 312 is located at the second contact position, the biasing force F3 of the driven roller 312 on the drive roller 311 can be effectively used as the second pressing force F2 on the drive roller 311 when located at the second contact position.

(Fourth embodiment)
In this embodiment, a biasing member 340 (a coil spring in this example) is provided to bias the support member 330 toward the drive roller 311. By biasing the support member 330 toward the drive roller 311 using the biasing member 340 in this way, the driven roller 312 supported by the support member 330 can be reliably biased toward the drive roller 311.

More specifically, the biasing member 340 is positioned between the bottom surface 330c at the downstream end of the support member 330 in the discharge direction D1 and the bottom plate of the image forming apparatus main body 110 (main body frame) so as to press the driven roller 312 of the support member 330 toward the drive roller 311. One end 341 of the biasing member 340 is inserted into a protrusion 333 provided on the bottom surface 330c of the support member 330.

Fifth Embodiment
In this embodiment, the imaginary line Lb (Lb1) (see FIG. 5A ) connecting the rotation axis λ of the drive roller 311 and the rotation axis α (α1) of the driven roller 312 when positioned at the first contact position is inclined so that the rotation axis α (α1) of the driven roller 312 is located downstream in the discharge direction D1 of the rotation axis λ of the drive roller 311. In this way, the lower side of the imaginary line La connecting the rotation axis λ of the drive roller 311 and the rotation axis α of the driven roller 312 when positioned at the first contact position is inclined downstream in the discharge direction D1 of the sheet P, so that the sheet P can be reliably discharged diagonally upward, thereby further ensuring stackability.

Sixth Embodiment
In this embodiment, the imaginary line Lb (Lb2) (see FIG. 5B ) connecting the rotation axis λ of the drive roller 311 and the rotation axis α (α2) of the driven roller 312 when it is located at the second contact position is aligned with the vertical direction Z, which is the direction of gravity, or the approximately vertical direction Z. Here, the approximately vertical direction Z can be, for example, within a range of about ±5 degrees with respect to the vertical direction Z.

In this way, the imaginary line Lb (Lb2) connecting the rotation axis λ of the drive roller 311 and the rotation axis α (α2) of the driven roller 312 when positioned at the second contact position is aligned along the vertical direction Z or approximately the vertical direction Z, so that the second travel direction W2 of the sheet P at the second contact point N2 can be aligned horizontally or approximately horizontally, thereby further preventing the leading edge of the sheet P from contacting the sheet transport path S1.

(Other embodiments)
In the embodiment described above, the driven roller 312 is located below the drive roller 311, but the driven roller 312 may be located above the drive roller 311. In this case, a predetermined movement mechanism can be used to move the driven roller 312 in the reverse direction D2 by rotating the drive roller 311 in the forward direction R1, and to move the driven roller 312 in the discharge direction D1 by rotating the drive roller 311 in the reverse direction R2.

In addition, in this embodiment, the sheets are described as paper (recording paper), but they may also be original documents. In this case, the sheet discharge device 300 according to this embodiment can be applied to the sheet discharge device 240 in the original feeding device 200.

The present invention is not limited to the embodiments described above, and can be embodied in various other forms. Therefore, the embodiments are merely illustrative in all respects and should not be interpreted as limiting. The scope of the present invention is defined by the claims and is not bound by the text of the specification. Furthermore, all modifications and variations that fall within the equivalent scope of the claims are within the scope of the present invention.

100 Image forming apparatus 110 Image forming apparatus main body 12a Conveying roller 12b Reverse conveying roller 14 Discharge tray 300 Sheet discharge device 301 Sheet discharge device main body 310 Discharge roller 311 Drive roller 311a Rotating shaft 311b Drive roller section 312 Driven roller 312a Rotating shaft 312b Driven roller section 320 Drive transmission mechanism 330 Support member 330a Rotating shaft 330b Long hole 330c Bottom surface 331 Side surface 333 Protrusion 340 Urging member D1 Discharge direction D2 Reverse direction F1 First pressing force F2 Second pressing force F3 Urging force H Width direction K1 Radial direction K2 Orthogonal direction L1 First linear distance L2 Second linear distance L3 Third linear distance La Virtual line Lb Virtual line Lc Virtual line N1 First contact portion N2 Second contact portion P Sheet Q Pressing point R1 Forward direction R2 Reverse direction S1 Sheet transport path S1a Branching section S2 Reverse sheet transport path T Branching claw W1 First proceeding direction W2 Second proceeding direction X Left-right direction Z Vertical direction f1 First moving force f1b First orthogonal direction component f2 Second moving force f2a Second radial direction component α Rotation axis β Pivoting axis θ Angle φ Angle λ Rotation axis

