JP2002326755A - Recording paper delivering mechanism for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent skew of recording paper without enlarging a device by equalizing carrying quantity difference between both end sides in a perpendicular direction to a recording paper delivery direction even when size of the recording paper to be delivered becomes smaller. SOLUTION: In a delivery roller 1, delivery roller bodies 1a-1c are disposed from both end parts of a delivery roller shaft 4 toward a center part, where diameters Da-Dc of the delivery roller bodies 1a-1c are set to satisfy Da>Db> Dc, with friction coefficients μa-μc set to satisfy μa<μb<μc. In a star roller 3, five star roller bodies 3a-3e are positioned between the delivery roller bodies in an axial direction of the delivery roller shaft 4, and they are disposed to be closer to the delivery roller shaft 4 as they get closer to the center part from both end parts in the axial direction of the delivery roller shaft 4. As the size of the recording paper P becomes smaller, so that only a part of the delivery roller bodies are abutted on the recording paper P at plural positions in the perpendicular direction to the delivery direction, roughly uniform carrying force is applied from the respective delivery roller bodies to the recording paper P, thereby skew of the recording paper P is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a recording sheet discharging mechanism for discharging a recording sheet after an image forming process is completed on an output tray in an image forming apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus such as a printer, a facsimile or a copying machine, a discharge port is formed on one side of the apparatus, a discharge roller is disposed inside the discharge port, and a discharge port on an outer surface of this side. The recording sheet after the image forming process is completed is dropped onto the discharge tray by the rotation of the discharge roller and discharged. In such an image forming apparatus, when an image forming process is continuously performed on a plurality of recording papers, the plurality of recording papers continuously fall on a discharge tray, and the second and subsequent recording papers are discharged. The recording paper falls onto the previous recording paper already discharged onto the discharge tray.

In general, recording paper such as paper or film is flexible. Therefore, when only a conveying force in a direction parallel to the discharge direction is applied to the recording paper from a discharge roller, the front end of the recording paper is lower than the discharge port. It moves in the discharge direction while hanging down. For this reason, when a plurality of recording sheets are continuously ejected, the second and subsequent recording sheets are ejected in such a manner that the front ends thereof move in the ejection direction while rubbing the upper surface of the previously ejected recording sheet. Is done. At this time, if the image formed on the upper surface of the previously discharged recording paper is not completely fixed on the surface of the recording paper, it is discharged first by contact with the front end of the recording paper discharged later. Unfixed images are degraded, and image quality is degraded, such as contamination of the front end of the paper discharged later. Such a phenomenon is likely to occur in an image forming apparatus such as an ink jet system using a liquid ink that requires a relatively long time for fixing to the surface of the recording paper.

Therefore, in the conventional image forming apparatus, the recording paper to be discharged onto the discharge tray after the image forming process is completed is curved in a direction orthogonal to the discharge direction, and the rear end of the recording paper passes through the discharge port. So that the front edge of the recording paper does not hang down until the entire lower surface of the second and subsequent recording papers fall almost simultaneously onto the upper surface of the previously discharged recording paper. This prevents the deterioration of the image quality on the recording paper discharged earlier due to the contact with the copy unit.

[0005] As such an image forming apparatus, there is an image forming apparatus in which a contact member for pressing downward a central portion of a top surface of a recording sheet in a direction orthogonal to a discharge direction is provided downstream of a discharge roller in a discharge direction. However, since the contact member comes into contact with the upper surface of the recording paper after the image forming process is completed with a predetermined pressing force, an image that is not completely fixed on the upper surface of the recording paper is opposite to the discharge direction due to contact with the contact member. , And the image quality deteriorates on the upper surface of the recording paper.

For this reason, Japanese Patent Application Laid-Open No. 9-315651 discloses a configuration of a recording paper discharge mechanism of an image forming apparatus in which a plurality of discharge rollers attached to a discharge roller shaft have different diameters. For example, two types of discharge rollers having different diameters are attached to the discharge roller shaft two by two,
It is stated that the recording paper can be curved in a direction perpendicular to the discharge direction without causing deterioration in image quality on the upper surface of the recording paper due to the difference in diameter between the four discharge rollers.

