JPH06286904A - Paper conveying mechanism for image forming device - Google Patents

Abstract

PURPOSE:To suppress vibration of paper so as to prevent deviation in transference by arranging a pair of upper/lower conveying rollers upstream and the downstream in a paper conveying direction, and setting a peripheral speed of the downstream conveying roller relatively increased, to also provide a one- way clutch in a rotary shaft of the upstream conveying roller. CONSTITUTION:In a paper conveying mechanism wherein paper fed from a paper feed cassette is fed to a photoreceptor 23 by rollers and discharged after forming an image, a pair of upper/lower PS (paper stop) rollers 30 and a pair of upper/lower fixing rollers 31 are respectively arranged upstream and the downstream relating to the photoreceptor 23. Roller shafts 30a of the PS rollers 30 are rotated in a direction of arrow mark (a) by a drive part 36 through one-way clutches 37 internally fitted to gears 39, 40 meshed with each other, and also the fixing rollers 31 are rotated by drive force of a motor at a peripheral speed about 1 to 2% faster than that of the PS roller 30. Thus by applying large tension to gradually act on a paper sheet Y, the PS roller 30 is idly rotated by prescribed or larger tension, so as to remove the paper sheet Y.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper carrying mechanism for carrying paper in an image forming apparatus such as an electrophotographic copying machine and a laser printer.

[0002]

2. Description of the Related Art In a conventional image forming apparatus such as a copying machine or a laser printer, a fixing roller and a paper stop roller (PS roller) arranged with a photoconductor interposed therebetween are provided in order to prevent the slack of the paper when the paper is conveyed. Giving a difference in peripheral speed,
The paper was always conveyed while being pulled by the fixing roller. However, when the trailing edge of the sheet comes out of the PS roller, the trailing edge of the sheet vibrates at that moment, and the vibration propagates in the front direction of the sheet and reaches the transfer device. Because of this,
There has been a problem that transfer deviation occurs and the image quality is adversely affected.

In order to solve this problem, as shown in FIG.
In the conveying path 3 between the fixing roller 1 and the PS roller 2, especially near the photoconductor 4 and the transfer device 5 on the PS roller 2 side,
By providing a pressing member 7 (PET material, thin elastic plate, cushion material, etc.) forcibly pressing the paper Y to the transfer case 6 side, the vibration when the trailing edge of the paper Y comes out of the PS roller 2 is suppressed. The sheet Y is prevented from propagating in the forward direction on the transfer device 5 side.

[0004]

However, in this conventional method, when the trailing edge of the sheet Y comes out of the pressing member 7, the trailing edge of the sheet Y vibrates, so that the transfer deviation can be completely prevented. There wasn't.

Further, the pressing member 7 is provided as much as possible to the transfer device 5.
Since it is necessary to provide it in the vicinity of the
Assembling work in the vicinity has very poor workability, and there is a problem that the stability of the quality of the image forming apparatus deteriorates.

Further, since the sheet Y is always pulled toward the fixing roller 1 between the fixing roller 1 and the PS roller 2, at the moment when the sheet Y comes out of the PS roller 2, the driving force of the PS roller 2 is generated by its reaction. In this case, a large load fluctuation occurs, which causes uneven rotation of the PS roller 2. Since the drive system of the PS roller 2 and the drive system of the other transport rollers are the same, it also affects the drive of the other transport rollers and induces rotation unevenness of the other transport rollers, which causes transfer deviation. There was a problem that occurred.

In view of the above, it is an object of the present invention to provide a sheet conveying mechanism of an image forming apparatus capable of suppressing the vibration of the sheet being conveyed and preventing the transfer deviation.

[0008]

According to a first aspect of the present invention, a pair of upper and lower sheet conveying rollers are arranged on the upstream side in the sheet conveying direction, and a pair of upper and lower sheet conveying rollers are arranged on the downstream side. A drive unit 36 for rotating and driving one of the upper and lower rollers of the upstream side sheet transport roller and the downstream side sheet transport roller is provided, and the peripheral speed of the downstream side sheet transport roller is set. One direction that is set to be slightly higher than the peripheral speed of the upstream paper transport roller and is rotationally driven only between the rotation axis of the upstream paper transport roller and the drive unit 36 in the same direction as the rotation direction of the roller. The clutch 37 is interposed.

