JP2012254873A - Sheet discharging device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably fulfill a function to detect an amount of sheets stored, and achieve reduced size and cost.SOLUTION: A sheet discharging device includes: discharging means 19a and 19b for discharging sheets; a stacking part 20 on which sheets discharged from the discharging means 19a and 19b are stacked; and a stack amount detector 29 for detecting an amount of sheets stacked on the stacking part 20. The discharging means 19a and 19b are configured to bring a sheet P0 on the top of the sheets stacked on the stacking part 20 to near the stack amount detector 29 so that the top sheet P0 is detected by the stack amount detector 29.

Description

  The present invention relates to a sheet discharging apparatus and an image forming apparatus including the sheet discharging apparatus.

  In recent years, image forming apparatuses such as copiers, printers, facsimiles, and multi-function machines have been demanded to improve operability as well as downsizing the apparatus. One of the functions for improving the operability in the image forming apparatus is a full load detection function for detecting that the paper discharged to a stacking unit such as a paper discharge tray is full.

  For example, as described in Patent Document 1, as a means for detecting the full state of paper, a filler that detects the amount of paper loaded by contacting the upper surface of the paper (paper bundle) stacked on the stacking unit, etc. There is. However, in this configuration, there is a filler at the top of the stacked paper, and thus there is a problem that the filler becomes an obstacle when the user handles the stacked paper.

Therefore, conventionally, Patent Document 2 proposes a paper stacking device that can detect the full state of paper without using a filler.
As shown in FIG. 7, the paper stacking device described in Patent Document 2 includes a paper discharge tray 200 having an inclined placement surface and a paper rear end that regulates the rear end of the paper P discharged to the paper discharge tray 200. A regulating member 300 and a transmissive photo interrupter 400 as a detecting means for detecting the paper P are provided. In this sheet stacking apparatus, the sheet P discharged onto the sheet discharge tray 200 by the pair of sheet discharge rollers 500a and 500b moves downward of the inclined sheet discharge tray 200, and the sheet trailing edge regulating member 300 moves the sheet. The rear end of P is supported. However, when the height of the stacked paper P exceeds the upper end position of the paper trailing edge regulating member 300, the uppermost paper moves to the photo interrupter 400 side, and the photo interrupter 400 is shielded by the paper. Thereby, it is detected that the paper is full.

  However, the paper stacking device described in Patent Document 2 has the following problems.

  Since the paper stacking apparatus described in Patent Document 2 uses the self-weight generated in the paper as a conveying force for moving the paper to the photo interrupter side by inclining the stacking surface of the discharge tray, the stacking surface Must have a certain inclination angle. For this reason, there is a problem that the apparatus size is increased.

  Further, in the paper stacking device described in Patent Document 2, when the resistance due to friction between the papers increases due to the type of paper, the size of the papers (contact area between the papers), the moisture content of the papers, and the like, Even if is tilted, the paper may be stationary and the paper may not be transported to the photo interrupter side. In addition, even if an adsorption force is generated between the stacked sheets due to the influence of the charge received when the sheet passes through the image transfer apparatus, the sheet may not be conveyed to the photo interrupter side due to the adsorption force. In addition, even if the transport force due to the weight of the paper is superior to the friction force between the paper and the suction force due to charging, and the paper can be transported to the photo interrupter side, the time required for the transport becomes longer and the load is full. May not be detected at a stable timing.

  Furthermore, in the configuration in which the conveyance force is obtained by the weight of the paper, since a large conveyance force cannot be obtained, a general-purpose contact type such as a filler and a photo interrupter that detects the paper by contact with the paper or a switch sensor. This detection means cannot be used, and the manufacturing cost may increase. In order to obtain a sufficient sheet conveying force, it may be proposed to separately provide a conveying unit such as a conveying roller. In this case, however, the conveying unit, a driving unit for driving the conveying unit, or an existing driving unit may be proposed. It is necessary to provide a transmission member such as a gear for transmitting the driving force from the means to the conveying means, which increases the number of parts and makes it difficult to reduce the cost and size.

  Therefore, in view of such circumstances, the present invention can stably exhibit a sheet stacking amount detection function, and can reduce the size and cost, and the sheet discharging apparatus. An image forming apparatus provided with

  In order to solve the above-described problems, the present invention provides a discharge unit that discharges a sheet, a stacking unit that stacks sheets discharged by the discharge unit, and a stacking amount that detects a stacking amount of sheets stacked on the stacking unit. In the sheet discharge apparatus including the detection unit, the uppermost sheet stacked on the stacking unit is conveyed to the stacking amount detection unit side by the discharge unit, and the uppermost sheet is detected by the stacking amount detection unit. It is configured as described above.

