JPH0597305A - Sheet reversing device - Google Patents

Abstract

PURPOSE:To minimize the continuous carrying interval of sheets and provide a higher copying speed by enabling the superposed carrying of a continuous sheet while a driven-side roller is being separated from a drive-side roller. CONSTITUTION:A switch back passage B is interposed in the course of a sheet carrying passage from an upper stream A having a roller 12 to a lower stream having a roller pair 14, so that a sheet is carried with a space by the length obtained by adding at least the distance between the base end of the switch back passage and a second detecting means SW2 on the lower stream passage to the sheet length. A reversing roller 51 on the switch back passage is formed of a driving roller 13 and a roller 131 attachable to and separable from the driving roller, and when the top end of the sheet carried from the switch back passage reaches a second roller pair, the roller 131 is separated from the roller 13. During this, the sheet under carrying and the following sheet under carrying are carried in opposite directions while they are mutually superposed in the switch back passage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet reversing device for reversing and retransmitting a sheet such as a transfer sheet, which is used when performing double-sided copying in an image forming apparatus or the like, and more particularly to sheet conveyance from upstream to downstream. The present invention relates to a sheet reversing device having a sheet conveying path on which a switchback path is provided.

[0002]

2. Description of the Related Art FIGS. 11 to 14 are views for explaining reversal conveyance of a sheet in a sheet conveyance path in a conventional sheet reversing device. The rollers 11, 12, 14, 15 and the reversing roller pair 13 are always rotating during the sheet conveyance.

FIG. 11 shows a state in which the sheet P ₁ is conveyed from the upper flow path A. When the leading edge of the _first sheet P ₁ is conveyed to the switch SW1 by the roller pair 11, the reversing roller pair is conveyed. 13 forward rotation is started.

FIG. 12 shows a state in which the trailing edge of the sheet P ₁ has reached the switch SW1.
When the sheet P ₁ is guided from the state shown in FIG. 11 to the switchback path B by the reversing roller pair 13 and the rear end of the sheet P ₁ is conveyed to the switch SW1, the control unit (not shown) causes a time-dependent operation by a timer. Is started.

In FIG. 13, the sheet P ₁ has a switchback path B.
12 shows that the sheet P ₁ has been conveyed to the switchback path B when the timer has elapsed time T 1 from the state of FIG. The sheet P ₁ is started to be discharged from the switchback path B to the lower flow path C.

FIG. 14 shows a state in which the sheet P ₁ has been conveyed to the lower flow path C. The rear end of the sheet P ₁ conveyed by the reversing roller pair 13 and the roller pairs 14 and 15 is at least the switchback path. If you release from the base end B _{T of} B,
Or, the rear end of the sheet P ₁ to be carried out is the switch SW2.
When the sheet is unloaded to the end, the leading edge of the next sheet P ₂ is switched to the switch S.
After being conveyed to W1, the reversing roller pair 13 is changed from reverse rotation to normal rotation as shown in FIG. In this way, the sheets P that are continuously conveyed from the upper flow path A are sequentially reversed in the switchback path B and carried out to the lower flow path C.

[0007]

In the above-described conventional sheet reversing device, after the sheet P ₁ completely exits the switchback path B, the rotation direction of the reversing roller pair 13 is changed to move the next sheet P ₂ upstream. Since the structure is such that the sheet P is carried in from the path A to the switchback path B, there is a problem that the continuous conveyance interval of the sheet P becomes large and the copy speed becomes slow. That is, when the length of the conveyed sheet is L _A and the distance from the switch SW1 position to the reversing roller pair 13 is L ₂ ,
In order for the continuously conveyed sheets P ₁ and P ₂ to be conveyed without overlapping, the next sheet P ₂ has at least the reciprocating length of the preceding sheet P ₁ (length L _A ) in the switchback path B. Two
It must be carried in at an interval of the length of L _A plus L ₂ above.

The present invention has been made in view of the above circumstances, and makes it possible for the driven-side roller forming the reversing roller pair to be brought into contact with and separated from the driving-side roller, and the roller can be moved with respect to the driving-side roller. (EN) A sheet reversing device capable of generating a separated period, enabling continuous conveyance of continuous sheets during this period, reducing the continuous conveyance interval of sheets, and achieving high copy speed. is there.

[0009]

According to the present invention, there is provided a sheet conveying path having a switchback path provided in the middle of a sheet conveying path from upstream to downstream, and a sheet from upstream has the above switch at least at the sheet length. A sheet reversing device which is carried in at an interval of a length including a distance between a base end of a back path and a second detecting means described below, and which is a first roller pair provided in an upper flow path and configured to convey a sheet. A second roller pair provided in the lower flow path for conveying the sheet, a roller provided in the switchback path, a roller capable of coming into contact with and separating from the roller, and the sheet conveyed to the first roller pair. First detecting means for detecting or calculating that the sheet is conveyed to the second roller pair, second detecting means for detecting or calculating that the sheet is conveyed to the second roller pair, and rotation for rotationally driving the roller in the forward and reverse directions. Direction driving means, and A contact / separation drive means for contacting and separating the roller with the roller; and a roller for contacting the roller with the roller and driving the roller in reverse to carry out the sheet of the switchback path to the lower flow path, and the carried-out sheet. After the leading edge of the sheet is detected or calculated by the second detecting means, the roller is separated from the roller, and then the trailing edge of the discharged sheet is carried into the switchback path from the time when the trailing edge of the sheet is separated from the roller. While the trailing edge of the sheet is detected or calculated by the first detecting means, the rollers are brought into contact with the rollers, and the trailing edge of the next sheet is conveyed to the switchback path. Includes at least the control means for driving the roller in the normal direction and then changing the roller to the reverse direction when the trailing edge of the next sheet is conveyed to the switchback path. Than it (claim 1).

Further, the control means is configured to bring the roller into contact with the roller when the trailing edge of the next sheet is detected by the first detection means (claim 2).

Further, the control means is at least the second
The roller is driven in the normal direction from the time when the leading edge of the discharged sheet is detected or calculated by the detecting means to the time when the first detecting means detects or calculates the trailing edge of the next sheet. Claim 3).

The first detecting means is provided upstream of the first roller pair to detect a sheet, and the second detecting means is downstream of the second roller pair. The sheet is provided on the side to detect the sheet (claims 4 and 5).

[0013]

According to the first aspect of the present invention, the roller is driven in the reverse direction while the roller is in contact with the roller of the switchback path, and the sheet of the switchback path is carried out to the lower flow path. When the leading edge of the conveyed sheet is detected or calculated by the second detection unit, the roller is separated from the roller. When the rollers are separated from the rollers, the next sheet conveyed at the predetermined interval by the first roller pair in the upper flow path is carried into the switchback path. At this time, since the roller and the roller are separated from each other, the sheet to be carried out and the next sheet to be carried in are conveyed in the opposite directions while overlapping each other in the switchback path.

Next, from the time when the trailing edge of the discharged sheet leaves the roller to the time when the trailing edge of the next sheet is detected or calculated by the first detecting means, the position where the roller contacts the roller. And the roller is driven in the normal direction until the trailing edge of the next sheet is conveyed to the switchback path. Next, when the trailing edge of the next sheet is carried into the switchback path, the rollers are changed to the reverse drive, and the next sheet is carried out to the lower flow path.

According to the second aspect of the invention, the roller is brought into contact with the roller by the control means when the rear end of the next sheet is detected by the first detection means.

According to the third aspect of the invention, in the roller, from the time when the second detecting means detects or calculates the leading edge of the discharged sheet until the first detecting means detects or calculates the trailing edge of the next sheet. In the meantime, the normal rotation drive is started by the control means.

According to the fourth aspect of the present invention, the sheet carried in from the upstream side is detected by the first detecting means immediately before the rear end of the sheet is separated from the first roller pair.

