JP2714521B2 - Paper transport device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper transporting device provided in an image forming apparatus such as a printer for performing pre-feeding while separating transfer paper.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, when a transfer sheet is fed from a paper feed cassette, a transfer sheet for the next feed is fed simultaneously with the transfer sheet, so-called double feed. In recent years, there has been developed an apparatus configured to guide only the transfer paper to a photoconductor and perform transfer by loosening the transfer paper in such a multi-feed state at a predetermined position in a conveyance path. Provided.

FIG. 4 shows an example of this type of apparatus. In FIG. 4, reference numeral 50 denotes a pair of registration rollers, and the registration roller pair 50 aligns the leading end of the transfer paper.
At a position upstream of the registration roller pair 50 in the transport direction, a normal rotation roller 51 and a
Are arranged, and two registration sensors 53 are arranged in the width direction between the pressure contact position of the two rollers 51 and 52 and the registration roller pair 50. This registration sensor 53
After the leading edge of the transfer paper reaches the registration roller pair 50, the conveyance drive is stopped, and the timing for operating the registration roller pair 50 is detected. After a predetermined time has elapsed, the rotation drive of the normal rotation roller 51 is stopped.

In such an apparatus, when the transfer paper is conveyed in a double feed state and reaches between the rollers 51 and 52,
The forward rotation roller 51 is driven to rotate in the direction of transporting the transfer paper (forward rotation direction; the direction of the arrow in FIG. 4), and the reversing roller 52 is rotated in the reverse direction (direction of the arrow in FIG. 4) to move the transfer paper forward. The transfer paper is conveyed toward the registration roller pair 50 by the transfer roller 51, and the double fed transfer paper is separated by the reversing roller 52. Then, after the leading end of the conveyed transfer paper is detected by the registration sensor 53, the registration roller pair 50 is driven for a predetermined time, so that the leading end of the transfer paper is nipped by the registration roller pair 50 and is brought into a standby state. (Pre-feed). In addition, the normal rotation roller 51 is stopped in synchronization with the pre-feed by the registration roller pair 50. However, even after the normal rotation roller 51 is stopped, the driving of the reversing roller 52 is continued to reliably separate the multi-fed transfer paper. When a print signal is input from a terminal or the like, the registration roller pair 50 is driven, and the transfer paper in the standby state is carried out toward the photoconductor.

[0005]

In the above-described paper conveying apparatus, the time from when the leading edge of the transfer paper is detected by the registration sensor 53 to when it reaches the registration roller pair 50 is determined by the material of the transfer paper or the paper thickness. There is variation, and therefore, the nip state of the registration roller pair 50 due to pre-feeding also varies. Therefore, if the rotation of the reversing roller 52 in the reversing direction is continued after the normal rotation roller 51 is stopped as described above, the registration roller pair 50
The transfer paper that has not been nipped securely, or that has a relatively small thickness and a low nip pressure, is conveyed backward by the reversing roller 52 during the pre-feed state by the registration roller pair 50. Sometimes. In this case, even if a print signal is input and the registration roller pair 50 is driven,
The transfer paper is not carried out or is not carried out at an appropriate timing, resulting in a disadvantage that a transfer deviation occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and conveys a sheet (transfer sheet) downstream while separating the sheet , and prevents reverse conveyance of the sheet after pre-feeding to properly discharge the sheet. It is an object of the present invention to provide a paper transport device that enables the above.

[0007]

The invention according to claim 1 is
The separating means is driven in synchronization with the feeding of the sheet, the fed sheet is transported downstream while being separated, and the leading end thereof is once nipped to the roller pair, and then the roller pair is driven to be further discharged downstream. A paper transport device for achieving the above object.
In the direction in which the paper is transported downstream.
A rotating forward roller, and a counter-rotating roller
Reversing roller that rotates in the direction to reverse the paper
And independent drive and stop of the forward and reverse rollers
And switching means for switching
The leading edge of the paper is nipped by the roller pair.
When the forward rotation roller is stopped,
At the same time as or after stopping the roller,
Has been stopped.