  According to the sheet discharging apparatus of the present invention, the uppermost sheet stacked on the stacking unit is conveyed to the stacking amount detecting unit side by the discharging unit, so that the sheet stacking amount can be detected. As described above, according to the present invention, since the conveying force when the uppermost sheet is conveyed to the stacking amount detecting means side is obtained by the discharging means, a sufficient conveying force can be obtained. As a result, even if an increase in frictional force between sheets due to the type of sheet or the like, or adsorption due to electrification between sheets occurs, the uppermost sheet is reliably transferred to the stacking amount detection means side regardless of them. It can be transported and a stable load detection function can be exhibited.

  Further, since the discharging means is used as the means for conveying the uppermost sheet, it is not necessary to separately provide a dedicated conveying means or a driving means for conveying the uppermost sheet. For this reason, the increase in the number of parts can be suppressed, and cost reduction and size reduction can be achieved.

  Further, according to the sheet discharging apparatus according to the present invention, it is not necessary to incline the mounting surface of the stacking unit in order to obtain the conveying force of the uppermost sheet, which can contribute to downsizing of the apparatus.

  Further, according to the sheet discharging apparatus according to the present invention, since a sufficient conveying force can be obtained, it is possible to use a general-purpose contact type detection unit as the stacking amount detection unit.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a paper discharge device mounted on the image forming apparatus. It is an enlarged view of the paper discharge device. It is a schematic block diagram of other embodiment of the said paper discharge apparatus. It is a schematic block diagram of further another embodiment of the paper discharge device. FIG. 3 is a schematic configuration diagram of an embodiment in which the paper discharge device includes a suppressing member that suppresses curling of paper. It is a schematic block diagram of the conventional paper discharge apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, in each drawing for explaining the embodiment of the present invention, components such as members and components having the same function or shape are once described by giving the same reference numerals as much as possible. The description is omitted.

First, an overall configuration and operation of an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG.
The image forming apparatus shown in FIG. 1 is a color laser printer, and four process units 1Y, 1M, 1C, and 1Bk as image forming units are detachably mounted on the apparatus main body 100. Each process unit 1Y, 1M, 1C, 1Bk contains developers of different colors of yellow (Y), magenta (M), cyan (C), and black (Bk) corresponding to the color separation components of the color image. The configuration is the same except that. As the developer, a one-component developer composed of toner may be used, or a two-component developer composed of toner and carrier may be used.

  Specifically, each of the process units 1Y, 1M, 1C, and 1Bk includes a drum-shaped photosensitive member 2 as a latent image carrier, a charging roller 3 that charges the surface of the photosensitive member 2, and the like, A developing device 4 that supplies toner to the surface of the photoreceptor 2 and a cleaning device that includes a cleaning blade 5 for cleaning the surface of the photoreceptor 2 are provided. In FIG. 1, only the photoconductor 2, the charging roller 3, the developing device 4, and the cleaning blade 5 included in the yellow process unit 1 </ b> Y are denoted by reference numerals. Omitted.

  In FIG. 1, an exposure device 6 as an exposure means for exposing the surface of the photoreceptor 2 is disposed above each process unit 1Y, 1M, 1C, 1Bk. The exposure device 6 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each photoreceptor 2 with laser light based on image data.

  A transfer device 7 is disposed below each process unit 1Y, 1M, 1C, 1Bk. The transfer device 7 has an intermediate transfer belt 8 constituted by an endless belt as a transfer body. The intermediate transfer belt 8 is stretched around a driving roller 9 and a driven roller 10 as support members. When the driving roller 9 rotates counterclockwise in the figure, the intermediate transfer belt 8 is in a direction indicated by an arrow in the figure. It is comprised so that it may run around (rotate).

  Four primary transfer rollers 11 a to 11 d as primary transfer means are disposed at positions facing the four photoconductors 2. Each primary transfer roller 11a to 11d presses the inner peripheral surface of the intermediate transfer belt 8 at each position, and a primary transfer nip is formed at a position where the pressed portion of the intermediate transfer belt 8 and each photoconductor 2 are in contact with each other. Is formed. The primary transfer rollers 11a to 11d are connected to a power source (not shown), and a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied to the primary transfer rollers 11a to 11d. ing.