According to the fifth aspect of the invention, the sheet carried out to the downstream side is detected by the second detecting means immediately after the leading end of the sheet is made conveyable by the second roller pair.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 9 is an overall configuration diagram showing an embodiment of an image forming apparatus to which a sheet reversing device according to the present invention is applied.

The image forming apparatus 20 comprises an automatic document feeder (ADF) 21, an optical system L, an image forming section G and a transfer sheet conveying section S.

The ADF 21 is composed of a document table 211, a paper feed roller 212, a conveyor belt 213, a discharge roller 214, a discharge guide 215 and a paper discharge table 216. The document D set on the document table 211 is conveyed one by one by the paper feed roller 212 and the conveyance belt 213 and temporarily stopped at a predetermined position on the contact glass 22. After that, when the reading operation of the document D is finished, the document D is conveyed. The belt 213 and the discharge roller 214 pass through the discharge guide 215 and the discharge tray 2
It is discharged to 16.

The optical system L comprises a halogen lamp 23 and a reflecting mirror 23R, and is a reciprocating light source 24 and a reflecting mirror 25.
a, 25b, 25c, a lens unit 26, and a reading unit 27 including a CCD, and scanning light from the light source 24 is reflected by the document D at a predetermined position on the contact glass 22, and reflecting mirrors 25a, 25b, 25c and lenses are provided. It is guided to the reading unit 27 via the unit 26, read by the reading unit 27, and stored in an image memory (not shown).

The image forming section G includes a laser emitting section 28, a polygon mirror 29a, fixed mirrors 29b and 29c, a SELFOC lens 30, a photosensitive drum 31, a charging device 32, a blank lamp 33, and a developing device 34 for multicolor copying. , 3
5, a transfer device 36, a separation device 37, and a cleaning device 38. The laser emission unit 28 emits laser light obtained by optically modulating the original image signal read from the image memory, and the laser light is emitted by the polygon mirror 29.
a, fixed mirrors 29b and 29c, selfoc lens 3
The surface of the photoconductor drum 31 uniformly charged by the charging device 32 through 0 is exposed to expose the photoconductor drum 31.
An electrostatic latent image is formed on it. Then, the electrostatic latent image is made visible by the developing devices 34 and 35, transferred to the transfer paper by the transfer device 36, and then separated from the photosensitive drum 31 by the separating device 37.

Further, in the transfer sheet conveying section S, sheet feeding cassettes 390 and 391, a manual sheet feeding section 392, from the upstream side in the feeding direction,
Paper feed rollers 393, 394 and registration roller pair 39
5, 396, and 44 are provided, and a conveyance belt 45, a fixing device 46,
A retransmitting mechanism Q, a pair of discharge rollers 47 and the like are provided.
The transfer paper is fed from the paper feed cassette 390 or the like to the transfer device 36, further fixed by the fixing device 46, and then discharged to the paper discharge tray 57 or conveyed to the resending mechanism Q for double-sided copying or the like. ..

The resending mechanism Q is a mechanism for resending the transfer sheet to the pair of registration rollers 44 again and copying it to both sides of the transfer sheet. The switching guide 48 to the resending side and the switching for double-sided / composite switching. The guide 49, a pair of reversing rollers 51 for switchback, and a reversing guide portion 50 including a switchback path 52, an intermediate tray 53, a front shifting roller 54, a front shifting belt 55, a re-feeding roller 56, and the like. The detailed configuration of the periphery of the inversion guide unit 50 will be described with reference to FIG.