Claims (10)

A sheet discharge device including a pair of discharge rollers each composed of a drive roller and a driven roller, the pair of discharge rollers discharging a sheet onto a discharge tray,
a support member that supports the driven roller rotatably about a rotation axis,
the support member rotates about a rotation axis parallel to the rotation axis of the driven roller, and when the drive roller rotates to discharge the sheet in a discharge direction onto the discharge tray while being biased toward the drive roller, the support member moves the driven roller to a first contact position where a first traveling direction of the sheet at a first contact portion between the driven roller and the drive roller is inclined upward downstream in the discharge direction,
When the drive roller rotates to transport the sheet in a reverse direction opposite to the discharge direction, the driven roller is moved to a second contact position where a second travel direction of the sheet at a second contact portion between the driven roller and the drive roller is closer to a horizontal direction than the inclination of the first travel direction or is horizontal ,
The driven roller is located below the drive roller,
the first contact position is a position downstream and above the second contact position in the discharge direction,
The sheet discharging device according to claim 1, wherein the rotation axis of the support member is located upstream of the rotation axis of the driven roller in the discharging direction . A sheet discharge device including a pair of discharge rollers each composed of a drive roller and a driven roller, the pair of discharge rollers discharging a sheet onto a discharge tray,
a support member that supports the driven roller rotatably about a rotation axis,
the support member rotates about a rotation axis parallel to the rotation axis of the driven roller, and when the drive roller rotates to discharge the sheet in a discharge direction onto the discharge tray while being biased toward the drive roller, the support member moves the driven roller to a first contact position where a first traveling direction of the sheet at a first contact portion between the driven roller and the drive roller is inclined upward downstream in the discharge direction,
When the drive roller rotates to transport the sheet in a reverse direction opposite to the discharge direction, the driven roller is moved to a second contact position where a second travel direction of the sheet at a second contact portion between the driven roller and the drive roller is closer to a horizontal direction than the inclination of the first travel direction or is horizontal,
The support member is provided with a slot through which the rotation shaft of the driven roller moves,
10. A sheet discharging device according to claim 9, wherein the elongated hole is formed so that the downstream side in the discharging direction is inclined upward more than the upstream side. A sheet discharge device including a pair of discharge rollers each composed of a drive roller and a driven roller, the pair of discharge rollers discharging a sheet onto a discharge tray,
a support member that supports the driven roller rotatably about a rotation axis,
the support member rotates about a rotation axis parallel to the rotation axis of the driven roller, and when the drive roller rotates to discharge the sheet in a discharge direction onto the discharge tray while being biased toward the drive roller, the support member moves the driven roller to a first contact position where a first traveling direction of the sheet at a first contact portion between the driven roller and the drive roller is inclined upward downstream in the discharge direction,
When the drive roller rotates to transport the sheet in a reverse direction opposite to the discharge direction, the driven roller is moved to a second contact position where a second travel direction of the sheet at a second contact portion between the driven roller and the drive roller is closer to a horizontal direction than the inclination of the first travel direction or is horizontal,
a virtual line connecting the rotation axis of the drive roller and the rotation axis of the driven roller when positioned at the first contact position, the virtual line being inclined so that the rotation axis of the driven roller is located downstream of the rotation axis of the drive roller in the discharge direction. 3. The sheet ejection device according to claim 2 ,
The sheet ejection device according to claim 1, wherein the elongated hole is formed in an arc shape centered on the rotation axis of the drive roller. 5. The sheet ejection device according to claim 1,
A sheet ejection device characterized in that the angle between an imaginary line passing through the rotation axis of the drive roller and the rotation axis of the driven roller and an imaginary line passing through the rotation axis of the driven roller and the pivot axis of the support member is greater than 90 degrees and less than 180 degrees. 6. The sheet ejection device according to claim 5,
4. A sheet ejection device according to claim 1, wherein the angle is an angle when the driven roller is positioned at the second contact position. 7. The sheet ejection device according to claim 1,
A sheet discharging device comprising: a biasing member that biases the support member toward the drive roller. 8. The sheet ejection device according to claim 1 ,
A sheet ejection device characterized in that an imaginary line connecting the rotation axis of the drive roller and the rotation axis of the driven roller when positioned at the second contact position is aligned along a vertical direction or an approximately vertical direction, which is the direction of gravity. 9. The sheet ejection device according to claim 1,
The sheet ejection device, wherein the driven roller moves to both sides of the first contact position and the second contact position by rotation of the drive roller. An image forming apparatus comprising the sheet discharge device according to any one of claims 1 to 9 and the discharge tray.