阅读说明：本技术 成像设备 (Image forming apparatus ) 是由 水口浩平 于 2020-09-30 设计创作，主要内容包括：本发明涉及一种成像设备,包括成像部、片材排出部和片材堆叠部。堆叠部包括第一构件和第二构件,第一构件包括朝片材排出方向的下游侧向上倾斜的倾斜表面,第二构件包括从倾斜表面向上突出并且在其上堆叠被排出片材的堆叠表面。第二构件能够相对于第一构件围绕相对于片材排出方向设置在堆叠表面上游的支点旋转。根据堆叠在堆叠表面上的片材数量的增加,第二构件能够围绕支点沿堆叠表面向下移动的方向旋转。(The present invention relates to an image forming apparatus including an image forming portion, a sheet discharging portion, and a sheet stacking portion. The stacking portion includes a first member including an inclined surface that is inclined upward toward a downstream side in a sheet discharging direction, and a second member including a stacking surface that protrudes upward from the inclined surface and on which discharged sheets are stacked. The second member is rotatable relative to the first member about a fulcrum provided upstream of the stacking surface with respect to the sheet discharging direction. The second member is rotatable about the fulcrum in a direction in which the stacking surface moves downward in accordance with an increase in the number of sheets stacked on the stacking surface.)

1. An image forming apparatus comprising:

an image forming portion configured to form an image on a sheet;

a discharging portion configured to discharge a sheet on which an image is formed by the image forming portion; and

a stacking portion configured to stack the sheet discharged by the discharging portion in a state where an upstream end of the sheet with respect to a sheet discharging direction is lower than a downstream end of the sheet with respect to the sheet discharging direction,

wherein the stacking portion includes:

a first member including an inclined surface that is inclined upward toward a downstream side in a sheet discharging direction; and

a second member including a stacking surface that protrudes upward from the inclined surface and on which the discharged sheets are stacked,

wherein the second member is rotatable with respect to the first member about a fulcrum provided upstream of the stacking surface with respect to a sheet discharging direction; and is

Wherein the second member is rotatable about a fulcrum in a direction in which the stacking surface moves downward in accordance with an increase in the number of sheets stacked on the stacking surface.

2. An apparatus according to claim 1, wherein said fulcrum of said second member is disposed upstream of an intermediate position between an upstream end and a downstream end of said stacking portion with respect to a sheet discharging direction, and a distance from said fulcrum of said second member to the upstream end of said stacking portion with respect to the sheet discharging direction is smaller than a distance from said fulcrum of said second member to said intermediate position of said stacking portion with respect to the sheet discharging direction.

3. An image forming apparatus according to claim 1, wherein said second member is locatable below said inclined surface at least in a range from a predetermined position of said second member with respect to a sheet discharging direction to a downstream end of said second member with respect to the sheet discharging direction.

4. An image forming apparatus according to claim 1, wherein in a state where sheets are not stacked on said stacking portion, said stacking surface is inclined upward toward a sheet discharging direction.

5. The image forming apparatus according to claim 4, wherein in a state where sheets are not stacked on the stacking portion, the following relationship is satisfied:

θc>θa，

wherein θ c is an inclination angle of the stacking surface with respect to a horizontal plane in an end region of the stacking surface on an upstream side with respect to a sheet discharging direction, and θ a is an inclination angle of the inclined surface with respect to a horizontal plane.

6. An image forming apparatus according to claim 1, wherein said first member includes a support portion capable of supporting the sheet on a downstream side of said second member with respect to a sheet discharging direction and above said stacking surface of said second member, and

wherein the sheet is supported by the stacking surface and the support portion.

7. An image forming apparatus according to claim 1, wherein said stacking surface of said second member is curved such that an inclination degree thereof with respect to a horizontal plane becomes smaller from an upstream side to a downstream side with respect to a sheet discharging direction.

8. An image forming apparatus according to claim 1, further comprising an alignment portion configured to align the sheets in contact with an upstream end of the sheets stacked on said stacking portion with respect to a sheet discharging direction.

9. An image forming apparatus according to claim 1, wherein a distance from an upstream end of said stacking surface to an upstream end of said stacking portion with respect to a sheet discharging direction is smaller than a distance from the upstream end of said stacking surface to an intermediate position of said stacking portion with respect to the sheet discharging direction.

10. An image forming apparatus according to claim 9, wherein in a state in which sheets are not stacked on said stacking portion, said stacking surface is located above said first member at said intermediate position of said stacking portion, and

wherein the second member is rotatable to a position in which the stacking surface is located below the inclined surface at the intermediate position of the stacking portion.

11. An image forming apparatus according to claim 1, further comprising a force application portion configured to apply a force to said second member in a direction in which said stacking surface moves upward.

12. An image forming apparatus according to claim 1, further comprising a drive source configured to rotate said second member.

13. An image forming apparatus according to claim 1, wherein said inclined surface of said first member is provided with a plurality of slits each extending in a sheet discharging direction at a plurality of positions with respect to a sheet width direction perpendicular to the sheet discharging direction,

wherein the second member is provided with a rib protruding upward from the inclined surface of the first member through the slit, and

wherein the stacking surface is disposed on the rib.

14. An apparatus according to claim 13, wherein said ribs include a first rib and a second rib shorter in length than said first rib with respect to a sheet discharging direction.

15. An image forming apparatus according to claim 1, further comprising an image reading device provided above said stacking portion and configured to read image information from an original.

16. The imaging apparatus of claim 15, further comprising:

another discharging portion configured to discharge the sheet on which the image is formed by the image forming portion; and

another stacking portion provided above the stacking portion and below the image reading device and configured to stack thereon the sheet discharged by the other discharging portion.

17. The imaging apparatus of claim 1, further comprising:

another discharging portion configured to discharge the sheet on which the image is formed by the image forming portion; and

another stacking portion disposed above the stacking portion and configured to stack thereon the sheet discharged by the other discharging portion.

