JPH03106740A - Automatic original carrying device - Google Patents

Abstract

PURPOSE:To perform reliable carriage of an original by a method wherein before a subsequent original is delivered, an original size detecting signal generated through the passage of a preceding original is outputted, a control part compares the original size detecting signal with a preset original size to detect a difference between the lengths of the originals, and when it is decided that abnormality occurs to a temporary stop mode, control of the temporary stop and the carriage stop of an original is varied. CONSTITUTION:A detecting means PS3 to detect the front end and the rear end of an original passing the downstream side, in the direction of the feed of an original, of a separating means is provided. An original size detecting signal generated through the passage of a preceding original before delivery of a subsequent original is outputted from the detecting means PS3. A control part CPU compares a preset original size with the original size detecting signal to detect a difference between lengths of the originals. When it is decided that abnormality occurs to a temporary stop mode, control of the temporary stop and the carriage of an original is varied. This constitution conveys an original at a high speed even when an off-specification original is mixed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in an automatic document feeder in a recording apparatus such as an electrophotographic copying machine.

[Background of the invention]

An automatic document feeder is generally used by being mounted on a document table glass (platen glass) of an image exposure unit of a copying machine or the like.

In an optical system movable copying machine equipped with this automatic document feeder, a document tray with a sheet-like document (hereinafter simply referred to as a document) of a standard size (for example, JIS standard A column, B column or USA standard size) is placed. Automatic document transport from the stacking table (stack section). The originals are fed out one by one by the paper feed rollers of the feeding device, and are fed onto the document table glass by a conveyor belt, where they are exposed to light for a predetermined number of copies by the exposure section lamp inside the copying machine main body. , and is further carried out onto a document eject table.

Conventionally, the operation of exchanging originals on the original platen glass by such an automatic document feeder can only be used with originals of standard sizes, such as A size and B size, and control is performed according to these standard sizes. Further, after a paper ejection sensor detects that the preceding original on the original platen glass has been ejected, the subsequent original is sent out from the stack section, conveyed onto the original platen glass, and stopped at a predetermined position. As a result, it takes a lot of time to exchange originals, and therefore a lot of time is required for copy processing, and originals of sizes other than the standard cannot be used, resulting in a decrease in productivity.

[Problem to be solved by the invention]

Operations required to exchange the preceding and following originals during the exposure time or during the return time of the scanning optical system during the original exchange operation in which the automatic document feeder is used to automatically feed and eject originals onto the document table. In some cases, we have eliminated wasted time by doing this. However, both automatic document feeders are designed and controlled to use standard-sized documents. Therefore, there is a problem in that a document of a size other than the standard (hereinafter referred to as a non-standard size) cannot be used in the automatic document feeder at all.

[Means to solve the problem]

The object of the present invention is to solve the above-mentioned problems in an automatic document feeder and to increase the number of copies processed.

The automatic document feeder of the present invention, which achieves the above object, uses a separation means to separate the documents one by one from a stack of documents stacked on a document placement table, feeds the documents, and then transports them to an image exposure section. After that, the original is stopped at the image exposure section, the optical system is moved to perform scanning exposure, and after the exposure, the original is carried out of the machine by a paper ejecting means, and before the exposure operation for the original is finished, The automatic document feeder is configured to start feeding a succeeding document and temporarily stop it at a predetermined position before the image exposure section for waiting, the document feeder starting to feed a subsequent document, and causing the document to pass downstream of the separating means in the paper feeding direction. A detection means for detecting the front edge and the rear edge is provided, and the detection means issues a document size detection signal by passing the preceding document before sending out the next document, and the control unit compares the document size with a preset document size and determines the length of the document. The present invention is characterized in that when a difference is detected and it is determined that an abnormality occurs in the temporary stop mode, the document temporary stop conveyance control is changed.

Further, the automatic document feeder of the present invention is characterized in that, when it is determined that the abnormality has occurred, subsequent document feed is switched to a feed mode in which the document is not temporarily stopped and on standby.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a structural diagram showing the document conveyance path of the automatic document feeder according to the present invention, and FIG. 2 is a diagram showing the drive system of the automatic document feeder (
FIG. 3 is a perspective view showing the document conveying system and drive system inside the apparatus, and FIG. 4 is a plan view of the main parts of the automatic document conveying device. Figure 5 is a perspective view of the upper part of the copying machine equipped with an automatic document feeder. FIG. 6(A) is a schematic diagram showing the document conveyance path. The illustrated devices are automatic document feeders (RADF) with an automatic document reversing function.

