JPH11228005A - Sheet conveying device and image forming device - Google Patents

Abstract

An object of the present invention is to make a correction amount of a reverse curl variable, and to flatten a sheet material by rubbing it in a conveyance direction, so that a corner is broken in subsequent conveyance and discharge. It is an object of the present invention to provide a sheet conveying apparatus and an image forming apparatus capable of preventing occurrence of a sheet jam. SOLUTION: In order to solve the above problem, a typical configuration of a sheet conveying device and an image forming apparatus according to the present invention is as follows.
A drive source capable of normal and reverse rotation and temporary stop, two transport rollers driven by the drive source, a driven roller urged and driven by the two transport rollers, and a transport roller and the driven roller A convex member protruding from the nip is provided so that the sheet material being conveyed is curved in the conveying direction and the direction perpendicular thereto, and is reciprocated to pass through the nip a plurality of times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer, a facsimile, and a copying machine for conveying a sheet material to an image forming section.

[0002]

2. Description of the Related Art As an example of a conventional image forming apparatus, FIG.
The schematic configuration of the laser beam printer will be described using FIG. A laser printer 101 shown in FIG. 10 includes a main body 103 capable of forming an image on one surface of a sheet material, and a reversing device 102 for reversing the sheet material and re-feeding the sheet material.

In the laser printer 101, a video controller board (image signal generating means) 113 generates an image signal based on information transmitted from an external information device such as a personal computer or a word processor, and a process unit is generated based on the image signal. An electrostatic latent image is formed on the photosensitive drum 104a, and the toner image is developed by a developing unit (not shown).

On the other hand, the sheet material S
Are stacked and stored, and the toner image on the photosensitive drum 104a is transferred one by one from the uppermost sheet material. After the toner image on the photosensitive drum 104a is transferred, the toner image is applied to the sheet surface by applying heat and pressure by the fixing roller 106. Be established. If the laser printer 101 is set to form an image on one side only, the sheet material S that has been subjected to the toner image fixing process is deflector 10
7 is switched to the position indicated by 107a in the figure, and is discharged onto the discharge tray 108 on the upper part of the main body.

When the laser printer 101 is set to form an image on both sides, the sheet material S after the fixing process of the toner image is deflected by the deflector 107 in FIG.
The position is switched to the position indicated by b. As a result, the sheet material S is discharged out of the main body 103 through the reverse connection path 109.

The sheet material S discharged out of the main body 103 has a downward curl. So the reversing device 10
A curl removing roller pair 110 is provided in 2 and corrects curls and crimps by giving the sheet material S an upward curl.

The sheet material S is reversed by the switchback roller pair 112 and the reversing path 112a, and is conveyed with the first surface on which the toner image is formed up with the rear end of the sheet material S at the top. After that, feed cassette
The toner is conveyed to the main body 103 from the re-feeding path 105a in the printer 105, the toner image is transferred and fixed on the second surface, and then discharged onto the discharge tray.

[0008]

In the curl removing roller pair 110 of the image forming apparatus as described above, the curl in the downward direction is merely corrected to the curl in the upward direction. May occur. Therefore, the curl cannot be actively corrected.

In addition, since the ability to correct upward curl is always constant, there is another problem that it is not possible to cope with a change in curl amount due to the type of sheet material or environment.

Therefore, the present invention makes the correction amount of the reverse curl variable, and flattens the sheet material by rubbing it in the conveying direction, thereby causing corners and jams in subsequent conveying and discharging. It is an object of the present invention to provide a sheet conveying apparatus and an image forming apparatus capable of preventing the occurrence of the sheet.