According to a second aspect of the present invention, the sheet conveying roller on the downstream side in the sheet conveying direction is the fixing roller 31, and the sheet conveying roller on the upstream side is the PS roller 30.

According to a third aspect of the present invention, in the means for solving the problem, the paper carrying roller on the downstream side in the paper carrying direction is the PS roller 30, and the paper carrying roller on the upstream side is the PS roller for the paper Y fed from the paper feeding cassette 26. It is a paper feed roller 32 for feeding to 30.

According to a fourth aspect of the present invention, there is provided a means for solving the problems, in which the sheet conveying roller on the downstream side in the sheet conveying direction is the fixing roller 31, the sheet conveying roller on the upstream side is the PS roller 30, and the sheet on the upstream side of the PS roller 30. A feed roller 32 is provided, and the paper feed roller 32 is also an upstream side paper feed roller.

According to a fifth aspect of the present invention, the one-way clutch 37 is provided on either or both of the pair of upper and lower sheet conveying rollers.

[0013]

In the means for solving the problems according to the above-mentioned claim 1, when the sheet is conveyed, a large tension is gradually applied to the sheet Y due to the peripheral speed difference between the sheet conveying roller on the upstream side and the sheet conveying roller on the downstream side. Then, when the tension of the sheet Y becomes large to some extent, the one-way clutch 37 interposed between the rotary shaft of the upstream-side sheet transport roller and the drive unit 36 causes the upstream-side sheet transport roller to drive the driving force of the drive unit 36. Is not affected by the above, the rear end of the sheet Y is smoothly removed from the upstream sheet transport roller by rotating in the same peripheral speed as the downstream sheet transport roller in the same direction.

In the means for solving the problems according to claims 2, 3 and 4, when the trailing edge of the paper Y comes out of the PS roller 30 or the paper feed roller 32 during the paper transport, the rollers 30,
The one-way clutch 37 provided in 32 absorbs the shock and suppresses the load fluctuation of the driving force of each roller 30, 32.

In the means for solving the problem according to the fifth aspect, when the tension of the sheet Y is increased during the sheet conveyance, the roller is rotated in the direction of rotation thereof by the one-way clutch 37 provided on both or one of the pair of upper and lower rollers. It is rotated in the same direction, eliminating uneven rotation of the rollers.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a sheet conveying mechanism of an image forming apparatus showing an embodiment of the present invention, FIG. 2 is a sectional view showing a drive portion of a PS roller of the present embodiment, and FIG. 3 is a one-way clutch. The operating mechanism is shown, (A) is a figure which shows the time of clutch engagement,
FIG. 4B is a diagram showing a state in which the clutch is idling, and FIG.

The overall structure of the laser printer of this embodiment will be described with reference to FIG. In FIG. 4, 20 is a printer main body, 21 is an optical system unit such as a semiconductor laser, and 2
2 is a drum cartridge in which a charging device and a cleaning device are integrated, 23 is a photoconductor, 24 is a developing cartridge, 25 is a transfer device, 26 is a paper feed cassette, 27 is a paper feed roller, and 28 is a paper feed cassette 26. A paper detector 29 for detecting the presence or absence of paper, and a paper transport mechanism 29 for sending the paper fed from the paper feed cassette 26 to the photoconductor 23 by the rollers and then ejecting the paper.

Then, the paper transport mechanism 29 is provided with the photoconductor 23.
A pair of upper and lower PS rollers 3 are provided on the upstream side in the paper transport direction with respect to
0 is arranged, and a pair of upper and lower fixing rollers 31 is arranged on the downstream side. In FIG. 4, 32 is a paper feed roller, 33 is a paper discharge roller, and 34 and 35 are paper passage detectors.

The PS roller 30 is the printer body 20.
A roller shaft 30a rotatably supported on the roller shaft 30a and a roller body 30b externally fitted and fixed to the roller shaft 30a are provided, and a rubber body 30c is externally fitted and fixed to the surface of the roller body 30b. Then, as shown in FIG. 1, a drive unit 36 for rotating the roller shaft 30a in the direction of the arrow a is provided.
A one-way clutch 37 that is rotationally driven in the same direction as the rotation direction of the roller is interposed between the drive unit 36 and the drive unit 36.