First, the structure and operation of the automatic document feeder will be explained with reference to FIGS. 1, 3, 5, and 6(A).

A document placement table l is provided on the left side of the upper surface of the automatic document feeder, and allows documents to be stacked on top of each other.

A document setting solenoid SDI and a document leading end stopper ID swingable by the solenoid SDI are provided below the leading end of the document placing table l. With the upper end of the leading edge stopper 1D protruding near the leading edge of the document mounting table l, place the document stack on the document mounting table l, and abut the leading edge of the document stack against the document leading edge stopper ID. Arrange the paper.

When a stack of originals is placed on the original platen l, the presence or absence of originals on the original platen is detected by the original set detection sensor (zero original detection sensor) PS2, and the ADF mode is displayed on the control panel 110 of the copying machine main body 100. is displayed.

Width regulating plates IA, IA are provided on the document mounting table l to regulate the width direction of the document. The width regulating plate IA is provided with rack gears 1 that can alternately slide laterally across the binion gear IB on the lower surface of the original table L.
c and IG, and are movable symmetrically around the center. The rack gears IC, 1G are connected to width regulating plates lA, IA, respectively, and the amount of movement thereof is detected by a document size detection sensor PSl, so that the width size of the document can be read. The standard size of a manuscript is, of course, determined by its width and length (for example, A4 has a width of 2
57 mm, length 364a+m), the length is uniquely determined when the width is detected, so the CPU automatically converts the length of the standard size document D based on the width read value. Therefore, a stack of originals is placed on the original placing table L, and the width regulating plate IA. By sliding the lA into contact with the width of the document, the CPU detects the width of the standard size document, and also converts the length of each document corresponding to the various standard sizes.
It is stored in memory and the control described below is performed.

A big up roller 2 is located above the tip of the document table L, and is movable up and down by the operation of a paper feed solenoid SD2 and spring pressure, and is also rotatable by the drive force of a drive motor M. There is. By operating the copy button 111 of the control panel 110 (7), the automatic document feeder is started, and the paper feeding lens SD2 is energized and operated, lowering the big-up roller 2 connected thereto and transferring the document. It comes into pressure contact with the top surface of the stack, and at the same time begins to rotate under the drive force of the drive motor M, and the document is sent out.

On the document feeding downstream side of the big up roller 2, there is a 7-eed belt 3 that winds and rotates a feed roller 3A.
Separating paper feeding means is provided which separates the paper from the double-feed prevention roller 4 located below it. The separation sheet feeding means is driven by a drive motor M.
The driving force is transmitted through the electromagnetic clutch K2, and only the uppermost one of the plurality of originals sent out by the pickup roller 2 is separated and sent out.

A document passage detection sensor PS3, an intermediate conveyance roller 5, and a curved guide plate 6 are provided on the downstream side of the document feeding unit L:rj.

The passage of the leading edge of the original sheet sent out by the separation feeding means is detected by the original passage detection sensor PS3, and is then fed by a pair of intermediate conveyance rollers 5 in the vicinity, passing between the guide plates 6. will be delivered. When the leading edge of the document passes the document synchronization sensor PS5 disposed in the middle of the feeding path, a detection signal is generated to control document conveyance. The document synchronization sensor PS5 is connected to a document stopper 10, which will be described later.
2. Drive motor M. Paper feed clutch K2, transport clutch K
1 etc. is controlled via a clock timer.

Next, the rotating conveyor belt 8 and the copying machine main body 100
The document is conveyed while being pinched between the original platen glass for exposing the original image on the upper surface (hereinafter referred to as the document platen glass) 101, and is projected from the upper surface of the left end of the document platen glass 101 by the operation of the document stopper solenoid (latch type') SD3. The document stops at the position where the leading edge of the document abuts the document stopper 102 which is set to .

The conveyance belt 8 is stretched between a conveyance belt drive roller 9, 1013 driven rollers, a document holding roller N, and a tensile roller 12.

The original is exposed to light by an exposure lamp 103 inside the copying machine main body at a stop position on the original platen glass 101.
An original image is formed on a recording medium by scanning with an optical system such as a mirror.