[0007]

However, in the configuration disclosed in Japanese Patent Laid-Open No. 9-315651, the amount of recording paper transported by each discharge roller attached to the discharge roller shaft, and the amount of recording paper transmitted from each discharge roller. Is not taken into consideration, and when the size of the recording paper is reduced, skew occurs and the mounting posture of the recording paper on the discharge tray cannot be kept constant. Handling becomes complicated.

That is, if the diameter of the plurality of discharge rollers attached to a single discharge roller shaft is different, the rotation amount of the peripheral surface of each discharge roller per unit rotation amount of the discharge roller shaft is different, and the plurality of discharge rollers are different. When the peripheral surface state is constant for all the rollers, the conveyance amount of the recording paper changes in proportion to the diameter of the discharge roller. For this reason, when the size of the recording paper to be subjected to the image forming process is reduced and the width of the recording medium passing through the discharge rollers in the direction perpendicular to the discharge direction is reduced, one of the plurality of discharge rollers having a different diameter from each other is used. In a situation where only the discharge roller of the recording sheet faces the recording sheet, a large-diameter discharge roller contacts one end of the recording sheet and a small-diameter discharge roller contacts the other end in a direction perpendicular to the discharge direction. Therefore, a difference occurs in the conveyance amount of the recording sheet at both ends in a direction orthogonal to the discharge direction, and the recording sheet is skewed.

In this case, as shown in FIG. 5, a contact member 50 in which a plurality of ribs 52a to 52c whose heights Ha, Hb, Hc are set to Ha>Hb> Hc is formed on the upper surface of the base body 51 is formed. The recording paper P that has passed through the discharge roller is discharged by providing star roller bodies 53a to 53e that sandwich the recording paper P between the ribs 52a to 52c and the discharge rollers in the discharge direction of the recording paper. Although it is conceivable to bend in a direction perpendicular to the direction, in this configuration, there is a problem that the discharge path becomes long because the contact member 50 is disposed, and the apparatus becomes large.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the size of a recording sheet to be discharged by individually determining the conveying force acting on the recording sheet from each position in consideration of the diameter of the discharge roller at each position in the axial direction. Even in the case of becoming, the difference in the transport amount at both ends in the direction perpendicular to the recording paper discharge direction is made uniform by the transport force, without increasing the size of the apparatus.
An object of the present invention is to provide a recording sheet discharging mechanism of an image forming apparatus that can prevent skewing of recording sheets.

[0011]

The present invention has the following arrangement as means for solving the above-mentioned problems.

(1) The diameter of the central portion in the axial direction of the discharge roller disposed between the image forming section and the discharge tray is made smaller than the diameter of both ends, and recording is performed from the central portion in the axial direction of the discharge roller. The conveying force per unit area acting on the sheet is made larger than the conveying force acting on the recording sheet from both ends.

In this configuration, the diameter of the discharge roller is increased from the center in the axial direction to both ends, and the conveying force of the recording paper per unit area of the discharge roller is increased from the both ends in the axial direction to the center. It gets larger as you go. Therefore, the recording paper that has passed through the discharge roller is curved in a direction perpendicular to the discharge direction, and the strength of the recording paper increases, and after passing through the discharge roller, the front end of the recording paper does not sag downward due to its own weight. The recording paper may fall onto the discharge tray such that the entire surface is substantially parallel to the upper surface of the discharge tray, and the image quality may deteriorate due to the front edge of the recording paper rubbing the image surface of the previously discharged recording paper. Absent.

When the size of the recording paper to be discharged is reduced by the rotation of the discharge roller, a large-diameter discharge roller contacts one end of the recording paper in a direction perpendicular to the discharge direction of the recording paper, and the other end of the discharge roller contacts the other end. In the situation where the small-diameter discharge roller contacts, even when a difference occurs in the conveyance amount of the recording paper per unit rotation amount of the discharge roller in a direction orthogonal to the recording paper discharge direction, the recording in which the small-diameter discharge roller comes into contact. A large conveying force acts on the other end of the sheet as compared with the one end where the large-diameter discharge roller is in contact, and as a result, the conveying force at both ends of the recording sheet becomes uniform, and the recording sheet is skewed. Will not occur.

