JP2011057428A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device having a paper ejecting device for coping with a high quality and silencing, without causing paper damage and an abnormal sound caused by a paper ejecting roller and a nip part of paper ejecting roller pairs. <P>SOLUTION: This image forming device is composed of the rotatingly driving paper ejecting roller 14 and a driven paper ejecting roller 15 constituted so as to freely advance-retreat between a nip position 15b brought into pressure contact with the paper ejecting roller and a separate position 15b being separated from the same, and has a paper ejecting means for ejecting paper P to a paper ejecting part 240 while nipping the paper by the nip part Nh of the respective paper ejecting rollers. When the driven paper ejecting roller exists in the separate position, when the tip Pa of the paper is carried downstream by a predetermined distance A from a position corresponding to the nip part of the paper ejecting roller pairs based on a detection result of a detecting means 11, the driven paper ejecting roller is moved to the nip position. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a paper discharge device that discharges a sheet on which an image is formed to a paper discharge unit.

In the image forming apparatus, a paper discharge device for discharging paper on which image formation has been performed to a paper discharge unit such as a paper discharge tray includes a paper discharge roller and a driven paper discharge roller, and a nip portion formed by these roller pairs The paper to be ejected is ejected while being nipped.
FIG. 9 is a schematic diagram for explaining a conventional paper discharge device. FIG. 9 shows a part of an electrophotographic image forming apparatus. As shown in the figure, the image forming apparatus 100 nips a paper P0 on which a toner image is formed at a fixing nip portion Nt0 formed by a heating roller 111 and a pressure roller 112, and fixes the image by heat and pressure. A fixing device 103 is provided. The paper P0 on which the image has been fixed by the fixing device 103 is conveyed to the paper discharge device 113 disposed on the downstream side, and the front and back surfaces of the paper P0 are guided by the paper guide plates 108 and 109, respectively, so The paper is discharged to the paper discharge unit 141 after being nipped by a paper discharge nip Nh0 formed by the paper discharge roller 102 and the driven paper discharge roller 101 disposed downstream.
At the moment when the paper P0 conveyed from the fixing device 103 reaches the paper discharge nip Nh0, the leading edge of the paper P0 collides with the paper discharge nip Nh0. The paper P0 buckled due to this collision, and a paper damage called PN occurred in the wave. As shown in the figure, the wave PN occurs immediately downstream in the conveyance direction of the fixing nip Nt0. The sheet P0 immediately after passing through the fixing nip portion Nt0 is immediately after being heated by the fixing device 103, and the sheet P0 where the PN is generated is at a high temperature. It was stored in P0 and remained after paper discharge.

Further, when the leading edge of the paper P0 collides with the paper discharge nip portion Nh0, an abnormal sound is generated, which is a problem.
In order to solve these problems, in the prior art, the shape of the paper guide plate 108 and the paper guide plate 109 installed upstream in the conveyance of the paper discharge nip portion Nh0 has been optimized. Patent Documents 1 and 2 propose a method of installing a movable guide plate upstream of the conveyance of the paper discharge nip Nh0, and Patent Document 3 proposes a method of changing the position of the nip Nh0.

However, since all of the above-described conventional techniques have a configuration in which the paper P0 collides with the paper discharge nip portion Nh0, the generation of PN and abnormal noise among waves can be reduced, but these problems are completely solved. There is a problem that has not been reached.
The present invention has been made in view of the above-described circumstances, and does not cause paper damage or abnormal noise caused by the nip portion of the paper discharge roller and the paper discharge roller pair, and discharge paper corresponding to high quality, low noise, and the like. An object of the present invention is to provide an image forming apparatus including the apparatus.

  In order to solve the above-described problems, in the invention described in claim 1, image formation is performed by a conveying unit that conveys a sheet, an image forming unit that forms an image on the conveyed sheet, and an image forming unit. A paper discharge device that discharges the paper to a paper discharge unit, wherein the paper discharge device includes a paper discharge roller that rotates and a nip position that is in pressure contact with the paper discharge roller. A discharged paper discharge roller configured to move back and forth between the separated positions, and discharges the paper to the paper discharge unit while nipping the paper at a nip formed by each of the paper discharge rollers. Means, a contact / separation mechanism for bringing the driven paper discharge roller into and out of contact with the paper discharge roller, and a detection means for detecting the presence / absence of the paper to be transported disposed upstream of the nip portion in the paper transport direction; , Based on the detection result of the detection means Control means for controlling the operation of the contact / separation mechanism, wherein the control means is configured such that when the driven paper discharge roller is at the separation position, the leading edge of the sheet is niped based on the detection result of the detection means. And an image forming apparatus that moves the driven paper discharge roller to the nip position when it is determined that the paper is conveyed downstream by a predetermined distance from a position corresponding to the portion.