Technical Field

The present invention relates to an image forming apparatus for forming an image on a sheet.

Background

In an image forming apparatus such as a printer, a copying machine, or a multi-function machine, a sheet on which an image is formed by an inkjet type printing unit or an electrophotographic mechanism is stacked on a discharge tray by a discharge roller pair.

Japanese laid-open patent application No. 2000-38247 discloses an image forming apparatus in which a rib guide is provided which protrudes upward from a discharge tray and on which sheets are to be stacked. The rib guide is lowered in accordance with the number of stacked sheets of sheets stacked thereon.

The rib guide rotates with its downstream end portion with respect to the sheet discharging direction as a fulcrum. As the number of stacked sheets of sheets stacked on the rib guide increases and thus the rib guide is lowered, the inclination angle of the rib guide with respect to the horizontal plane becomes larger. As a result, a newly discharged sheet in a state where the number of stacked sheets of sheets on the rib guide is large is susceptible to a large feeding resistance from sheets already stacked on the rib guide during its discharge by the pair of discharge rollers. The newly discharged sheet is subjected to a large sheet resistance that has come from the already stacked sheets, whereby the newly discharged sheet is liable to positional deviation. Therefore, there is a possibility that the alignment of the stacked sheets is deteriorated.

Disclosure of Invention

A main object of the present invention is to provide an image forming apparatus in which registration of stacked sheets is good even if the number of stacked sheets becomes large.

According to an aspect of the present invention, there is provided an image forming apparatus including: an image forming portion configured to form an image on a sheet; a discharging portion configured to discharge the sheet on which the image is formed by the image forming portion; and a stacking portion configured to stack the sheet discharged by the discharging portion in a state where an upstream end of the sheet with respect to a sheet discharging direction is lower than a downstream end of the sheet with respect to the sheet discharging direction, wherein the stacking portion includes: a first member including an inclined surface that is inclined upward toward a downstream side in a sheet discharging direction; and a second member including a stacking surface that protrudes upward from the inclined surface and on which the discharged sheet is stacked, wherein the second member is rotatable with respect to the first member about a fulcrum that is provided upstream of the stacking surface with respect to the sheet discharging direction; wherein the second member is rotatable about the fulcrum in a direction in which the stacking surface moves downward in accordance with an increase in the number of sheets stacked on the stacking surface.

Other features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

Drawings

Fig. 1 is a schematic view of an image forming apparatus according to embodiment 1.

Fig. 2 is a perspective view of the discharge tray (first discharge tray) in embodiment 1 on the upper (front) surface side.

Fig. 3 is a perspective view of the discharge tray (first discharge tray) in embodiment 1 on the lower (back) surface side.

Fig. 4 is a sectional view (standby state) of the discharge tray in embodiment 1.

Fig. 5 is a sectional view of the discharge tray in example 1 (fully stacked state).

Fig. 6 is a sectional view showing a state of a sheet discharging operation in embodiment 1.

Fig. 7 is a sectional view showing the movement of a sheet discharged onto a discharge tray in embodiment 1.

Fig. 8 is a sectional view showing a state where a plurality of sheets are stacked in embodiment 1.

Fig. 9 is a sectional view showing a state where a plurality of sheets are stacked in the comparative (reference) example.

Fig. 10 is a perspective view of the movable tray in embodiment 2.

Detailed Description

Exemplary embodiments for implementing the present invention will be described below with reference to the accompanying drawings.

Fig. 1 is a schematic diagram of an image forming apparatus 100 according to embodiment 1. The apparatus main assembly 101 of the image forming apparatus 100 accommodates an image forming portion 140 as an electrophotographic mechanism of an intermediate transfer cascade type in which four image forming stations 1Y, 1M, 1C, and 1K for forming toner images of four colors are disposed along an intermediate transfer belt 145.

In each of the image forming stations 1Y, 1M, 1C, and 1K, a toner image is formed by an electrophotographic process. That is, the photosensitive member 141 as an image bearing member is uniformly charged in advance by a charger and then scan-exposed with light emitted from the exposure device 142, thereby writing (forming) an electrostatic latent image on the surface of the photosensitive member 141. The electrostatic latent image is developed as a toner image by the charged toner particles supplied from the developing device 143. The toner image carried on the photosensitive member 141 is temporarily transferred onto an intermediate transfer belt 145 as an intermediate transfer member by a primary transfer roller 144. At this time, the toner images of yellow, magenta, cyan, and black formed by the respective image forming stations 1Y, 1M, 1C, and 1K are superimposed on the intermediate transfer belt 145, thereby forming a full-color toner image. The full-color toner image is carried on the intermediate transfer belt 145 and is fed to the secondary transfer portion 130.

In parallel with such image forming processing, feeding processing of the sheet S as a recording material is performed. In a state where the sheet S is stacked on the lifting means included in the sheet feeding apparatus, the sheet S is accommodated in a cassette which is insertable into and withdrawable from the apparatus main assembly 101 of the image forming apparatus 100. Incidentally, as the sheet S, various sheet materials different in size and material may be used, such as paper including plain paper, thick paper, and the like, a plastic film, cloth, a surface-treated sheet material such as coated paper, and a special-shaped sheet material such as an envelope or index paper. Based on the progress of the image forming operations performed by the image forming stations 1Y, 1M, 1C, and 1K, the sheets S accommodated in the cassettes are fed one by a feeding unit 110 as a feeding means.

The sheet S fed by the feeding unit 110 is conveyed to the skew movement correcting device 120 through a conveying path, and skew movement correction and timing correction are performed in the skew movement correcting device 120, and then sent to the secondary transfer portion 130. The secondary transfer portion 130 is a nip portion formed by an inner secondary transfer roller 131 and an outer secondary transfer roller 132 that oppose each other while sandwiching the intermediate transfer belt 145. The toner image carried on the intermediate transfer belt 145 is transferred onto the sheet S with the application of a mechanical pressing force and an electrostatic load bias at the secondary transfer portion 130.