(2) The discharge roller is characterized in that the surface of the discharge roller has a higher coefficient of friction at the center in the axial direction than at both ends.

In this configuration, the surface friction coefficient at the center of the discharge roller is made larger than the surface friction coefficient at both ends. Therefore, the frictional force with the recording paper at the center of the discharge roller, which has a relatively small diameter and therefore has a small amount of conveyance per unit rotation, is relatively large, and the conveyance amount per unit of rotation is large because of the relatively large diameter. The frictional force with the recording paper at both ends of the roller is larger than the frictional force with the recording paper, and the difference in the transport amount due to the difference in diameter between the center and both ends of the discharge roller is offset by the frictional force with the recording paper. The conveying force for the recording paper is made uniform over the entire area of the recording paper. For this reason, when the size of the recording paper to be discharged is reduced due to the rotation of the discharge roller, a large-diameter discharge roller abuts on one end side in a direction orthogonal to the recording paper discharge direction, and a small-diameter discharge roller on the other end side. Even when the discharge roller is in contact with the recording sheet, skewing does not occur on the recording sheet.

(3) The vertical resistance of the surface of the discharge roller to the recording paper is greater at the center of the discharge roller in the axial direction than at both ends.

In this configuration, the normal force of the central portion of the discharge roller against the surface of the recording sheet is made larger than the normal force of the both ends of the surface against the surface of the recording sheet. Therefore, the discharge roller having a relatively small diameter and having a small conveyance amount per unit rotation amount has a large vertical resistance against the recording paper at the center of the discharge roller, and having a relatively large diameter having a large conveyance amount per unit rotation amount. Is greater than the vertical drag on the recording paper at both ends, and the difference in transport amount due to the difference in diameter between the center and both ends of the discharge roller is offset by the vertical resistance on the recording paper, and the entire area in the axial direction of the discharge roller is The conveying force for the recording paper is made uniform. For this reason, when the size of the recording paper to be discharged is reduced due to the rotation of the discharge roller, a large-diameter discharge roller abuts on one end side in a direction orthogonal to the recording paper discharge direction, and a small-diameter discharge roller on the other end side. Even when the discharge roller is in contact with the recording sheet, skewing does not occur on the recording sheet.

(4) The discharge roller is divided and arranged at each of a plurality of positions in the axial direction of the discharge roller shaft, and a plurality of driven rollers for nipping the recording paper between the discharge roller and the discharge roller are used to drive the recording paper. It is characterized in that it is rotatably arranged at a position facing each discharge roller sandwiching it or at a position closer to the center in the axial direction between two adjacent discharge rollers.

In this configuration, a plurality of discharge rollers are separately mounted at a plurality of positions in the axial direction of the discharge roller shaft, and the discharge rollers are opposed to each other with the recording paper interposed therebetween or adjacent to each other. A plurality of driven rollers are rotatably arranged at a position near the center in the axial direction between the two discharge rollers. Therefore, the front and back surfaces of the recording paper are sandwiched between the discharge roller and the driven roller at a plurality of identical positions in a direction orthogonal to the discharge direction or at a plurality of alternately different positions. When the front and back surfaces of the recording paper are sandwiched between the discharge roller and the driven roller at a plurality of identical positions in a direction orthogonal to the discharge direction, the surface state of each discharge roller against the recording paper or the normal drag against the recording paper is reduced. By applying the corresponding conveying force, the conveying force at a plurality of positions of the recording sheet in the direction orthogonal to the discharge direction is made uniform.

When the front and back surfaces of the recording sheet are sandwiched between a discharge roller and a driven roller at a plurality of alternately different positions in a direction orthogonal to the discharge direction, each driven roller is driven by a discharge roller shaft. The recording paper comes into contact with the recording paper at a position close to the central discharge roller in the direction, so that the vertical resistance of the central discharge roller against the recording paper is greater than the vertical resistance of the discharge rollers at both ends on the recording paper. Thus, the conveyance force at a plurality of positions of the recording paper in the direction orthogonal to the discharge direction is made uniform.