[0011]

In order to solve the above-mentioned problems, a representative configuration of a sheet conveying apparatus and an image forming apparatus according to the present invention includes a driving source capable of normal and reverse rotation and a temporary stop,
Providing two transport rollers driven by the drive source, a driven roller biased and driven by the two transport rollers, and a convex member protruding from a nip between the transport roller and the driven roller. The sheet material is curved in the conveying direction and the direction perpendicular thereto, and is reciprocated so as to pass through the nip a plurality of times.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A first embodiment of a sheet conveying apparatus and an image forming apparatus according to the present invention will be described with reference to the drawings. 1 is an overall configuration diagram of the image forming apparatus, FIG. 2 is an enlarged explanatory view showing the vicinity of a pair of curl removing rollers, FIG.
FIG. 5 is a front view of a state in which a pair of curling rollers sandwiches a sheet material. A laser printer 1 shown in FIG. 1 includes a main body 3 capable of forming an image on one surface of a sheet material, and a reversing device 2 for reversing and re-feeding the sheet material S.

[Overall Configuration] In the laser printer 1,
A video controller board (image signal generating means) 4 generates an image signal based on information transmitted from an external information device such as a personal computer or a word processor.
In the figure, various electronic components installed on the video controller board 4 are not shown.

The laser scanner 5 irradiates a laser beam L according to the image signal generated by the video controller board 4 to form an electrostatic latent image on the photosensitive drum 6a rotating clockwise. The electrostatic latent image formed on the photosensitive drum 6a is sequentially visualized by toner supplied from a developing unit (not shown) in the process unit 6, and moves to a transfer portion between the transfer roller 7 and the transfer unit.

On the other hand, the sheet material S is loaded and stored in the feeding cassette 8, and is sequentially fed one by one from the uppermost sheet material S by a half-moon-shaped feeding roller 9 rotating in a counterclockwise direction. It is sent out to 10 a and is conveyed to the registration roller pair 12 whose rotation is stopped by the conveyance roller pair 11. The sheet material S that has reached the registration roller pair 12 is continuously conveyed until a predetermined loop is formed after the leading end of the sheet material S hits the nip of the registration roller pair 12, thereby correcting the skew state.

The sheet material S whose skew has been corrected is
The toner image on the photosensitive drum 6a is transferred to the nip between the photosensitive drum 6a and the transfer roller 7 by the registration roller pair 12 which starts rotating at the timing of aligning the position with the toner image on the photosensitive drum 6a. The sheet material S after the transfer of the toner image is conveyed to the fixing roller 14 through the conveyance guide 13, where the transferred toner image is fixed on the sheet surface by applying heat and pressure. It is formed.

Sheet material S after fixing process of toner image
In the case where the laser printer 1 is set to form an image on only one side, the deflector 15
The position is switched to the position indicated by a. As a result, the sheet material S is conveyed through the discharge path 16 by the conveying roller pair 18 and is discharged onto the discharge tray 17 on the upper portion of the main body by the discharge roller 19.

When the laser printer 1 is set to form an image on both sides, the deflector 15 is switched to the position indicated by 15b in FIG. . Thereby, the sheet material S is discharged out of the main body 3 through the reverse connection path 20.

The sheet material S discharged out of the main body 3 includes:
A downward curl has occurred. Therefore, a pair of conveying rollers 23 and a pair of curling rollers 24, which will be described in detail later, are provided in the reversing device 2 to correct the curl and crimp of the sheet material S.

The transport path 25 is provided with a sensor arm 26 as means for detecting the leading end and the trailing end of the sheet material S. The sensor arm 26 includes a detection arm 26a that rotates by the conveyance force of the sheet material S, and a shielding arm 26 that shuts off a light source of the photo interrupter 27 in accordance with the movement.
b. When there is no sheet material S, the sensor arm 26 is located in the transport path 25 as shown by a solid line in the figure, and the shielding arm 26b does not block the light source of the photo interrupter 27. When the sheet material S is sent out by the conveying roller pair 24 and is rotated by the conveying force as shown by the broken line in the figure, the shielding arm 26b shields the light source of the photo-interrupter 27 and detects the existence of the sheet material S. Can be detected.