The fixing roller 31 is the printer body 20.
Is rotatably supported by the motor and is driven at a peripheral speed that is 1 to 2% faster than the peripheral speed of the PS roller 30 by a driving force from a motor (not shown).

As shown in FIG. 2, the drive unit 36 includes a gear 38 rotated by a drive force from a motor, a drive gear 39 engaged with the gear 38 and rotated by a drive force from the gear 38, and the drive gear. It is composed of a driven gear 40 meshed with 39 and driven to rotate. Then, the drive gear 39 rotates the lower side of the PS roller 30, and the driven gear 40 rotates the upper side of the PS roller 30.

The one-way clutch 37 has a drive gear 39.
It is also fitted and fixed to the driven gear 40. Then, as shown in FIG. 3A, when the drive gear 39 and the driven gear 40 rotate in the arrow a direction, the outer ring 41 of the clutch 37 tries to rotate in the same direction, and the spring action of the spring 42 causes
The roller 43 advances to the meshing position of the outer ring cam surface 44, and drives the roller shaft 30a by the wedge action of the outer ring cam surface 44 and the roller shaft 30a of the PS roller 30.

Further, as shown in FIG. 3B, when the outer ring 41 is stopped and the roller shaft 30a is rotated in the direction of arrow a, the roller is separated from the meshing position of the outer ring cam surface 44,
The roller shaft 30a idles with respect to the outer ring 41.

Therefore, the gears 39 and 40 rotate in the direction of arrow a, the clutch 37 is engaged, and the PS roller 30 is engaged.
When driving the PS roller 30, each gear 39, 4
If a driving force larger than 0 is applied in the same direction, P
The S roller 30 rotates in the direction of arrow a prior to the rotation of the gears 39 and 40.

In the above structure, the paper Y fed from the paper feed cassette 26 is conveyed from the paper feed roller 32 to the PS roller 30. Here, after being temporarily stopped, the PS roller 30 is driven at the timing of the rotation of the photoconductor 23 and is fed to the photoconductor 23 side.

Then, after the toner image is transferred onto the paper Y by the transfer device 25, the paper Y is conveyed to the fixing roller 31 side and caught in the fixing roller 31.

At this time, the trailing edge of the sheet Y is the PS roller 30.
As the sheet Y is bitten into the fixing roller 31, a large tension gradually acts on the sheet Y due to the difference in peripheral speed between the fixing roller 31 and the PS roller 30. However, when the tension of the sheet Y becomes large to some extent, the PS roller 30 is actuated by the action of the one-way clutch 37 interposed between the roller shaft 30a of the PS roller 30 and the gears 39 and 40.
Rotates faster than the peripheral speed obtained by the driving force of the gear 38,
The paper Y starts to rotate at the same speed as the conveyance speed.

Then, the conveyance of the sheet Y depends on the driving force of the fixing roller 31, and the sheet Y is applied with a tension not to bend, and is conveyed between the rollers 30 and 31 without bending. The rear end of Y smoothly comes out of the PS roller 30.

After that, the sheet Y is sent to the discharge roller 33 by the fixing roller 31 and discharged by the discharge roller 33. Then, the above operation is repeated a predetermined number of times.

As described above, the fixing roller 31 is used when the sheet is conveyed.
Even if the tension acting on the sheet Y increases due to the difference in peripheral speed between the PS roller 30 and the PS roller 30, the roller shaft 3 of the PS roller 30
The one-way clutch 37 interposed between 0a and the gears 39 and 40 enables the PS roller 30 to rotate in the same direction as the fixing roller 31 at the same peripheral speed without being affected by the driving force from the gear 39. Become.

Therefore, the tension is applied to the paper Y so that it does not bend, and the paper Y is conveyed between the rollers 30 and 31 without bending, and the rear end of the paper Y is smoothly removed from the PS roller 30 and vibration is eliminated. The transfer deviation in the transfer device 25 can be prevented, and the image quality can be improved. Further, the load fluctuation of the driving force of the PS roller 30 is suppressed, and P
Since the rotation unevenness of the S roller 30 can be eliminated, P
It does not adversely affect other paper transport rollers that are driven in association with the driving of the S roller 30.

The present invention is not limited to the above embodiment, and it goes without saying that many modifications and changes can be made to the above embodiment within the scope of the present invention.