The invention described in claim 2 includes a conveying unit that conveys a sheet, an image forming unit that forms an image on the conveyed sheet, a pressure roller, and a heating roller, and image formation is performed by the image forming unit. An image forming apparatus comprising: a fixing unit that fixes an image on the paper that has been fixed; and a paper discharge device that discharges the paper on which the image has been fixed to a paper discharge unit, wherein the paper discharge device is driven A nip portion formed by each of the paper discharge rollers, comprising: a paper discharge roller that rotates, and a driven paper discharge roller that is configured to be movable back and forth between a nip position pressed against the paper discharge roller and a spaced apart position. A paper discharge unit that discharges the paper to a paper discharge unit while niping the paper, a contact / separation mechanism that contacts and separates the driven paper discharge roller with respect to the paper discharge roller, and an upstream side in the paper conveyance direction of the fixing device The paper to be transported Detecting means, and control means for controlling the operation of the contact / separation mechanism based on the detection result of the detection means, wherein the control means is configured such that when the driven paper discharge roller is in the separation position, When it is determined that the trailing edge of the sheet has been conveyed a predetermined distance upstream from the nip portion of the pressure roller and the heating roller based on the detection result of the detection means, the driven paper discharge roller is moved to the nip position. An image forming apparatus is characterized.
According to a third aspect of the present invention, when the control unit determines that the sheet has been conveyed downstream by a predetermined distance from the nip portion of each sheet discharge roller based on the sheet detection result of the detection unit, the driven unit The image forming apparatus according to claim 1, wherein a sheet discharge roller is moved to the separation position.

According to a fourth aspect of the present invention, there is provided a paper passage detection means for detecting the rear end of the paper, and the paper passage detection means is located at a position separated by a predetermined distance upstream of the nip portion of the heating roller in the paper conveyance direction. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus is installed, and the control unit moves the driven sheet discharge roller to the separation position when it is determined that the sheet passage detection unit detects passage of the trailing edge of the sheet. Features.
According to a fifth aspect of the present invention, the control unit is configured such that the paper rear end is a nip of each paper discharge roller after a predetermined time has elapsed from the passage information of the paper rear end obtained from the paper detection result of the detection unit. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus determines that the sheet is conveyed to a position separated by a predetermined distance downstream from the sheet conveying direction, and moves the driven sheet discharge roller to the separation position.
According to a sixth aspect of the present invention, the contact / separation mechanism includes a pressure contact spring that presses the driven paper discharge roller against the paper discharge roller, a cam that moves the driven paper discharge roller to a nip position and a separation position, Drive means for driving a cam; a link piece that connects the cam and the pressure contact spring and has a fulcrum at a substantially central portion; and a tension spring that stretches the link piece in one direction. 6. The image forming apparatus according to claim 1, wherein the link piece is moved in a direction in which the driven paper discharge roller is brought into contact with or separated from the fulcrum by being rotationally driven by the driving unit. To do.

According to a seventh aspect of the present invention, the contact / separation mechanism includes: a pressure contact spring that presses the driven paper discharge roller against the paper discharge roller; and a solenoid that moves the driven paper discharge roller to a nip position and a separation position. An image forming apparatus according to claim 1, comprising the image forming apparatus according to claim 1.
According to an eighth aspect of the present invention, a pair of sheet guide plates for guiding both sides of the sheet is provided immediately upstream in the sheet conveyance direction of the pair of sheet discharge rollers, and the driven sheet discharge roller is separated from the sheet guide plate. When the sheet is in the position, the sheet that has passed through the sheet guide plate is disposed so as to pass between the sheet discharge rollers, and is formed at the downstream end of the sheet guide plate on the sheet discharge roller side. 8. The image forming apparatus according to claim 1, wherein the portion is located on the same straight line of a common tangent line between the paper discharge roller and the driven paper discharge roller or closer to the paper discharge roller than the common tangent line. It is characterized by.
The invention according to claim 9 is the image according to any one of claims 1 to 8, wherein the movement of the driven paper discharge roller from the separated position to the nip position is from the upstream side to the downstream side in the sheet conveying direction. Features a forming device.
According to a tenth aspect of the present invention, when the control unit determines that a paper jam has occurred inside the paper discharge device based on a paper detection result by the detection unit, the driven paper discharge roller is set to a separated position. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled to move.

  According to the present invention, when the driven paper discharge roller is in the separation position, the driven discharge is determined when it is determined that the leading edge of the paper is conveyed downstream by a predetermined distance from the position corresponding to the nip portion based on the detection result of the detection unit. Since the paper roller is moved to the nip position, it is possible to eliminate the collision of the front end of the paper with the paper discharge nip formed by the paper discharge roller and the driven paper discharge roller. Sound can be eliminated.

1 is a schematic cross-sectional view showing an internal structure of an image forming apparatus. 4A and 4B are schematic diagrams for explaining the forward and backward movement of the driven paper discharge roller. FIG. 4A is a diagram illustrating a state in which the driven paper discharge roller is in a separated position, and FIG. It is a figure which shows a state. (A), (b) is a schematic diagram explaining the movement of the driven paper discharge roller from the nip position to the separation position. (A), (b) is a schematic diagram which shows one Embodiment of an approach / separation mechanism. (A), (b) is a schematic diagram which shows other embodiment of the contacting / separating mechanism. 4A and 4B are schematic diagrams illustrating a relationship between a driven paper discharge roller, a paper discharge roller, and a sheet conveyance direction. FIG. 5A is a schematic diagram according to the present embodiment, and FIG. 5B is a schematic diagram according to a comparative example. It is a schematic diagram which shows the moving direction of a driven paper discharge roller, (a) is a figure which shows the movement from a separation position to a nip position, (b) is a figure which shows the movement from a nip position to a separation position. It is a schematic diagram concerning a comparative example. It is a schematic diagram for demonstrating the conventional paper discharge apparatus.