When the double-sided copy mode is selected, the transfer paper on which the original image is transferred to the front surface is
It is conveyed toward the reversing guide section 50 via the switching guides 48 and 49, and is once carried into the switchback path 52 by the forward rotation driving of the reversing roller pair 51. After that, the transfer paper is switched back to the switchback path 52 by the reverse drive of the reverse roller pair 51.
Is discharged to the intermediate tray 53 on the downstream side, and is temporarily stocked. After that, the transfer sheet on the intermediate tray 53 is conveyed to the registration roller pair 44 by the front shifting roller 54, the front shifting belt 55, and the re-feeding roller 56, and enters the standby state, and the back side is moved upward in synchronization with the next transfer operation. Transfer device 3
Delivered to 6. And when the transfer to the back side is completed,
After being fixed by the fixing device 46, it is discharged to the paper discharge tray 57 via the discharge roller 47.

FIG. 2 is a diagram showing the detailed structure of the periphery of the reversal guide section 50. In the figure, 11 is a transfer guide unit 50.
A pair of rollers provided in the upper flow path A for carrying the transfer paper carried from the switching guide 48. When the double-sided copy mode is selected, the switching guide 49 is at the solid line position in the figure (the virtual line is when the composite copy mode is selected), and the transfer paper conveyed by the roller pair 11 is switched back to the roller pair 12 and further switched back. It is designed to be carried into the road B (corresponding to 52 in FIG. 9). The switch SW1 is the roller pair 11 described above.
It is arranged at an appropriate position between the roller pair 12 and the roller pair 12 and detects the transfer paper.

The roller 13 and the roller 131 constitute a reversing roller pair 51 shown in FIG. 9, and the driven roller 131 can be brought into contact with and separated from the driving roller 13 by a rotating arm 132. Driving of the roller 131 to the contact position (shown by the solid line in the figure) and the separation position (shown by the chain double-dashed line in the figure) with respect to the roller 13 is performed by a well-known contact and separation driving means 6 (FIG. 1) such as a solenoid. Driven. In addition, the roller 13
Is rotationally driven in the forward and reverse directions by the rotational direction driving means 5 (FIG. 1).

Reference numeral 14 denotes a roller pair for carrying the transfer paper in the switchback path B out of the lower flow path C, and the roller pair 12 and the driving side roller are common. A pair of rollers 15 is provided in the lower flow path C and carries the transfer paper to the intermediate tray 53 on the downstream side. The switch SW2 is arranged between the roller pair 14 and the roller pair 15 and detects the transfer paper.
Reference numeral 16 is a guide piece for forming a part of the lower flow path C, and is arranged so as to face the outer guide member at a predetermined interval so as to form a passage. Reference numeral 17 denotes an end of the guide piece 16, which is an elastic guide provided at a position where the upper flow path A and the lower flow path C intersect, that is, at a base end B _T of the switchback path B and which regulates a transfer paper conveyance direction. ..
The elastic guide 17 ensures that the transfer paper is conveyed from the upper flow path A to the switchback path B and from the switchback path B to the lower flow path C.

FIG. 1 is a block diagram for controlling each part around the inversion guide part 50. Reference numeral 1 denotes a microcomputer that determines the state of switches and the contents of operations and outputs a necessary instruction signal to a required circuit section. Reference numeral 2 is a copy switch for instructing the start of copying, 3 is a double-sided copy mode key for selecting the double-sided copy mode, and SW1 and SW2 are switches for detecting the transfer paper.

When the double-sided copy mode is selected, the transfer paper conveyed is at least the length L _A of the transfer paper and the base end B _T of the switchback path B and the switch SW.
The continuous conveyance interval is set in advance so that the next transfer sheet is conveyed at an interval corresponding to the distance L ₁ (see FIG. 2) between the two. Further, if this interval is set for the longest size of the transfer sheet that can be used, regardless of the transfer sheet size, continuous transfer can always be performed at fixed intervals, and the transfer control can be simplified accordingly.

Reference numeral 4 denotes a feeding drive means for driving the paper feed roller 393 and the like, the registration roller pair 44 and the like, the conveyor belt 45, the discharge roller 47, and other conveyor means in a required rotation direction.
Is a rotation direction driving means for rotating the roller 13 in the forward and reverse directions, 6
Is a contact / separation drive unit that drives the roller 131 to and from the roller 13, and 7 is a roller rotation drive unit that drives the other roller pairs 11, 12, 14, and 15.

Next, the transfer operation of the transfer paper in the periphery of the reversing guide unit 50 will be described with reference to FIGS.
This is done using the flowchart in.

When the copy switch 2 is turned on in the double-sided copy mode and the feeding of the transfer paper is started, first the roller 131
Is off, that is, the roller 13 is driven to the separated position as shown in FIG. 3, and the roller 13 is driven to rotate normally (step S
1). In this state, the transfer paper P ₁ from the upper flow path A is carried by the roller pairs 11 and 12 and carried into the switchback path B. During this time, the switch SW1 is in the ON state to detect the transfer sheet P ₁ (YES at step S2).

Then, the rear end of the transfer sheet P ₁ is conveyed to the switch SW ₁ as shown in FIG.
When 1 is turned off (YES in step S3), roller 13
1 is turned on, that is, driven to the contact position as shown in FIG. 4, and the timer 10 is reset (T = 0) (step S4). After that, the timer 10 starts the aging operation (step S5), and when the time T of the timer 10 reaches T1 (YES in step S6), the trailing edge of the transfer paper P ₁ is switched as shown in FIG. When it is determined that the roller 13 has been conveyed to the base end B _T of the back path B, the driving direction of the roller 13 is changed from normal rotation to reverse rotation (step S7). When the roller 13 is driven in reverse, the transfer paper P ₁ in the switchback path B starts to be discharged toward the lower flow path C, and the leading end of the transfer paper P ₁ is transferred to the switch SW2 as shown in FIG. Then, the switch SW2 is turned on (Y in step S8).
ES), it is determined whether or not the copy is completed (step S
9). Whether or not copying is completed is managed on the image forming apparatus side, or when the next transfer sheet P ₂ is detected by the switch SW1, the determination in step S9 can be made based on the detection result.

When the next transfer sheet P ₂ is conveyed (NO in step S9), the process returns to step S1 and the roller 131
Is driven to the separated position as shown in FIG. 6, and the roller 13 is driven to rotate normally. Therefore, as shown in FIG. 7, while the transfer paper P ₁ is being carried out to the lower flow path C, the next transfer paper P ₂ to be carried in is conveyed in the opposite directions while overlapping in the switchback path B. .. Then, when the trailing edge of the next transfer sheet P ₂ is conveyed to the switch SW1 as shown in FIG. 8 and detected by the switch SW1 (YES in step S3), the roller 131 is moved as described above in step S3. The timer 10 is reset while being driven to the contact position. In this way, the above operation is repeated while the transfer paper is continuously carried in. And
When the copy operation is completed (YES in step S9), that is, when the next transfer sheet is carried in, the drive control by the microcomputer 1 is completed.

Although the present embodiment has been described in the case of being applied to the image forming apparatus which conveys the transfer paper, it is applicable not only to the transfer paper but also to a reversing device which needs to reverse and convey the sheet. ..

[0038]

As described above, according to the present invention,
The roller on the switchback path can be brought into contact with and separated from the roller that is driven to rotate, and while the roller is in the separated position with respect to the roller, the sheet to be carried out and the next sheet to be carried in are switched by this switch. Since the sheets can be conveyed in the opposite directions while overlapping in the back path, the interval between the sheets that are continuously conveyed can be reduced, thereby increasing the entire conveying speed.

[Brief description of drawings]

FIG. 1 is a block diagram for controlling each unit around a reversing guide unit 50.

FIG. 2 is a diagram showing a detailed configuration of a peripheral portion of an inversion guide unit 50.

FIG. 3 is a diagram showing a state in which a sheet P ₁ is conveyed from an upper flow path A.

FIG. 4 is a diagram showing a state where the rear end of the transfer paper P ₁ reaches the switch SW1.

FIG. 5 is a diagram showing a state in which a transfer sheet P ₁ is started to be carried out from a switchback path B.

