JP3169455B2 - Method and apparatus for detecting deviation of circulating conveyance sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting a deviation of a sheet in a width direction (lateral displacement with respect to a traveling direction) generated when a sheet is circulated and conveyed, and particularly to a copying machine and a printer. In the image forming apparatus such as
The present invention relates to a method and an apparatus for detecting a deviation in the width direction of a sheet that occurs when a sheet-shaped document is circulated a plurality of times along the same conveyance path.

[0002]

2. Description of the Related Art In an image forming apparatus as described above, for example, in order to obtain a plurality of identical copies, a sheet-shaped document is repeatedly circulated along the same transport path, and image exposure is performed during the transport. Document circulation devices are known. In such an apparatus, a document that is repeatedly circulated is shifted gradually in any width direction and is shifted according to the number of circulations due to variations in the diameter of the transport roller or uneven contact pressure. This offset causes an inconvenience that the position of the image of the first copy and the position of the image of the copy after multiple circulations are shifted, and an image in which the "displacement" can be clearly recognized even by visual inspection is formed. I will.

It is naturally preferable to correct such a deviation of the document. For this reason, a detection device for detecting the state of the deviation of the document is provided in the document conveyance path. When it is detected that the misalignment has occurred, the misalignment is corrected by operating a misalignment correction device provided on the document conveying path.

Conventionally, in order to detect a deviation, a plurality of photosensors are provided at a position interval corresponding to each original size in a direction crossing the original transport path, and the original passing therethrough corresponds to the original size. When the photo sensor at the position is not operated, it is detected that the document is conveyed with a deviation from the reference position.

[0005]

In such a conventional method, a large number of photosensors must be required for each document size, and each photosensor is fixed at a predetermined position for each document size. Therefore, when the degree of deviation of the document is small, there is a problem that this cannot be detected. In particular, in order to detect a shift with high detection accuracy in such a conventional method, the interval between the photosensors must be sufficiently narrowed so that a larger number of photosensors must be arranged in tandem. This is not preferred.

Further, when the original is supplied to the circulating conveyance path manually, if the original is considerably offset from the beginning, the original is moved to a predetermined position in the conventional method. Thus, the first image and the second and subsequent images are remarkably shifted.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is possible to quickly and accurately detect a deviation of a document with a single photo sensor. It is an object of the present invention to provide a detection method with less deviation from an image. Another object of the present invention is to provide an apparatus embodying such a method with a simple configuration.

[0008]

In order to solve the above-mentioned problems, a detection method according to the present invention detects a side edge position of a sheet.
Detection sensor crosses the sheet to be circulated and conveyed
Scanning direction, and scanning by this detection sensor.
The side edge position of the sheet during the first transport
The reference position of the side edge of the sheet to be conveyed is
The reference position is set to wait for the detection sensor when the sheet is circulated.
Machine position and the detection sensor
When it is detected that there is a sheet at the
The scanner to the outside in the width direction of the sheet.
When it is detected that there is no sheet in the
By scanning inward, a piece of the sheet
It is characterized by detecting a shift.

[0009] Preferably, the circulating conveying method for conveying and circulating a plurality of sizes of sheets centered, to wait for the sensing sensor prior to the time of transportation of the first, the standard position corresponding to the sheet size to be transported, first After the sheet at the time of conveyance is conveyed to the detection position, when it is detected that the sheet is at the standard position, the sheet is scanned outward in the width direction of the sheet, and when there is no sheet at the standard position. Then, scanning is performed inward in the width direction of the sheet to detect the side edge reference position.

[0010]

Still further, a detecting device according to the present invention comprises a size detecting sensor for detecting the size of a sheet to be conveyed on a conveying path capable of conveying a plurality of sizes of sheets in a center-aligned manner, A shift detection sensor that scans in a direction crossing the sheet to detect a side edge position of the sheet, wherein the shift detection sensor includes a side edge of a maximum-size sheet that can be conveyed and a side edge of a minimum-size sheet. The size detection sensor detects the size of the sheet to be conveyed at the time of the first conveyance, and the deviation detection sensor responds to the size signal detected by the size detection sensor. Then, it moves to a standard position corresponding to the preset side edge position of each sheet size and waits for the arrival of the sheet. Scans in the direction across the sheet to detect a sheet side edge position at the time of the first conveyance, and detects the deviation of the sheet as the reference position of the sheet side edge at the time of the circulating conveyance. .