[0022]

FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus to which a recording sheet discharging mechanism according to an embodiment of the present invention is applied. The image forming apparatus 10 is an inkjet printer that forms an image by selectively discharging liquid ink on the surface of a recording sheet, and is provided in a sheet supply tray 11 that stores a plurality of recording sheets, and is stored in the sheet supply tray 11. Feed roller 1 that feeds out recording paper one by one
2. A pinch roller 13 for nipping and transporting the recording paper fed by the feed roller 12 between the feed roller 12 and an ink tank and an ink head, and a direction perpendicular to the recording paper transport direction (main scanning direction). ), A transport roller 15 for transporting the recording sheet passing through a position facing the carriage 14 to a sheet ejection position, an ejection roller 1 for ejecting the recording sheet to the outside of the apparatus, and an ejection roller 1 ejected. A discharge tray 2 for stacking and storing the recording paper, and star rollers 16 and 3 abutting on the upper surface of the recording paper between the position where the transport roller 15 is disposed and the position where the discharge roller 1 is disposed are provided.

When an image is formed in the image forming apparatus 10, the feed tray 11 is rotated by the rotation of the feed roller 12.
Is fed from the feed roller 12
And, by the rotation of the pinch roller 13, the sheet is intermittently conveyed between the carriage 14 and the platen 17. While the conveyance of the recording paper is stopped, the carriage 14 reciprocates in the main scanning direction while driving the ink head based on the image data, and ink is ejected on the surface of the recording paper. The recording paper on which the image formation has been completed is conveyed by the transport roller 15,
The rotation of the star rollers 16 and 3 causes the conveyance guide 1
The paper 8 is discharged onto the paper discharge tray 2 with the image forming surface facing upward via the paper 8. The discharge tray 2 is disposed below the position between the discharge roller 1 and the star roller 3 by a predetermined distance, and can store a predetermined number of recording sheets on the discharge tray 2.

In the above configuration, the star roller 3 corresponds to the driven roller of the present invention, and together with the discharge roller 1 and the discharge tray 2, constitutes the recording sheet discharge mechanism of the present invention.

Further, when the star rollers 16 and 3 come into contact with the recording paper P on which an image is formed, the peripheral surface thereof is point-contacted with the upper surface of the recording paper P in order to prevent deterioration in image quality due to image offset. It is made into a shape.

FIG. 2 is a diagram showing the configuration of the recording paper discharge mechanism according to the first embodiment of the present invention. In the recording sheet discharge mechanism according to this embodiment, the discharge roller bodies 1a to 1c, 1c to
1a to form a discharge roller 1 and 5
Star roller 3 including a plurality of star roller bodies 3a to 3e
Has been arranged. In the discharge roller 1, the discharge roller bodies 1 a to 1 are arranged from both ends of the discharge roller shaft 4 toward the center.
c is arranged, and the diameters Da to Dc of the discharge roller bodies 1a to 1c are set to Da>Db> Dc. The friction coefficients μa to μc of the respective surfaces of the discharge roller bodies 1a to 1c are set to μa <μb <μc.

The friction coefficient μa to μc of the surface of each of the discharge roller bodies 1a to 1c gives a difference in the frictional force between each of the discharge roller bodies 1a to 1c and the recording sheet P. Recording paper P per unit rotation amount of the discharge roller shaft 4 caused by the difference between the diameters Da to Dc of 1a to 1c
Of each of the discharge roller bodies 1a to 1c
Are set so that the conveying force acting on the recording paper P becomes substantially uniform. The setting of the friction coefficients μa to μc can be performed, for example, by adjusting the surface roughness of the surface of each of the discharge roller bodies 1a to 1c by spraying a ceramic material.

On the other hand, five star roller bodies 3a to 3e
Have the same diameter and surface friction coefficient. Further, each of the five star roller bodies 3a to 3e is located between the respective discharge roller bodies in the axial direction of the discharge roller shaft 4, and further, from both ends in the axial direction of the discharge roller shaft 4 to the center. The discharge roller shaft 4
It is arranged close to. That is, the distance between the star roller body 3c located at the center and the discharge roller shaft 4 is d1, the star rollers 3b located outside the star roller body 3c,
Assuming that the distance between 3d and the discharge roller shaft 4 is d2 and the distance between the outermost star roller bodies 3a and 3e and the discharge roller shaft 4 is d3, d1 <d2 <d3.

With this configuration, the recording sheet P conveyed while being nipped between the discharge roller 1 and the star roller 3 has its central portion downward in the direction orthogonal to the discharge direction (the axial direction of the discharge roller shaft 4). It curves in a convex state. For this reason, the strength of the recording paper P increases, and the front end of the recording paper P does not sag downward by its own weight even after passing between the discharge roller 1 and the star roller 3, and the rear end of the recording paper P is After passing between the discharge roller 1 and the star roller 3, the recording paper P falls onto the discharge tray 2 such that the entire lower surface is substantially parallel to the upper surface of the discharge tray 2.

Accordingly, even when a plurality of recording papers P are continuously discharged onto the discharge tray 2 by performing the image forming process continuously, the recording papers previously discharged onto the discharge tray 2 An incompletely fixed image on the upper surface of P
It is possible to prevent the recording paper P to be discharged next from being rubbed by the front end portion, and to prevent the image quality from deteriorating.

Further, the difference in the conveyance amount of the recording paper P due to the difference in diameter between the discharge roller bodies 1a to 1c is canceled out, and the conveyance force acting on the recording medium from each of the discharge roller bodies 1a to 1c becomes substantially uniform. As described above, since the friction coefficient of the surface of each of the discharge roller bodies 1a to 1c is set, when the size of the recording sheet P to be discharged becomes small, the size of the six discharge roller bodies 1a to 1c is reduced. Even in a situation where only some of the discharge roller members contact a plurality of positions in a direction orthogonal to the discharge direction of the recording sheet P, a substantially uniform conveying force acts on the recording sheet P from each discharge roller member, and There is no skewing of P.

Accordingly, even when the image forming process is continuously performed and a plurality of recording sheets P are successively discharged onto the discharge tray 2, the recording sheets P are discharged in a state where they are aligned with each other. It is possible to easily handle a plurality of recording sheets P stored and discharged at an appropriate position on the tray 2.

FIG. 3 is a diagram showing a configuration of a recording paper discharge mechanism according to a second embodiment of the present invention. The recording paper discharging mechanism according to this embodiment includes a discharging roller 21 and a star roller 31 instead of the discharging roller 1 and the star roller 3 in the configuration of the recording paper discharging mechanism according to the first embodiment shown in FIG. It is a thing. Discharge roller 21
Are attached at six positions in the axial direction of the discharge roller shaft 4 from both ends thereof toward the center, and the diameter Da of each of the discharge roller members 21a to 21c is set.
ＤDc is equal to the discharge roller 1 in that Da>Db> Dc, but each of the discharge roller bodies 21a to 21c
Are different from the discharge rollers 1 in which the friction coefficients of the surfaces of the respective discharge roller bodies 1a to 1c are different from each other in that the friction coefficients of the surfaces are the same.

The star roller 23, which is a driven roller according to the present invention, is constituted by six star roller bodies 23a to 23c which abut the recording paper P on each of the six discharge roller bodies 21a to 21c. This is different from the star roller 3 composed of the five star roller bodies 3a to 3e. In addition, each star roller body 23
The contact forces Pa to Pc of the discharge roller bodies 21a to 21c of a to 23c are set to Pa <Pb <Pc.

The contact forces Pa to Pc of the star roller members 23a to 23c are different from each other in the perpendicular resistance of the discharge roller members 21a to 21c to the recording paper P, so that the diameter of each of the discharge roller members 21a to 21c is changed. The difference in the conveyance amount of the recording sheet P per unit rotation amount of the discharge roller shaft 4 caused by the difference between Da and Dc cancels out, and the conveying force acting on the recording sheet P from each of the discharge roller bodies 21a to 21c is substantially reduced. It is set to be uniform.

Also according to this configuration, the recording paper P nipped and conveyed between the discharge roller 21 and the star roller 23 has a central portion in a direction perpendicular to the discharge direction (axial direction of the discharge roller shaft 4). It curves in a state of being convex downward. For this reason, the strength of the recording paper P increases, and the discharge rollers 2
1 and the recording paper P after passing between the star rollers 23.
The front end of the recording paper P does not hang down due to its own weight, and after the rear end of the recording paper P passes between the discharge roller 21 and the star roller 23, the entire lower surface is formed in the discharge tray 2.
The recording paper P falls onto the discharge tray 2 so as to be substantially parallel to the upper surface of the recording paper P.

Accordingly, even when the image forming process is continuously performed and a plurality of recording papers P are continuously discharged onto the discharge tray 2, the recording papers previously discharged onto the discharge tray 2 An incompletely fixed image on the upper surface of P
It is possible to prevent the recording paper P to be discharged next from being rubbed by the front end portion, and to prevent deterioration of the image quality.

Further, the difference in the transport amount of the recording paper P due to the difference in diameter between the discharge roller bodies 21a to 21c is offset, and the transport force (perpendicular force) acting on the recording medium from each of the discharge roller bodies 21a to 21c is substantially reduced. Since the contact force of each of the star roller bodies 23a to 23c with respect to each of the discharge roller bodies 21a to 21c is set so as to be uniform, when the size of the recording paper P to be discharged is reduced, six Even when only a part of the discharge roller bodies 21a to 21c contact a plurality of positions in a direction orthogonal to the discharge direction of the recording paper P, the recording paper P
, A substantially uniform conveying force acts on the recording paper P, and no skew occurs on the recording paper P.

Accordingly, even when the image forming process is continuously performed and a plurality of recording sheets P are continuously discharged onto the discharge tray 2, the recording sheets P are discharged in a state where they are aligned with each other. It is possible to easily handle a plurality of recording sheets P stored and discharged at an appropriate position on the tray 2.

FIG. 4 is a diagram showing a configuration of a recording paper discharge mechanism according to a third embodiment of the present invention. In the recording paper discharge mechanism according to this embodiment, the star roller 3 in the configuration of the recording paper discharge mechanism according to the first embodiment shown in FIG. 2 and the recording paper according to the second embodiment shown in FIG. It has a discharge roller 21 in the configuration of the discharge mechanism.

However, the star rollers 3a, 3b, 3d and 3e of the star roller 3 are disposed between the discharge roller 21a and the discharge roller 21b of the discharge roller 21 and between the discharge roller 21b and the discharge roller 21c. Between the discharge roller body 21c and the discharge roller body 21b, and between the discharge roller body 21b and the discharge roller body 21a, and are arranged at a position closer to the center of the discharge roller shaft 4. ing. That is, the distance L between the discharge roller body 21a and the discharge roller body 21a at the end of the discharge roller shaft 4 is between the discharge roller body 21a and the discharge roller body 21b.
1, the discharge roller body 21 on the end side of the discharge roller shaft 4.
The distance L2 is shorter than the distance a, and the same applies to the star roller bodies 3b, 3d, and 3e.

The star roller bodies 3a, 3b, 3d,
The amount of deviation of 3e gives a difference in the vertical resistance of each of the discharge roller bodies 21a to 21c to the recording sheet P,
The difference in the transport amount of the recording paper P per unit rotation amount of the discharge roller shaft 4 caused by the difference between the diameters Da to Dc of the respective discharge roller members 21a to 21c is canceled, and
The transport force acting on the recording paper P from a to 21c is set to be substantially uniform.

According to this configuration, the recording paper P conveyed while being nipped between the discharge roller 21 and the star roller 3 is also provided.
In the direction perpendicular to the discharge direction (the axial direction of the discharge roller shaft 4), the central portion is curved so as to be convex downward. For this reason, the strength of the recording paper P increases, and the discharge rollers 2
The front end of the recording paper P does not hang down by its own weight even after passing between the star roller 3 and the star roller 3.
After the trailing edge of the recording paper P passes between the discharge roller 21 and the star roller 3, the recording paper P falls onto the discharge tray 2 such that the entire lower surface is substantially parallel to the upper surface of the discharge tray 2. .

Accordingly, even when the image forming process is continuously performed and a plurality of recording sheets P are continuously discharged onto the discharge tray 2, the recording sheets discharged first onto the discharge tray 2 can be used. An incompletely fixed image on the upper surface of P
It is possible to prevent the recording paper P to be discharged next from being rubbed by the front end portion, and to prevent deterioration of the image quality.

Further, the difference in the transport amount of the recording paper P due to the difference in diameter between the discharge roller bodies 21a to 21c is offset, and the transport force (vertical force) acting on the recording medium from each of the discharge roller bodies 21a to 21c is substantially reduced. Since the deviation amounts of the star roller bodies 3a, 3b, 3d, and 3e are set so as to be uniform, when the size of the recording paper P to be discharged is reduced, six discharge rollers are used. Even in a situation where only a part of the discharge roller members among the members 21a to 21c contact a plurality of positions in a direction orthogonal to the discharge direction of the recording sheet P, substantially uniform conveyance from each discharge roller member to the recording sheet P is performed. The force does not act, and the recording paper P does not skew.

Thus, even when the image forming process is continuously performed and a plurality of recording sheets P are continuously discharged onto the discharge tray 2, the recording sheets P are discharged in a state where they are aligned with each other. It is possible to easily handle a plurality of recording sheets P stored and discharged at an appropriate position on the tray 2.

In the first to third embodiments, the discharge roller is constructed by attaching a plurality of discharge roller bodies to the discharge roller shaft, but the diameter gradually increases from both ends in the axial direction toward the center. The present invention can be implemented in the same manner even when a single discharge roller formed so as to be small in size is used.

In the first to third embodiments, an ink jet printer using a liquid ink has been described as an example. However, an electrophotographic image forming apparatus or a combination of the electrophotographic method and the ink jet method is used. The present invention can be similarly implemented in the image forming apparatus described above.

[0049]

According to the present invention, the following effects can be obtained.

(1) The diameter of the discharge roller is increased from the center in the axial direction to both ends, and the conveying force of the recording sheet per unit area of the discharge roller is increased from both ends in the axial direction to the center. , The recording paper that has passed through the discharge roller is curved in a direction perpendicular to the discharge direction, and the front end of the recording paper hangs down by its own weight even after passing through the discharge roller with increased strength of the recording paper. The recording paper can be dropped onto the discharge tray such that the entire lower surface is substantially parallel to the upper surface of the discharge tray. As a result, it is possible to prevent the deterioration of the image quality due to the front end of the recording paper rubbing the image surface of the recording paper discharged first. When the size of the recording paper to be discharged is reduced by the rotation of the discharge roller, a large-diameter discharge roller contacts one end of the recording paper in a direction orthogonal to the discharge direction of the recording paper, and a small-diameter discharge roller contacts the other end. Even if the conveyance amount of the recording paper per unit rotation amount of the discharge roller in the direction orthogonal to the discharge direction of the recording paper in the situation where the roller comes into contact, a difference occurs in the recording paper that the small-diameter discharge roller contacts. A large conveying force can be applied to the end side as compared with the one end side where the large-diameter discharge roller contacts. This makes it possible to equalize the conveying force at both ends of the recording paper to prevent skew of the recording paper, and to store a plurality of recording papers at an appropriate position on a discharge tray in a state where they are aligned with each other. It is possible to easily handle the plurality of recording papers.

(2) By making the friction coefficient of the surface at the central portion of the discharge roller larger than the friction coefficient of the surface at both end portions, the discharge roller having a relatively small diameter and a small transport amount per unit rotation amount is used. The frictional force with the recording paper at the center is made larger than the frictional force with the recording paper at both ends of the discharge roller, which has a relatively large diameter and therefore has a large transport amount per unit rotation because of its relatively large diameter. The difference in the conveyance amount due to the difference in diameter between the recording paper and both ends is offset by the frictional force with the recording paper, so that the conveyance force on the recording paper over the entire area of the discharge roller in the axial direction can be made uniform. As a result, when the size of the recording paper to be discharged is reduced due to the rotation of the discharge roller, the large-diameter discharge roller abuts on one end side in the direction orthogonal to the recording paper discharge direction, and the small-diameter discharge roller on the other end side. Even in a situation where the discharge roller is in contact, the plurality of recording sheets can be stored at an appropriate position on the discharge tray in a state where they are aligned with each other,
It is possible to easily handle a plurality of discharged recording sheets.