Thereafter, when the sheet material S is conveyed to the reversing path 41a by the switchback roller pair 41 and the rear end of the sheet material S passes through the sensor arm 26, the sensor arm
By returning the posture, the light source 26 does not block the light source of the photo interrupter 27. As a result, the switchback roller pair 41 rotates in the reverse direction, and the sheet material S is conveyed from the reversing path 41a to the reference plate path 29 through the conveying path 28 with the rear end of the sheet material S as the head. Therefore, when the sheet material S reaches the pair of transport rollers 42, the first surface of the sheet material S on which the toner image is formed faces upward.

In the reference plate path 29, a reference plate 32 is provided, and the sheet material S is conveyed by a pair of oblique feed rollers 30, 31 pressed against rollers having a predetermined inclination, and the sheet material S is transferred to the reference plate.
By imitating the sheet 32, the transport position of the sheet material S is corrected. Thereafter, the sheet is sent from the conveying path 33 to the pair of conveying rollers 34 of the re-feeding unit 40, passes through the re-feeding path 35, and is conveyed from the re-feeding path 8 a in the feeding cassette 8 to the main body 3 by the re-feeding roller 36. Is done.

Thereafter, the sheet material S is conveyed from the conveying roller pair 11 to the registration roller pair 12 whose rotation is stopped in the same manner as described above, and after the transfer and fixing of the toner image on the second surface are performed,
The sheet is discharged onto the discharge tray 17.

[Curl Removal Roller Pair] As shown in FIG. 2, the curl removal roller pair 24 includes a drive roller 43, a drive roller 44 arranged in parallel with the drive roller 43 on the transport path, and a pair of these two rollers. And a driven roller 45 urged by an elastic body 43a. These drive rollers 43,
The drive roller 44 is rotationally driven by a drive source 48, and the driven roller 45 is driven accordingly. An elastic body portion 43 a is provided on the outer periphery of only the driving roller 43, and is configured to generate a greater conveying force than the driving roller 44.

As a result, the nip shape at the pressure contact portion of the curl removing roller pair 24 becomes a curved shape protruding downward. Then, the sheet material S follows this nip shape when passing through the curl removing roller pair 24, and the curl is corrected in the upward direction.

The driving source 48 can selectively drive the sheet material S in the normal rotation direction (CCW direction) and the reverse direction (CW direction) for conveying the sheet material S. As a result, the driving rollers 43 and 44 reciprocate the sheet material and can pass the curl removing roller pair 24 a plurality of times. On the upstream side of the curl removing roller pair 24, a curl straightening path 50 composed of conveyance guides 50a and 50b is formed. When the curl removing roller pair 24 is driven to rotate in the reverse direction, the sheet material S It is configured to enter the correction path 50.

As shown in FIG. 3, the driven roller 45 of the curl removing roller pair 24 is provided with a roller portion 46 and a roller portion 47 having different diameters. The roller portion 46, which is a pressure contact portion, is in pressure contact with the drive roller 43 and the drive roller 44, and is able to pinch and convey the sheet material S following the pressure. On the other hand, the roller portion 47, which is a non-pressing portion, has a larger diameter than the roller portion 46, and the drive rollers 44, 45 are not provided with a corresponding roller portion. That is, the roller portion 47 forms a convex member that protrudes from a nip between the drive rollers 43 and 44 that are transport rollers and the driven roller.

Therefore, when the sheet material S is conveyed, the sheet material is curved in the vicinity of the roller portion 47 so as to be convex downward. As a result, the sheet material S is stiffened in a direction parallel to the conveying direction, and as a result, the curl is corrected.

A lever 49 is provided upstream of the curl removing roller pair 24 in the transport direction, and is configured to rotate as the sheet material S passes. The rotation of the lever 49 is detected by a photo sensor (not shown), and the arrival of the rear end of the sheet material S near the nip portion of the curl removing roller pair 24 is detected.

[Operation] FIG. 4 is a flowchart showing the control of the operation of the curl removing roller pair 24 configured as described above. First, image formation is started (S1), and when there is a drive start signal for re-feeding (S2), the drive source 48 is driven to rotate in the normal rotation direction (CCW direction in FIG. 2).