According to a second aspect of the present invention, the switching means is provided with
Forward rotation before the nip of the paper edge by the roller pair
By driving the roller, between the roller pair and the separating means
The paper is configured to bend.

[0009]

According to the first aspect of the present invention, when the paper conveyed while being separated by the forward rotation roller and the reverse roller reaches the roller pair, the leading end of the paper is nipped by the roller pair, The sheet is put on standby at that position. When the paper is in the standby state, the normal rotation roller is stopped, and at the same time when the normal rotation roller is stopped.
Or after that, the reverse roller stops and the paper is transported in reverse.
Is prevented.

According to the second aspect of the present invention, the paper
Before the tip is nipped, drive the forward roller
Therefore, bending of the sheet is formed between the roller pair and the separating means.
It is. At this point, the paper is put on standby, and
The reversing roller has been driven for a while after the
The paper is transported backward by the drive of the reversing roller
However, the deflection is only slightly reduced, and the paper
Is not conveyed out of the nip.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 2 shows a schematic configuration of an image forming apparatus provided with the sheet conveying device of the present invention. In this apparatus, paper feed cassettes 1 and 2 for accommodating transfer paper are detachably mounted in two upper and lower stages. As the paper feed cassette 2, a paper feed cassette that accommodates narrow paper such as an envelope in a parallel state can be applied. In this case, two stored narrow papers are simultaneously placed in a parallel state. It is designed to be transported.

As shown in FIG. 2, each paper feed cassette 1, 2
The paper feed rollers 3 and 4 are provided at the positions corresponding to. Near the downstream of the mounting position of the paper cassette 1,
A first separating roller pair 7 including a forward roller 5 and a reversing roller 6 is provided, and a second separating roller pair 10 including a forward roller 8 and a reversing roller 9 is provided near the downstream of the mounting position of the sheet cassette 2. Is provided. The transfer paper in the paper cassette 1 is conveyed to the registration roller pair 11 via the first separation roller pair 7, while the transfer paper in the paper cassette 2 is transferred to the second separation roller pair 10 and The sheet is conveyed to the registration roller pair 11 via one separation roller pair 7. When a thick envelope is fed from the paper feed cassette 2, the envelope is separated by the second separation roller pair 10, and the first separation roller pair 7 rotates together with the normal rotation roller 5. It has become.

An image forming unit 13 integrally including a photoreceptor 12, a charging device, a developing device, a cleaning device, and the like is installed downstream of the pair of registration rollers 11, and a light emitting unit 14 and a polygon are provided around the image forming unit 13. An optical unit 16 including a mirror 15 and the like, a transfer unit 17 and the like are provided. Further, a fixing unit 18, discharge roller pairs 19 and 20, a discharge guide 21, a discharge tray 22, and the like are disposed downstream of the fixing unit 18. The light emitting section 14 of the optical unit 16 receives the image data from inside or outside and outputs a modulated optical signal.

In the middle of the transfer paper conveyance path from the paper feed cassettes 1 and 2 to the discharge tray 22, a jam detection for detecting a jam generated when the transfer paper is fed from the paper feed cassette 2 is detected. Switch 23, registration roller pair 1
1, a registration sensor 24 for setting the operation timing
Sensors such as a light emission timing sensor 25 and a discharge sensor 26 are provided at appropriate locations. Two detection units of these sensors are arranged in parallel at corresponding positions in the width direction so as to detect each sheet when narrow paper such as an envelope is conveyed in parallel.

Now, when the transfer paper is fed from the paper feed cassette 2, the transfer paper is sent to the registration roller pair 11 through the first separation roller pairs 7, 10, where the leading end is adjusted and the registration roller pair 11 is set. Are driven for a predetermined time, and the standby state is set in a state where the leading end of the transfer sheet is nipped by the pair of registration rollers 11 (hereinafter, referred to as pre-feeding). Thereafter, the registration roller pair 11 is driven by a predetermined control signal,
The transfer paper is fed to the photoconductor 12. Then, the fixing unit 18
, The discharge roller pairs 19 and 20 and the discharge guide 21
Through the discharge tray 22.