  A secondary transfer roller 12 as a secondary transfer unit is disposed at a position facing the drive roller 9. The secondary transfer roller 12 presses the outer peripheral surface of the intermediate transfer belt 8, and a secondary transfer nip is formed at a location where the secondary transfer roller 12 and the intermediate transfer belt 8 are in contact with each other. Similarly to the primary transfer rollers 11 a to 11 d, the secondary transfer roller 12 is connected to a power source (not shown), and a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to the secondary transfer roller 12. It is to be applied.

  A belt cleaning device 13 for cleaning the surface of the intermediate transfer belt 8 is disposed on the outer peripheral surface on the right end side of the intermediate transfer belt 8 in the drawing. A waste toner transfer hose (not shown) extending from the belt cleaning device 13 is connected to an entrance of a waste toner container 14 disposed below the transfer device 7.

  A sheet feeding device 15 as a sheet feeding device is disposed below the apparatus main body 100. The paper feeding device 15 includes a paper feeding cassette 16 that stores paper P as a sheet (recording medium) for recording an image, and a paper feeding roller 17 that feeds the paper P stored in the paper feeding cassette 16. The paper P includes thick paper, postcard, envelope, plain paper, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, and the like. Further, the sheet feeding device 15 according to the present embodiment is configured to be able to supply an OHP sheet or an OHP film as a sheet other than the sheet.

  On the other hand, a paper discharge device 18 as a sheet discharge device is disposed on the upper portion of the apparatus main body 100. The paper discharge device 18 includes a pair of paper discharge rollers 19a and 19b that are a pair of discharge rotating bodies as discharge means for discharging paper, and a stacking unit 20 on which the paper discharged by the paper discharge rollers 19a and 19b is stacked. .

  In the apparatus main body 100, a conveyance path R for conveying the paper P from the paper feed cassette 16 through the secondary transfer nip to the paper discharge rollers 19a and 19b is disposed. In the transport path R, a pair of registration rollers 21 a and 21 b serving as a feeding unit that feeds the paper P to the secondary transfer nip is disposed upstream of the position of the secondary transfer roller 12 in the paper transport direction. Yes. Further, a fixing device 22 for fixing the unfixed image transferred to the paper P is disposed downstream of the position of the secondary transfer roller 12 in the paper transport direction. The fixing device 22 includes a fixing roller 23 as a fixing member that is heated by a heat source, and a pressure roller 24 as a pressure member that pressurizes the fixing roller 23. A fixing nip as a fixing unit is formed at a position where the fixing roller 23 and the pressure roller 24 are in pressure contact with each other.

The image forming apparatus operates as follows.
When the image forming operation is started, the photosensitive members 2 of the process units 1Y, 1M, 1C, and 1Bk are rotated in the clockwise direction in FIG. 1, and the surface of each photosensitive member 2 is made to have a predetermined polarity by the charging roller 3. It is charged like this. Next, based on the image information of the original read by a reading device (not shown), the exposure device 6 irradiates the charged surface of each photoconductor 2 with laser light, and an electrostatic latent image is formed on the surface of each photoconductor 2. Is done. At this time, the image information to be exposed on each photoconductor 2 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. As the electrostatic latent image formed on the photosensitive member 2 is supplied with toner by each developing device 4, the electrostatic latent image is visualized (visualized) as a toner image.

  Subsequently, the driving roller 9 that stretches the intermediate transfer belt 8 is rotationally driven, and the intermediate transfer belt 8 is caused to run in the direction of the arrow in the drawing. In addition, a constant voltage having a polarity opposite to the toner charging polarity or a voltage controlled by a constant current is applied to each primary transfer roller 11 a to 11 d, so that each primary transfer roller 11 a to 11 d and each photoconductor 2 are connected to each other. A transfer electric field is formed at the primary transfer nip. Then, the toner images of the respective colors on the respective photoconductors 2 are sequentially superimposed and transferred onto the intermediate transfer belt 8 by the transfer electric field formed in the primary transfer nip. Thus, the intermediate transfer belt 8 carries a full-color toner image on its surface.

  Further, the toner on each photoreceptor 2 that could not be transferred to the intermediate transfer belt 8 is removed by the cleaning blade 5. Next, the surface of each photoconductor 2 is subjected to a static elimination action by a static eliminator (not shown), and the surface potential is initialized to prepare for the next image formation.

