JP2681698B2 - Automatic document feeder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an improvement of an automatic document feeder in a recording apparatus such as an electrophotographic copying machine.

BACKGROUND OF THE INVENTION Generally, an automatic document feeder is used by being mounted on a platen 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, sheets are fed one by one from an original placing table (stack section) on which sheet-like originals (hereinafter simply referred to as originals) are placed. The document is fed onto the platen glass by a conveyor belt, exposed here by an exposure section lamp in the main body of the copying machine, and then carried out onto the document discharge table.

In the document exchange operation on the platen glass by such an automatic document feeder, conventionally, after detecting that the document on the platen has been ejected by the sheet ejection sensor, the next document is sent out from the stack section and the original platen glass is ejected. It was transported to the top and stopped at a predetermined position. For this reason, it takes a long time to replace the original, and thus a long copy processing time, resulting in low copy productivity.

[Problems to be solved by the invention]

When using the automatic document feeder to exchange documents within the return time of the scanning optical system during the document exchange operation in which documents are automatically fed and ejected onto the platen, copy productivity will be 10%.
It is 0% and no wasted time is required.

For this purpose, it is necessary to increase the document conveyance speed from the document double feed prevention position of the stack portion to the document stop position on the platen glass surface.

However, increasing the document conveying speed causes various problems such as an increase in the size of the motor, an increase in power consumption, an increase in the degree of document breakage, and a decrease in document separation performance.

[Means for solving the problem]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problem in the automatic document feeder and to improve the number of copies to be processed.

The automatic document feeder of the present invention that achieves the above-mentioned object conveys a plurality of sheet-like documents sequentially to the image exposure unit, stops the documents at the image exposure unit, and moves the optical system to perform scanning exposure. In an automatic document feeder that carries out the document to a document delivery table after exposure, a document size detection unit that detects the size of the sheet document on the document table, and before the exposure operation of the preceding sheet document, A feeding unit that starts feeding the succeeding sheet-like document, a detection sensor that detects passage of the succeeding sheet-like document, and conveys the succeeding sheet-like document that has been conveyed after a predetermined time has elapsed based on the detection sensor signal. An automatic document feeder having a stop means for temporarily stopping in the path and waiting until the preceding sheet-like document starts to be discharged from the exposure position, wherein the temporary stop position stopped by the stop means is the original position. At least two stop positions that differ depending on the original size are provided based on the original size detection signal from the size detecting means, and the stop positions are such that the original stop position of a small original is larger than the stop position of a large original in the document feeding direction. The distance from the leading edge of the succeeding original, which is on the downstream side and is stopped by the stopping means, to the leading edge of the preceding original, which is stopped in the image exposure unit, is the distance from the trailing edge of the preceding original to the discharging means. An automatic document feeder, which is set to be longer than the distance to the discharge position.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram showing a document conveyance path of the automatic document conveyance device according to the present invention, FIG. 2 is a configuration diagram showing a drive system (power transmission system) of the automatic document conveyance device, and FIG. FIG. 4 is a perspective view showing a transport system and a drive system, and FIG. 4 is a plan view of a main part of the automatic document transport device. FIG. 5 is an external perspective view of the upper part of the copying machine equipped with the automatic document feeder. FIG. 6A is a schematic diagram showing a document conveying 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 described with reference to FIGS. 1, 3, 5, and 6A.

A document placing table 1 is provided on the upper left side of the automatic document feeder so that documents can be stacked and placed. A document setting solenoid SD1 and a document leading end stopper 1 swingable by the solenoid SD1 are provided below the leading end of the document placing table 1.
D is provided. With the upper end of the leading end stopper 1D protruding near the leading end of the original placing table 1, the original bundle is placed on the original placing table 1, and the leading end of the original bundle abuts against the original leading end stopper 1D. Align the paper.

When the stack of originals is placed on the original mounting table 1, the presence or absence of the originals on the original mounting table is detected by the original set detection sensor (zero original detection sensor) PS2, and the control panel 110 of the copier body 100 displays the ADF mode. Is displayed.

On the document mounting table 1, there are provided width regulating plates 1A, 1A for regulating the width direction of the document. The horizontal width regulating plate 1A is provided on the lower surface of the document table 1 with a pinion gear.
The rack gears 1C, 1C, which can alternately slide sideways across the 1B, are connected to each other, and are symmetrically movable about the center. The rack gears 1C, 1C are connected to the width regulating plates 1A, 1A, respectively, and the movement amount thereof is detected by the document size detection sensor PS1, so that the horizontal size of the document can be read. The length of the document D of the standard size is automatically converted based on the read value. Therefore, by placing the original bundle on the original placing table 1 and sliding the lateral width regulating plates 1A, 1A to abut on the lateral width of the original, various original sizes, that is, each original length can be stored. Has become.

Above the vicinity of the leading end of the document placing table 1, the pickup roller 2 can be moved up and down by the operation of a sheet feeding solenoid (latch type) SD2 and spring pressure, and can be rotated by the driving force of a driving motor M. ing. By operating the copy button 111 of the control panel 110, the automatic document feeder is activated, the power supply solenoid SD2 is energized and operated, and the pickup roller 2 connected thereto is lowered, thereby moving the original bundle. The document is pressed against the upper surface, and at the same time, starts to rotate by the driving force of the driving motor M, and the document is sent out.

On the downstream side of the pickup roller 2 from the feeding of the original, there is provided a separating feeding means including a feed belt 3 which is wound around a feed roller 3A which is a registration roller and which rotates, and a double feed preventing roller 4 which is located below the feed belt 3. There is. The separating / feeding means separates and sends out only one of the uppermost originals among the plurality of originals sent out by the pickup roller 2 when the driving force of the drive motor M is transmitted through the electromagnetic clutch K2. .

A document passage detection sensor PS3, an intermediate conveyance roller 5, a curved guide plate 6
Is provided.

One original fed by the separating / feeding means is detected by the original passage detection sensor PS3 as the passage of the leading edge of the original, then fed by a pair of intermediate conveying rollers 5 in the vicinity thereof, and passed between the guide plates 6. Will be delivered. When the leading edge of a document passes through a document passing synchronization sensor (reversed document passing detection sensor) PS5 arranged in the middle of the feeding path, a detection signal is issued to control document transport. The document passing synchronous sensor
The PS5 controls the operation of a later-described original stopper 102, a drive motor M, a paper feed clutch K2, a transport clutch K1, and the like via a timer.

Next, the rotating conveyor belt 8 and the copier body 100
The original platen glass 1 (hereinafter referred to as the original platen glass) is conveyed while being nipped and held between the original platen glass for exposure of the original image (hereinafter, referred to as the original platen glass) 101 and the original stopper solenoid (latch type) SD3 is operated.
Original stopper 10 protruding from the upper left end of 01
Stop at the position where the leading edge of the document hits 2.

The transport belt 8 is stretched between a transport belt driving roller 9, a driven roller 10, three document pressing rollers 11A, 11B, 11C, and a tension roller 12.

The original document is exposed by the exposure lamp 103 in the main body of the copying machine at the stop position on the original platen glass 101, and the original image is formed on the recording medium by the scanning of the optical system including the lens and the mirror.

When a series of copy processes for the manuscript is completed,
The abutting portion of the document stopper 102 retracts from the upper surface of the document table glass 101 to release the leading edge of the document, and the document is carried out by the transport belt 8 and the pair of discharge rollers 13 that have started to rotate again, and After the end passage is detected by the document discharge detection sensor PS4, the document is discharged and placed on a discharge tray (document discharge table) 14.

Further, this automatic document feeder is provided with a document reversing unit 30 for reversing the front and back of a document through a document reversing path. The document reversing section 30 includes transport roller groups 31, 32, and 33, a guide plate 34, and a reversing document passage detection sensor PS5 for detecting a document passing through the reversing section 30.