The sheet S passing through the secondary transfer portion 130 is conveyed to the fixing device 150. The fixing device 150 includes a pair of rotatable members rotatable while nipping the sheet S, and a heat source such as a halogen lamp, and heats and presses the toner image on the sheet S while feeding the sheet S. Thereby, the toner particles are melted and then fixed, thereby fixing the toner image on the sheet S. The sheet S on which the fixed image is obtained is guided by the first flapper 151 as a switching member to a path toward the first discharge roller 160 (lower discharge path) or a path toward the second discharge roller 161 (upper discharge path).

The image forming apparatus 100 of the present embodiment is provided with a first discharge tray 170 and a second discharge tray 171 as discharge designation of the image-formed sheet S. The sheet S guided to the lower discharge path is discharged to the outside of the apparatus main assembly 101 by the first discharge roller 160 and stacked on the first discharge tray 170. The sheet S guided to the upper discharge path is discharged to the outside of the apparatus main assembly 101 by the second discharge roller 161 and stacked on the second discharge tray 171. The first discharge roller 160 and the first discharge tray 170 constitute a first discharge section 190, and the second discharge roller 161 and the second discharge tray 171 constitute a second discharge section 191. Each of the first discharge portion 190 and the second discharge portion 191 is an example of a sheet discharge device for discharging the sheet S.

On the other hand, in the case of performing double-sided printing, the sheet S on which image formation is performed on the first side is guided to the upper discharge path by the first flapper 151, and then is fold-fed by the reverse operation of the second discharge roller 161. The second shutter 152 guides the sheet S to the double-sided feeding path 180 after the sheet S is folded back. Then, the sheet S that has reached the skew movement correcting device 120 again through the double-side feed path 180 forms an image on the second side through processing similar to the first side, and is then discharged onto the first discharge tray 170 or the second discharge tray 171.

Incidentally, each of the first discharge tray 170 and the second discharge tray 171 includes an inclined surface inclined upward with respect to the vertical direction toward the downstream side with respect to the sheet discharging direction (leftward direction in the drawing). Thus, the sheet S discharged on each discharge tray is returned to the upstream side with respect to the sheet discharging direction by its own weight, and is aligned in contact with the alignment reference wall provided to the apparatus main assembly 101.

Further, the image forming apparatus 100 of the present embodiment has a so-called in-apparatus discharge type configuration in which a sheet discharge space is provided between the image forming portion 140 and the image reading device 102 provided at an upper portion of the apparatus main assembly 101 with respect to the vertical direction. Of the first discharge tray 170 and the second discharge tray 171 provided at the upper and lower stages in the discharge space, the first discharge tray 170 provided at the lower stage is mounted at the upper portion of the apparatus main assembly 101. Incidentally, the image reading apparatus 102 is an apparatus which reads image information by scanning an original document by an image sensor unit provided with a pickup element, and transmits the image information to a control circuit of the apparatus main assembly 101.

[ discharge tray ]

Hereinafter, the first discharge portion 190 as a sheet discharge device will be described. In the following description, description will be made by simply referring to the first discharge tray 170 and the first discharge roller 160 as "discharge tray 170" and "discharge roller 160", respectively. In addition, the moving direction of the sheet discharged from the discharge roller 160 with respect to the horizontal direction is referred to as "sheet discharging direction D1", and the axial direction of the discharge roller 160 (the direction perpendicular to the vertical direction and the sheet discharging direction D1) is referred to as "width direction D2".

Fig. 2 is a perspective view of the discharge tray 170 as viewed from the upper side (front side), and fig. 3 is a perspective view of the discharge tray 170 as viewed from the lower surface (back side). The discharge tray 170 as a stacking portion in the present embodiment is a tray unit including a fixed tray 20 as a first member forming a first stacking surface and a movable tray 21 as a second member forming a second surface and movable relative to the fixed member. The sheets S discharged by the discharge rollers 160 are stacked on these fixed tray 20 and movable tray 21.

On the front side (fig. 2) of the fixed tray 20, there are provided an upper surface 20s constituting a first stacking surface, and a plurality of slits 20b arranged along the width direction D2 from an upstream-side end portion with respect to the sheet discharging direction D1 toward the center portion. As described later, the arc-shaped ribs 21d of the movable tray 21 protrude from the respective slits 20b provided in the upper surface 20 s. Incidentally, on the upper surface 20s, at positions corresponding to the respective slits 20b with respect to the width direction D2, a plurality of guide ribs 20g extend in the sheet discharging direction D1. That is, the arc-shaped rib 21D of the movable tray 21 and the guide rib 20g of the fixed tray 20 are arranged in the sheet discharging direction D1.

On the back side (fig. 3) of the fixed tray 20, a rotation hole 20d is provided at an upstream-side end portion with respect to the sheet discharging direction, and two fixed tray hooks 20e to which an urging spring 22 is attached are provided at a central portion with respect to the sheet discharging direction. Further, the fixing tray 20 is mounted on the image forming apparatus and fixed to the apparatus main assembly 101 by engaging the four mounting portions 20c with portions to be engaged of the apparatus main assembly 101 (fig. 1).

The movable tray 21 is provided with a plurality of arc-shaped ribs 21d (fig. 2) forming the second stacking surface. The plurality of arc-shaped ribs 21D are provided at positions corresponding to the slits 20b of the fixed tray 20 with respect to the width direction D2, and at least a part of the arc-shaped ribs extend from the upstream side end portion toward the downstream side end portion of the movable tray 21 with respect to the sheet discharging direction D1. Further, the upper end portion of each of the arc-shaped ribs 21D is inclined upward toward the downstream side in the sheet discharging direction D1 and is curved in a substantially arc shape such that the inclination angle of the arc-shaped rib with respect to the horizontal plane becomes smaller toward the downstream side in the sheet discharging direction D1. Incidentally, 9 arc-shaped ribs 21d are provided in the present embodiment. A distance (interval) M between adjacent arc ribs 21d of the 5 central arc ribs 21d with respect to the width direction is narrower than a distance (interval) N between adjacent (two) arc ribs 21d at each of the opposite sides with respect to the width direction.