Next, an example of a detailed configuration of the first separating roller pair 7 will be described with reference to FIG. The separating roller pair 7 separates the transfer paper conveyed from the paper feed cassettes 1 and 2 to the registration roller pair 11 while separating the transfer paper, and, for example, places narrow paper such as an envelope in the paper feed cassette 2 in parallel. When the sheets are stored, they can be switched to a normal transport state in which the two narrow sheets that have been carried out in a parallel state and have already been separated by the second separation roller pair 10 pass through without being separated.

As shown in FIG. 1, both the normal rotation roller 5 and the reversing roller 6 are side plates 2 constituting an image forming apparatus.
The pair of rollers 9 and 30 are rotatably supported and fixed to a single forward roller shaft 27 and a reverse roller shaft 28 extending in a direction parallel to the registration roller pair 11. Further, the normal rotation roller 5 and the reverse roller 6 are provided at a plurality of locations corresponding to the conveying path of narrow paper such as an envelope, and each of the reverse rollers 6 is mounted on the reverse roller shaft 28 so as to be relatively rotatable.

A gear 33 is mounted on one end of the forward rotation roller shaft 27, and rotational drive from a motor (not shown) is transmitted to the forward rotation roller shaft 27 via the gear 33. ing. The forward rotation roller shaft 27 can be switched between a forward rotation drive state in which the transfer paper is transported in a forward direction and a free rotation state by turning on and off a clutch (not shown).

On the other hand, the reversing roller shaft 28 has a reversing roller clutch 31 (switching means) such as an electromagnetic spring clutch mounted on one end thereof, and is transmitted to the gear 34 when the clutch 31 is turned on and off. The rotational drive is transmitted to or blocked by the reversing roller shaft 28, so that the state can be switched between a reversing driving state in which the driving is rotationally driven in the direction of the arrow in FIG. 2 (reversing direction) and a free rotation state.

A friction clutch 3 for limiting torque is provided between each reversing roller 6 and the reversing roller shaft 28.
2 are interposed. Each friction clutch 32
It is configured to transmit only a torque equal to or less than a certain value between the reversing roller 6 and the reversing roller shaft 28. This torque limit value is determined by the reverse roller shaft 28 generated by the frictional force caused by the pressure contact between the reverse roller 6 and the forward roller 5 in the forward drive state of the forward roller 5 and the reverse drive state of the reverse roller 6. Reversing roller shaft 28 which is smaller than the surrounding torque and is generated by frictional force due to pressure contact of a plurality of multi-feed transfer papers
The value is set to a value larger than the surrounding torque.

Next, the operation of the first separating roller pair 7 will be described with reference to the timing chart of FIG.

First, when the power of the image forming apparatus is turned on, the image forming apparatus is started, and is brought into a stable state (printable state) after a predetermined time. And at time t1,
When, for example, plain paper is selected and operated by a paper feed cassette selection switch 38 on an operation unit (not shown) provided in the image forming apparatus, at time t2, the reversing roller clutch 31 is switched on and the reversing roller shaft 31 is turned on. Rotational drive is transmitted to 28, and the reversing roller shaft 28 is rotationally driven in the reversing direction, that is, in the direction of the arrow in FIG. At this point, the forward rotation roller clutch 35 is in the off state, that is, the forward rotation roller 5 is in a free rotation state, so that the forward rotation around the reversing roller shaft 28 generated by the frictional force due to the pressure contact between the reversing roller 6 and the normal rotation roller 5 Direction torque is lower than the transmittable torque of the friction clutch 32, the reversing roller 6 is rotated in the reversing direction integrally with the reversing roller shaft 28 via the friction clutch 32, and the forward roller 5 is also driven by the reversing roller 6. Rotated in the reverse direction.