[0012]

In such a means, when a sheet to be circulated is supplied into the conveyance path, the detection sensor scans in a direction crossing the sheet to detect a side edge position of the sheet.
This first detection position is set as a side edge reference position of the sheet. Next, in the second and subsequent cycles, it is detected whether or not the sheet has shifted in accordance with whether or not the side edge of the circulated sheet coincides with the side edge reference position.
For detection after the second cycle, the detection sensor is in standby at the side edge reference position in advance, and starts scanning from the standby position as a starting point.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 shows a sheet circulating apparatus for a document or the like used in an image forming apparatus or the like. The circulating device 1 circulates and conveys a sheet-shaped document P to be copied or printed along a conveying path a set number of times, and provides the document P for image reading. The transport path of the circulating device 1 is roughly divided into a lower transport path 2, a U-turn path 3, an upper transport path 4, and a U-turn path 5, and has a peripheral length longer than at least the maximum document size that can be copied. ing. The lower conveyance path 2 is continuous with the document insertion path 6 and guides the document P inserted through the insertion path 6 to the exposure position 7. The light image formed by the exposure is formed on the image forming body 9 of the image forming unit by the image forming lens 8 to form a reproduced image. The reproduced image is visualized by a well-known developing unit, is transferred onto a transfer sheet, and is fixed.

Driving rollers 10, 20, 30, and 40 for document transport are arranged in the lower transport path 2 and the upper transport path 4 of the circulating device 1 so as to allow a part of the peripheral surface to be viewed. The driving roller includes an upper driven roller 11,
21, 31, 41 and lower driven rollers 12, 22, 3
2 and 42 are placed in contact with it at a suitable pressure and are driven by drive rollers 10-40. Drive roller 1
0 to 40 are connected to and driven by a drive source such as a stepping motor (not shown).

Adjacent to the drive roller 10, the upper conveying path 4
There is provided a finger 50 that can move up and down so as to protrude or retract. The finger 50 is the driving roller 1
0, and has an arc-shaped guide surface adjacent to the drive roller 10.
A U-turn path 5 is formed with the peripheral surface. Finger 50
In a normal state, is located at a position retracted from the upper transport path 4 as shown in FIG. 1, and moves upward by an appropriate driving means such as an electromagnetic solenoid to traverse the upper transport path 4 in a circulation mode described later. To protrude.

The original P inserted from the original insertion path 6 is conveyed by the driving rollers 10 to 30 and the lower driven rollers 12 to 32 through the lower conveying path 2 so as to cross the original exposure position 7. The document exposure position 7 is generally made of a transparent glass plate, and the document P is conveyed along its upper surface with the image surface facing downward.

The exposed document P is U-turned upward by a driving roller 40, driven rollers 42 and 41 and a guide 43, and is guided to the upper transport path 4. An operator sets the number of copies before inserting a document. The transport apparatus 1 is operated in a one-sheet copy mode when the number of sheets set is one, and in a circulation mode when a plurality of sheets are set.
In the single-sheet copy mode, the finger 50 is located at a position retracted downward from the upper transport path 4, so that the original P travels straight along the upper transport path 4, and the discharge roller 51 and the guide 5
The air is discharged outside through the space 53 between the two. In the case of the circulation mode, the finger 50 is urged to move across the upper transport path 2 so that the original is returned to the lower transport path 2 along the U-turn path 5 and a circulation path is formed. You. The document is circulated through the circulation path for a set number of times to receive exposure. When the final number of exposures is completed, the finger 50 moves downward to open the upper conveyance path 4, and the document is sent to the discharge roller 51. Let go.

A gate 61 is protrudably disposed near the entrance of the document insertion path 6 so as to cross the insertion path 6, and a fixed size document detection sensor 62 is provided upstream of the gate 61. The gate 61 is a device for circulating the original which is still in circulation.
When the original is located in the circulation path, the insertion path 67 is closed, and the next original is made to stand by until the original in the circulation path is discharged.