  On the other hand, in the paper feeding device 15, the paper feeding roller 17 rotates to feed the paper P from the paper feeding cassette 16 to the transport path R. The fed paper P is timed by the registration rollers 21 a and 21 b and fed to the secondary transfer nip between the secondary transfer roller 12 and the intermediate transfer belt 8. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 8 is applied to the secondary transfer roller 12, thereby forming a transfer electric field in the secondary transfer nip. Then, the toner image on the intermediate transfer belt 8 is collectively transferred onto the paper P by the transfer electric field formed in the secondary transfer nip. Alternatively, the toner image on the intermediate transfer belt 8 may be transferred onto the paper P by applying a transfer voltage having the same polarity as the toner charging polarity to the driving roller 9.

  Further, the toner remaining on the intermediate transfer belt 8 that could not be transferred onto the paper P is removed by the belt cleaning device 13. The removed toner is conveyed to the waste toner container 14 through a waste toner transfer hose (not shown) and collected.

  The sheet P on which the toner image has been transferred is conveyed to the fixing unit 22 and the sheet P is heated and pressed by the fixing roller 23 and the pressure roller 24 to fix the toner image. Thereafter, the paper P is conveyed between the pair of paper discharge rollers 19a and 19b, and the paper discharge rollers 19a and 19b rotate while sandwiching the paper P, whereby the paper P is discharged to the stacking unit 20.

  The above description is an image forming operation when a full-color image is formed on a recording medium. A single color image is formed using any one of the four process units 1Y, 1M, 1C, and 1Bk, and 2 Two or three process units can be used to form a two or three color image.

Next, the configuration of the paper discharge device will be described in detail with reference to FIG.
As shown in FIG. 2, the stacking unit 20 supports a placement surface 25 that supports the lower surface of the discharged paper P and a rear end of the discharged paper P in the discharge direction (the direction of arrow A in the figure). And a rear end support surface 26. The pair of paper discharge rollers 19 a and 19 b are disposed at a predetermined height from the placement surface 25 above the rear end paper surface 26 side of the stacking unit 20. Further, a top of the rear support surface 26, a pair of discharge rollers 19a, the lower portion near the lower side of the discharge roller 19a of 19b, which can penetrate the rear end of the specific paper P ₀ recess 27 is formed. A transmissive optical sensor 29 having a light emitting part and a light receiving part is disposed in the vicinity of the concave part 27, and light emitted from the light emitting part passes through the concave part 27 and is received by the light receiving part. It has become so.

The paper discharge device configured as described above operates as follows.
When the paper P is sequentially discharged out of the apparatus by the pair of paper discharge rollers 19 a and 19 b rotating in the direction of the arrow in FIG. 2, the discharged paper P is stacked on the placement surface 25 of the stacking unit 20. . After that, when the stacking amount of the sheets P gradually increases, the uppermost sheet P ₀ among the stacked sheets P comes into contact with the lower discharge roller 19a. In this state, the pair of paper discharge rollers 19a and 19b rotate in the same direction as the rotation direction when discharging the paper P (the direction of the arrow in FIG. 2), and as shown in FIG. P ₀ is conveyed into the recess 27 by the rotating lower discharge roller 19a. Then, the uppermost sheet P ₀ sent into the recess 27 abuts against the abutting portion 28 on the back side of the recess 27 and stops. As described above, when the uppermost sheet P ₀ is stationary in the recess 27, the light emitted from the light emitting unit of the optical sensor 29 is blocked by the sheet P ₀ and is not received by the light receiving unit. As a result, it is detected that the stacked sheets P are full.

  When the full state is detected by the optical sensor 29, the fact is notified to the user or the like, and the subsequent discharge of the paper is stopped, so that the paper can be prevented from overflowing from the stacking unit 20. Alternatively, when the full load state is detected, if there are sheets to be discharged such as sheets in the middle of printing in the apparatus, the driving of the discharge rollers 19a and 19b is continued until at least the sheets are discharged outside the apparatus. You may comprise as follows. In this case, when the driving of the apparatus is resumed, it is possible to avoid the occurrence of a problem such as a jam due to the paper remaining in the apparatus being jammed.

In the embodiment shown in FIG. 2, a transmission type optical sensor is used as the stacking amount detection means for detecting the stacking amount (full load state) of paper. However, a reflection type optical sensor can also be used. . When a reflection type optical sensor is used, the light from the light emitting portion irradiated by the concave portion 27 is reflected by the uppermost sheet P ₀ that has entered the concave portion 27, and the light receiving portion receives the reflected light. Light is received and a full state is detected. Further, as the load amount detection means, instead of the non-contact detection means such as the optical sensor, a general-purpose contact detection means for detecting the paper by contacting the paper can be used. Examples of the contact-type detection means include a filler, a photo interrupter, and a switch sensor that detect the sheet by contacting the sheet.