Embodiments of the present invention will be described below with reference to the drawings.
[Electrophotographic image forming apparatus]
An image forming apparatus to which a paper discharge device according to the present invention is applied will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing the internal structure of the image forming apparatus.
The image forming apparatus 200 includes a paper feed cassette 201 on which a plurality of papers P are placed at the bottom of the apparatus, and a paper feed for separating and feeding the papers P one by one from a paper bundle placed on the paper feed cassette 201. A roller 202, and registration rollers 203 and 204 that are disposed downstream of the paper feed roller 202 in the paper conveyance direction, stop the paper P that has been fed once and stop, and convey the paper at a timing.
An image forming apparatus 200 shown in FIG. 1 is an electrophotographic image forming apparatus, and includes a photoreceptor unit 210 (210Y, 210M, 210C, 210K) for each toner color. The photoconductor unit 210 includes a photoconductor 211 (211Y, 211M, 211C, 211K) that carries an electrostatic latent image, and a charging roller 212 (212Y, 212M, 212C, 212K) that uniformly charges the photoconductor 211, A developing unit 213 (213Y, 213M, 213C, and 213K) that develops the electrostatic latent image formed on the photoconductor 211 with toners of different colors. Further, an exposure device 220 that forms an electrostatic latent image by irradiating the photoconductor 211 with the laser light L is provided above the photoconductor unit 210.
Below the photoreceptor unit 210, an intermediate transfer belt 225, which is a transfer medium, is provided along the horizontal direction. Further, a driving transfer roller 205 and a driven transfer roller 206 for transferring an image to the paper P are arranged downstream of the registration rollers 203 and 204 in the paper conveyance direction. The driving transfer roller 205 winds the intermediate transfer belt 225 together with other rollers.
On the downstream side of the paper transfer direction of the drive transfer roller 205 and the driven transfer roller 206, there are a heating roller 231 and a pressure roller 232, a fixing device 230 for fixing the toner image on the paper P by heat and pressure, the paper discharge roller 14, And a driven paper discharge roller 15 and a paper discharge device for discharging the paper P to the paper discharge tray 240 while nipping it.

An image forming operation by the image forming apparatus 200 will be briefly described.
The sheet fed from the sheet feeding cassette 201 by the sheet feeding roller 202 is sent out in synchronization by the registration rollers 203 and 204 and reaches the driving transfer roller 205 and the driven transfer roller 206. The drive transfer roller 205 is located inside the intermediate transfer belt 225, and rotates the intermediate transfer belt 225.
In the photoconductor unit 210, the charging roller 212 first comes into contact with the surface of the photoconductor 211 to uniformly charge the surface of the photoconductor 211.
Subsequently, the exposure device 220 exposes the surface of the photoconductor 211 with the laser light L to form an electrostatic latent image on the surface of the photoconductor 211. Subsequently, the developing device 213 visualizes the electrostatic latent image formed on the surface of the photoconductor 211 with toner, and forms a toner image on the surface of the photoconductor 211. Subsequently, a toner image is transferred from the surface of the photoreceptor 211 to the surface of the intermediate transfer belt 225. Through the image forming process as described above, the toner image on the intermediate transfer belt 225 is transferred onto the sheet by the driving transfer roller 205 and the driven transfer roller 206, and conveyed to the fixing device 230, and the image is output by the heating roller 231 and the pressure roller 232. Is fixed on the paper. The paper discharge device 1 having the paper discharge roller 14 and the driven paper discharge roller 15 discharges the paper onto the paper discharge tray 240, and printing is completed.
These operations are controlled by control means (not shown).

[First embodiment]
A first embodiment of the present invention will be described with reference to FIG. The paper discharge device according to this embodiment is characterized in that the driven paper discharge roller moves forward and backward according to the transport position of the paper P. 2A and 2B are schematic diagrams for explaining the forward and backward movement of the driven paper discharge roller. FIG. 2A is a diagram illustrating a state in which the driven paper discharge roller is in the separated position, and FIG. It is a figure which shows the state in a nip position.
The paper discharge device 1 is disposed immediately downstream of the fixing device 230 in the paper conveyance direction, and includes a paper discharge sensor filler 11 that detects the passage of the paper P, and a pair of paper guide plates 12 that guide both sides of the paper P to be conveyed. 13 and a paper discharge roller 14 and a driven paper discharge roller 15 for discharging the paper P to the paper discharge tray 240 while nipping the paper P.
The paper discharge sensor filler 11 (detection means) is disposed in the conveyance path between the fixing device 230, the paper discharge roller 14, and the driven paper discharge roller 15 (paper discharge roller pair, paper discharge means), and at least a part thereof. It is pivotally supported and rotates as the paper P passes. The front shape of the sheet discharge sensor filler 11 shown in the figure is substantially elliptical. When the paper P does not pass, the front end portion falls due to its own weight and is positioned at the initial position 11a. Rotate to position 11b. The turning operation of the paper discharge sensor filler 11 is detected by a paper discharge sensor (not shown), and a central processing unit (control means) (not shown) can detect whether or not the paper P is passing.