The document detection sensor 62 faces the insertion path 6,
Photosensors a to f (FIG. 2) are arranged in a line in a direction crossing the direction perpendicular to the document moving direction.
Each photo sensor is provided corresponding to the side edge position of the document size A4 to A0, and the size of the document is detected by which photo sensor of the document located in the insertion path 6 biases. For detecting the document size, a known configuration can be used.

In addition to the above configuration, the driving roller 30
Gate 90 is located in front of the lower conveyance path 2 (upstream position).
A detection sensor 100 for detecting a deviation of the circulated and conveyed document is provided further in front of the detection sensor 100. The gates 90 are provided in tandem in a direction perpendicular to the document transport direction.
When the document is protruded, the leading edge of the conveyed document is contacted to correct the skew of the document, and then the document is retracted from the conveyance path 2 at a predetermined timing to open the document.

As the detection sensor 100, a reflection type photo sensor can be suitably used, and is provided so as to be scannable in a direction (perpendicular to the direction) transverse to the document conveyance direction by a guide / drive unit (not shown). By this scanning, the side edge position of the document stopped there is detected.

The operation and operation of the detection sensor 100 will be described with reference to FIGS. For convenience, the maximum size of a transportable document is described as A0 size, and the minimum size is described as A4 size. In FIG. 2, reference numerals 200, 300, 400, and 500 denote an A0 size sensor position, an A4 size sensor position, a sensor center position, and a home position sensor, respectively, and are tandemly arranged in a direction perpendicular to the document conveyance direction. , The position to which the detection sensor 100 moves. A4 size sensor position 200 and A0 size sensor position 300
Is a standard position set corresponding to the side edge position of the original of the size, and is a standard position where the side edge of the original is located when the original is conveyed without deviation. The center position 300 of the sensor is the center position between the side edge position of the largest size document that can be conveyed and the side edge position of the smallest size document. Therefore, in this example, the middle position between the A0 size sensor position 200 and the A4 size sensor position 300 is used. Position. The home position sensor 500 includes a photo sensor and the like, and is a reference position of a pulse count for moving the sensor 100 to the sensor center position when the power is turned on.

When the power of the circulation device is turned on, first, it is detected whether or not the detection sensor 100 is located at the home position 500. When the detection sensor 100 is not located at the home position sensor 500,
Detection sensor 100 is once home position sensor 5
00 and then the home position sensor 50
Starting from 0, it moves to the sensor center position 400 according to a predetermined distance counted by an encoder or the like. Such a home position sensor 5 when the power is turned on
The movement to 00 is a preliminary means for moving the detection sensor 100 located at the unfixed position to the sensor center position 400. In this way, the detection sensor 100 preliminarily stands by at the sensor center position 400. The standby at the sensor center position 400 of the detection sensor 100 is performed according to the size of the document to be conveyed.
The time for moving 0 to the standard position corresponding to the size is set to the shortest.

When the print preparation is made, the number of copies (the number of circulations) is set, and the original is supplied, the size of the original to be circulated and conveyed is detected by the standard size original detection sensor 62 as described above. In accordance with the detected size signal, the detection sensor 100 moves from the sensor center position 400 on standby to a standard position set in advance corresponding to the side edge position of the size, and waits there. For example, if the detected document size is A0 size, this standard position is A0 size sensor position 200,
In the case of the A4 size, the position is the A4 size sensor position 300. Positions for other sizes are not shown, but are predetermined standard positions between positions 200 and 300, respectively.

After (or during) the detection sensor 100 moves to a standard position corresponding to the size of the document, the conveyed document is temporarily stopped by the gate 90 and its leading end is aligned as described above. In this state, the detection sensor 100 is scanned in a direction across the document. This scanning, when the sensor 100 located in the standard position is detected that there is a document is performed toward outwardly in the widthwise direction of the document, in the absence of the document in the width direction inwardly of the document It is done towards.