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

The drive motor M is a servomotor in which a DC motor and a speed control device (encoder, tachogenerator or the like) are integrated. A toothed belt B1 is stretched between each pulley of the toothed pulley P1 integral with the drive shaft 20 of the servomotor M and the toothed pulley P2 fixed to the intermediate shaft 21. It is rotated by the driving rotation of the motor M.

On the intermediate shaft 21, in addition to the toothed pulley P2, toothed pulleys P3, P4 and an electromagnetic clutch K1 are journaled. A toothed belt B2 is provided between the pulley P3 and the pulley P5 fixed to the shaft end of the transport belt driving roller 9.
Are wound and meshed to be rotatable.

The driven roller 10 is rotated via the conveyor belt 8 by the rotation of the conveyor belt driving roller 9, and the toothed pulley P10 fixed to the shaft end of the driven roller 10 is toothed to the toothed pulley P11 via the toothed belt B5. Then, the paper discharge roller 13 is rotated.

Further, a toothed belt B3 that winds around and meshes with the outer periphery of the toothed pulley P4 provided on the intermediate shaft 21 has a shaft at a shaft end of a feed roller shaft 22 that rotates the feed roller 3A via gears G1 and G2. The toothed pulley P6 and the toothed pulley P7 attached to the shaft end of the intermediate transport roller shaft 23 integral with the intermediate transport roller 5 are wound and meshed with the respective outer peripheral teeth. Note that R
Reference numerals 1 and R2 denote tension rollers which circumscribe the outer peripheral surface of the toothed belt B3 and tension them.

By 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 G1, G2, and thereby the feed roller wound around the driven roller 3B. The belt 3 is rotated, and the toothed pulley is further rotated.
The pickup roller 2 is rotated by P8, 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 the pickup roller 2 to feed a document.

At the time of double-sided document copying, the document whose first surface has been exposed by the above-described process is rotated counterclockwise by the transport belt driving roller 9 in synchronization with the completion of the exposure. It is transported to the right.
The right end of the conveyed document is sent to the document reversing unit 30. Therefore, the document D is circulated and conveyed in the document reversing section 30 along the guide plate 34 by the conveyance rollers 31, 32, and 33, and thereafter, the right end portion of the document D, that is, the leading end portion in this case, is placed on the platen glass. Before being fed, the rotation of the conveyor belt driving roller 9 is switched again in the clockwise direction based on the signal from the reverse passage detection sensor PS5.

The above is a schematic configuration of a drive system in which power is transmitted by the drive motor M. Next, an operation of conveying a document by the drive system will be described.

FIG. 6 (B) is a schematic view showing a feeding / conveying process of small-sized originals D11, D12, D13, D14 (for example, B5 size, A4 size, etc.). Here, D11 is the preceding discharged document discharged from the discharge roller 13 of the discharge means to the outside of the machine. D12 is the platen glass 101
The original document is placed on the surface of the document and is in a stopped state because the preceding position is regulated by the document stopper 102. D13 is a succeeding manuscript in the vicinity of the right end of the original platen glass 101, the leading end of which enters the wedge-shaped space formed by the original platen glass 101 and the conveyor belt 8 and is temporarily stopped and in a standby state.
D14 is an undelivered original placed on the original placing table 1.

The leading end portion S1 of the succeeding original document D13 in the sheet feeding direction is in a pause standby state at a distance of x1 from the protruding leading end position of the original document stopper 102. Further, the distance between the position of the leading edge portion S1 and the trailing edge portion of the preceding document D12 is kept at the distance l1. This distance l1 is set to be larger than the distance m1 from the protruding tip of the document stopper 102 to the nip position of the paper discharge roller 13 of the paper discharge means (l1> m1). Therefore, the distance x1 is equal to the preceding document D1.
It is set to be larger than the distance y1 from the rear end portion of the sheet 2 to the discharge roller 13 (x1> y1).

By thus determining the position of the trailing edge of the succeeding document D13, the preceding document D12 and the succeeding document D13 are simultaneously conveyed by the conveying belt 8 at the interval l1.
When the leading end of the document collides with the document stopper 102 and is stopped, the trailing part of the preceding document D12 is ejected from the paper ejection roller 13 as shown in the figure.
Since the paper is ejected from the paper, the paper ejection failure due to the trailing edge gripping does not occur.