At time t3, the paper feed roller clutch 35 and the normal rotation roller clutch 36 are turned on, and the rotation of the paper feed roller 4 and the normal rotation roller 5 is started.

When the paper feed roller 4 is driven to rotate, the transfer paper is fed from the paper feed cassette 2 and the second separation roller pair 1
0 and is conveyed toward the first separating roller pair 7. At this time, the second separating roller pair 10 is driven to rotate in the normal rotation direction (the direction of the arrow in FIG. 2) to transport the transfer paper.

On the other hand, when the normal rotation roller 5 is driven to rotate,
Until the transfer paper reaches between the rollers 5 and 6, the rotation of the normal rotation roller 5 in the normal rotation direction causes the rotation of the normal rotation roller 5 in the normal rotation direction around the reversing roller shaft 28 generated by the frictional force caused by the pressure contact between the two rollers 5 and 6. Since the torque exceeds the transmittable torque of the friction clutch 32, each of the reversing rollers 6 rotates in the normal rotation direction opposite to the rotation direction (reversal direction) of the reversing roller shaft 28.

Next, if double feed occurs at the time when the leading edge of the transfer paper reaches between the rollers 5 and 6, the forward rotation torque is reduced to be lower than the transmittable torque. Thus, each reversing roller 6 is rotationally driven in the reversing direction integrally with the reversing roller shaft 32 via the friction clutch 32. Therefore, the transfer paper is conveyed toward the registration roller pair 11 by the normal rotation roller 5 while the reversing roller 6 separates the multi-fed transfer paper.

Then, when the leading edge of the transfer paper is detected by the registration sensor 24 (time t4), that is, when both the two registration sensors 24a and 24b arranged side by side on the transport path detect the leading edge of the transfer paper. From a predetermined time T
After 1 elapses, the paper feed roller clutch 35 is switched off, the rotation of the paper feed roller 4 is stopped, and
The registration roller clutch 37 is turned on, and the registration roller pair 11 is driven to rotate (time t5). The rotation of the registration roller pair 11 is stopped at time t7 after a very short time (T2 + T3). In other words, the transfer paper is kept on standby with the leading edge of the transfer paper securely nipped by the registration roller pair 11 (pre-feed), and can be immediately carried out toward the photoconductor 12 by a predetermined print signal.

At time t5, the registration roller pair 11
Between the start and stop of the rotation drive of
When the time T2 elapses from the time point t5, the normal rotation roller clutch 36 is switched off, and the normal rotation roller 5 is freely rotated (time point t6). Further, in synchronization with this, the reversing roller clutch 31 is switched off (time t7). That is, the rotation drive of the forward rotation roller 5 is stopped (t6
During the time T3 from the time (time point) until the reversing roller 6 is stopped, only the reversing roller 6 is rotationally driven, so that the multi-fed transfer paper is reliably separated. At this time, the transfer paper after the pre-feed is transferred to the registration roller pair 11.
Is continuously conveyed by the forward rotation roller 5 during the time T1 until the is driven, so that the nip is securely nipped in a slightly bent state. Therefore, even if the reversing roller 6 is driven to rotate in the reversing direction during the time T3, the transfer paper is slightly relieved of bending, and the registration roller pair 11
So that it does not come out of the nip and reversely convey.

After time t7, the reverse roller clutch 31
Is turned off and the reversing roller 6 is stopped,
As in the conventional example, the transfer paper nipped by the pair of registration rollers 11 after the pre-feeding is prevented from being reversely conveyed by the rotation of the reversing roller 6 in the reversing direction.

At time t7, the reversing roller clutch 3
After the first and first registration clutches 37 are switched off, the transfer paper is nipped by the pair of registration rollers 11 and is in a standby state. Image formation from the pair of registration rollers 11 is synchronized with a print signal from a terminal (not shown). It is configured to be carried out to the unit 13.