Referring to FIG. 3, the lower side of the discharge roller 19a will be described conveying force at the time of conveying the paper P ₀ of the highest level.
Stacking amount of the sheets P in the stacking portion 20 increases, the sheet P ₀ of the uppermost contacts the lower side of the discharge rollers 19a, between the lower discharge roller 19a and the sheet P ₀ of the uppermost The contact force (repulsive force) N shown in FIG. The greater the contact force N is, that is, the stronger the uppermost sheet P ₀ and lower discharge roller 19a are in contact, the lower the discharge roller 19a the conveying force F applied to the uppermost sheet P _0. Will grow. The transport force F also increases as the friction coefficient μ1 between the uppermost sheet P ₀ and the lower discharge roller 19a increases. Accordingly, when the conveyance force F applied to the uppermost sheet P ₀ is expressed using the contact force N and the friction coefficient μ1, the following equation (1) is obtained.

  F = μ1 × N (1)

However, in practice, with respect to the conveyance force F applied to the sheet P ₀ of the uppermost, the frictional force generated between the sheet P ₀ of the uppermost and the sheet P ₁ thereunder acts become resistant R. For this reason, when the conveying force F is expressed by using the friction coefficient μ2 between the uppermost sheet P ₀ and the lower sheet P ₁ in addition to the contact force N and the friction coefficient μ ₁ , the following formula ( 2).

  F = (μ1−μ2) × N (2)

From the formula (2), to obtain the conveying force F, the friction coefficient μ1 between the discharge roller 19a of the sheet P ₀ and the lower top-level therebelow the sheet P ₀ of the uppermost sheet P _It is necessary to set larger than the friction coefficient μ2 between ₁ . For this reason, it is preferable to use a member such as rubber having a high friction coefficient as the surface material of the lower paper discharge roller 19a. Further, by using a material of high friction coefficient on the surface material of the lower discharge roller 19a, it is possible to reliably conveyed without slip sheets P ₀ of the highest level.

  However, when the image forming surface of the paper may come into contact with the lower paper discharge roller 19a, a developer such as toner or ink that forms an image is used to prevent the image from being transferred to the paper discharge roller 19a. It is preferable to select a material having a low affinity for the contained component as the surface material of the roller. Therefore, the surface material of the lower discharge roller 19a can be selected from the materials commonly used for the discharge roller such as EPDM (ethylene-propylene-diene copolymer rubber), urethane, silicone, sponge, etc. The product life may be selected as appropriate.

Further, as shown in FIG. 3, when the sheet P ₀ of the uppermost abuts the abutting portion 28, the same size in the opposite direction from the sheet P ₀ is the abutting portion 28 of the uppermost and the conveying force F is Receive the static force Q. Here, also the paper P ₀ is subjected to static force Q and the conveying force F, By sheet P ₀ has a stiffness which is not deformed, without or jam of bent or paper P _0, the lower The paper P ₀ can be slipped between the paper discharge rollers 19a.

Further, abutting portions 28 of the present embodiment is constituted by the rigid wall surface disposed perpendicular to the conveying direction for conveying the sheet P ₀ of the uppermost into the recess 27, the sheet P ₀ In order to prevent damage at the rear end of the paper P ₀ when abutting, the abutting portion 28 may be made of a soft member such as a sponge.

In addition, when both the discharge rollers 19a and 19b are configured to be able to rotate in the direction opposite to the rotation direction (the direction of the arrow shown in FIG. 2) when discharging the paper, by rotating the discharge rollers 19a, and 19b in the opposite direction, it is possible to return the sheet P ₀ of the uppermost to the stacking unit 20 side. In this case, by returning the uppermost sheet P ₀ to the stacking unit 20 side, when the user or the like collects the sheet P from the stacking unit 20, the uppermost sheet P ₀ is not caught in the recess 27. Damage to the paper P ₀ can be avoided and workability is improved.

FIG. 4 is a schematic configuration diagram of another embodiment of the paper discharge device.
The paper discharge device 18 according to the embodiment shown in FIG. 4 is different from the configuration of the above-described embodiment shown in FIG. 2 in that it includes three paper discharge rollers 19a, 19b, and 19c. In FIG. 4, an upper discharge roller 19c and a lower discharge roller 19a are in contact with an intermediate discharge roller 19b, respectively, and paper can be discharged from the contact portion of either roller. ing. Each of the paper discharge rollers 19a, 19b, and 19c is configured to be able to rotate forward and backward. Other than that, it is basically the same as the configuration of the embodiment shown in FIG.