(3) By making the vertical reaction force of the central portion of the discharge roller against the recording sheet on the front surface larger than the vertical reaction force of the front surface on the recording sheet at both ends, the conveyance per unit rotation amount due to the relatively small diameter. The normal force of the discharge roller with a small amount at the center of the discharge roller at the center is larger than the normal force of the discharge roller at both ends of the discharge roller with a relatively large diameter and a large amount of conveyance per unit rotation amount. The difference in the transport amount due to the difference in diameter between the central portion and both end portions can be canceled out by the normal force against the recording sheet, and the transport force on the recording sheet can be made uniform over the entire area of the discharge roller in the axial direction. As a result, when the size of the recording paper to be discharged is reduced due to the rotation of the discharge roller, the large-diameter discharge roller abuts on one end side in the direction orthogonal to the recording paper discharge direction, and the small-diameter discharge roller on the other end side. Even in a situation where the discharge roller is in contact, the plurality of recording sheets can be stored at an appropriate position on the discharge tray in a state where they are aligned with each other,
It is possible to easily handle a plurality of discharged recording sheets.

(4) A plurality of discharge rollers are divided and attached to each of a plurality of positions in the axial direction of the discharge roller shaft, and the discharge rollers are opposed to each other with a recording sheet therebetween, or two adjacent discharge rollers. A plurality of driven rollers are rotatably disposed at a position near the center in the axial direction between the discharge roller and the driven roller at a plurality of the same positions in the direction orthogonal to the discharge direction. When the recording paper is conveyed at a plurality of positions in a direction orthogonal to the discharge direction, a conveying force is applied to the recording paper in accordance with the surface condition of each discharge roller or a perpendicular reaction against the recording paper. The force can be made uniform. Further, when the front and back surfaces of the recording paper are sandwiched between the discharge roller and the driven roller at a plurality of alternately different positions in a direction orthogonal to the discharge direction, each driven roller is disposed at a central portion in the axial direction of the discharge roller shaft. The recording paper is brought into contact with the recording paper at a position close to the discharge roller on the side, and the vertical resistance of the central discharge roller against the recording paper is made larger than the vertical resistance of the discharge rollers on both ends on the recording paper, so that the discharge direction is increased. The conveyance force at a plurality of positions of the recording paper in the direction perpendicular to the direction can be made uniform.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus to which a recording paper discharge mechanism according to an embodiment of the present invention is applied;

FIG. 2 is a diagram illustrating a configuration of a recording paper discharge mechanism according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration of a recording paper discharge mechanism according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating a configuration of a recording paper discharge mechanism according to a third embodiment of the present invention.

FIG. 5 is a diagram illustrating a configuration of a main part of a conventional recording sheet discharging mechanism.

[Explanation of symbols]

 1-discharge roller 1a-1c-discharge roller body 2-discharge tray 3-star roller (driven roller) 3a-3e-star roller body 4-discharge roller shaft P-recording paper

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H072 CA01 FB01 FB08 JA02 3F049 AA02 CA02 CA05 CA31 DA12 DB11 LA02 LA05 LA07 LB03 3F053 HA06 HB01 LA02 LA05 LA07 LB03

Claims (4)

[Claims] A discharge roller disposed between an image forming section and a discharge tray, wherein the diameter of a central portion in the axial direction is smaller than the diameters of both ends of the discharge roller; Wherein the conveying force per unit area acting on the recording paper is greater than the conveying force acting on the recording paper from both ends. 2. A recording sheet discharging mechanism according to claim 1, wherein a coefficient of friction of a surface of said discharging roller is larger at a central portion in an axial direction of said discharging roller than at both ends. 3. The recording sheet discharge of an image forming apparatus according to claim 1, wherein a vertical reaction force of the surface of the discharge roller against the recording sheet is larger at a central portion in the axial direction of the discharge roller than at both ends. mechanism. 4. A discharge roller, wherein said discharge roller is divided into a plurality of positions in an axial direction of a discharge roller shaft, and a plurality of driven rollers for holding a recording sheet between the discharge roller and the discharge roller are provided. The recording sheet of the image forming apparatus according to claim 1, wherein the recording sheet is rotatably disposed at a position facing each discharge roller or at a position near a center in an axial direction between two adjacent discharge rollers. Discharge mechanism.