Further, the movable tray 21 includes a plate-shaped main body portion 21f connecting a plurality of arc-shaped ribs 21d, two rotation shafts 21a as rotation fulcrums of the movable tray 21, and two movable tray hook portions 21b at the back side (fig. 3) of the fixed tray 20. Each of the arc-shaped ribs 21d extends upward from the plate-shaped main body portion 21f with respect to the vertical direction, and can protrude upward from the fixed tray 20 through the slit 20b of the fixed tray 20.

The two rotation shafts 21a are provided at the upstream-side end portions of the movable tray 21 with respect to the sheet discharging direction D1, and are engaged in the rotation holes 20D of the fixed tray 20, respectively. Thus, the movable tray 21 is configured to be rotatable with respect to the fixed tray 20 about a rotation axis (i.e., an imaginary straight line passing through the two rotation shafts 21 a) extending in the width direction D2. The two movable tray hook portions 21b are provided at the downstream side end portions of the movable tray 21 with respect to the sheet discharging direction D1. Between each of the two sets of the movable tray hook portions 21b and the fixed tray hook portions 20e, an urging spring 22 is installed and the urging spring 22 urges the movable tray hook portion 21b to approach the fixed tray hook portion 20e (i.e., urges the movable tray 21 upward). Incidentally, at the downstream-side end of the movable tray 21 with respect to the sheet discharging direction D1, an abutting portion 21c (fig. 4 and 5) contactable with the back surface of the fixed tray 20 is provided. The position where the abutting portion 21c contacts the fixed tray 20 (fig. 4) is the upper limit position of the rotation range of the movable tray 21.

The discharge tray 170 assembled as described above is mounted to the apparatus main assembly 101 by the four mounting portions 20c of the fixing tray 20. Incidentally, the discharge tray 170 (and the second discharge tray 171 located above the discharge tray 170) is mountable in and dismountable from the apparatus main assembly 101, and by removing both the discharge trays from the apparatus main assembly 101, a space for mounting the post-processing devices is secured in the intra-apparatus discharge space of the image forming apparatus 100.

[ details of the shape of the tray ]

Next, the shape and operation of the stacking surface formed by the discharge tray 170 including the movable tray 21 will be described. Fig. 4 is a sectional view of the discharge tray 170 when the movable tray 21 is in a standby state, and fig. 5 is a sectional view of the discharge tray 170 when the movable tray 21 is in a maximum rotation state. However, the standby state refers to a state in which no sheet is stacked on the discharge tray 170, and the maximum rotation state refers to a state in which the movable tray 21 is rotated downward most from the position of its standby state. The position of the movable tray 21 in the stand-by state is the first position in the present embodiment, and the position of the movable tray 21 in the maximum rotation state is the second position in the present embodiment. Further, in the following description, "upstream" or "downstream" indicates a positional relationship on an upstream side or a downstream side with respect to the sheet discharging direction D1.

The first stacking surface WX is a surface formed by the stationary tray 20 from the position W to the position X. The position W is a position of an upstream end with respect to the sheet discharging direction D1 in a region where the fixed tray 20 can support the lower surface of the sheet by the upper surface thereof, and the position X is a position of a downstream end with respect to the sheet discharging direction D1 in the region.

The second stacking surface YZ is a surface formed by the arc-shaped rib 21d of the movable tray 21 from the position Y to the position Z. That is, the second stacking surface YZ in the present embodiment is an imaginary surface that connects the upper end portions of the plurality of arc-shaped ribs arranged in the width direction. The position Y is a position of an upstream end with respect to the sheet discharging direction D1 in a region where the arc-shaped rib 21D can support the lower surface of the sheet, and the position Z is a position of a downstream end with respect to the sheet discharging direction D1 in the region.

The movable tray 21 is arranged offset toward the upstream side of the discharge tray 170 with respect to the sheet discharging direction D1. For example, an intermediate position V (a midpoint between the position Y and the position Z) of the second stacking surface with respect to the sheet discharging direction D1 is located upstream of an intermediate position U (a midpoint between the position W and the position X) of the first stacking surface, which is also an intermediate position of the entire discharge tray 170. A distance from an upstream end of the first stacking surface WX to an upstream end of the second stacking surface YZ is shorter than a distance from a downstream end of the first stacking surface WX to a downstream end of the second stacking surface YZ (WY < XZ).

An upstream end (Y) of the second stacking surface YZ is located in an upstream-side end region of the discharge tray 170. For example, when the range of the stacking surface of the discharge tray 170 is divided into four equal parts with respect to the sheet discharging direction D1, the upstream end (Y) of the second stacking surface YZ is located upstream of the upstream side quartering point Q1. On the other hand, the downstream end (Z) of the second stacking surface YZ extends to the downstream side of the intermediate position U of the discharge tray 170 with respect to the sheet discharging direction D1. However, when the range of the stacking surface of the discharge tray 170 is divided into four equal parts with respect to the sheet discharging direction D1, the downstream end (Z) of the second stacking surface YZ is located upstream of the downstream side quartering point Q3.

The rotation fulcrum P of the movable tray 21 is provided near the upstream end of the discharge tray 170. Specifically, the rotation fulcrum P is located upstream of the intermediate position U of the discharge tray 170 with respect to the sheet discharge direction D1, and the distance from the rotation fulcrum P to the position W is smaller than the distance from the rotation fulcrum P to the intermediate position U. In other words, the rotation fulcrum P is located on the upstream side of the upstream side quartering point Q1 of the stacking surface of the discharge tray 170 with respect to the sheet discharging direction D1.