The paper guide plates 12 and 13 are guides that determine the transport path of the paper P. The paper P that has been transported upward in the drawing is guided so as to be transported in the horizontal direction, and the paper P is guided between the paper discharge roller 14 and the driven paper discharge roller 15. The paper guide plate 12 is a paper discharge roller side paper guide disposed on the paper discharge roller 14 side, and the paper guide plate 13 is a driven paper discharge roller side paper guide disposed on the driven paper discharge roller 15 side.
The driven paper discharge roller 15 is configured to be movable back and forth with respect to the paper discharge roller 14. When the driven paper discharge roller 15 is at the nip position 15b pressed against the paper discharge roller 14, a paper discharge nip portion Nh is formed between the driven paper discharge roller 15 and the paper discharge roller 14, and the paper P is nipped at the paper discharge nip portion Nh. The paper is discharged while being discharged. Further, when the paper P is at the separation position 15 a separated from the paper discharge roller 14, the paper P is discharged without contacting the driven paper discharge roller 15. The driven paper discharge roller 15 is moved back and forth by an approach / separation mechanism described later.

The operation of the paper discharge device 1 will be described. Before the conveyance of the paper P, the paper discharge sensor filler 11 is in the initial position 11a, and the driven paper discharge roller 15 is in the separation position 15a.
The paper leading edge Pa of the paper P conveyed from the fixing device 230 abuts on the paper discharge sensor filler 11 and pushes up the paper discharge sensor filler 11 to the detection position 11b, and is conveyed along the paper guide plates 12 and 13. It passes between the paper discharge roller 14 and the driven paper discharge roller 15 at the separation position 15a. When the paper discharge sensor filler 11 is pushed up onto the paper P, its operation is detected by a paper discharge sensor (not shown).
By moving the paper discharge sensor filler 11 to the detection position 11b, the central processing unit (not shown) can obtain information that the paper front end Pa has passed through the paper discharge sensor filler 11. The central processing unit calculates the position where the paper front end Pa is transported from this information, the transport speed information of the paper P, and the elapsed time information after the paper front end Pa passes the paper discharge sensor filler 11. Can be sought.
Then, on the condition that the paper P has been transported to the downstream in the paper transport direction by a predetermined distance A from the position corresponding to the paper discharge nip Nh of the paper discharge roller 14 by the above calculation, the driven paper discharge roller 15 Is moved from the separation position 15a to the nip position 15b. In addition, the driven paper discharge roller 15 may be controlled to move to the nip position 15b based only on the elapsed time information after passing through the paper discharge sensor filler 11 without using the information regarding the conveyance speed.

Based on the detection information of the paper discharge sensor filler 11 described above, the central processing unit (control means) issues a signal for moving the driven paper discharge roller 15 to the nip position, and the driven paper discharge roller 15 is accompanied by this signal. Moves and comes into pressure contact with the paper discharge roller 14.
The movement of the driven paper discharge roller 15 described above is performed based on the position information of the paper front end Pa, that is, whether or not the passage of the paper front end Pa is detected, so that the position of the paper front end Pa can be accurately grasped. . Such a control for moving the driven paper discharge roller 15 based on the detection of the paper front end Pa is, for example, the driven paper discharge roller 15 immediately after the paper front end Pa passes between the driven paper discharge roller 15 and the paper discharge roller 14. This is particularly effective when it is necessary to move to the nip position 15b.
An example of urgently moving to the nip position 15b is a case where the rigidity of the paper P is low. Specifically, this is the case where the paper P is thin or the image forming apparatus is in a high temperature environment. When the rigidity of the sheet P is low, the sheet P is discharged onto the sheet discharge tray 240 unless both the sheet leading end Pa side and the sheet trailing end Pb side are nipped by the sheet discharge nip portion Nh and the fixing nip portion Nt. This is because the behavior of the paper P to be unstable becomes unstable, and there is a risk of paper jam such as a stack failure.

  As described above, according to the present embodiment, the driven paper discharge roller is moved to the nip position after the leading edge of the paper is conveyed downstream by a predetermined distance from the position corresponding to the paper discharge nip portion. It is possible to eliminate the collision of the leading edge of the sheet with the sheet discharge nip formed by the sheet discharging roller, and it is possible to eliminate the sheet damage and the sheet collision noise caused by the collision of the sheet leading end. In addition, the driven paper discharge roller is moved to the nip position when the paper needs to be conveyed while being nipped at the paper discharge nip portion, and when it is not necessary to nip the paper, the driven paper discharge roller is kept at the separation position. Therefore, the wear of the paper discharge roller can be reduced, and the life of the paper discharge roller can be extended.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIG. In the first embodiment, the driven paper discharge roller is moved to the nip position based on the information on the paper leading edge Pa. The present embodiment is characterized in that the driven paper discharge roller is moved to the nip position based on the information on the rear end Pb of the paper and the information on the length in the conveyance direction of the paper.
In the present embodiment, the paper passage sensor 16 (paper passage detection means) for detecting the paper rear end Pb is installed at a position separated by B from the fixing nip portion Nt on the upstream side in the paper conveyance direction. When the trailing edge Pb of the sheet passes through the location where the sheet passage sensor 16 is installed, the leading edge Pa of the sheet is conveyed by a distance A from a position corresponding to the sheet discharge nip portion Nh of the sheet discharge roller 14 (FIG. 2 (a)).
The central processing unit controls the driven paper discharge roller 15 to move to the nip position 15b based on the detection information that the paper passage sensor 16 has detected the passage of the paper rear end Pb, so that the same as in the first embodiment. Can be controlled.