When a side edge (edge) of the document is detected by such scanning, the detected side edge position is determined as a side edge reference position of the document to be conveyed.
0 stands by at this side edge reference position. The offset of the document after the second circulation is performed with reference to the side edge reference position determined in the first transport.

In the second cycle, the original is stopped again by the gate 90. The detection sensor 100 detects whether or not the side edge of the document is at the side edge reference position, and if it is not present, that is, if it detects that the document is offset, scanning is performed in the same manner as described above. The direction in which the document is shifted is detected, and the shift correcting means provided in the transport path is operated to correct the shift of the document.

As the offset correcting means, for example, the drive roller 40 of the U-turn path 3 can be used. That is, by making one end of the drive roller 40 movable back and forth, the axis of the drive roller can be tilted back and forth. The document is conveyed so as to be inclined in a direction opposite to the direction in which the document is offset. This inclined document is placed at the gate 90
Alignment is performed correctly by abutment with the above, but at that time, the offset in the opposite direction is performed according to the inclination, whereby the offset can be corrected.

In the above example, the document in the image forming apparatus is described as the circulating sheet to be detected. However, the present invention is not limited to this, and the present invention can be similarly applied to an apparatus that circulates and uses the sheet.

As described above, according to the present invention, since the detection sensor itself is configured to scan, it is possible to detect the deviation with high accuracy by using a single photo sensor or the like. In particular, the detection sensor is located at the center of the sensor,
By waiting in order before the size standard position and the side edge reference position at the time of the initial conveyance, respectively, before the detection, the sensor movement time (detection time) can be minimized, and the sheet conveyance speed can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a document circulation device to which a shift detection method according to the present invention can be applied.

FIG. 2 is a diagram for explaining a displacement detection method according to the present invention.

FIG. 3 is a block diagram of a displacement detection device according to the present invention.

FIG. 4 is a flowchart of a displacement detection method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circulation device 2-5 Conveyance path 62 Document size detection sensor 90 Gate 100 Detection sensor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-36072 (JP, A) JP-A-3-73551 (JP, U) JP-B-2-41731 (JP, B2) (58) Field (Int.Cl. ⁷ , DB name) B65H ^7/ 00-7/20

Claims (3)

(57) [Claims] 1. A detection sensor for detecting a side edge position of a sheet.
Can be scanned across the sheet to be circulated
The first time detected by scanning of this detection sensor
The side edge position of the sheet when the sheet is conveyed
The reference position of the side edge of the sheet and this reference position
The standby position of the detection sensor during the cyclic transfer of
When transporting the loop, the detection sensor moves the sheet to the standby position.
When it is detected that there is
Scans outward in the width direction of the
When it is detected that the
Detecting deviation of the sheet by scanning
A method for detecting a shift of a circulating conveyance sheet. 2. A circulating conveyance method for circulating and conveying sheets of a plurality of sizes in a center-aligned manner, wherein the detection sensor is made to stand by at a standard position corresponding to a sheet size to be conveyed before the first conveyance, after conveying the sheet when the detection position, the standard position when it is detected that there is a sheet is scanned toward outwardly in the widthwise direction of the sheet, in the absence of sheets in the standard position in the width direction of the sheet shift detection method of circulating transfer sheet according to claim 1, wherein the detecting the side edge reference position is scanned toward the person. 3. A size detection sensor for detecting a size of a sheet to be conveyed on a conveyance path which can convey a plurality of sizes of sheets circulated in the center, and scans the sheet in a direction transverse to the sheet. A shift detection sensor for detecting a side edge position of the sheet is provided in order, and the shift detection sensor waits at a central position between a side edge of the largest sized sheet and a side edge of the smallest sized sheet that can be conveyed. The size detection sensor detects the size of the sheet to be conveyed at the time of the first conveyance, and the shift detection sensor detects each preset sheet based on the size signal detected by the size detection sensor. Moves to the standard position corresponding to the side edge position of the size and waits for the arrival of the sheet. A sheet side edge position at the time of detection, and using the detected side edge position as a reference position of the sheet side edge at the time of circulating conveyance, to detect a sheet side shift, wherein a skew detection of the circulating conveyance sheet is performed.