Hereinafter, the operation of the paper discharge device 18 shown in FIG. 4 will be described.
Here, for convenience, the three paper discharge rollers 19a, 19b, and 19c are referred to as a first paper discharge roller 19a, a second paper discharge roller 19b, and a third paper discharge roller 19c in order from the bottom of the figure. To.

Normally, when the paper in the apparatus is discharged, the paper is conveyed between the first and second paper discharge rollers 19a and 19b, and each of the paper discharge rollers 19a, 19b and 19c is in the direction of the arrow in FIG. Is rotated in the opposite direction (the same direction as the direction of the arrow in FIG. 2), so that the paper is discharged from the first and second paper discharge rollers 19a and 19b to the stacking unit 20. Thereafter, when the loading amount of the sheets P is increased and the uppermost sheet P ₀ is in contact with the lower discharge roller 19a, that is, in the full state, the first rotating (lower) as in the above embodiment. The uppermost sheet P ₀ is conveyed into the recess 27 by the paper discharge roller 19 a, and the full state is detected by the optical sensor 29.

Thereafter, in the paper discharge device 18, the respective paper discharge rollers 19a, 19b, 19c are rotated in the direction opposite to the rotation direction (the direction of the arrow in FIG. 4), and the uppermost paper P ₀ is moved to the stacking unit 20 side. return. Further, when detecting full load, when there is a sheet P ₂ that is to be discharged into the device continues to drive until the discharging at least it out of the apparatus. However, during the returning operation of the uppermost sheet P ₀ , the rotation direction between the first sheet discharge roller 19a and the second sheet discharge roller 19b is opposite to the rotation direction when the sheet is discharged (in FIG. 4). Since the roller surface rotates in the direction of the arrow), the sheet P ₂ in the apparatus cannot be discharged from between the first paper discharge roller 19a and the second paper discharge roller 19b.

Therefore, during the returning operation of the uppermost sheet P ₀ , the sheet P ₂ in the apparatus is conveyed between the third sheet discharge roller 19 c and the second sheet discharge roller 19 b. At this time, the surface of the roller rotates in the rotational direction in which the paper can be discharged between the third paper discharge roller 19c and the second paper discharge roller 19b. The sheet P ₂ can be discharged from between the sheet discharge rollers 19 b.

Thus, the sheet discharging device 18 shown in FIG. 4, while returning the sheet P ₀ of the uppermost to the loading unit 20 side, it is possible to discharge the sheet P ₂ in the apparatus, the uppermost paper P ₀ There is no need to perform control such as temporarily stopping the discharge operation of the paper P ₂ in the apparatus until the return operation is completed. For this reason, it is possible to smoothly discharge the sheet P ₂ in the apparatus, and it is possible to avoid problems such as subsequent sheet jamming.

Further, in the paper discharge device 18 shown in FIG. 4, the uppermost paper P ₀ is returned to the stacking unit 20 side, so that when the user or the like collects the paper P from the stacking unit 20 as described above. Further, it is possible to prevent the uppermost sheet P ₀ from being caught in the recess 27, to avoid damage to the sheet P ₀ and to improve workability.

FIG. 5 is a diagram showing a configuration of still another embodiment.
The paper discharge device 18 illustrated in FIG. 5 includes two stacking units 20 and 30. The upper stacking unit 20 in the figure is a first stacking unit 20 that stacks sheets discharged after image fixing as in the above-described embodiments, and the lower stacking unit 30 in the diagram is a first stacking unit. The second stacking unit 30 stacks sheets to be discharged after 20 is fully loaded.

  The paper discharge device 18 includes transport means for transporting paper from the first stacking unit 20 to the second stacking unit 30. Specifically, the transport means includes a transport path 31 communicating from the first stacking unit 20 to the second stacking unit 30, and a plurality of transport roller pairs 32a, 32b and 33a disposed in the transport path 31. 33b. A pair of paper discharge rollers 34 a and 34 b for discharging paper to the second stacking unit 30 is disposed at the downstream end in the paper transport direction of the transport path 31. In addition, an optical sensor 29 similar to that in the above embodiment is disposed on the upstream side of the conveyance path 31 in the sheet conveyance direction. 5 is the same as the configuration of the embodiment shown in FIG. 2 except for the configuration described above, but the (first) stacking unit 20 is the same as that of the embodiment shown in FIG. It is also possible to have a configuration in which three paper discharge rollers 19a, 19b and 19c are provided.