In addition, the paper passage sensor 16 may be installed at a location farther than the distance B from the fixing nip portion Nt. In this case, the same control as that in the first embodiment is performed by moving the driven paper discharge roller 15 on condition that a predetermined time has elapsed after the paper passage sensor 16 detects the paper trailing edge Pb. be able to.
In addition, the central processing unit detects detection information of the trailing edge Pb of the sheet by the sheet passage sensor 16, conveyance speed information of the sheet P, elapsed time information after the sheet trailing edge Pb passes the sheet passage sensor 16, and fixing. Since the position where the paper leading edge Pa is conveyed can be obtained from the distance information between the nip portion Nt and the paper discharge nip portion Nh and the conveyance direction length information of the paper P, the size of the paper P differs. The same control as in the first embodiment can be performed.

In the control method of the driven paper discharge roller 15 in the present embodiment, since the paper rear end Pb is detected by the paper passage sensor 16, the position of the paper rear end Pb can be accurately grasped. Accordingly, it is possible to lengthen the time until the driven paper discharge roller 15 is moved to the nip position 15b after the paper front end Pa passes the position corresponding to the paper discharge nip portion Nh of the paper discharge roller 14 as much as possible.
In this control, for example, when there is no possibility of a problem such as a stack failure when discharging the paper P to the paper discharge tray 240, specifically, at least one of the fixing nip portion Nt and the paper discharge nip portion Nh is This is effective when the sheet P is nipped and the rigidity of the sheet P is high. Examples of the case where the rigidity of the paper P is high include a case where the paper P is a thick paper or a case where the installation environment of the image forming apparatus is not a high temperature environment. As described above, when there is little possibility of a stack failure or the like, it is preferable to control the driven paper discharge roller to move to the nip position based on the detection of the paper rear end Pb.
By extending the state in which the driven paper discharge roller 15 is at the separation position 15a in time, the service life of the paper discharge roller 14 and the driven paper discharge roller 15 can be extended, and the paper discharge device 1 can be made quieter during the image forming operation. It is advantageous from the viewpoint.

[Third embodiment]
The present embodiment is characterized in that the driven paper discharge roller is moved to the separated position not only when paper is discharged but also when a paper jam occurs.
The central processing unit recognizes the conveyance direction length of the paper P by setting the paper P and the like, and after the paper leading edge Pa passes the paper discharge sensor filler 11 and the paper passage sensor 16, the paper trailing edge Pb passes. Can be obtained by calculation. Therefore, when the paper discharge sensor filler 11 and the paper passage sensor 16 detect the paper P for a time longer than the average paper P passage time, a paper jam occurs inside the paper discharge device 1. Can be determined.
At this time, the central processing unit controls the driven paper discharge roller 15 to move to the separation position. The paper P that has jammed in the paper discharge device 1 is not sandwiched between the driven paper discharge roller 15 and the paper discharge roller 14 (not nipped by the paper discharge nip portion Nh), and therefore, jam processing is performed. Can be easily performed.

[Fourth embodiment]
A fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, the driven paper discharge roller moved to the nip position in the first and second embodiments is moved to the separation position. Hereinafter, the movement timing will be described. 3A and 3B are schematic diagrams for explaining the movement of the driven paper discharge roller from the nip position to the separation position.
When the paper trailing edge Pb of the paper P conveyed from the fixing device 230 passes through the paper discharge sensor filler 11, the paper discharge sensor filler 11 returns to the initial position 11a. Further, the paper rear end Pb passes through the paper discharge nip Nh. The central processing unit, based on the passing information of the paper rear end Pb obtained by the operation of the paper discharge sensor filler 11, is a position where the paper rear end Pb is separated from the paper discharge nip Nh by a predetermined distance C downstream in the paper transport direction. When it is determined that the paper has been transported to a position separated by a predetermined distance C, it is determined that a time corresponding to the time when the paper is transported to a position separated by a predetermined distance C has passed. Then, the driven paper discharge roller 15 is separated from the paper discharge roller 14.
As described above, according to the present embodiment, the driven paper discharge roller is driven at a timing at which the paper rear edge is separated from the paper discharge nip portion by a predetermined distance downstream in the paper conveyance direction based on the detection information of the paper rear edge by the paper discharge sensor filler. Since the sheet is separated from the sheet discharge roller, the sheet after passing through the fixing nip can be reliably discharged to the sheet discharge tray.

[Contact / separation mechanism 1 of driven paper discharge roller]
Hereinafter, a specific embodiment of the contact / separation mechanism for moving the driven paper discharge roller back and forth with respect to the paper discharge roller will be described with reference to FIG. 4A and 4B are schematic views showing an embodiment of the contact / separation mechanism.
The contact / separation mechanism 20 that moves the driven paper discharge roller 15 forward and backward with respect to the paper discharge roller 14 adjusts the pressure contact spring 21 that presses the driven paper discharge roller 15 against the paper discharge roller 14 and the pressure contact force of the pressure spring 21. And the link piece 23 that connects the eccentric cam 26 and the pressure contact spring 21.
The driven paper discharge roller 15 is rotatably supported by a bearing 22, and one end 21 a of a pressure spring 21 that presses the driven paper discharge roller 15 against the paper discharge roller 14 is fixed to the bearing 22. The other end portion 21 b of the press contact spring 21 is fixed to the one end portion 23 a side of the link piece 23. A regulating piece 21 c that regulates the expansion and contraction direction of the pressure contact spring 21 in the axial direction is included inside the pressure contact spring 21.