The temporary stop position of the leading end S1 of the succeeding document D13 is set to the length of various small size documents and the document pressing roller 11
Although it is restricted by the pressure contact position of A, the distance m1, etc.,
The original replacement time can be shortened by approaching the preceding original D12 as close as possible.

FIG. 6 (C) is a schematic diagram showing a feeding / conveying process of large-sized originals D21, D22, D23, D24 (for example, B4 size, A3 size, etc.). Here, D21 is the preceding discharged document discharged from the discharge roller 13 of the discharge means to the outside of the machine. D22 is the platen glass 101
The leading document is placed on the surface of the document and is in a stopped state because the leading edge position is regulated by the document stopper 102. D23 is a succeeding document that is in a conveyance standby state, and its leading end portion S2 is temporarily stopped at a predetermined position downstream of the intermediate conveyance roller 5 in the feeding direction. D24 is an undelivered original placed on the original placing table 1.

The leading end portion S2 of the succeeding original document D23 in the sheet feeding direction is in a pause standby state at a distance of x2 from the protruding leading end position of the original document stopper 102. Also, the position of the leading edge S1 and the preceding document
The distance from the rear end of D22 is kept at a distance l2. This distance l
2 is set to be larger than the distance m2 from the projecting tip of the document stopper 102 to the nip position of the discharge roller 13 of the discharge means (l2> m2). Therefore, the distance x2 is set larger than the distance y2 from the trailing end of the preceding document D22 to the paper discharge roller 13 (x2> y2).

In this way, by determining the temporary stop position of the leading end of the succeeding document D23, the preceding document D22 and the succeeding document D23 are simultaneously conveyed by the conveying belt 8 at the interval l2.
When the leading edge of the document abuts against the document stopper 102 and is stopped, the trailing part of the preceding document D22 is ejected from the discharge roller 13 as shown.
Since the paper is ejected from the paper, the paper ejection failure due to the trailing edge gripping does not occur.

The temporary stop position of the leading end portion S2 of the succeeding original document D23 is set under the same conditions as in the case of the small size succeeding original document D13, and the original replacement time is shortened as much as possible.

Next, FIG. 7 is a diagram showing the rotation speed of each sheet feeding roller by the drive system, FIG. 8 is a block diagram of the drive system, and FIG. 9 is a time chart.

With reference to these drawings, a description will be given of the driving and the document transport process by the automatic document transport device.

When a bundle of originals is stacked on the original placing table 1 and abuts against the original leading edge stopper 1D stopped at the raised position, the original set detection sensor PS2 detects the presence or absence of the original and is set to the ADF mode.

When the lateral width regulating plates 1A, 1A are moved to touch the lateral side edges of the bundle of originals, the original size detection sensor PS1 detects the original lateral width, and the CPU converts and stores the original length.

When the copy button 111 is pressed, a copy start signal is input, and the copier body 100 and the automatic document feeder are activated.

This ADF activation signal causes the original set solenoid SD1
Is applied, and the leading edge of the document leading edge stopper 1D is lowered. At the same time, a voltage is applied to the paper feeding solenoid SD2, and the pickup roller 2 descends to press the uppermost layer of the document bundle.

At the same time, when the drive motor M starts to drive, the toothed pulley P1 on the motor drive shaft 20 rotates, and the toothed belt B1
, The intermediate shaft 21 having the toothed pulley P1 is rotated.
At this time, the electromagnetic clutches K1 and K2 are both ON, and the feed roller shaft 22 is driven and rotated by the rotation of the toothed belt B3, and the feed belt 3 is rotated via the gears G1, G2 and the feed roller 3A. Then, the pickup roller 2 is further rotated by the toothed belt B4. At the same time the above toothed belt
The toothed pulley P7 meshing with B3 is also rotated to rotate the intermediate transport roller shaft 23, and the intermediate transport roller shaft 5 is in a rotating state.