For example, in the above embodiment, the PS roller 30
Although the one-way clutch 37 is provided in the above, the one-way clutch 37 may be provided in the PS roller 30 and the paper feed roller 32 on the upstream side thereof as shown in FIG. Alternatively, the paper feed roller 32 may be provided with the one-way clutch 37. Further, although the one-way clutch 37 is provided on both the pair of rollers, only one of them may be provided.

Further, the fixing roller 31 and P of the above embodiment are used.
As for the peripheral speed difference with the S roller 30, the rotational speeds of the roller shafts 30a and 31a were changed by using the driving force from the motor via gears, but the rotational speeds of the roller shafts 30a and 31a are the same. In addition, the diameter of the fixing roller 31 is set to the PS roller 3
The peripheral speed difference may be set to be larger than the diameter of 0.

[0035]

As is apparent from the above description, according to claims 1 and 5 of the present invention, even if a force larger than the driving force is applied to the upstream side sheet conveying roller by the tension received from the sheet, it is unidirectional. Since the peripheral speed is increased by the clutch and the downstream side sheet conveying roller is driven to rotate in the same direction at the same speed, the adverse effect on the sheet is eliminated.

Therefore, tension is applied to the paper so that the paper is not bent, and the paper is conveyed between the rollers without bending, and the trailing edge of the paper is smoothly removed from the paper conveyance roller on the upstream side to eliminate vibration. It is possible to prevent transfer deviation in the apparatus and improve image quality. Further, the load fluctuation of the driving force of the upstream-side sheet conveying roller is suppressed, and the uneven rotation of the roller can be eliminated.

According to the second, third, and fourth aspects, by providing the one-side clutch on the PS roller, the PS roller and the paper feed roller, or the paper feed roller, the shock when the paper comes out of each roller is reduced, There is an excellent effect that the load fluctuation of the driving force of the roller is suppressed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a sheet conveying mechanism of an image forming apparatus showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a drive unit of the PS roller of this embodiment.

FIG. 3A is a diagram showing a one-way clutch when the clutch is engaged, and FIG. 3B is a diagram showing a one-way clutch when the clutch is idling.

[Fig. 4] Overall configuration of laser printer

FIG. 5 is a configuration diagram of a sheet transport mechanism of an image forming apparatus according to another embodiment.

FIG. 6 is a configuration diagram of a sheet transport mechanism of a conventional image forming apparatus.

[Explanation of symbols]

 30 PS roller 31 Fixing roller 32 Paper feed roller 36 Drive unit 37 One-way clutch

Claims (5)

[Claims] 1. A pair of upper and lower sheet conveying rollers is arranged on the upstream side in the sheet conveying direction, and a pair of upper and lower sheet conveying rollers is arranged on the downstream side, and the upstream sheet conveying roller and the downstream sheet conveying roller are arranged. On the other hand, a drive unit for rotating and driving one of the upper and lower rollers is provided, and the peripheral speed of the downstream side paper transport roller is set to be slightly higher than the peripheral speed of the upstream side paper transport roller. , Between the rotary shaft of the upstream side sheet transport roller and the drive unit,
A sheet conveying mechanism for an image forming apparatus, comprising a one-way clutch that is rotationally driven only in the same direction as the roller rotation direction. 2. The sheet transport mechanism of the image forming apparatus according to claim 1, wherein the downstream sheet transport roller in the sheet transport direction is a fixing roller, and the upstream sheet transport roller is a paper stop roller. The paper transport mechanism of the image forming apparatus. 3. The paper transport mechanism of the image forming apparatus according to claim 1, wherein the paper transport roller downstream of the paper transport direction is a paper stop roller, and the upstream paper transport roller is fed from a paper feed cassette. A paper feed mechanism for an image forming apparatus, which is a paper feed roller that feeds the formed paper to a paper stop roller. 4. The paper transport mechanism of the image forming apparatus according to claim 2, wherein a paper feed roller is arranged upstream of the paper stop roller, and the paper feed roller is the upstream paper transport roller according to claim 1. A sheet conveying mechanism for an image forming apparatus characterized by the above. 5. The sheet conveying mechanism of an image forming apparatus, wherein the one-way clutch according to claim 1 is interposed between both or one of the pair of upper and lower sheet conveying rollers.