Then, the same exposure is repeated for the set number of copies, and when the series of copying processes for the original is completed, the abutting portion of the original stopper 102 hits the original platen glass 1.
The leading edge of the original document is retracted from the upper surface of 01, and the original is transported out by the conveyor belt 8 and the pair of paper ejection rollers 13, which start rotating again, and the passage of the trailing edge of the original is detected by the original ejection detection sensor PS4. Thereafter, it is discharged and placed on a paper discharge tray (original paper discharge tray) 14.

Furthermore, this automatic document feeder is provided with a document reversing section 30 for reversing the front and back of the document using the document reversing path. The document reversing section 3o has transport roller details 31.32.3.
3, a guide plate 34, and a document synchronization detection sensor PS5 for detecting a document passing through the reversing section 30, which is also used as a sensor for detecting the passage of a reversed document.

Next, the power drive system for the roller group and belt will be explained with reference to FIGS. 2, 3, and 4.

The drive motor M is a servo motor that integrates a DC motor and a speed control device (encoder, tachogenerator, etc.). A toothed pulley PI that is integral with the drive shaft 20 of the servo motor M, and a toothed pulley P2 that is fixed to the intermediate shaft 2l.
A toothed belt Bl is stretched between each pulley, and the intermediate shaft 2l is rotated by the driving rotation of the motor M.

In addition to the toothed pulley P2, toothed pulleys P3 and P4 and an electromagnetic clutch Kl are mounted on the intermediate shaft 2l. The toothed pulley P3 and the conveyor belt drive roller 9
There is a toothed pulley P5 fixed to the shaft end of the
The toothed belt B2 is wound and meshed to be rotatable.

The conveyor belt 8 is rotated by the rotation of the conveyor belt drive roller 9.
The driven roller lO rotates via the driven roller lO, and the toothed pulley PlO fixed to the shaft end of the driven roller lO meshes with the toothed pulley Pll via the toothed belt B5, thereby rotating the paper discharge roller l3.

Further, a toothed belt B3 that winds around and meshes with the outer periphery of a toothed pulley P4 provided on the intermediate shaft 2l is connected to a feed roller 3.
A toothed pulley P6 is pivoted on the shaft end of the 7-eed roller shaft 22 that rotates A through the life wheels Gl and G2, and a toothed pulley P6 is pivoted on the shaft end of the intermediate conveyance roller shaft 23 that is integral with the intermediate conveyance roller 5. It is wound around and meshes with each outer peripheral tooth portion of the toothed pulley P7. In addition, Rl. R2 is a tension roller which is placed under tension in circumferential contact with the outer peripheral surface of the toothed pelt B3.

Due to the rotation of the toothed belt B3, the feed roller shaft 22, which is integral with the toothed pulley P6, rotates the feed roller 3A via the gears Gl and G2.
Rotate the belt 3 wound between P8. The pickup roller 2 is rotated by P9 and the toothed belt B4. On the other hand, an electromagnetic clutch K2 is attached to the other end of the feed roller shaft 22, and is controlled based on an input signal to rotate the feed belt 3 and pickup roller 2 to feed the original.

During duplex original copying, the conveyor belt drive roller 9 starts rotating counterclockwise in synchronization with the completion of exposure of the document whose first side has been exposed in the above-described process, so that the conveyor belt 8
The document is conveyed rightward on the document table glass 101 by the document table glass 101.

The right end portion of the transported document is sent to the document reversing section 30. Therefore, the document D is conveyed in the document reversing section 30 along the guide plate 34 while being sequentially supported by the conveyance rollers 31, 32, 33, and then the right end of the document D, that is, the leading edge in this case, However, before the leading edge of the document is sent onto the lath 101, the rotation of the conveyor belt drive roller 9 is switched clockwise again based on a signal from the document synchronization sensor (reversed document passage detection sensor) PS5. It looks like this.

The above is a general outline of the drive system through which power is transmitted by the drive motor M. Next, the operation of the drive system will be explained. Figure 6 (B). (C) is a schematic diagram showing the document feeding/conveying process, FIG. 7 is a diagram showing the rotational speed of each paper feed roller by the drive system, FIG. 8 is a block diagram of the drive system, and FIG.
The figure is a time chart.

All these controls are performed by the CPU.

(2) When a stack of originals is stacked on the original table L and hits the original leading edge stopper ID stopped at the raised position, the original set detection sensor PS2 detects the presence or absence of originals and the ADF mode is set.