At the same time, the toothed belt B2 wound around the intermediate shaft 21 rotates the transport belt driving roller 9 having the toothed pulley P5. This allows the roller 9 and the driven roller
The conveyor belt 8 wound between 10 is rotated. At this time, the peripheral speeds of the pickup roller 2, the feed belt 3, the intermediate transport roller 5, and the transport belt 8 are all in the high-speed transport mode v ₁ (for example, the peripheral speed v ₁ = 1200 mm / sec).

By the rotation of each roller and the rotation of the belt, the document table 1
The uppermost original D11 of the upper original bundle is sent out by the pickup roller 2, and is separated by the feed belt 3 and the double feed prevention roller 4, and the uppermost first original D11 is separated and fed.

When the leading edge of the separately fed document D11 passes through the document passage detection sensor PS3, a leading edge passing signal is issued, the timer starts counting from this signal generation, and the feeding clutch K2 is turned off after t3 timing. To do. As a result, the leading edge of the document D11 passes through the nip position of the intermediate conveying roller 5, and then the driving rotation of the pickup roller 2 and the feed belt 3 is stopped and the driven rotation is achieved.

Subsequently, the intermediate conveyance roller 5 is driven to rotate and the document D11 is rotated.
Is fed, passes through the document passage synchronization sensor PS5, and then is pinched by the transport belt 8 in a rotating state to feed the document table glass 10
Glide over 1

The document stopper solenoid SD3 is actuated and the document stopper 102 projects to the upper surface of the left end of the document table glass 101 after t6 from the time when the document is passed by the synchronous sensor PS5.

After t9 from the time when the synchronous sensor PS5 passes the original, the drive motor M is temporarily turned off and stopped before the position where the leading edge of the original abuts the original stopper 102, and the motor brake is applied to the inertial force. The document stopper 102. In this embodiment, the motor is turned off about 5 to 10 mm before the stopper.

After that, at time t8, the transport clutch K1 is turned off and the transport belt 8 is stopped. At almost the same time, the clock is switched from high speed to low speed.

At time t10, the feed clutch K2 is turned on and the drive motor M is turned on.
Drive. As a result, the next original D12 is fed by the pickup roller 2 and the feed roller 3.

In the original stationary state in the image exposure section, scanning exposure by the optical system 103 on the copying machine main body 100 side is started. At this time, before or during scanning exposure, the next original D12 is sent out and fed through the feed roller 3 and the intermediate conveying roller 5, and the leading edge of the next original D12 is the original notification detection sensor PS3.
When it passes through, it emits a detection signal, and by the time measured by the timer t (or the pulse count by the counter),
The document D12 is stopped at a predetermined position and kept waiting. During this period, the feeding electromagnetic clutch K2 is ON, and the feeding electromagnetic clutch K1
Is OFF, the preceding document D11 being exposed is in a stopped state, but the following document D12 is fed in the low-speed transport mode v ₂ during this period, and its leading end is near the platen glass 101. It has reached and is waiting. However, the operation during this period is
The speed of v ₂ (for example, v ₂ = 500 mm / sec) is determined so that it is completed at least after the end of scanning and before the restart signal is generated.

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

6 (B) and 6 (C) show the ejected preceding originals D11, D21, the preceding originals D12, D22, and the succeeding originals D13, D2.
FIG. 6 is a schematic diagram showing a paper feeding / conveying process of 3.

In FIG. 6 (B), the timer starts timing when the leading edge of the succeeding document D13 passes the document passage detection sensor PS3, and after t2, the sheet feeding clutch K2 is turned off and the sheet feeding is stopped. Next, from the time when the leading edge of the document D13 passes through the document synchronization sensor PS5, the time measured by the timer t
After 14 minutes, the drive of the drive motor M is stopped. The leading end of the document D13 at the temporary stop position S1 is a position near the document table glass 101 where it is not pressed against the conveyor belt 8, and thus is close to the trailing end of the preceding document by a short distance l. .