As described above, according to the paper conveying apparatus of the present invention, the rotational drive is transmitted to the reversing roller at a predetermined timing by turning on and off the reversing roller clutch 31.
Alternatively, since the transfer paper can be cut off, not only the transfer paper can be transported while being reliably separated, but also
, And the transfer paper in the standby state can be carried out to the photoconductor 12 without being reversely conveyed.

In the above embodiment, the rotation of the reversing roller 6 is stopped at time T3 after the rotation of the normal roller 5 is stopped, that is, at the timing when the pre-feed of the registration roller pair 11 is completed. It is not necessary to stop at this timing,
For example, the rotation of the normal rotation roller 5 and the reversing roller 6 may be stopped at the same time as the end of the pre-feed by the registration roller pair 11. That is, the timing may be appropriately set so as to prevent reverse conveyance of the transfer paper after pre-feeding while separating the multi-fed transfer paper.

In the embodiment, the reversing roller clutch 3
Although an electromagnetic spring clutch is used as 1, the transmission drive switching means is not limited to this, and any device that can transmit and cut off the rotational drive can be applied.

[0035]

As described above, according to the present invention, the separating means includes a forward rotation roller which rotates in a direction for transporting the sheet downstream, and a separating roller which is disposed opposite to the forward rotation roller, and which is arranged in the direction in which the sheet flows backward. A rotating reversing roller, and switching means for independently switching between driving and stopping of the normal roller and the reversing roller. When the leading edge of the sheet is nipped by the pair of rollers, the switching means changes the normal roller. It stops the, use since it is configured so as to stop the reverse roller stops simultaneously with or subsequent to the said forward roller, not only conveyed while separating the sheets reliably, which is pre-fed sheet
There is no need to reverse the paper . Therefore, it is possible to carry out the sheet to the photosensitive member at an appropriate timing.

[Brief description of the drawings]

FIG. 1 is a view of a sheet conveying device according to the present invention as viewed from an arrow A in FIG. 2;

FIG. 2 is an overall configuration diagram of an image forming apparatus provided with the paper transport device.

FIG. 3 is a timing chart illustrating the operation of the paper transport apparatus.

FIG. 4 is a schematic cross-sectional view showing an example of a conventional paper transport device.

[Explanation of symbols]

 5 Forward Roller 6 Reverse Roller 7 First Separation Roller Pair 10 Second Separation Roller Pair 27 Forward Roller Shaft 28 Reverse Roller Shaft 31 Reverse Roller Clutch

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akinobu Nakahata 1-2-28 Tamazo, Chuo-ku, Osaka-shi Inside Mita Kogyo Co., Ltd. Co., Ltd. (72) Inventor Wataru Sasaki 1-2-2, Tamazo, Chuo-ku, Osaka Mita Kogyo Co., Ltd. (56) References JP-A-63-22446 (JP, A) JP-A-60-1667836 (JP) , A) JP-A-63-189345 (JP, A) Japanese Utility Model Laid-Open No. 1-85348 (JP, U)

Claims (2)

(57) [Claims] 1. A separating means is driven in synchronization with the feeding of a sheet, the fed sheet is transported downstream while being separated, and the leading end thereof is once nipped by a pair of rollers, and then the pair of rollers is driven. In the paper transport device for further transporting the paper downstream, the separating means includes a forward rotation roller rotating in a direction for transporting the paper downstream, and a reversing roller disposed opposite to the forward rotation roller and rotating in a direction to reverse the paper. A roller, and switching means for independently switching between driving and stopping of the normal rotation roller and the reversing roller. The switching means is such that the leading end of the paper is nipped by the roller pair.
When the forward rotation roller is stopped,
At the same time as or after stopping the roller,
A paper transport device characterized in that it is stopped . 2. The switching means according to claim 1, wherein said switching means comprises a pair of rollers.
Prior to the nip at the leading edge of the paper, drive the forward roller
The sheet is bent between the roller pair and the separating means.
2. The sheet transporting device according to claim 1, wherein the sheet transporting device is configured to: