JPH06115743A - Paper conveyer - Google Patents

Abstract

PURPOSE:To properly carry out transfer paper after prefed by preventing reverse conveyance of the paper while conveying the transfer paper, while separated, to the downstream. CONSTITUTION:The first separation paired rollers 7 are constituted by providing forward rotary rollers 5 rotated in a direction of conveying paper to the downstream, reverse rotary rollers 6 arranged to be opposed to this forward rotary roller 5 and rotated in a direction of reversely flowing the paper and a reverse rotary roller clutch 31 in a reverse rotary roller shaft 28 of mounting this reverse rotary roller 6, and by on-off operating the reverse rotary roller clutch 31, the reverse rotary roller 6 is stopped at least after stopping the forward rotary roller 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus which is provided in an image forming apparatus such as a printer and which pre-feeds a transfer sheet while separating it.

[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, the transfer sheet for the next feeding is fed at the same time as the transfer sheet, so-called double feeding. Recently, an apparatus configured to guide and transfer only the transfer paper to the photoconductor by separating the transfer paper in the double feed state at a predetermined position in the conveyance path has been recently developed. It is provided.

An example of this type of device is shown in FIG. In FIG. 4, reference numeral 50 denotes a registration roller pair, and the registration roller pair 50 aligns the leading edge of the transfer paper.
At the position upstream of the registration roller pair 50 in the transport direction, a forward rotation roller 51 and a reversal roller 52 that are in pressure contact with each other.
Two registration sensors 53 are arranged in the width direction between the pressure contact positions of the rollers 51 and 52 and the registration roller pair 50. This registration sensor 53
After the leading edge of the transfer sheet reaches the registration roller pair 50, the conveyance drive is stopped and the timing of operating the registration roller pair 50 is detected. From the time point when both registration sensors 53 detect the passage of the leading edge of the transfer sheet. The rotation drive of the forward rotation roller 51 is stopped after a predetermined time has elapsed.

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 rotationally driven in the direction in which the transfer paper is conveyed (normal rotation direction; arrow direction in FIG. 4), and the reverse roller 52 is rotated in the reverse direction (arrow direction in FIG. 4) to correct the transfer paper. The transfer roller 51 conveys the transfer paper toward the registration roller pair 50, and the transfer paper that has been double-fed is separated by the reversing roller 52. Then, after the leading edge of the transferred transfer paper is detected by the registration sensor 53, the registration roller pair 50 is driven for a predetermined period of time, so that the leading end of the transfer paper is nipped by the registration roller pair 50 and is put in a standby state. (Pre-paper feed). Further, the forward rotation roller 51 is stopped in synchronization with the pre-feeding by the registration roller pair 50. However, even after the forward rotation roller 51 is stopped, the reversal roller 52 is continuously driven in order to reliably separate the double-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 sheet in the standby state is carried out toward the photoconductor.

[0005]

In the above-described sheet conveying device, the time from when the leading edge of the transfer sheet is detected by the registration sensor 53 to when it reaches the registration roller pair 50 depends on the material of the transfer sheet or the thickness of the transfer sheet. Since there is variation, the nip state between the registration roller pair 50 also varies due to pre-feeding. Therefore, if the rotation of the reverse roller 52 in the reverse direction is continued after the forward rotation roller 51 is stopped as described above, the registration roller pair 50
A transfer sheet whose nip is not securely formed, or a transfer sheet having a relatively small paper thickness and a low nip pressure is reversely conveyed by the reversing roller 52 during the pre-feeding state by the registration roller pair 50. Sometimes. In this case, even if the 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, which causes a problem that transfer deviation occurs.

The present invention has been made in order to solve the above-mentioned problems, and while transporting the transfer paper to the downstream side while separating it, it is possible to prevent the transfer paper from being reversely transported after the pre-feeding and to properly carry out the transfer paper. It is an object of the present invention to provide a sheet conveying device that does.

[0007]

The invention according to claim 1 is
The separating means is driven in synchronism with the feeding of the sheet, and the fed sheet is conveyed to the downstream side while being separated, and the leading end of the sheet is once nipped with the roller pair, and then the roller pair is driven to carry it out further downstream. In the paper transporting device, the separating means includes a forward rotation roller that rotates in a direction in which the paper is transported downstream, a reversing roller that is disposed to face the forward rotation roller and that rotates in a direction in which the paper flows backward, and the forward rotation roller. The switching means independently switches between driving and stopping of the rolling roller and the reversing roller, and the switching means stops the reversing roller at least after stopping the forward rotation roller.

According to a second aspect of the invention, the switching means comprises:
The forward rotation roller and the reverse roller are stopped at the same time.

[0009]

According to the first aspect of the present invention, when the transfer sheet conveyed while being separated by the forward rotation roller and the reverse roller reaches the roller pair, the leading end of the transfer sheet is nipped by the roller pair. Then, the transfer paper is put in a standby state at that position. Then, when the transfer sheet is put in the standby state, the forward rotation roller is stopped and the reversal roller is stopped in synchronization with this.

According to the second aspect of the present invention, the rotational driving of the forward rotation roller and the reverse rotation roller is stopped at the same time.

[0011]

Embodiments of the present invention will be described with reference to FIGS.

FIG. 2 shows a schematic configuration of an image forming apparatus equipped with the sheet conveying apparatus of the present invention. Paper feed cassettes 1 and 2 for accommodating transfer paper are removably mounted in two upper and lower stages in this apparatus. It is also possible to apply to the paper feed cassette 2 a paper feed cassette that accommodates narrow sheets of paper such as envelopes in a parallel state. In this case, the two narrow sheets of paper stored in a parallel state at the same time. It is designed to be transported.

As shown in FIG. 2, each of the paper feed cassettes 1 and 2
Paper feed rollers 3 and 4 are provided at positions corresponding to, respectively. In the vicinity of the downstream of the mounting position of the sheet cassette 1,
A first separating roller pair 7 including a normal rotating roller 5 and a reverse roller 6 is provided, and a second separating roller pair 10 including a normal rotating roller 8 and a reverse roller 9 is provided in the vicinity of the downstream of the mounting position of the sheet feeding cassette 2. Is provided. Then, the transfer sheet in the sheet feeding cassette 1 is conveyed to the registration roller pair 11 via the first separating roller pair 7, while the transfer sheet in the sheet feeding cassette 2 is transferred to the second separating roller pair 10 and the second separating roller pair 10. It is configured to be conveyed to the registration roller pair 11 via the one separating roller pair 7. When a thick envelope is fed from the paper feed cassette 2, the second separation roller pair 10 separates the envelope, and the first separation roller pair 7 rotates together with the forward rotation roller 5. It is like this.

An image forming unit 13 having a photosensitive member 12, a charging device, a developing device, a cleaning device and the like integrally formed is installed on the downstream side of the registration roller pair 11, and a light emitting portion 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, a pair of discharge rollers 19 and 20, a discharge guide 21, a discharge tray 22 and the like are arranged on the downstream side thereof. The modulated light signal is output to the light emitting section 14 of the optical unit 16 by receiving image data from inside or outside.

A jam detection for detecting a jam generated when the transfer paper is fed from the paper feed cassette 2 is provided in the transfer paper conveyance path from the paper feed cassettes 1 and 2 to the discharge tray 22. Switch 23, registration roller pair 1
Registration sensor 24 for timing the operation of 1.
Each sensor such as the light emission timing sensor 25 and the discharge sensor 26 is arranged at an appropriate place. 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 sheets such as envelopes are conveyed in parallel.

Now, when the transfer paper is fed from the paper feed cassette 2, it is sent to the registration roller pair 11 through the first separating roller pair 7 and 10, where the leading edge alignment is performed and the registration roller pair 11 is also performed. Is driven for a predetermined time, and the front end of the transfer paper is nipped by the registration roller pair 11 and stands by (hereinafter referred to as pre-paper feeding), and then 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
After passing through the discharge roller pair 19, 20 and discharge guide 21
After that, the sheet is discharged to the discharge tray 22.

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

As shown in FIG. 1, the forward rotation roller 5 and the reverse rotation roller 6 together form a side plate 2 which constitutes an image forming apparatus.
It is rotatably supported between 9 and 30, and is fixed to a single forward rotation roller shaft 27 and reverse rotation roller shaft 28 extending in a direction parallel to the registration roller pair 11. Further, the forward rotation roller 5 and the reversal roller 6 are provided at a plurality of locations corresponding to the conveyance path for narrow paper such as envelopes, and each reversal roller 6 is mounted on the reversal roller shaft 28 so as to be relatively rotatable.

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

On the other hand, the reversing roller shaft 28 is equipped with a reversing roller clutch 31 (switching means) such as an electromagnetic spring clutch at one end thereof, and is transmitted to the gear 34 by turning the clutch 31 on and off. Rotational drive is transmitted to or cut off from the reversing roller shaft 28 so that it can be switched between a reversing drive state in which it is rotationally driven in the direction of the arrow in FIG.

Between each reversing roller 6 and the reversing roller shaft 28, a friction clutch 3 for limiting torque is provided.
2 is installed. Each friction clutch 32
Only the torque equal to or less than a certain value is transmitted between the reversing roller 6 and the reversing roller shaft 28. The limit value of this torque is the reversing roller shaft 28 generated by the frictional force due to the pressure contact between the reversing roller 6 and the normal rotating roller 5 in the normal rotation driving state of the normal rotating roller 5 and the reverse rotation driving state of the reversing roller 6. The reversing roller shaft 28, which is smaller than the surrounding torque and is generated by the frictional force due to the pressure contact of a plurality of multi-feed transfer sheets
It is set to a value larger than the torque around it.

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 source of the image forming apparatus is turned on, the image forming apparatus is started up and is brought into a stable state (printable state) after a predetermined time. Then, at time t1,
When, for example, plain paper is selected and operated by the paper feed cassette selection switch 38 on the operation unit (not shown) provided in the image forming apparatus, the reversing roller clutch 31 is switched on at the time t2 to reverse the reversing roller shaft. Rotational drive is transmitted to 28, and the reversing roller shaft 28 is rotationally driven in the reversing direction, that is, the direction of the arrow in FIG. At this time point, the forward rotation roller clutch 35 is in the OFF state, that is, the forward rotation roller 5 is in the free rotation state, so that the forward rotation around the inversion roller shaft 28 caused by the frictional force between the inversion roller 6 and the forward rotation roller 5 is caused. The torque in the direction is lower than the torque that can be transmitted by 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 rotation roller 5 is also driven by the reversing roller 6. It is rotated in the reverse direction.

At time t3, the paper feed roller clutch 35 and the forward rotation roller clutch 36 are turned on to start the rotational driving of the paper feed roller 4 and the forward rotation roller 5.

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

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

Next, at the time when the leading edge of the transfer sheet reaches between the rollers 5 and 6, if double feeding occurs, the forward rotation torque decreases and becomes lower than the transmissible torque. As a result, 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 reversing roller 6 separates the double-fed transfer paper, and the transfer paper is conveyed toward the registration roller pair 11 by the forward rotation roller 5.

When the leading edge of the transfer paper is detected by the registration sensor 24 (time t4), that is, when the two registration sensors 24a and 24b arranged side by side on the conveying path detect the leading end of the transfer paper. From the predetermined time T
When 1 has elapsed, the paper feed roller clutch 31 is switched off to stop the rotation drive of the paper feed roller 4, and
The registration roller clutch 37 is turned on and the registration roller pair 11 is rotationally driven (at time t5). The rotational drive of the registration roller pair 11 is stopped at time t7 after a short time (T2 + T3). That is, by this, the front end of the transfer paper is waited in a state where it is securely nipped by the registration roller pair 11 (pre-paper feeding), and can be immediately carried out toward the photoconductor 12 by a predetermined print signal.

