JP5643727B2 - Medium discharging apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a medium discharge device and an image forming apparatus that discharge a medium to a discharge tray.

  Conventional image forming apparatuses such as printers and copiers feed and convey media one by one from a paper feed tray, correct skew by a registration roller, and then transport the media to an image forming unit. The toner image is formed on the medium at the part. Thereafter, the image forming apparatus conveys the medium on which the toner image has been formed by the image forming unit to the fixing device, and fixes the toner image by heat and pressure. Further, the image forming apparatus conveys the medium, on which the toner image is fixed by the fixing apparatus, to the outside of the apparatus by a medium discharging apparatus for conveying the medium to the upper part of the apparatus, and sequentially onto a discharge tray formed on the upper part of the apparatus. Are loaded (see, for example, Patent Document 1).

JP 2010-159142 A (paragraph “0027” to “0030”, FIGS. 1 and 2)

However, in the above-described conventional technology, the front end of the medium discharged from the apparatus by the medium discharge device hangs down in the direction of gravity due to its own weight, and is in contact with the back and end portions of the medium stacked on the discharge tray. When a medium with a rough surface or cut surface is discharged to the discharge tray, the leading edge of the discharged medium is caught on the back or end of the medium loaded on the discharge tray, and the loaded medium The stacking condition of the media in the output tray, such as pushing out and tilting, dropping from the output tray, and the medium being ejected bent from the leading edge caught on the loaded media There is a problem that gets worse.
SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem, and to improve the medium stacking state of a paper discharge tray.

Therefore, the present invention includes a discharge roller pair that rotates while pinching a medium and discharges the medium pinched toward a stacking unit on which the medium is stacked, and the discharge roller pair rotates with the rotation of the medium. And a pair of discharge rollers includes a discharge roller that rotates by rotation of a rotation shaft, and a driven roller that contacts the outer peripheral surface of the discharge roller. The discharge roller and the driven roller form the clamping portion, and the discharge roller is attached to the rotation shaft so that the distance between the rotation shaft and the outer periphery is different at least at two locations. Rotating drive means that rotates at an angular velocity is provided, and the rotational shaft of the discharge roller is rotated by the rotation drive means so that the peripheral speed of the discharge roller in the clamping portion is constant .

  According to the present invention as described above, an effect that the medium stacking state of the paper discharge tray can be improved can be obtained.

Sectional drawing which shows the structure of the discharge part in 1st Example The perspective view which shows the structure of the discharge part in 1st Example. 1 is a schematic side sectional view showing a configuration of a printer in a first embodiment. Explanatory drawing which shows the paper discharge operation in the first embodiment. Explanatory drawing of a comparative example Explanatory drawing which shows the structure of the drive transmission means of the medium discharge apparatus in 2nd Example.

  Embodiments of a medium discharge apparatus and an image forming apparatus according to the present invention will be described below with reference to the drawings.

FIG. 3 is a schematic sectional side view showing the configuration of the printer in the first embodiment.
In FIG. 3, reference numeral 1 denotes a printer as an image forming apparatus, which includes a discharge unit 15 as a medium discharge device.
The printer 1 is detachably mounted on the bottom of the printer 1 with a paper feed cassette 3 that stores and stores sheets 2 as media for recording images. A pickup roller 4 is rotatably disposed above the paper 2 stored in the paper feed cassette 3, and the paper 2 is pressed against the peripheral surface of the pickup roller 4 by an urging means (not shown). The pickup roller 4 rotates counterclockwise in the drawing to feed the paper 2 stacked and stored in the paper feed cassette 3.

In the vicinity of the downstream side of the pickup roller 4 in the paper feeding direction, the paper feeding roller 5 and the retard roller 6 for feeding the paper 2 one by one from the paper feeding cassette 3 are arranged to face each other. ing.
A transport roller pair 7 is rotatably disposed downstream of the paper feed roller 5 and the retard roller 6 in the transport direction of the paper 2 (the direction indicated by the one-dot chain line arrow in the figure). A conveyance roller pair 8 is disposed downstream in the conveyance direction, and conveys the sheet 2 to the image forming unit 9.

  The image forming unit 9 transfers a toner cartridge 9a containing toner as a developer, a recording head 9b as an exposure device, a photosensitive drum 9c as an image carrier, and a toner image formed on the photosensitive drum 9c onto the paper 2. The transfer roller 9d is configured to transfer a toner image corresponding to the recording data to the conveyed paper 2.