Further, the rotation fulcrum P of the movable tray 21 is provided in the vicinity of the upstream side end portion of the movable tray 21 itself. Specifically, the rotation fulcrum P is located upstream of the intermediate position V of the movable tray 21 with respect to the sheet discharging direction D1, and the distance from the rotation fulcrum P to the position Y is smaller than the distance from the rotation fulcrum P to the intermediate position V. In other words, when the range of the second stacking surface is divided into four equal parts with respect to the sheet discharging direction D1, the rotation fulcrum P is located on the upstream side of the upstream side quartering point q1 of the second stacking surface of the movable tray 21 with respect to the sheet discharging direction D1.

Incidentally, in the illustrated configuration example, the rotation fulcrum P of the movable tray 21 is provided at a position closer to the upstream end of the discharge tray 170 within the above-described range and the upstream end of the movable tray 21 itself within the above-described range. For example, the distance (PW) from the rotation fulcrum P to the upstream end (W) of the discharge tray 170 with respect to the sheet discharge direction D1 is smaller than 1/8 of the range (WX) of the entire first stacking surface of the discharge tray 170. Further, the distance (PY) from the rotation fulcrum P to the upstream end (Y) of the second stacking surface YZ with respect to the sheet discharging direction D1 is smaller than 1/8 of the range (YZ) of the entire second stacking surface of the discharge tray 170.

In the standby state, the first stacking surface WX and the second stacking surface YZ are each constituted by an inclined surface inclined upward with respect to the vertical direction toward the downstream side with respect to the sheet discharging direction D1. That is, the fixed tray 20 and the movable tray 21 are inclined in the standby state, thereby generating a force for returning the sheet discharged on the discharge tray 170 toward the upstream side with respect to the sheet discharging direction.

The inclination angles of the first stacking surface WX and the second stacking surface YZ will be described specifically. The average inclination angle of the first stacking surface WZ differs between an upstream portion 91(W to Z) located on the upstream side of the downstream end of the second stacking surface YZ and a downstream portion 92(Z to X) located on the downstream side of the downstream end of the second stacking surface YZ. When the inclination angle in the upstream portion 91(W to Z) of the first stacked surface WX is θ a (degrees) and the inclination angle of the downstream portion 92(Z to X) of the first stacked surface WX is θ b (degrees), θ a > θ b is satisfied. Incidentally, the upstream portion and the downstream portion of the first stack surface WX are each formed in a planar shape inclined at a specific inclination angle θ a or θ b in the present embodiment. In the case where the inclination angle in each portion is not a specific angle, each of θ a and θ b refers to an average inclination angle.

The second stacking surface YZ is constituted such that an inclination angle of at least a portion upstream thereof is larger than an inclination angle θ a in an upstream portion of the first stacking surface WX in which positions of the second stacking surface YZ and the first stacking surface overlap with each other with respect to the sheet discharging direction D1. That is, when the inclination angle of the tangent to the arc rib 21d with respect to the horizontal plane is θ c (degrees), the inclination angle θ c gradually decreases from the upstream side toward the downstream side. At this time, such a structure is adopted that θ c > θ a is satisfied at least in an upstream-side end region where the inclination angle θ c of the second stacking surface YZ becomes maximum. In other words, when the inclination angle θ c of the second stacking surface YZ in the upstream side end portion region of the second stacking surface YZ is θ cmax, θ cmax is a value larger than θ a.

In the configuration example shown, settings are made such that θ a is 20 (degrees), θ b is 6 (degrees), and θ cmax is 32 (degrees). However, the inclination angle of the stacking surface is not limited thereto, but may also be appropriately changed according to the material and size of the main sheet assumed to be used, the surface properties of the material constituting the discharge tray 170, and the like.

When no sheet is stacked on the discharge tray 170, the movable tray 21 is held in a standby state in which the second stacking surface YZ protrudes the most upward from the first stacking surface WX due to the urging force of the urging spring. At this time, as shown in fig. 4, the entire second stacking surface YZ is located above the first stacking surface WX. The movable tray 21 rotates downward in accordance with a force from above, i.e., in accordance with the weight of the discharged sheets, as indicated by arrow B in fig. 5. The urging force of the urging spring 22 is set so that the abutting portion 21c of the movable tray 21 is held in contact with the fixed tray 21 even if a small force is applied, and therefore vibration noise is less likely to be generated.

On the other hand, the urging force of the urging spring 22 is set so that the movable tray 21 rotates to the maximum rotation state in accordance with the weight of the sheets in a state where a certain number or more of sheets are stacked on the discharge tray 170. As described later, in a state where the number of stacked sheets is small, the second stacking surface YZ having a larger inclination supports the sheets, so that the returning force acting on the sheets is larger, and thus higher alignment is obtained. As the stacking amount of sheets becomes larger, the lower end portion 21g of the movable tray 21 contacts the mounting surface 210 of the apparatus main assembly 101, so that the downward rotation of the movable tray 21 is restricted, and therefore the movable tray 21 is in the maximum rotation state. At this time, the urging spring 22 is in the state of maximum extension, but is set so that the extended urging spring 22 does not fall within the plastic deformation range. By performing such setting, even when the movable tray 21 is artificially rotated by mistake, the action of the biasing spring 22 is not impaired. Further, in the maximum rotation state, the second stacking surface is withdrawn downward from the first stacking surface at least in a range from the intermediate position V to the downstream end (Z) of the second stacking surface.

With the movable tray 21 configured as described above, the rotation fulcrum thereof is provided at the upstream-side end portion of the discharge tray 170 with respect to the sheet discharge direction such that the inclination angle θ c of the second stacking surface YZ gradually approaches the inclination angle θ a from θ cmax as the number of stacked sheets increases. Therefore, when the number of stacked sheets increases, the returning force acting on the sheets by the second stacking surface YZ decreases, and on the other hand, as the second stacking surface YZ decreases, the degree of inclination of the sheets at the portion supported by the second stacking surface YZ becomes smaller. That is, the posture of the sheet bundle stacked on the discharge tray 170 approaches the horizontal plane, and the lower surface position of the sheet bundle is lowered. Therefore, as described later, even if the number of sheets stacked on the tray becomes large, the sheets can be smoothly discharged.