(2) When the width regulating plates IA, IA are moved and brought into contact with the width side edges of the document bundle, the document size detection sensor PS1 detects the document width, and the CPU converts and stores the document length.

(2) When the copy button 111 is pressed, a copy start signal is input, and the copying machine main body 100 and automatic document feeder are activated.

(2) This ADF activation signal applies voltage to the document setting solenoid SDI, and lowers the tip of the document leading edge stopper ID. At the same time, a voltage is applied to the paper feed solenoid SD2, and the pickup roller 2 descends to press the top layer of the document bundle.

(2) At the same time, when the drive motor M starts driving, the toothed pulley PI on the motor drive shaft 20 rotates, and the intermediate shaft 2l having the toothed pulley P1 is rotated via the toothed bell I-Bl. At this time, electromagnetic clutch K1. Both K2 are in the ON state, and the rotation of the toothed belt B3 causes the 7
The feed roller shaft 22 is driven and rotated, and the gears Gl, G2
, 7, the feed belt 3 is rotated via the feed roller 3A, and the big up roller 2 is also rotated by the toothed belt B4. At the same time, the toothed pulley P7 that meshes with the writing belt B3 is also rotated to rotate the intermediate conveyance roller shaft 23, and the intermediate conveyance roller shaft 5 is in a rotating state.

At the same time, the toothed belt B2 wound around the intermediate shaft 2l rotates the conveyor belt drive roller 9 having the toothed pulley P5. As a result, the conveyor belt 8 wound between the roller 9 and the driven roller IO is rotated. At this time, the circumferential speeds of the big up rollers 2, 7, the feed belt 3, the intermediate conveyance port roller 5, and the conveyor belt 8 are all set to the high speed conveyance mode v+ (for example, the circumferential speed v+−120
0 mm/see).

As a result of the above-mentioned rotation of each roller and rotation of the belt, the top layer document DI of the document stack on the document table l is sent out by the pickup roller 2, and is separated by the feed belt 3 and the double feed prevention roller 4, and then The th original DI is separated and fed.

■ When the leading edge of the document DI that has been separated and fed passes the document passing detection sensor PS3, a leading edge passing signal is generated, the clock timer starts measuring time from the generation of this signal, and after timing t3, the paper feed clutch K2 is activated. Turn off. As a result, after the leading edge of the document DI passes through the nip position of the intermediate conveyance roller 5, the driving rotation of the big up roller 2 and the feed belt 3 is stopped, and the driving rotation becomes driven rotation.

■ The intermediate conveyance roller 5 is then rotated and the document DI
The document is fed, passes the document synchronization sensor PS5, is then pinched by the rotating conveyor belt 8, and is placed on the document table glass 10.
Ski on 1.

■ Timed from the time the original passes through the synchronization sensor PS5.
After 6, the document stopper solenoid SD3 is activated, and the document stopper 102 protrudes to the upper surface of the left end of the document table glass 101. This solenoid SD3 is a latch type, and even if the power is turned off, the suction state is maintained unless reset.

(2) At the time before the leading edge of the document reaches the document stopper 102, that is, after t9 measured from the time when the document passes by the synchronization sensor PS5, the drive motor M is temporarily turned off and the brake is applied to stop the document. However, due to inertia, each drive unit continues to operate to some extent, and the document continues to be transported. For this motor brake, it is effective to short-circuit both terminals of the motor M or apply a reverse voltage.

[Phase] Then, at approximately t8, the transport clutch Kl is turned off.
F and controls the conveyor belt 8 to stop the conveyor belt 8. However, here as well, the conveyor belt 8 moves while decelerating due to the inertia of the conveyance system, but the document is moved to the document stopper 10.
2, the document does not move while hitting this document stopper 102.

Also, almost simultaneously with this time measurement t8, the clock is switched from high speed to low speed.

(2) Turn on the paper feed clutch K2 and drive the drive motor M at time tlO. As a result, the big up roller 2
Then, the next document D2 is fed by the feed roller 3.