Hereinafter, the operation of the paper discharge device 18 shown in FIG. 5 will be described.
First, until the first stacking unit 20 is full, the paper is discharged to the first stacking unit 20 by the pair of discharge rollers 19a and 19b. Thereafter, when the loading amount of the sheets P increases and the uppermost sheet P ₀ comes into contact with the lower sheet discharge roller 19a, the uppermost sheet P ₀ is conveyed by the rotating sheet discharge roller 19a. 31 and the full state is detected by the optical sensor 29.

Thereafter, the uppermost sheet P ₀ is discharged through the transport path 31 to the second stacking unit 30. Further, the paper discharged after that to the first stacking unit 20 is similarly discharged through the transport path 31 to the second stacking unit 30.

  As described above, since the paper discharge device 18 illustrated in FIG. 5 includes the second stacking unit 30, the amount of paper to be stocked can be afforded, so that even after the first stacking unit 20 is fully loaded, Subsequent paper discharge can be continued. In general, in an image forming apparatus, when a stacking unit is full, a user or the like is notified, and the printing operation is stopped until the user collects a sheet bundle. Thus, it is not necessary to stop the printing operation after full loading, so that productivity is not impaired. Further, by adopting this configuration, it is possible to avoid a state where the drive is stopped while the paper to be discharged is left in the apparatus. As a result, it is possible to prevent the paper remaining in the apparatus from being jammed and causing problems such as jamming after restarting the driving.

  In general, in an image forming apparatus such as a general-purpose printer or a multifunction peripheral, the exterior portion of the apparatus main body is configured by a rectangular parallelepiped case, and therefore, between various apparatuses mounted in the apparatus main body. Free space often exists. Therefore, by arranging the second stacking unit 30 in such an empty space, it is possible to increase the sheet stacking limit amount while suppressing an increase in the size of the apparatus. In particular, in the field of low-end printers, it is possible to expect downsizing of the apparatus by effectively utilizing such empty space.

  Note that the number of stacking units used after full loading is not limited to one (second stacking unit 30). Two or more stacking units used after full loading may be provided depending on the configuration of the apparatus and the usage situation.

FIG. 6 is a schematic configuration diagram of an embodiment in which the paper discharge device includes a holding member that suppresses curling of the paper.
As shown in FIG. 6, in this embodiment, a holding member 35 that suppresses curling of the paper is provided on the upper discharge roller 19b in the drawing. Specifically, the restraining member 35 includes an attachment portion 36 that is rotatably attached to the rotation fulcrum of the upper discharge roller 19b, and a restraining portion 37 that extends from the attachment portion 36 in the paper discharge direction. Other than that, it is the same structure as the structure of the said embodiment shown in FIG. In addition, also in the structure of the said embodiment shown in FIG.4 and FIG.5, you may provide the suppressing member 35 similarly.

  In this case, when the paper is discharged by the pair of paper discharge rollers 19a and 19b, the front end of the discharged paper comes into contact with the holding portion 37, so that the holding portion 37 rotates upwardly around the mounting portion 36 (see FIG. 6 indicates a solid line). As described above, the holding portion 37 rotates upward so as not to prevent the discharge of the sheet. When the paper is completely discharged and stacked on the stacking unit 20, the holding unit 37 rotates downward about the attachment unit 36 by its own weight (a state indicated by a two-dot chain line in FIG. 6).

Thereafter, when the loading amount of the sheets P increases and the uppermost sheet P ₀ comes into full contact with the lower sheet discharge roller 19a, the uppermost sheet P ₀ is rotated by the rotating sheet discharge roller 19a as in the above embodiment. Sheet P ₀ is conveyed to the optical sensor 29 side. At this time, since the restraining unit 37 restrains the trailing edge of the uppermost sheet P ₀ , curling is suppressed even if the trailing edge of the sheet P ₀ is largely curled due to the influence of the heat of the fixing device at the time of ejection. In this state, it can be conveyed to the recess 27. This makes it easy to allow the uppermost sheet P ₀ to enter the recess 27, and prevents the folding of the sheet and the occurrence of jamming due to the rear end of the largely curled sheet P ₀ coming into contact with the opening edge of the recess 27. can do.

  As described above, according to the paper discharge device according to each embodiment of the present invention, when the stacking unit is fully loaded, the uppermost paper is conveyed to the optical sensor side by the rotating paper discharge roller. Is possible. As described above, according to the paper discharge device according to each embodiment, since the transport force when transporting the uppermost sheet to the optical sensor side is obtained by the rotation of the paper discharge roller, a sufficient transport force is obtained. It is done. As a result, even if the frictional force between the sheets increases due to the type of the sheet or the like, or the adsorption due to the charging between the sheets occurs, the uppermost sheet is reliably conveyed to the optical sensor side regardless of those. And can exhibit a stable full load detection function.