Incidentally, the inclination angle θ b in the downstream side portion 92 of the fixed tray 20 is set to an angle smaller than the inclination angle θ a and the maximum inclination angle (θ cmax) in the upstream side portion 91. This is because the occupation range of the discharge tray 170 with respect to the vertical direction is prevented from being excessively increased, and in the case of the present embodiment, a space for the second discharge tray 171 disposed above the discharge tray 170 and sheets to be stacked thereon is ensured. In the downstream side portion 92 as a support portion, in a case where a long sheet is discharged in the sheet discharging direction, the discharge tray supports a downstream side portion of the long sheet above the second stacking surface YZ of the movable tray 21. Further, the inclination angle θ b of the downstream side portion 92 is set to a small value, and therefore, with a relatively large sheet, it is possible to suppress the feed resistance exerted on the sheet from the stacking surface during sheet discharge from becoming large and thus incorrect discharge from occurring. However, the reason why the inclination angle θ b is not made 0 or less at the downstream portion of the fixed tray 20 is that a returning force should be applied to the sheet even at an arbitrary position of the discharge tray 170.

Incidentally, the fixed tray 20 and the movable tray 21 that constitute the first stacking surface WX and the second stacking surface YZ include ribs each extending in the sheet discharging direction, and particularly the second stacking surface is formed by an arc-shaped rib 21 d. Such ribs effectively reduce the feeding resistance exerted on the sheet from the tray surface when the sheet is discharged onto the discharge tray 170. Further, the second stacking surface YZ is curved so that the degree of inclination becomes smaller toward the downstream side, and therefore, regardless of the rotation angle of the movable tray 21, it is possible to prevent a large step or groove from being generated at the boundary between the second stacking surface YZ and the first stacking surface, which causes sheet jamming.

Further, the arc-shaped rib 21d of the movable tray 21 slightly protrudes upward from the first stacking surface WX (i.e., upward from the guide rib of the fixed tray 20) in the vicinity of the upstream end position Y of the second stacking surface YZ and in the vicinity of the downstream end position Z of the second stacking surface YZ. By forming the arc-shaped ribs 21d at a slightly higher height, the front and rear ends of the sheet with respect to the sheet discharging direction can be prevented from being caught by the longitudinal end portions of the slits 20b of the fixing tray 20. Further, a downstream end of each slit 20b with respect to the sheet discharging direction is formed in a tapered shape such that the shape thereof becomes narrower toward the downstream side. Thus, even if the movable tray 21 is rotated downward from the standby state and a sheet is newly discharged in a state where the downstream end portion of each arc-shaped rib 21d is located below the associated slit 20b, the sheet can be prevented from being caught by the downstream end of the slit 20 b.

Further, the first stacking surface WX is constituted by an upper surface of a fixed tray 20, the fixed tray 20 being a plate-like member expanding in the sheet discharging direction and the width direction, and the second stacking surface YZ is constituted by a rib-like member protruding through a slit provided in the plate-like member and extending in the sheet discharging direction. Therefore, most of the openings of the slits 20b are closed by the arc-shaped ribs 21d when the movable tray 21 is in the standby state, and at least a part of the openings of the slits 20b are closed by the sheet in a state where the movable tray 21 is rotated downward by the weight of the sheet. Therefore, when the opening for moving the movable tray 21 upward and downward with respect to the fixed tray 20 is provided, the possibility of foreign matter falling on the back side of the discharge tray 170 can be suppressed.

Incidentally, the fixed tray 20 is provided with a removal groove 20a for allowing sheets to be removed therefrom. The removal groove 20a extends toward an end at one side (the front side of the image forming apparatus) of the discharge tray 170 with respect to the width direction D2. Further, the removal groove 20a is provided at a position overlapping the movable tray 21 with respect to the sheet discharging direction D1, and is formed as a concave shape portion that makes the upper surface 20s of the fixed tray 20 concave downstream. In order to allow the user to access the sheet through the removal groove 20a, the portion of the arc-shaped rib 21D that overlaps the removal groove 20a at a position relative to the width direction D2 is formed only outside the removal groove 20a with respect to the sheet discharging direction D1. Incidentally, the inclination angle of the downstream side wall surface of the removal groove 20a is also set to an angle capable of suppressing the leading end of the sheet from being jammed.

Further, each slit 20b provided in the fixed tray 20 has a minimum necessary length, and the fixed tray 20 is formed as a continuous member with respect to the width direction D2 at each of the upstream side and the downstream side with respect to the movable tray 21. This has not only an advantage of ensuring the rigidity of the fixing tray 20 but also a shape in which fluidity is taken into consideration when the fixing tray 20 is prepared by injection molding of a resin material. An example of the resin material is PC + ABS (a copolymer of polycarbonate and acrylonitrile-butadiene-styrene resin). Incidentally, the fixed tray 20 may be a single member as a whole, but may also be a combination of an upstream side portion and a downstream side portion molded as separate members, for example.

[ operation of the Movable tray ]

The state of the discharge tray 170 configured as described above when the sheets are discharged onto the stacking surface of the discharge tray will be described. Fig. 6 is a sectional view of the first discharge portion 190 illustrating a state during the discharge of the first sheet S by the discharge roller 160, and fig. 7 is a sectional view of the first discharge portion 190 illustrating a state in which the discharged first sheet S is aligned by the stacking surface of the discharge tray 170.