While the document is in a still state in the image exposure section, scanning exposure by the optical system 103 on the side of the main body 100 of the copying machine is started. At this time, the next document D2 is sent out before or during the scanning exposure, and is fed through the seven feed rollers 3 and the intermediate conveyance roller 5, and when the leading edge of the subsequent document D2 passes the document notification detection sensor PS3, a detection signal is sent. The document D2 is stopped at a predetermined position by timing t by a clock timer (or by counting pulses by a counter).
I'll keep it on standby. During this time, the feeding electromagnetic clutch K2
When the document is nipped by the intermediate conveyance roller 5, it is further turned OFF to prevent double feeding of subsequent documents. Since the transport electromagnetic clutch Kl is turned off, the preceding document D being exposed
Although the original document D2 is in a stopped state, the following original document D2 is being fed in the low-speed conveyance mode V during this time, and the first document D2 has reached the vicinity of the document table glass 101 and is waiting. however,
The operation during this period is completed at least after the end of scanning and before the restart signal is generated.
= 500+am/sea).

The above-mentioned subsequent document standby position is set differently depending on various document sizes, that is, the length of the document in the conveyance direction.

FIG. 6(B) is a schematic diagram showing the process of feeding and conveying the preceding document Di and the succeeding document D2.

The leading edge of the subsequent document D2 is detected by the document passage detection sensor P-33.
The clock timer starts measuring time from the moment the paper passes through t2, and after t2, the paper feed clutch K2 is turned OFF and paper feeding is stopped. Next, after time t14 is counted by the clock timer from the time when the leading edge of the document D2 passes the document synchronization sensor PS5, the drive of the drive motor M is stopped. Note that the leading edge of the document D2 at the temporary stop position P is located near the document table glass 101 and is not pressed against the conveyor belt 8, so it is close to the trailing edge of the preceding document at a short distance.

■ Next, at the end of the scanning exposure, from the copying machine main body 100
A DF start signal is issued and the exposure operation for the second original is performed. That is, by turning on the drive motor M and turning on the conveyance electromagnetic clutch Kl, the preceding document DI is conveyed by the conveyance belt 8, and is discharged and placed on the paper discharge tray l4 via the paper discharge roller l3. Ru. At the same time, the succeeding original D2 slides on the original platen glass 101 from the standby position, and reaches the original stopper 102 in the stopping operation, thereby completing the original exchange. At this time, the document conveyance by the clock timer t8 is in the high-speed conveyance mode Vl.

[Phase] Clock timer t is activated by the above ADF start signal 5. t6. t7. t 8, t 9, t lO
t starts at the same time. The clock timers t6 and t7 operate the setting of the document stopper solenoid SD3, and the clock timers t5 and tll operate the reset of the solenoid SD3. Further, the clock timer [8 outputs an OFF signal for the transport clutch Kl. Furthermore, the clock timers t91tlO and tl4 are activated when the drive motor M is ON. O
Controls FF.

The second document D2 is conveyed from the temporary stop position P2 to the document table glass 101 in the high speed mode v1, and the timer t
After a temporary stop at 9, the document goes through the same process as described above, and then due to inertia it hits the document stopper 102 and stops. Thereafter, it is operated in the same manner as the preceding document DI, and is subjected to exposure processing and discharged.

Also, when copying a double-sided original, when the original is reversely fed and reversed to the original reversing unit 30 and then transported to the original platen glass again, the timing starts from the passage detection of the reversed original passage detection sensor PS5, and the original is processed as described above. A similar effect can be obtained by setting a temporary stop position.

In this embodiment, one motor and two electromagnetic clutches were used to control and operate the two drive systems described above, but the same operation was performed using two motors and an electromagnetic clutch If! It is also possible to do this in step 2.

The above is an explanation of normal operation when a standard size original is used. Next, Fig. 9(A) shows the control for non-standard size originals. This will be explained with reference to FIG. 10 (B).

When the leading edge of the standard size document D (for example, A4 size) reaches the document passing sensor PS3, the document passing sensor PS3 is turned ON, and when the trailing edge of the document passes the document passing sensor PS3, it is turned OFF. Therefore, the CPU can detect the length of the document by counting the time during which the document passing sensor PS3 is ON. Therefore, the CPU detects the width of the standard size original in advance and compares the converted length of each standard size original with this counted length to detect whether the length is the standard size or a non-standard size. can do.

Assuming that a non-standard size document Ds whose length is different from the standard size document D by ΔL (either longer or shorter by ΔL) is fed and passes the document passing sensor PS3, the CPU detects that the document passing sensor PS3 detects the standard size document. It is detected that it is ON for a longer (or shorter) time than when D passes. Then, the time count value while the document passage sensor PS3 is ON, that is, the information on the length of the non-standard size document Ds is sent to the CPU.
stored in memory. Then, in order to cope with the fact that the subsequent document has a length different from the standard size document by ΔL, the control of the ADF is changed to one of the following controls.