At time t5, the pair of registration rollers 11
Between the start and stop of the rotation drive of
When time T2 elapses from the time point t5, the forward rotation roller clutch 36 is switched off, and the forward rotation roller 5 is brought into a free rotation state (time point t6). Further, in synchronization with this, the reversing roller clutch 35 is turned off (at time t7). That is, the rotation drive of the forward rotation roller 5 is stopped (t6
After the time point), the reversing roller 6 is rotated and driven only during the time T3 until the reversing roller 6 is stopped, so that the double-fed transfer sheets are reliably separated. At this time, the transfer paper after the pre-feed is the registration roller pair 11
Since it is continuously conveyed by the forward rotation roller 5 during the time T1 until it is driven, it is reliably nipped in a slightly bent state. Therefore, even if the reversing roller 6 is rotationally driven in the reversing direction for the time T3, the transfer paper is slightly relieved in its bending and the registration roller pair 11
It is designed so that it does not come out of the nip and is conveyed backwards.

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 sheet nipped by the pair of registration rollers 11 after the pre-feeding is prevented from being reversely conveyed by the rotational driving of the reverse roller 6 in the reverse direction.

Then, at time t7, the reverse roller clutch 3
1 and the registration clutch 37 are switched off, and then the transfer sheet in the standby state is nipped by the registration roller pair 11 and an image is formed from the registration roller pair 11 in synchronization 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 sheet conveying apparatus of the present invention, the reversing roller clutch 31 is turned on / off to transmit the rotational drive to the reversing roller at a predetermined timing.
Alternatively, since the transfer sheet can be blocked, not only is the transfer sheet reliably conveyed while being conveyed, but also the registration roller pair 11
The transfer paper in the nip state can be carried out to the photoconductor 12 without being reversely conveyed.

In the above embodiment, the rotational driving of the reversing roller 6 is stopped after the time T3 from the rotational driving of the forward rotation roller 5, that is, at the timing of ending the pre-feeding of the registration roller pair 11. However, it is not necessary to stop at this timing,
For example, the rotation driving of the forward rotation roller 5 and the reverse rotation roller 6 may be simultaneously stopped at the timing of the completion of pre-feeding by the registration roller pair 11. That is, the timing may be appropriately set while separating the double-fed transfer paper and preventing reverse transfer of the transfer paper after pre-feeding.

In the embodiment, the reversing roller clutch 3
Although the electromagnetic spring clutch is used as No. 1, the transmission drive switching means is not limited to this, and any transmission drive switching means can be applied as long as it can transmit and interrupt the rotation drive.

[0035]

As described above, according to the present invention, the separating means is provided with the forward rotation roller that rotates in the direction in which the sheet is conveyed downstream, and the forward rotation roller that is disposed so as to face the forward rotation roller and causes the sheet to flow backward. It is composed of a rotating reversing roller and a switching means for independently switching between driving and stopping of the forward rotating roller and the reversing roller, and the switching means stops the reversing roller at least after stopping the forward rotating roller. Therefore, not only can you transfer the transfer paper securely,
The pre-transferred transfer paper is never conveyed in reverse.
Therefore, it is possible to carry the transfer paper to the photoconductor at an appropriate timing.

[Brief description of drawings]

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

FIG. 2 is an overall configuration diagram of an image forming apparatus including the above-described sheet conveying device.

FIG. 3 is a timing chart showing the operation of the paper transport device.

FIG. 4 is a schematic cross-sectional view showing an example of a conventional sheet conveying 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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akinobu Nakahata 1-228 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo Co., Ltd. (72) Inventor Masahiro Shinohara 1-228 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo Co., Ltd. (72) Inventor Wataru Sasaki 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo Co., Ltd.

Claims (2)

[Claims] 1. A separating means is driven in synchronism with the feeding of a sheet to convey the fed sheet to the downstream side while separating the sheet, and the leading end of the sheet is once nipped by the roller pair, and then the roller pair is driven. In the paper transporting device that carries the paper further downstream, the separating means includes a forward rotation roller that rotates in a direction that conveys the paper downstream, and a reversal that is arranged to face the forward rotation roller and rotates in a direction that causes the paper to flow backward. It comprises a roller and a switching means for independently switching between driving and stopping of the forward rotation roller and the reversing roller, and the switching means stops the reversing roller at least after stopping the forward rotation roller. Paper transport device. 2. The switching means simultaneously stops the forward rotation roller and the reverse roller.
The paper transport device described.