The fixing unit 10 is disposed downstream of the image forming unit 9 in the conveyance direction of the paper 2 and fixes the toner image transferred to the paper 2 in the image forming unit 9 to the paper 2 by heating and melting. 11 and a pressure roller 12 that is pressed against and contacts the peripheral surface of the heating roller 11.
A conveyance roller pair 13 is disposed downstream of the fixing unit 10 in the conveyance direction of the sheet 2, and a discharge unit 15 is disposed downstream of the conveyance roller pair 13 in the conveyance direction of the sheet 2.

The discharge unit 15 serving as a medium discharge device includes a discharge roller pair 14 that is rotated by a drive source (not shown), and sandwiches the sheet 2 conveyed by the conveyance roller pair 13 by the discharge roller pair 14 and conveys the paper upward. Discharge out of the device. The paper 2 discharged out of the apparatus by the discharge unit 15 is stacked on a paper discharge tray 16 disposed on the upper portion of the printer 1.
In order to detect the position of the sheet 2 to be conveyed, a sensor 17 is disposed upstream of the conveyance roller pair 8 in the conveyance direction of the sheet 2, and a sensor 18 is provided between the conveyance roller pair 8 and the transfer roller 9d. A sensor 19 is disposed between the pair 10 and the conveying roller pair 13.

FIG. 1 is a cross-sectional view showing the configuration of the discharge portion in the first embodiment, and FIG. 2 is a perspective view showing the configuration of the discharge portion in the first embodiment.
1 and 2, the discharge unit 15 rotates while pinching the paper 2, discharges the paper 2 sandwiched toward a paper discharge tray 16 as a stacking unit on which the paper 2 is stacked, and with the rotation, the paper A nip portion 30 as a nip portion for clamping 2 is provided with a discharge roller pair 14 that moves up and down in the discharge direction of the paper 2.

  In the discharge roller pair 14, a discharge roller 20 that rotates by rotation of a rotary drive shaft 21 as a rotation shaft and a pinch roller 22 as a driven roller contact each other on the outer peripheral surface, and the discharge roller 20 is an abbreviation of the pinch roller 22. The discharge roller 20 and the pinch roller 22 form a nip portion 30 as a nip portion that nips and conveys the paper 2 and is opposed to the upper side. In this embodiment, the discharge roller 20 is described as being disposed so as to be substantially above the pinch roller 22, but the discharge roller 20 is upstream or downstream of the pinch roller 22 in the discharge direction of the paper 2. May be arranged opposite to each other.

  The discharge roller 20, which is the upper roller of the discharge roller pair 14, has a cylindrical shape made of a material having a large friction coefficient so that the rotation center 21 a of the rotary drive shaft 21 is different from the center 20 a on the outer periphery of the discharge roller 20. And is fixed to the rotary drive shaft 21. That is, the discharge roller 20 is provided with a rotation drive shaft 21 at a position different from the center of the outer periphery, and the distance between the rotation drive shaft 21 and the outer periphery is different at least at two locations.

  The pinch roller 22, which is the lower roller of the discharge roller pair 14, has a support shaft 22 a coaxial with the center of the outer periphery of the pinch roller 22 at both ends, and the support shaft 22 a is a part of the structure of the discharge unit 15. In the direction of approaching or separating from the rotation drive shaft 21 of the discharge roller 20 (with respect to the discharge direction of the paper 2 in the discharge unit 15 indicated by the arrows C and D in FIG. 1). It can move in the vertical direction.

  The tip of a torsion spring 24 as an urging means fixed to the structure of the discharge portion 15 supports the support shaft 22a and urges the support shaft 22a in the direction of the rotation drive shaft 21 of the discharge roller 20. doing. Therefore, the outer peripheral surface of the pinch roller 22 is always pressed against and in contact with the outer peripheral surface of the discharge roller 20, and can follow and rotate by frictional force with the outer peripheral surface of the discharge roller 20.

  That is, the nip portion 30 serving as a contact portion between the discharge roller 20 and the pinch roller 22 and sandwiching the paper 2 is accompanied by the rotation of the rotation drive shaft 21 and the eccentric discharge roller 20 in FIG. It moves up and down with respect to the discharge direction of the paper 2 in the discharge portion 15 as indicated by the arrows C and D.

Next, the structure of the paper travel path in the discharge unit will be described with reference to FIG.
A sheet traveling path 25 for conveying the sheet 2, which has been fixed by the fixing device 10, to the upper part of the image forming apparatus is curved between the conveying roller pair 13 and the discharging roller pair 14 of the discharging unit 15. ing. The paper travel path 25 has a sufficient height perpendicular to the paper travel surface, but the paper guide 26 and the paper guide are in the middle (near the center) of the travel path on which the paper 2 travels in a substantially vertical direction. 28, and the leading ends of the paper guide 26 and the paper guide 28 are adjacent to each other in the vicinity of the center at a height orthogonal to the paper running surface. Restricted.

  The paper guide 26 and the paper guide 28 are urged by a spring 27 and a spring 29 in the direction of the paper travel path 25 along which the passing paper 2 travels, and the leading ends of the paper guide 26 and the paper guide 28 are traveled by the paper. Adjacent near the center at a height orthogonal to the surface.

Further, the height perpendicular to the sheet running surface in the vicinity of the upstream side in the conveyance direction of the sheet 2 just before the pair of discharge rollers 14 in the sheet running path 25 is moved up and down even if the nip portion 30 of the pair of discharge rollers 14 moves up and down. The leading edge of the sheet 2 to be conveyed is at a height that can be securely held by the nip portion 30.
In addition, immediately before the pair of discharge rollers 14 in the paper traveling path 25, a paper guide configured to be in contact with the discharge roller 20 and the pinch roller 22 and to be rotatable is provided, and the leading end of the paper 2 to be conveyed is arranged at the nip portion. You may make it guide to 30.

The operation of the above configuration will be described.
First, the operation of the discharge roller pair 14 shown in FIGS. 1 and 2 will be described with reference to the explanatory view showing the paper discharge operation in the first embodiment of FIG.

  FIG. 4A is a view showing that the rotational drive shaft 21 of the discharge roller 20 and the nip portion 30 that is a contact portion between the eccentric discharge roller 20 and the pinch roller 22 are the most distant positions. At this time, the nip portion 30 is at the lowest position with respect to the discharge direction of the paper 2 and the conveyance speed of the paper 2 is maximized. The direction in which the sheet 2 is discharged from the nip portion 30 is a direction orthogonal to a straight line connecting the center of the outer periphery of the discharge roller 20 and the center of the outer periphery of the pinch roller 22. For example, the discharge direction of the sheet 2 is a substantially horizontal direction. .

  4B shows a position where the rotary drive shaft 21 in FIG. 4A is rotated 90 degrees counterclockwise in the drawing, and the height of the nip portion 30 is the same as that of the nip portion 30 in FIG. FIG. 5 is a diagram showing that the sheet 2 is moving upward (in the direction indicated by arrow C in FIG. 1) compared to the height, and at this time, the discharge direction of the sheet 2 is downward as compared with FIG. 4 (a).

  FIG. 4C is a view showing that the rotation drive shaft 21 in FIG. 4A is at a position rotated 180 degrees counterclockwise in the drawing, and the height of the nip portion 30 is the sheet 2 at this time. And the conveyance speed of the paper 2 is the minimum. The discharge direction of the sheet 2 is the same as that in FIG.

  FIG. 4D shows a position where the rotary drive shaft 21 in FIG. 4A is rotated 270 degrees counterclockwise in the drawing, and the height of the nip portion 30 is the same as that of the nip portion 30 in FIG. FIG. 5 is a diagram showing that the sheet 2 is moving downward (in the direction indicated by the arrow D in FIG. 1) compared to the height, and at this time, the discharge direction of the sheet 2 is upward as compared with FIG. 4 (c).

The transport speed of the paper 2 in FIGS. 4B and 4D is the same, and is between the transport speed of the paper 2 in FIG. 4A and the transport speed of the paper 2 in FIG. .
4A and 4C, the direction in which the sheet 2 is discharged from the nip portion 30 is orthogonal to a straight line connecting the center of the outer periphery of the discharge roller 20 and the center of the outer periphery of the pinch roller 22. Direction.

  In this way, the position of the nip portion 30 moves up and down relative to the discharge direction of the paper 2 in conjunction with the rotation of the rotation drive shaft 21, so that the paper 2 held between the discharge roller pair 14 moves up and down with respect to the discharge direction. Since the paper is discharged while moving, not only the nip portion 30 but also the leading edge of the paper 2 is discharged while vibrating up and down in the discharge direction.

Here, the operation of the comparative example in which the rotation drive shaft is attached to the center of the outer periphery of the discharge roller will be described with reference to FIG.
In FIG. 5, the sheet 2 on which the toner image is fixed is discharged from the discharge roller pair 14, the leading end of the sheet 2 hangs down in the direction of gravity, and enters the back surface of the sheet 2 stacked on the sheet discharge tray 16 at an entry angle θ. When the paper discharge proceeds further, the leading edge of the paper 2 moves along the back surface of the paper 2 loaded on the paper discharge tray 16, and when the trailing edge of the paper 2 moves away from the discharge roller 14, the trailing edge of the paper 2 is The paper 2 that has fallen by its own weight and slides toward the discharge unit 15 due to the inclination of the paper discharge tray 16, so that a plurality of papers 2 are stacked on the paper discharge tray 16 with the rear ends aligned.

  In the normal paper 2, when the leading edge moves along the back surface of the paper 2 loaded on the paper discharge tray 16, even if there is a slight catch, it receives a force in the discharge direction from the discharge roller pair 14 and immediately catches the catch. Therefore, the paper 2 stacked on the paper discharge tray 16 in contact with the leading end of the paper 2 to be discharged does not move, and the paper 2 can be stacked in an aligned state on the paper discharge tray 16.

  However, when the edge of the paper 2 is rough due to a cutting process of the paper 2 or the like, the end of the paper 2 discharged from the discharge roller pair 14 is recessed at the edge of the paper 2 loaded on the paper discharge tray 16. The paper 2 stacked on the paper discharge tray 16 is pushed out in the direction indicated by the arrow G in the drawing, so that the paper 2 on the paper discharge tray 16 is inclined and the paper 2 is not stacked. May end up. Similarly, when the surface of the paper 2 is rough, the stacking state of the paper 2 on the paper discharge tray 16 may be similarly deteriorated.

  In addition, the paper 2 having the leading end curled by the pressure at the fixing unit may have a large entry angle θ with the paper 2 stacked on the paper discharge tray 16. The force at which the leading end pushes the paper 2 stacked on the paper discharge tray 16 in the vertical direction is increased, the contact resistance is increased, the paper 2 stacked on the paper discharge tray 16 is pushed out, and the paper 2 on the paper discharge tray 16 is pushed. It may make the loading condition worse.

  In this embodiment, the position of the nip portion 30, which is a contact portion between the discharge roller 20 and the pinch roller 22 that is eccentric in conjunction with the rotation of the rotation drive shaft 21 of the discharge roller 20, is moved up and down with respect to the paper discharge direction. The leading edge of the discharged paper is made to vibrate up and down with respect to the paper discharging direction by moving up and down (in the directions indicated by arrows C and D shown in FIG. 1). Even if the portion is caught by a depression or protrusion at the end of the paper loaded on the paper discharge tray 16, the leading edge of the discharged paper vibrates up and down in the discharge direction of the paper 2 as shown by the arrow F in FIG. Therefore, a force (for example, a force indicated by an arrow E in FIG. 1) to release from the catch is applied, and the catch is immediately released. can do Uninaru.

  In this embodiment, the rotary drive shaft 21 is eccentric and attached to the discharge roller 20 so that the position of the nip portion 30 that is the contact portion between the discharge roller 20 and the pinch roller 22 is moved up and down to be discharged. However, the present invention is not limited to this, and the rotation shafts supporting the discharge roller 20 and the pinch roller 22 are moved up and down by a lifting mechanism such as a cam. Thus, the position of the nip portion 30 may be moved up and down with respect to the paper discharge direction.

  By the way, in this embodiment, as explained in the operation of the discharge roller pair 14 described above, the conveyance speed of the paper 2 discharged by the discharge roller pair 14 is unequal, so the discharge roller pair 14 shown in FIG. While the sheet 2 is nipped and conveyed at the same time by the conveying roller pair 13, the sheet 2 is slackened or pulled. It is assumed that the sheet conveyance speed of the conveyance roller pair 13 and the average sheet conveyance speed of the discharge roller pair 14 are substantially equal.

  Therefore, as shown in FIG. 1, the sheet 2 travels in the vicinity of the center of the travel path perpendicular to the sheet travel surface between the discharge roller pair 14 and the transport roller pair 13 of the sheet travel path 25. The paper guide 26 and the paper guide 28 urged by the spring 27 and the spring 29, respectively, are disposed so that the tips thereof are adjacent to each other at the approximate center in the height of the traveling path.