As illustrated in fig. 6, the discharge roller 160 is configured to discharge the sheet S in a posture such that the sheet S is inclined upward with respect to the horizontal direction toward the downstream side with respect to the sheet discharging direction D1. In other words, the discharge roller 160 includes a roller pair arranged at a nip angle (an angle with respect to a direction perpendicular to the inter-roller axial direction when the roller pair sends out a sheet from its nip) at which the sheet is slightly discharged upward. Further, the discharge roller 160 is provided with a rigidity imparting member that imparts rigidity to the sheet S by bending (waving) the sheet S as viewed from the downstream side in the sheet discharging direction D1. Therefore, the sheet S is discharged from the position where the sheet S is nipped by the discharge rollers 160 to the downstream side in the sheet discharging direction D1 while having an arc-shaped trajectory toward the leading end side thereof. The sheet S contacts the movable tray 21 of the discharge tray 170 in a standby state at its leading end at the position P1, and moves while sliding on the fixed tray 20 and the movable tray 21, and then the trailing end of the sheet is sent out by the discharge roller 160.

As shown in fig. 7, the sheet S whose rear end is sent out is returned toward the upstream side (arrow R) in the sheet discharging direction in accordance with the degree of inclination of the stacking surface of the discharge tray 170, particularly the degree of inclination of the stacking surface (second stacking surface) formed by the movable tray 21. Then, the sheet S is stopped by abutting the rear end of the sheet S with respect to the sheet discharging direction D1 against the registration wall 162 provided to the apparatus main assembly 101. The alignment wall 162 is a reference surface that aligns the position of the sheet S by its contact with the rear end of the sheet S discharged on the discharge tray 170.

The behavior of the first sheet S when the first sheet S moves toward the alignment wall 162 is affected by the magnitude of the frictional force acting between the sheet S and the stacking surface of the discharge tray 170. With respect to the second sheet S, the influence of friction between the sheet S and the discharge tray 170 becomes small, and instead, the influence between the sheets becomes large.

The above-described position P1 (a position where the leading end of the first sheet is assumed to be first in contact with the stacking surface of the discharge tray 170) may preferably be a position spaced apart from the discharge roller 160 to some extent in the sheet discharging direction D1, and may preferably be at substantially the same height as the height of the nip of the discharge roller 160. In addition, the movable tray 21 is formed such that the orientation of the sheets S at the leading end portion and the contact angle of the sheets S with the second stacking surface are not too large. With the movable tray 21 in the present embodiment, in the stand-by state, the inclination degree becomes gentle toward the downstream side from the maximum inclination angle (32 degrees) at the upstream end, which is substantially equal to the inclination angle (6 degrees) of the fixed tray 20 at the downstream portion. By adopting such a configuration, the feeding resistance exerted on the sheets S from the stacking surface is suppressed, and the maximum number of sheets that can be stacked on the discharge tray 170 is ensured, so that sheets with low rigidity (rigidity) can be stably discharged, and the alignment of the stacked sheets is improved.

Incidentally, the sheets discharged by the discharge roller 160 include sheets such as recycled paper and thin paper, and these sheets have a tendency that the degree of bending (curling) of the sheet end becomes large, for example, under a high humidity environment. Such a case where sheets having a large degree of curling are stacked relatively in large numbers will be described using fig. 8 and 9. Fig. 8 is a sectional view of the first discharge portion 190 and the second discharge portion 191 in a state where a plurality of curled sheets are stacked on the discharge tray 170. Fig. 9 is a sectional view of the first discharge portion 190 and the second discharge portion 191 in a state where the movable tray 21 is fixed at the stand-by state position as a reference example. However, in the present embodiment, the number of sheets illustrated in fig. 8 and 9 is not intended to designate the actual number of sheets.

In the image forming apparatus of the present embodiment, both a small-size sheet such as an a 4-size sheet and a large-size sheet such as an A3-size sheet can be used. In either size, curling occurs, but the curled sheet is raised at its ends in correspondence with the degree of bending (curvature). In particular, the small-sized sheet is short as compared with the large-sized sheet, so that the sheet is liable to form a steep inclined surface due to curling. In addition, as described above, the stacking surface of the discharge tray 170 is configured such that the inclination angle of the upstream side with respect to the sheet discharging direction is larger than the inclination angle of the downstream side with respect to the sheet discharging direction. The small-size sheets are mainly supported by the upstream-side stacking surface that is more inclined, so that the curling effect of the sheets is liable to occur due to the synergistic effect with the inclination of the stacking surface.

In fig. 8, the small-size sheets S are stacked in a curled state. In the case of the small-size sheets S, the leading end of the sheet is located on the upstream side of the downstream end of the movable tray 21 in a state where the trailing end of the sheet with respect to the sheet discharging direction D1 contacts the registration wall 162. The sheet S is curled such that a lower surface (a surface opposite to the stacking surface of the discharge tray 170) as an image surface takes a protruding shape. Therefore, the stacked sheaf T of the sheets S contacts and is supported by the stacking surfaces of the fixed tray 20 and the movable tray 21 at the middle inclined portion, and on the other hand, the stacked sheaf T is lifted at the end portion with respect to the sheet discharging direction D1.

Here, by the weight of the stacked sheaf T, the movable tray 21 is rotated downward from the position of the standby state (fig. 6 and 7), so that a part of the arc-shaped rib of the movable tray 21 is withdrawn downward from the upper surface of the fixed tray 20 through the slit. Further, the inclination degree of the stacking surface formed by the movable tray 21 also becomes gentle compared to the stand-by state. In other words, by increasing the stacking amount of the stacked sheaf, at least a part of the second stacking surface is withdrawn downward from the first stacking surface, so that the degree of inclination of the second stacking surface with respect to the horizontal plane becomes small. Therefore, in the case where the discharged sheets S are curled, a situation in which the discharge space on the discharge tray 170 is occupied by the stacked sheaf T made up of a relatively small number of sheets S is avoided.

Incidentally, in the reference example shown in fig. 9, the movable tray 21 is fixed at the position of the standby state by using the spacer 203, and therefore the inclination and height of the second stacking surface do not change even when the weight of the stacked sheaf T increases. Therefore, in a case where the discharged sheets S are curled, the downstream ends of the sheets are lifted, so that the discharge space on the discharge tray 170 is occupied by the stacked sheaf T composed of a relatively small number of sheets S.

In this case, compared to the state shown in fig. 8 in which the movable tray 21 is rotated, the contact angle at which the leading end of the sheet S discharged from the discharge roller 160 contacts the upper surface of the stacked sheaf T becomes large, with the result that the sheet S collides with the upper surface of the stacked sheaf T and is easily subjected to a large force. Further, when the sheet S is discharged while sliding on the upper surface of the stacked sheaf T (particularly on the curled portion at the downstream portion of the stacked sheaf T), the feeding resistance becomes large. As a result, there is a possibility that a state occurs in which the sheet S is not satisfactorily sent out from the discharge roller 160 and thus the trailing end of the sheet S is held in the nip of the discharge roller 160 without falling on the discharge tray 170 (trailing end inclination). Further, when the succeeding sheet reaches the discharge roller 160 in a state where the trailing end of the current sheet is held near the nip portion of the discharge roller 160, there is a possibility that the leading end of the succeeding sheet collides with the trailing end of the current sheet and thus the current sheet and the succeeding sheet cannot be correctly discharged.

On the other hand, in the present embodiment, as described above, the movable tray 21 is rotated about the rotation fulcrum provided in the vicinity of the upstream-side end portion of the discharge tray 170, so that the height of the upper surface of the stacked sheaf T is lowered, and therefore not only the discharge space is secured but also the degree of inclination of the stacked sheaf T of sheets is made small. In this way, as compared with the reference example shown in fig. 9, the resistance received by the discharged sheet is reduced, so that the occurrence of improper discharge is suppressed, and therefore, smooth discharge of the sheet can be achieved.

Further, in the present embodiment, an in-apparatus discharge type configuration is adopted, thereby limiting the height of the discharge space of the discharge tray 170. In this case, the configuration in which the movable tray 21 rotates about the rotation fulcrum provided in the vicinity of the upstream-side end portion of the discharge tray 170 has an advantage that a discharge space can be secured. In particular, in the present embodiment, above the discharge tray 170 as the first stacking portion, the second discharge tray 171 as the second (another) discharge portion is provided, and therefore, there is a great advantage of ensuring a discharge space. In the present embodiment, the gaps (intervals) M between the central five arc-shaped ribs 21d are narrow, so that a sheet having a small dimension with respect to the width direction can be stably supported by the central arc-shaped ribs 21 d.

[ example 2]

In embodiment 2, instead of the configuration of embodiment 1 in which the movable tray 21 is rotated by the sheet weight, a configuration example in which a driving source for driving and rotating the movable tray 21 is provided will be described. Hereinafter, elements similar in configuration and action to those in embodiment 1 are denoted by reference numerals or symbols common to embodiments 1 and 2, and descriptions thereof will be omitted.

Fig. 10 is a perspective view showing the movable tray 21 and its driving configuration in the present embodiment. The movable tray 21 is provided with sector gears 21e and 21e at two positions with respect to the width direction at a downstream-side end portion opposite to the rotation shaft 21a with respect to the sheet discharging direction D1. The sector gears 21e and 21e are connected to the input/output shaft 220 through output gears 222 and 222. At an end of the input/output shaft 220, an input gear 221 that meshes with a gear 211 of a rotation motor 212 as a drive source is provided. Therefore, by the forward rotation and the reverse rotation of the rotation motor 212, the movable tray 21 is driven through the gear train, so that the movable tray 21 is rotated upward and downward.

As the rotation motor 212, a stepping motor can be suitably used. In this case, the amount of rotation of the movable tray 21, that is, the inclination angle of the movable tray 21 can be set to an arbitrary value with high accuracy regardless of the weight of the sheet on the tray. Therefore, depending on whether the environment is a high humidity environment in which curling of sheets is likely to occur or whether the stacking height of each sheet (one sheet) is large, for example, setting may be made so that the amount of rotation of the movable tray 21 differs even when the number of stacked sheets is the same. That is, an appropriate amount of rotation may be set according to the operating conditions of the image forming apparatus.

By using a sensor for detecting the position of the movable tray 21 (for example, a switch for detecting whether or not the movable tray 21 is in the standby state position), the amount of rotation of the movable tray 21 can be controlled with high accuracy. Further, above the movable tray 21, a sensor for detecting the height of the upper surface of the sheet bundle stacked on the discharge tray 170 is provided, and the amount of rotation of the movable tray 21 is controlled based on the detection result thereof, so that the height of the upper surface of the sheet bundle can be accurately controlled.

Incidentally, in the present embodiment, the rotary motor 212 is used as a drive source, and the movable tray 21 is rotated by the gear transmission mechanism shown in fig. 10, but other drive configurations may be used.

(modified example)

In embodiments 1 and 2 described above, it is described that the inclined surface is constituted by the upper surface 20s of the fixed tray 20 and the stacking surface is formed by the plurality of arc-shaped ribs 21d provided on the movable tray 21. However, a configuration may also be adopted in which the inclined surface is constituted by a plurality of rib members and the stacked surface is provided on a plate-like member including slits through which the rib members pass.

Further, instead of the arc-shaped ribs 21d, ribs each having an upper end portion constituted by a curved portion other than the arc shape may be provided. Also, in this case, the upper end portion of each rib may be appropriately inclined upward toward the downstream side in the sheet discharging direction D1 in the standby state and may be appropriately curved (including a portion curved in a zigzag shape) such that the inclination angle with respect to the horizontal plane becomes smaller toward the downstream side in the sheet discharging direction D1.

Further, in the present embodiment, the image forming apparatus including the electrophotographic type image forming portion is described, but the present invention is also effective in other types of image forming apparatuses. For example, in an image forming apparatus including an ink jet type printing unit as an image forming portion, there is also a case where sheet curl occurs along with image formation, and therefore, the present invention is suitably applied thereto.

As the image forming apparatus, an image forming apparatus including a sheet processing portion in which a sheet on which an image is formed by the image forming portion is received and then punched, folded, or the like may also be used.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.