A central portion of the link piece 23 is pivotally supported by the support shaft 24, and the link piece 23 is freely rotatable. A cam follower 25 is rotatably supported on the other end 23 b side of the link piece 23. An eccentric cam 26 is in contact with the cam follower 25. The eccentric cam 26 is rotated by a rotation drive source (not shown) such as a motor.
Of the side surfaces of the eccentric cam 26 that contacts the cam follower 25, when the farthest point 26b farthest from the cam shaft 26a contacts the cam follower 25, that is, the eccentric cam 26 reaches a position where the farthest point 26b contacts the cam follower 25. When rotated by the rotational drive source, the eccentric cam 26 moves the driven paper discharge roller 15 to the nip position 15b via the link piece 23. The driven paper discharge roller 15 is pressed against the paper discharge roller 14 to form a paper discharge nip Nh. The pressure spring 21 is compressed by being sandwiched between the driven paper discharge roller 15 fixed to both ends (21a, 21b) and the link piece 23, thereby generating pressure on the paper discharge roller 14.
On the other hand, as shown in (b), when the eccentric cam 26 is further rotated by the rotational drive source, the driven paper discharge roller 15 is moved and is not in contact with the paper discharge roller 14. On the one end portion 23 a side of the link piece 23, a separation spring 27 (a tension spring) for urging the driven paper discharge roller 15 away from the paper discharge roller 14 and a separation position 15 a of the driven paper discharge roller 15 are determined. A stopper 28 is arranged. When the phase of the eccentric cam 26 is not in contact with the cam follower 25, the separation spring 27 prevents the driven paper discharge roller 15 from contacting the paper discharge roller 14. Further, when the link piece 23 comes into contact with the stopper 28 by the urging force of the separation spring 27, the separation position 15a is determined.

[Contact / separation mechanism 2 of driven paper discharge roller]
Another embodiment of a contact / separation mechanism for moving the driven paper discharge roller back and forth with respect to the paper discharge roller will be described with reference to FIG. FIGS. 5A and 5B are schematic views showing another embodiment of the contact / separation mechanism. The present embodiment is characterized in that the driven paper discharge roller 15 is moved forward and backward by a linear operation of a solenoid. In the following description, the same reference numerals are used for the same members as those described in “Following discharge roller contact / separation mechanism 1”.
In the contact / separation mechanism 40 according to the present embodiment, the paper discharge roller 14 is rotatably supported by a support shaft 18 that is supported by a paper discharge frame 17 that is a housing of the paper discharge device 1. The driven paper discharge roller 15 in contact with the paper discharge roller 14 is freely rotated by a rotation shaft 22 a that is pivotally supported by the bearing 22. Below the bearing 22 in the drawing, one end 21 a of a pressure spring 21 that presses the driven paper discharge roller 15 against the paper discharge roller 14 is fixed. The other end portion 21 b of the press contact spring 21 is fixed to a driven paper discharge roller base 43 that connects a linear motion portion 42 of a solenoid 41 (described later) and the press contact spring 21. A regulating piece 21c for regulating the expansion / contraction direction in the axial direction is included.

The solenoid 41 is fixed to the paper discharge frame 17 via the base 44. The linearly moving portion 42 of the solenoid 41 is movably moved by electromagnetic force and is connected to the driven paper discharge roller base 43. Accordingly, the driven paper discharge roller base 43 is configured to be movable back and forth in accordance with the forward / backward movement of the linear movement portion 42 of the solenoid 41. The driven paper discharge roller base 43 is supported by the paper discharge frame 17 through the base 45 so as to be movable forward and backward.
The driven paper discharge roller base 43 is provided with a separation spring 27 for urging the driven paper discharge roller 15 away from the paper discharge roller 14 and a stopper 28 for determining a separation position 15 a of the driven paper discharge roller 15. . One end portion 27 a of the separation spring 27 is fixed to the driven paper discharge roller base 43, and the other end portion 27 b is fixed to the paper discharge frame 17.

The contact / separation mechanism 40 according to the present embodiment moves the driven paper discharge roller 15 forward and backward as the linear motion portion 42 of the solenoid 41 moves forward and backward.
Specifically, as shown in (a), when the linear motion portion 42 is retracted, the driven paper discharge roller 15 moves to the nip position 15b via the driven paper discharge roller base 43 and the pressure contact spring 21, and the paper discharge roller 14 is moved. Pressure contact. The pressure spring 21 is sandwiched and compressed between a driven paper discharge roller 15 and a driven paper discharge roller base 43 fixed at both ends, thereby generating pressure applied to the paper discharge roller 14 by the driven paper discharge roller 15.
On the other hand, as shown in (b), when the linear movement portion 42 of the solenoid 41 advances, the driven paper discharge roller 15 moves via the driven paper discharge roller base 43 and the pressure contact spring 21 and is separated from the paper discharge roller 14. It becomes a state. At this time, the driven paper discharge roller base 43 is fixed in contact with the stopper 28 on the paper discharge frame 17 by the separation spring 27, so that the separation position 15a is determined.
As described above, according to the present embodiment, compared to the method using the cam described in FIG. 4, the shaft and gears for connecting the drive source and the cam are not required, so the contact / separation mechanism can be reduced in cost. It is feasible. Note that either method can be selected depending on the mounting conditions of the image forming apparatus.

[Relationship between paper discharge roller and paper guide plate]
Here, the relationship between each paper discharge roller and the paper guide plate will be described with reference to FIG. 6A and 6B are schematic diagrams illustrating the relationship between the driven paper discharge roller, the paper discharge roller, and the paper conveyance direction. FIG. 6A is a schematic diagram according to the present embodiment, and FIG. 6B is a schematic diagram according to a comparative example. is there.
The paper guide plate 12 and the paper guide plate 13 are guides for determining the transport direction D of the paper P that enters the paper discharge roller pair composed of the paper discharge roller 14 and the driven paper discharge roller 15. A broken line is a common tangent line 50 between the paper discharge roller 14 and the driven paper discharge roller 15 at the nip position. The paper guide plate 12 and the paper guide plate 13 are positioned so that the transport direction D is closer to the driven paper discharge roller 15 than the common tangent line 50 and the separation position 15a is not present on the transport direction D. Is set. In other words, the conveyance direction D when the driven paper discharge roller 15 is at the separation position 15a is set between the paper discharge roller 14 and the separation position 15a.
In this way, when the driven paper discharge roller 15 moves to the nip position 15b, the paper P being conveyed can be securely nipped at the paper discharge nip portion Nh.

Further, in the present embodiment, the folded portion 12a is provided at the front end portion of the paper guide plate 12, and the folded portion 12a is arranged on the same straight line as the common tangent line 50, or the discharge roller from the common tangent line 50 by the clearance t. It is arranged at a position retracted to the 14 side. With this configuration, it is possible to prevent the sheet P from being bent as shown in the broken-line circle in (b), and it is possible to avoid sheet damage caused by the bending.
As described above, the paper discharge device is provided with the contact / separation mechanism, and the shape of the paper guide plates 12 and 13 is set as described above, so that the front end of the paper collides with the paper discharge roller and the driven paper discharge roller. The paper can be discharged to the paper discharge section. Accordingly, it is possible to avoid the occurrence of a wave due to the front end of the sheet colliding with the roller nip portion described with reference to FIG.

[Movement direction of driven paper discharge roller]
Next, the moving direction of the driven paper discharge roller according to the embodiment of the present invention will be described with reference to FIGS. 7A and 7B are schematic views showing the movement direction of the driven paper discharge roller, where FIG. 7A is a view showing the movement from the separation position to the nip position, and FIG. 7B is a view showing the movement from the nip position to the separation position. FIG. FIG. 8 is a schematic diagram according to a comparative example.
As shown in FIG. 7A, when the driven paper discharge roller 15 moves from the separation position 15a to the nip position 15b with respect to the paper discharge roller 14, the movement direction X of the driven paper discharge roller 15 is from the upstream side in the paper P conveyance direction. The direction is downstream. When moving from the nip position 15b to the separation position 15a, the direction is the reverse direction (movement direction Y). By doing so, paper damage and paper jam are prevented.
As shown in FIG. 8, when the paper P being conveyed is between the paper discharge roller 14 and the driven paper discharge roller 15 and moves from the separation position 15a to the nip position 15b, the paper P is opposite to the paper conveyance direction. Or, when the driven paper discharge roller 15 is pressed against the paper discharge roller 14 by operating in a right angle direction, a braking force F is generated in the paper discharge nip portion Nh with respect to the paper P being conveyed, and the paper front end Pa shown in FIG. The same paper damage and paper jam as when colliding with the paper discharge roller pair occur.

By implementing the present invention described above, it is possible to eliminate paper damage and noise caused by the paper leading edge entering the paper discharge nip portion. Further, by carrying out the contact / separation operation according to the present invention in accordance with the type of paper, environment, and the presence / absence of jamming, improvement of paper conveyance performance, longer life of the paper discharge roller, and improvement of jam handling performance were also achieved.
In the above, the example of the electrophotographic image forming apparatus has been described. However, the present invention can be applied to an image forming apparatus having a paper discharge roller pair in the paper discharge apparatus. For example, the present invention can be applied to an ink jet recording apparatus.

  DESCRIPTION OF SYMBOLS 1 ... Paper discharge apparatus, 11 ... Paper discharge sensor filler, 11a ... Initial position, 11b ... Detection position, 12, 13 ... Paper guide board, 12a ... Folding part, 14 ... Paper discharge roller, 15 ... Driven paper discharge roller, 15a ... Separation position, 15b ... Nip position, 16 ... Paper passage sensor, 17 ... Discharge frame, 18 ... Support shaft, 20 ... Contact / separation mechanism, 21 ... Pressure contact spring, 21a ... One end, 21b ... Other end, 21c ... Restricting piece, 22 ... bearing, 22a ... rotating shaft, 23 ... link piece, 23a ... one end, 23b ... other end, 24 ... support shaft, 25 ... cam follower, 26 ... eccentric cam, 26a ... cam shaft, 26b ... most Distant point, 27: separation spring, 27a ... one end, 27b ... other end, 28 ... stopper, 40 ... contact / separation mechanism, 41 ... solenoid, 42 ... linear motion part, 43 ... driven paper discharge roller base, 44, 45 ... base, 50 ... both Tangential line, 230 ... fixing device, 231 ... heating roller, 232 ... pressure roller, 240 ... discharge tray, P ... paper, Pa ... paper front end, Pb ... paper rear end, Nh ... paper discharge nip, Nt ... fixing nip Part