  For example, when the leading end of the sheet 2 conveyed at the position of the discharge roller pair 14 shown in FIG. 4A enters the nip portion 30, the sheet conveyance speed of the discharge roller pair 14 is maximum, and the rotational drive shaft Since the sheet conveyance speed is reduced during one rotation of the sheet 21, the sheet 2 conveyed through the sheet traveling path 25 is slackened.

  When the paper 2 is slack as described above, the paper travel path 25 is curved so as to protrude in the direction indicated by the arrow A in the drawing as shown in FIG. The intermediate portion of the sheet 2 is slackened in the direction indicated by the arrow A in the figure and travels in the vicinity of the outer peripheral surface side of the curved sheet traveling path 25 while moving the sheet guide 26 in the direction indicated by the arrow A in FIG. At this time, the paper guide 26 receives a force from the paper 2 conveyed through the paper travel path 25, but the biasing force of the spring 27 urging the paper guide 26 is set to be weaker than the force received from the paper 2. Therefore, the paper guide 26 moves in the direction indicated by the arrow A in the figure, and the slackness of the paper 2 can be allowed.

  On the other hand, for example, when the front end of the sheet 2 conveyed at the position of the discharge roller pair 14 shown in FIG. 4C enters the nip portion 30, the sheet conveyance speed of the discharge roller pair 14 is minimum, and the rotation Since the sheet conveyance speed increases while the drive shaft 21 makes one rotation, the sheet 2 conveyed through the sheet traveling path 25 is pulled.

  As described above, when the paper 2 is pulled, the paper travel path 25 is curved so as to protrude in the direction indicated by the arrow A in FIG. The intermediate portion of the sheet 2 is pulled in the direction indicated by the arrow B in the figure, and while moving the sheet guide 28 in the direction indicated by the arrow B in FIG. Run.

  At this time, the paper guide 28 receives a force from the paper 2 conveyed through the paper travel path 25, but the biasing force of the spring 29 that biases the paper guide 28 is set to be weaker than the force received from the paper 2. Therefore, the paper guide 28 moves in the direction indicated by the arrow B in the figure, and can allow the paper 2 to be pulled.

  In the present exemplary embodiment, the paper travel path when the paper transport speed of the transport roller pair 13 and the average paper transport speed of the discharge roller pair 14 are substantially equal has been described, but depending on the paper transport speed ratio of the two roller pairs. The paper guide 26 or the paper guide 28 may not be provided.

  As described above, in the first embodiment, the discharge roller that is attached to the position where the rotational drive shaft is eccentric is used as the discharge portion for discharging the paper, so that the leading edge of the paper to be discharged is It can be vibrated up and down with respect to the discharge direction, and even when using paper with a rough surface that easily catches the leading edge of the discharged paper, stackability and alignment of the paper discharged to the paper output tray As a result, it is possible to obtain an effect that the paper stacking state of the paper discharge tray can be improved.

  The configuration of the second embodiment is configured to include a rotation drive means for rotating the rotation drive shaft of the discharge roller at a sine wave angular velocity.

  The configuration of the discharge portion in the second embodiment is a configuration that does not include the paper guide 26, the paper guide 28, the spring 27, and the spring 29 in the configuration of the discharge portion of the first embodiment shown in FIG. The rest of the configuration in FIG. 1 is the same as that of the first embodiment.

  Further, since the configuration of the printer in the second embodiment is the same as the configuration of the printer in the first embodiment shown in FIG. 3, the description thereof is omitted, and a perspective view of the discharge portion in the second embodiment is also shown in FIG. Since it is the same as the perspective view of the discharge part shown, the description is omitted. Further, the same parts as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.

FIG. 6 is an explanatory diagram showing the configuration of the drive transmission means of the medium discharging apparatus in the second embodiment. 6 (a) is a side view of the gear 31 and the gear 36, FIG. 6 (b) is a front view of the drive transmission means 40, and FIG. 6 (c) is a side view of the non-circular gear 33 and the non-circular gear 34. FIG.
In FIG. 6, a drive transmission means 40 functions as a rotation drive means for rotating the rotation drive shaft 21 of the discharge roller 20 shown in FIGS. 1 and 2 at an angular velocity of a sine wave, and is driven from a drive source (not shown). The gear 31 to be transmitted, the non-circular gear 33 that rotates coaxially with the gear 31 and the shaft 32, the non-circular gear 34 that meshes with the non-circular gear 33, the coaxial rotation with the non-circular gear 34 and the shaft 35, and the rotation of the discharge roller The gear 36 is configured to transmit a driving force to the driving shaft 21.

The non-circular gear 33 and the non-circular gear 34 are, for example, elliptical gears, and when one non-circular gear rotates at a constant angular velocity, the angular velocity of the other non-circular gear becomes a sine wave. Is formed.
In this way, by rotating the rotational drive shaft 21 of the discharge roller 20 shown in FIGS. 1 and 2 by the drive transmission means 40 as the rotational drive means that rotates at the angular velocity of the sine wave, in the nip portion 30 as the clamping portion. The peripheral speed of the discharge roller 20 is made constant.

The operation of the above configuration will be described.
In the second embodiment, the operation of the discharge roller pair 14 (discharge roller 20, pinch roller 22 and nip portion 30) shown in FIGS. 1 and 2 is the same as that of the first embodiment described with reference to FIG. Therefore, the explanation is omitted.
Further, as shown in FIG. 4, the position of the nip portion 30 moves up and down relative to the paper discharge direction in conjunction with the rotation of the rotation drive shaft 21 of the discharge roller 20. The sheet 2 to be discharged is discharged while moving up and down with respect to the discharge direction, and the leading end of the sheet 2 is discharged while vibrating up and down with respect to the discharge direction as in the first embodiment.

  In the present embodiment, a gear train in which a non-circular gear is combined in addition to the normal circular gear shown in FIG. 6 between the drive source (not shown) of the discharge unit 15 shown in FIGS. 1 and 2 and the rotary drive shaft 21. The drive transmission means 40 is provided. The operation of the drive transmission means 40 and the rotary drive shaft 21 will be described with reference to FIG.

  A driving force is transmitted to a gear 31 from a driving source that rotates at a constant angular velocity (not shown), and a non-circular gear 33 that is fixed to the gear 31 and the shaft 32 and rotates coaxially rotates to rotate with the non-circular gear 33. The drive is transmitted to 34. The non-circular gear 33 rotates at a constant angular velocity, but the non-circular gear 34 that meshes with the non-circular gear 33 rotates at a sine wave angular velocity.

  The non-circular gear 34 that rotates at the angular velocity of the sine wave transmits the driving force to the gear 36 connected by the shaft 35, and further, the gear provided at the end of the rotary drive shaft 21 to which the discharge roller is fixed is moved to the sine wave. Rotate at angular velocity. Therefore, the rotary drive shaft 21 rotates at an angular velocity of a sine wave.

  In the first embodiment, since the rotary drive shaft 21 rotates at a constant angular velocity, the sheet is discharged at a conveyance speed that changes at a sine wave cycle corresponding to the eccentricity of the discharge roller 20, but this embodiment In the example, since the gear ratio and the gear arrangement are set so that the drive transmission unit 40 cancels this cycle, the conveyance speed of the discharged paper can be made constant.

Further, by making the conveyance speed of the discharged paper constant, the paper guide 26, the paper guide 28, the spring 27, and the spring 29 in FIG. 1 of the first embodiment can be omitted.
In the present embodiment, the rotary drive shaft 21 is rotated at a sine wave angular velocity by the drive transmission means using a non-circular gear. However, the present invention is not limited to this, and a normal circular gear is used for the drive transmission means. In addition, a drive source such as a motor as a rotation drive means may be rotated at a sine wave angular velocity.

As described above, in the second embodiment, in addition to the effects of the first embodiment, a non-circular gear is combined in addition to a normal circular gear between the drive source of the discharge unit and the rotary drive shaft. By providing drive transmission means that is a gear train, the rotational drive shaft can be rotated at a sine wave angular velocity, and a paper guide, spring, etc. for absorbing slack and tension of the paper in the paper travel path in the discharge section The number of parts can be reduced, and the manufacturing cost can be reduced.
In addition, since the structure of the paper travel path is simplified, it is possible to obtain an effect that the travel of the paper in the discharge unit can be stabilized.

  In the first and second embodiments, the image forming apparatus has been described as a printer. However, the image forming apparatus is not limited to this, and any image forming apparatus having a medium discharge device may be a facsimile machine, a copying machine, a composite machine ( MFP).

DESCRIPTION OF SYMBOLS 1 Printer 2 Paper 3 Paper feed cassette 4 Pickup roller 5 Paper feed roller 6 Retard roller 7, 8, 13 Conveying roller pair 9 Image forming part 10 Fixing part 14 Ejection roller pair 15 Ejection part 16 Ejection tray 20 Ejection roller 21 Rotation drive Shaft 22 Pinch roller 23 Guide 24 Torsion spring 25 Paper travel path 26, 28 Paper guide 27, 29 Spring 30 Nip part 31, 36 Gear 32, 35 Shaft 33, 34 Non-circular gear 40 Drive transmission means

Claims (8)

A pair of discharge rollers that rotate while pinching the medium and discharging the medium pinched toward the stacking unit on which the medium is stacked;
As the discharge roller pair rotates, a holding portion that holds the medium moves up and down with respect to the discharge direction of the medium .
The pair of discharge rollers includes a discharge roller that rotates by rotation of a rotation shaft, and a driven roller that contacts an outer peripheral surface of the discharge roller,
The clamping portion is formed by the discharge roller and the driven roller,
The discharge roller is attached to the rotation shaft so that the distance between the rotation shaft and the outer periphery is different at least in two places.
Furthermore, it comprises a rotational drive means that rotates at an angular velocity of a sine wave,
The medium discharging apparatus according to claim 1, wherein a rotation shaft of the discharging roller is rotated by the rotation driving unit, and a peripheral speed of the discharging roller in the clamping portion is made constant . A pair of discharge rollers that rotate while pinching the medium and discharging the medium pinched toward the stacking unit on which the medium is stacked;
As the discharge roller pair rotates, a holding portion that holds the medium moves up and down with respect to the discharge direction of the medium.
The pair of discharge rollers includes a discharge roller that rotates by rotation of a rotation shaft, and a driven roller that contacts an outer peripheral surface of the discharge roller,
The clamping portion is formed by the discharge roller and the driven roller ,
The discharge roller has the rotating shaft attached to a position different from the center of the outer periphery,
Furthermore, it comprises a rotational drive means that rotates at an angular velocity of a sine wave,
The medium discharging apparatus according to claim 1, wherein a rotation shaft of the discharging roller is rotated by the rotation driving unit, and a peripheral speed of the discharging roller in the clamping portion is made constant . A pair of discharge rollers that rotate while pinching the medium and discharging the medium pinched toward the stacking unit on which the medium is stacked;
As the discharge roller pair rotates, a holding portion that holds the medium moves up and down with respect to the discharge direction of the medium.
The pair of discharge rollers includes a discharge roller that rotates by rotation of a rotation shaft, and a driven roller that contacts an outer peripheral surface of the discharge roller,
The clamping portion is formed by the discharge roller and the driven roller,
The driven roller is driven to rotate around a support shaft while being pressed against and contacted with the outer peripheral surface of the discharge roller, and the support shaft is guided by a guide member so as to be close to or from the rotation shaft of the discharge roller. Move in the direction of separation,
Furthermore, it comprises a rotational drive means that rotates at an angular velocity of a sine wave,
The medium discharging apparatus according to claim 1, wherein a rotation shaft of the discharging roller is rotated by the rotation driving unit, and a peripheral speed of the discharging roller in the clamping portion is made constant . The medium discharging apparatus according to claim 2 or 3 ,
The medium discharge device, wherein the discharge roller is attached with the rotation shaft so that the distance between the rotation shaft and the outer periphery is different at least at two places. The medium discharging apparatus according to claim 3 , wherein
The medium discharge device according to claim 1, wherein the rotation shaft is attached to the discharge roller at a position different from the center of the outer periphery. The medium discharging apparatus according to claim 2 , wherein
The discharge roller is attached to the rotation shaft so that the distance between the rotation shaft and the outer periphery is different at least in two places.
The driven roller is driven to rotate around a support shaft while being pressed against and contacted with the outer peripheral surface of the discharge roller, and the support shaft is guided by a guide member so as to be close to or from the rotation shaft of the discharge roller. A medium discharging apparatus characterized by being movable in a separating direction. The medium discharging apparatus according to any one of claims 1 to 6 ,
The medium discharging apparatus according to claim 1, wherein the rotation driving means is a drive transmission means for converting a rotation drive of a drive source rotating at a constant angular velocity into a rotation drive rotating at a sine wave angular velocity by a non-circular gear.   An image forming apparatus comprising the medium discharge device according to claim 1.

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