FIG. 6 is a diagram showing a state in which the front end of the transfer paper P ₁ reaches the switch SW2.

FIG. 7 is a diagram showing a state in which, while the transfer paper P ₁ is being carried out, the next transfer paper P _{2 that} is carried in is overlapped in the switchback path B but is conveyed in opposite directions.

FIG. 8 is a diagram showing a state in which the rear end of the next transfer sheet P ₂ has reached the switch SW1.

FIG. 9 is an overall configuration diagram showing an embodiment of an image forming apparatus to which the sheet reversing device according to the present invention is applied.

FIG. 10 is a flowchart illustrating a transfer paper transport operation in the periphery of the reversal guide unit 50.

FIG. 11 is a diagram showing a state in which the sheet P ₁ is conveyed from the upper flow path A in the conventional apparatus.

FIG. 12 is a diagram showing a state in which the rear end of the sheet P ₁ in the conventional apparatus has reached the switch SW1.

FIG. 13 is a diagram showing a state in which the sheet P ₁ in the conventional apparatus is carried into the switchback path B.

FIG. 14 is a diagram showing a state in which the carry-out to the lower flow path C of the sheet P ₁ in the conventional apparatus is completed.

[Explanation of symbols]

1 Microcomputer 2 Copy Switch 3 Double-sided Copy Mode Key 4 Conveyance Driving Means 5 Roller 13 Rotation Direction Driving Means 6 Rollers 131 Contact / Separation Driving Means 7 Other Roller Rotation Driving Means 10 Timers 11, 15 Roller Pairs 12 Roller Pairs (First Roller) Pair) 14 Roller pair (second roller pair) 13 Roller 131 Roller 132 Rotating arm SW1, SW2 Switch A Upper flow path B Switchback path BT Switchback path base end C Lower flow path P ₁ Current transfer paper P _2nd transfer paper

Claims (5)

[Claims] 1. A sheet conveyance path having a switchback path interposed midway from the upstream side to the downstream side, and a sheet from the upstream side has a base end of the switchback path at least at the sheet length and A sheet reversing device that is carried in at an interval of a length including the distance between the two detection means, wherein the first roller pair is provided in the upper flow path and conveys the sheet, and the sheet is provided in the lower flow path. A second roller pair that conveys a sheet, a roller provided on the switchback path, a roller that can be brought into contact with and separated from the roller, and a sheet that detects or calculates that a sheet has been conveyed to the first roller pair. 1 detecting means, 2nd detecting means for detecting or calculating that the sheet is conveyed to the 2nd pair of rollers, rotation direction driving means for rotating the rollers in forward and reverse directions, and the roller. Move to and from the above roller A contact / separation drive means, and the roller is brought into contact with the roller, and the roller is reversely driven to carry out the sheet of the switchback path to the lower flow path;
After the leading edge of the conveyed sheet is detected or calculated by the second detecting means, the roller is separated from the roller, and the trailing edge of the discharged sheet is separated from the roller to the switchback path. The roller is brought into contact with the roller until the trailing edge of the next sheet that has been carried in is detected or calculated by the first detecting means, and the trailing edge of the next sheet is conveyed to the switchback path. And a control means for changing the roller to a reverse drive at the time when the trailing edge of the next sheet is conveyed to the switchback path. Sheet reversing device. 2. The control means is configured to bring the roller into contact with the roller when the trailing edge of the next sheet is detected by the first detection means. Sheet reversing device. 3. The control means at least between the time point when the second detecting means detects or calculates the leading edge of the discharged sheet and the first detecting means detects or calculates the trailing edge of the next sheet. The sheet reversing device according to claim 1, wherein the roller is driven to rotate normally. 4. The sheet reversing device according to claim 1, wherein the first detection unit is provided upstream of the first roller pair and detects a sheet. 5. The sheet reversing device according to claim 1, wherein the second detection unit is provided downstream of the second roller pair and detects a sheet.