In the first control, feeding of the non-standard size subsequent document Ds2 is started after the preceding document reaches the document discharge sensor PS4. That is, after the document discharge sensor PS4 is turned on, the subsequent document Ds2 of non-standard size is fed by the operation process described in (1) and (2) above, and the subsequent document is not kept waiting at a predetermined position.

In the second control, the CPU uses the length of the standard-sized original, which is longer than the length of the non-standard-sized original, among the length information of various standard-sized originals obtained by converting the length of the standard-sized original from the detection of the standard-sized original. Take control.

That is, for example, if the supplied non-standard size document has a width of A4, a length longer than A4, and shorter than B4, this subsequent non-standard size document DS2 is controlled as a B4 size document. These controls are similar when ΔL is short.

This eleventh second control is selected in advance by a control selection switch SW on the operation panel.

In this way, even if standard size originals and non-standard size originals coexist, the ADF 6 can operate.

〔Effect of the invention〕

As described above, the automatic document feeder of the present invention can be used even when non-standard size documents are mixed, unlike the conventional ADF which can only use standard size documents. It has also become possible to reliably transport the original at high speed, which not only makes it possible to shorten the original transport time, but also to improve the efficiency of the copying operation as a whole. Since the present invention is mainly controlled by a CPU, the control program is simple and clear, there are few causes of malfunctions, and manufacturing costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the structure of the document conveyance path of the automatic document feeder according to the present invention, and FIG. 2 is a diagram showing the drive system of the automatic document feeder (
FIG. 3 is a perspective view showing the document conveying system and drive system inside the apparatus, and FIG. 4 is a plan view of essential parts of the automatic document conveying device. Furthermore, FIG. 5 is an external perspective view of the upper part of the copying machine equipped with an automatic document feeder. Figure 6 (
A). (B). (C) is a schematic diagram showing the document conveyance process, Figure 7 is a diagram showing the rotational speed of each paper feed roller by the drive system, Figure wi8 is a block diagram of the drive system, Figure 9 (A),
(B) is a time chart of the document feeding and conveying process, and FIG. 10 is a flowchart of conveying a standard size document. l... Original table IA... Width regulation plate 1B
...Binion gear 1c...Rack gear LD...
・Document leading edge stopper 2... Big up roller 3... Feed belt 3A... Feed roller 4... Double feed prevention roller 5... Intermediate conveyance roller 6
... Guide plate 8 ... Conveyor belt 9 ...
Conveying belt drive roller l3... Paper ejection roller l4... Paper ejection tray 3
0... Original reversing section 31.32.33... Conveyance roller group 34... Guide plate 100...
Copying machine main body 101...image exposure section (original table glass) 1
02... Original stopper 110... Control panel Ill... Copy button K1. K2...Electromagnetic clutch (MC:) M...Drive motor D...Document Di...Standard size preceding document D2...Standard size succeeding document Ds...Non-standard size preceding document DS2... Non-standard size subsequent document PSl...Document size detection sensor PS2...Document set detection sensor PS3...Document passage detection sensor PS4...Document discharge detection sensor PS5...Document synchronization sensor SW...Control Selection switch v1...High speed transport mode v1...Low speed transport mode

Claims (2)

[Claims] (1) Separate the originals one by one from the stack of originals stacked on the original stack by the separating means, feed them, and further transport them to the image exposure section, and then stop the originals at the image exposure section. The optical system is moved to perform scanning exposure, and after the exposure, the original is carried out of the machine by a paper ejecting means, and before the exposure operation for the original is finished, feeding of the subsequent original is started and the image exposure is performed. An automatic document feeder is configured to temporarily stop and wait at a predetermined position in front of the separating device, and includes a detection device for detecting a front end and a rear end of a document passing downstream of the separation device in the paper feeding direction, The detection means generates a document size detection signal by passing the preceding document before sending out the next document;
When the control unit detects a difference in length of the original by comparing it with a preset original size, and determines that an abnormality occurs in the pause mode, the control for pausing and conveying the original is changed. An automatic document feeder characterized by: (2) An automatic document feeder characterized in that, when it is determined that the abnormality has occurred, the subsequent document feed is switched to a transfer mode that does not pause and wait.