JP 2007-29881 A JP 2004-309875 A Japanese Patent Laid-Open No. 2005-3940

Claims (10)

A transport unit that transports the paper; an image forming unit that forms an image on the transported paper; and a paper discharge device that discharges the paper on which the image has been formed by the image forming unit to a paper discharge unit. An image forming apparatus,
The paper discharge device includes a drive-rotating paper discharge roller, and a driven paper discharge roller configured to be movable back and forth between a nip position pressed against the paper discharge roller and a spaced apart position. A paper discharge means for discharging the paper to a paper discharge portion while nipping the paper at a nip portion formed by a roller;
A contact / separation mechanism for contacting and separating the driven paper discharge roller with respect to the paper discharge roller;
Detecting means for detecting the presence or absence of the paper that is arranged and conveyed upstream of the nip portion in the paper conveyance direction;
Control means for controlling the operation of the contact / separation mechanism based on the detection result of the detection means,
The control unit determines that the leading edge of the sheet is conveyed downstream by a predetermined distance from a position corresponding to the nip portion based on a detection result of the detection unit when the driven sheet discharge roller is in the separation position. The driven sheet discharge roller is moved to the nip position. A conveying unit that conveys a sheet, an image forming unit that forms an image on the conveyed sheet, a pressure roller, and a heating roller, and fixes the image on the sheet on which the image is formed by the image forming unit. An image forming apparatus comprising: a fixing unit; and a paper discharge device that discharges the paper on which the image is fixed to a paper discharge unit.
The paper discharge device includes a drive-rotating paper discharge roller, and a driven paper discharge roller configured to be movable back and forth between a nip position pressed against the paper discharge roller and a spaced apart position. A paper discharge means for discharging the paper to a paper discharge portion while nipping the paper at a nip portion formed by a roller;
A contact / separation mechanism for contacting and separating the driven paper discharge roller with respect to the paper discharge roller;
Detecting means for detecting the presence or absence of the paper sheet disposed and conveyed upstream of the sheet conveying direction of the fixing device;
Control means for controlling the operation of the contact / separation mechanism based on the detection result of the detection means, wherein the control means uses the detection result of the detection means when the driven paper discharge roller is in the separation position. Based on this, when it is determined that the trailing edge of the sheet has been conveyed to a predetermined distance upstream from the nip portion between the pressure roller and the heating roller, the driven sheet discharge roller is moved to the nip position. Forming equipment.   The control means moves the driven paper discharge roller to the separation position when it is determined that the paper is conveyed downstream from the nip portion of each paper discharge roller by a predetermined distance based on the paper detection result of the detection means. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises:   A paper passage detection means for detecting the trailing edge of the paper, and the paper passage detection means is installed at a position separated by a predetermined distance upstream of the nip portion of the heating roller in the paper transport direction; 3. The image forming apparatus according to claim 1, wherein the driven paper discharge roller is moved to the separation position when the paper passage detection unit determines that the passage of the trailing edge of the paper is detected.   The control means has a predetermined distance from the nip portion of each paper discharge roller to the downstream side of the paper conveyance direction after the predetermined time has elapsed from the passage information of the paper rear edge obtained from the paper detection result of the detection means. 3. The image forming apparatus according to claim 1, wherein the driven sheet discharge roller is moved to a separation position by determining that the sheet is conveyed to a separation position. The contact / separation mechanism includes a pressure contact spring that presses the driven paper discharge roller against the paper discharge roller, a cam that moves the driven paper discharge roller to a nip position and a separation position, drive means that drives the cam, A link piece that connects the cam and the pressure contact spring and has a fulcrum at a substantially central portion, and a tension spring that stretches the link piece in one direction,
6. The link piece is moved in a direction in which the driven paper discharge roller is brought into contact with or separated from the fulcrum by rotating the cam by the driving means. The image forming apparatus described.   The contact / separation mechanism includes a pressure contact spring that presses the driven paper discharge roller against the paper discharge roller, and a solenoid that moves the driven paper discharge roller to a nip position and a separation position. The image forming apparatus according to any one of 1 to 5. A pair of paper guide plates for guiding both sides of the paper immediately upstream of the paper discharge direction of the pair of paper discharge rollers,
The paper guide plate is disposed so that the paper that has passed through the paper guide plate passes between the paper discharge rollers when the driven paper discharge roller is in the separation position.
The folded portion formed at the downstream end of the sheet guide plate on the sheet discharge roller side is on the same straight line as the common tangent line between the sheet discharge roller and the driven sheet discharge roller or the sheet discharge roller from the common tangent line. The image forming apparatus according to claim 1, wherein the image forming apparatus is located near the image forming apparatus.   9. The image forming apparatus according to claim 1, wherein the driven paper discharge roller moves from the separation position to the nip position from the upstream side to the downstream side in the sheet conveyance direction. 10.   The control means controls to move the driven paper discharge roller to a separation position when it is determined that a paper jam has occurred inside the paper discharge device based on a paper detection result by the detection means. The image forming apparatus according to any one of claims 1 to 9.

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