  In addition, since the paper discharge roller is used as the means for conveying the uppermost sheet, it is not necessary to separately provide a dedicated conveying means or driving means for conveying the uppermost sheet. For this reason, the increase in the number of parts can be suppressed, and cost reduction and size reduction can be achieved.

  In addition, according to the paper discharge device according to each embodiment, it is not necessary to incline the placement surface of the stacking unit in order to obtain the conveyance force of the uppermost sheet, which can contribute to downsizing of the device.

  In addition, according to the paper discharge device according to each embodiment, since a sufficient transport force can be obtained, a general-purpose contact-type detection unit can be used as the load amount detection unit.

  The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention. Further, the paper discharge device according to the present invention is not limited to the color laser printer shown in FIG. 1, but can be mounted on a monochrome printer, an ink jet printer, a copying machine, a facsimile, or a complex machine thereof.

18 Paper discharge device (sheet discharge device)
19a Paper discharge roller (first discharge rotating body)
19b Paper discharge roller (second discharge rotating body)
19c Paper discharge roller (third discharge rotating body)
20 Loading section (first loading section)
28 Abutting section 29 Optical sensor (loading amount detection means)
30 Loading section (second loading section)
35 Holding member F Conveying force Q Static force

JP 2003-81525 A JP 2002-128389 A

Claims (10)

In a sheet discharge apparatus comprising a discharge unit that discharges a sheet, a stacking unit that stacks sheets discharged by the discharge unit, and a stack amount detection unit that detects a stack amount of sheets stacked on the stack unit.
The uppermost sheet stacked on the stacking unit is transported to the stacking amount detecting unit by the discharging unit, and the uppermost sheet is detected by the stacking amount detecting unit. apparatus. The discharge means includes first and second discharge rotating bodies that are disposed above and below and discharge the sheet by sandwiching and rotating the sheet,
Disposing the first and second discharge rotating bodies at a predetermined height above the stacking unit;
The same direction as the rotation direction when the first and second discharge rotators discharge the sheets in a state where the sheets are stacked on the stacking unit and the uppermost sheet is in contact with the lower first discharge rotator. The sheet discharge device according to claim 1, wherein the sheet discharge device is configured to convey the uppermost sheet to the stacking amount detection unit side by rotating in the forward direction. The first discharge rotating body is configured to be rotatable in a direction opposite to the rotation direction when discharging the sheet,
3. The apparatus according to claim 2, wherein after the uppermost sheet is detected by the stacking amount detection unit, the first discharge rotating body is rotated in the reverse direction to return the uppermost sheet to the stacking unit side. The sheet discharging apparatus as described. A third discharge rotator is provided in contact with the second discharge rotator;
The sheet discharged after discharging the uppermost sheet is conveyed between the second discharge rotating body and the third discharge rotating body, and the sheet is sandwiched by the rotating second and third discharge rotating bodies. The sheet discharging apparatus according to claim 3, wherein the sheet discharging apparatus is configured to discharge the sheet.   And a conveying unit configured to convey the uppermost sheet conveyed from the stacking unit to the stacking amount detection unit side and a sheet discharged to the stacking unit after the uppermost sheet to another stacking unit. Item 5. The sheet discharging apparatus according to any one of Items 1 to 4.   The surface material of the first discharge rotator is such that the friction coefficient between the uppermost sheet and the first discharge rotator is larger than the friction coefficient between the uppermost sheet and the lower sheet. The sheet discharging apparatus according to claim 2, wherein the sheet discharging apparatus is made of a material.   The sheet discharging apparatus according to any one of claims 1 to 6, further comprising a suppressing member that suppresses the curling of the sheet discharged by the discharging unit.   An abutting portion that abuts the uppermost sheet conveyed from the stacking portion to the load amount detecting means side and stops the uppermost sheet at a position that can be detected by the load amount detecting means; The sheet discharging apparatus according to any one of claims 1 to 7, wherein the sheet discharging apparatus has a rigidity that prevents the upper sheet from being deformed even if the upper sheet receives a conveying force by the discharging unit and a stationary force by the butting portion. When the uppermost sheet is detected by the load amount detection unit,
The sheet discharge according to any one of claims 1 to 8, wherein when there are sheets scheduled to be discharged in the apparatus, the discharge unit is continuously driven until at least the sheets are discharged outside the apparatus. apparatus.   An image forming apparatus comprising the sheet discharge device according to claim 1.

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