When the rear end of the conveyed sheet S is detected by the lever 49 (S4), if the curl correction process is not performed, the sheet S is conveyed as it is (S5). On the other hand, when performing the curl correction processing, the set curl correction length and the number of repetitions are acquired (S6), and the curl correction processing is started (S7).

First, the driving source 48 is turned in the reverse direction (CW direction in FIG. 2).
And the drive rollers 43 and 44 are rotated in the opposite directions (S8). Then, since the nip of the curl removing roller pair 24 is curved downward, the rear end of the sheet material S is lifted up and enters the curl correction path 50 as shown by the two-dot line in FIG.

The sheet S is conveyed by a predetermined amount by reversal driving of the drive source 48 (S9), and the leading end of the sheet material S
Before passing through 50c, the drive source 48 is switched to forward drive (S10). Then, the sheet material S is conveyed again until the rear end thereof approaches the curl removing roller pair 24. If the predetermined curl correction processing has been performed here (S12), the sheet material S is conveyed as it is (S13). The driving source 48 is driven in the reverse direction (S8).

By repeating the above-described repetitive operations, the curl removing roller pair 24 is passed a plurality of times, and a curl correcting force corresponding to the number of times can be applied. Therefore, it is possible to adjust the curl correcting ability according to the situation.

At the same time, the stiffening is performed by the roller unit 47 in a direction parallel to the conveying direction.
, And jams, corner breaks, discharge, and improper stacking can be prevented.

Further, since the elastic portion 43a is formed only on the drive roller 43 on the upstream side in the transport direction, the transport force of the drive roller 43 is larger than that of the drive roller 44. Thus, the sheet material can be conveyed without being stagnated after being nipped by the drive roller 43 on the upstream side, until it is conveyed by the drive roller 44 on the downstream side, and also when it is nipped by the drive roller 44. .

Second Embodiment Next, a second embodiment of the sheet conveying apparatus and the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 5 is a side view of the curl removing roller pair according to the present embodiment, and FIG. 6 is a front view of the curl removing roller pair. The same parts as those in the first embodiment will be denoted by the same reference numerals, and description thereof will be omitted. This embodiment is another example of a configuration for stiffening a sheet material in the first embodiment.

The curl removing roller pair 51 according to the present embodiment shown in FIG. 5 includes driving rollers 43 and 44 and a driven roller 52 urged by these two rollers by an elastic body 45a. The driven roller 52 has a plurality of roller portions 52a and 52b all having the same diameter, and can be conveyed by sandwiching a sheet material between the driven rollers 43 and 44.

FIG. 6 is a diagram viewed from the direction C in FIG. As shown in the figure, a transport guide 53 projecting downward is provided between a roller portion 52a outside the driven roller 52 and a roller portion 52b at the center. At positions corresponding to the transport guide 53, the roller portions 43a, 44a of the drive rollers 43, 44
Is not arranged, and the leading end of the transport guide 53 is
And the drive roller 44, it protrudes from the nip.

The positional relationship between the curl removing roller pair 51 will be described with reference to FIG. FIG. 5 is a sectional view taken along the line BB in FIG. The sheet material S conveyed from the main body 3 is once conveyed in the reverse direction, and has entered the curl correction path 50 as shown by a two-dot line in the figure.

Here, the distance L2 from the shaft center 52c of the driven roller 52 to the tip of the transport guide 53 is the distance L1 from the shaft center 52c to the nip between the driven roller 52 and the downstream drive roller 44.
Greater than. As a result, the passing sheet material is curved downward as shown in FIG. 6, and the sheet material has undulation in a direction perpendicular to the conveying direction, is stiffened in a direction parallel to the conveying direction, and the curl is corrected. It will be.

Third Embodiment Next, a third embodiment of the sheet conveying apparatus and the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 7 is a side view of the curl removing roller pair according to the present embodiment, and FIG. 8 is a front view of the curl removing roller pair. The same parts as those in the first embodiment will be denoted by the same reference numerals, and description thereof will be omitted. This embodiment is an example of another configuration of the curl removing roller pair in the first embodiment.

The curl removing roller pair 54 shown in FIG. 7 includes a driving roller 55 driven by a driving source 60 and a driven roller 56 driven by the driving roller 55. The driven roller 56 is supported by the holder 58 so as to be slidable in a direction in which the driven roller 56 moves toward and away from the drive roller 55. An elastic body 59 is attached to the holder 58, and urges the driven roller 52 against the drive roller 55. The drive roller 55 and the driven roller 56 are in contact with each other at a predetermined angle, and the nip thereof is disposed so as to face the curl correction path 50.

A curl straightening guide 57 that forms a curved transport path along the driven roller 56 is provided downstream of the drive roller 55 in the transport direction. Therefore, the decurling roller pair
The nip shape at 54 becomes a curved shape protruding downward, and the curl of the sheet material S is corrected upward.

FIG. 8 shows a pair of curl removing rollers in FIG.
Reference numeral 54 is a view of the state in which the sheet material S is held when viewed from the F direction. The driven roller 56 includes a pressing roller portion 56a that presses against the elastic roller portion 55a of the driving roller 55, and a squeezing roller portion 56b having a larger diameter. As shown in the figure,
The stiffening roller portion 56b is an elastic roller portion 55 of the driving roller 55.
a and projecting downward from the nip between the pressing roller portion 56a and
Further, the drive roller 55 is not provided with a roller that presses against it.

Accordingly, when the sheet material S is nipped and conveyed by the curl removing roller pair 54, the sheet material S is undulated by the stiffening roller portion 56b so as to protrude downward. As a result, stiffening is performed in a direction parallel to the transport direction, and the curl is corrected.

[Fourth Embodiment] Next, a fourth embodiment of the sheet conveying apparatus and the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 9 is a side view of the curl removing roller pair according to the present embodiment, and the same reference numerals are given to the same portions as those in the first embodiment, and the description will be omitted. This embodiment is an example of another configuration of the curl removing roller pair in the first embodiment.

The drive rollers 43 and 44 of the curl removing roller pair 61 shown in FIG. 9 are provided with bearings 62 and 63 each having one spring supporting portion. The driven roller 45 has two spring supporting portions. Is mounted. bearing
The two spring support portions 64 are arranged at a predetermined angle so as to face the axial centers of the drive rollers 43 and 44, and the two springs 6
The driven rollers 45 are pressed against the drive rollers 43 and 44 by drawing the bearings 62 and 63 by 5 and 66.

Of the two springs 65 and 66, the sheet material S
The tension of the spring 65 provided on the upstream side with respect to the transport direction is larger than that of the spring 66 provided on the downstream side. Thereby, the conveying force of the sheet material S by the upstream drive roller 43 becomes larger than that of the downstream drive roller 44. Therefore, after the sheet material is nipped by the upstream drive roller 43, until the sheet material is conveyed to the downstream drive roller 44,
Also, when the sheet is nipped by the driving roller 44, the sheet can be conveyed without stagnation.

According to the above-described configuration, the sheet material S can be curled in the opposite direction to the curl generated in the same manner as in the first to third embodiments, and can be stiffened in the conveying direction. Can correct the curl.

[0051]

As described above, in the sheet conveying apparatus and the image forming apparatus according to the present invention, the sheet material is passed through the curling roller pair a plurality of times, so that the curl in the opposite direction applied to the sheet material is improved. Can be adjusted, and appropriate curl correction can be performed according to the curl state that differs depending on the paper type and environment. Therefore, there is an effect that jamming and corner breakage can be avoided in subsequent conveyance, discharge, and stacking.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an enlarged explanatory view near a curl removing roller pair.

FIG. 3 is a front view of a state in which a pair of curl removing rollers sandwich a sheet material.

FIG. 4 is a flowchart illustrating an operation of removing curl.

FIG. 5 is a side view of a curl removing roller pair according to a second embodiment.

FIG. 6 is a front view of a curl removing roller pair.

FIG. 7 is a side view of a curl removing roller pair according to a third embodiment.

FIG. 8 is a front view of the curl removing roller pair.

FIG. 9 is a side view of a curl removing roller pair according to a fourth embodiment.

FIG. 10 is a diagram illustrating a schematic configuration of a conventional image forming apparatus.

[Explanation of symbols]

 S ... Sheet material 1 ... Laser printer 2 ... Reversing device 3 ... Main body 4 ... Video controller board 5 ... Laser scanner 6 ... Process unit 6a ... Photosensitive drum 7 ... Transfer roller 8 ... Supply cassette 8a ... Refeed path 9 ... Supply Feed roller 10a… Sequential feed path 11… Transport roller pair 12… Registration roller pair 13… Transport guide 14… Fixing roller 15… Deflector 16… Discharge path 17… Discharge tray 18… Convey roller pair 19… Discharge roller 20… Reverse connection Path 23… Conveying roller pair 24… Curl removing roller pair 25… Conveying path 26… Sensor arm 26a… Detecting arm 26b… Shielding arm 27… Photo interrupter 28… Conveying path 29… Reference plate path 30, 31… Slanting roller pair 32… Reference plate 33… Convey path 34… Convey roller pair 35… Re-feed path 36… Re-feed roller 40… Re-feed unit 41… Switch Roller pair 41a… Reversing path 42… Conveying roller pair 43,44… Drive roller 45… Driving roller 45a… Elastic body 46,47… Roller part 48… Drive source 49… Lever 50… Curl straightening path 51… Curl removing roller pair 52 … Following roller 53… Conveying guide 54… Curl removing roller 55… Drive roller 56… Following roller 57… Curl straightening guide 58… Holder 59… Elastic body 60… Drive source 61… Roller pair 62, 63, 64… Bearing 65, 66… spring

Claims (8)

[Claims] A driving source capable of rotating forward and backward and temporarily stopping;
It has a transport roller driven by the drive source, and a driven roller that is urged and driven by the transport roller, and provided a convex member protruding from a nip between the transport roller and the driven roller, and transported. A sheet material that is bent in a direction perpendicular to the conveying direction. 2. The driven roller has a pressure contact portion that presses against the transport roller, and a non-pressure contact portion that is the convex member and does not press against the transport roller. The diameter of the non-pressure contact portion is the diameter of the pressure contact portion. 2. The sheet conveying device according to claim 1, wherein the sheet conveying device is formed larger than the sheet conveying device. 3. A transport guide, which is the convex member, is provided at a position where the transport roller and the driven roller are not arranged at positions facing each other, and a leading end of the transport guide is connected to the transport roller and the transport roller. 2. The sheet conveying device according to claim 1, wherein the sheet conveying device is configured to protrude from a nip between the driven roller and the driven roller. 4. The apparatus according to claim 1, wherein two of said conveying rollers are pressed against said driven roller to convey a sheet material by curving the sheet material along said driven roller. Sheet conveying device. 5. The sheet conveying device according to claim 4, wherein the two conveying rollers that are in pressure contact with the driven roller have different conveying forces at respective pressure contacts. 6. The sheet conveying apparatus according to claim 5, wherein, of the two conveying rollers, only the conveying roller on the upstream side in the conveying direction is constituted by a roller having elasticity. 7. The pressing force of each of the two conveying rollers pressing against the driven roller is set such that the pressing force of the upstream conveying roller in the conveying direction is larger than the pressing force of the downstream conveying roller. The sheet conveying apparatus according to claim 5, wherein 8. An image forming apparatus comprising: a supply unit for supplying a sheet material; an image forming unit for forming an image on the sheet material; and the sheet conveying device according to claim 1. .