Next, at the end of the scanning exposure, an ADF start signal is issued from the copying machine main body 100 to perform an exposure operation on the second document. That is, by turning on the drive motor M and turning on the electromagnetic clutch K1 for carrying, the preceding document D12 is carried by the carrying belt 8 and is discharged and placed on the paper discharge tray 14 via the paper feed roller 13. It At the same time, the succeeding original document D13 slides from the standby position on the original platen glass 101, and reaches the original document stopper 102 by the stopping operation to complete the original document replacement.
Original conveyance by the timer t8 timing at this time is the high-speed transport mode v _1.

Timers t5, t6, t7, t8, t by the above ADF start signal
9, t10 starts at the same time. Timers t6 and t7 activate setting of document stopper solenoid SD3, and timers t5 and t11 activate resetting of solenoid SD3. Also, timer t
8 issues an OFF signal of the transport clutch K1. In addition, a timer
t9, t10 and t14 control ON / OFF of the drive motor M.

Second document D12 is a high-speed mode v ₁ from the temporary stop position S1, it is conveyed onto the platen glass 101, after a pause in timing t9, and stopped abuts the document stopper 102 by inertia. Thereafter, the same operation as the preceding document D11 is performed, and the exposure process and the sheet discharge are performed.

In this embodiment, one motor and two electromagnetic clutches control and operate the above two drive systems. However, a similar operation can be performed by two motors and one electromagnetic clutch. .

Also, when copying a double-sided original, when the original is fed back to the original inverting section 30 and inverted and conveyed again to the platen glass, the timing is started from the detection of passage of the reverse original passage detection sensor PS5 The same effect can be obtained by setting the pause position of.

〔The invention's effect〕

As described above, according to the automatic document feeder of the present invention, not only is it possible to shorten the document replacement time, but it is also effective in facilitating the document transportation and preventing the document leading edge from being damaged.
In particular, the document transport is controlled by the document size detection signal and the preceding document passage detection means by starting the motor, clutch, solenoid and various timers based on the ADF start signal from the copying machine body. Has advantages that it is simple and clear, there are few malfunction factors, and the manufacturing cost can be reduced.

Furthermore, depending on the size of the original, the temporary stop position of the subsequent original can be set to 2
By maintaining the space between the preceding document and the succeeding document at a necessary minimum by having more than one place, the document replacement time was minimized, and the interference between the documents and the discharge failure were also improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a document conveyance path of the automatic document conveyance device according to the present invention, FIG. 2 is a configuration diagram showing a drive system (power transmission system) of the automatic document conveyance device, and FIG. FIG. 4 is a perspective view showing a transport system and a drive system, and FIG. 4 is a plan view of a main part of the automatic document transport device. FIG. 5 is an external perspective view of the upper part of the copying machine equipped with the automatic document feeder. 6A, 6B, and 6C are schematic diagrams showing a document conveying process;
FIG. 7 is a diagram showing the rotation speed of each paper feed roller by the drive system, FIG. 8 is a block diagram of the drive system, and FIG. 9 is a time chart of the process of feeding and transporting the original. 1 ... Original platen, 1A ... Width control plate 1B ... Pinion gear, 1C ... Rack gear 1D ... Document end stopper 2 ... Pickup roller 3 ... Feed belt, 3A ... Feed roller 4 ... Heavy weight Anti-feed rollers, 5 ... Intermediate transport roller 6 ... Guide plate, 8 ... Transport belt 9 ... Transport belt drive roller 11A ... Original pressing roller 13 ... Discharge roller, 14 ... Discharge tray 30 ... Document reversal part, 31, 32, 33 …… Conveying roller group 34 …… Guide plate, 100 …… Copier body 101 …… Image exposure part (document table glass) 102 …… Document stopper 110 …… Control panel 111 …… Copy button K1, K2 …… electromagnetic clutch (MC) M …… drive motor, D …… original D12, D22 …… preceding document, D13, D23 …… subsequent document D11, D12, D13, D14 …… small size document D21 , D22, D23, D24 …… Large size original PS1 …… Original size detection sensor PS2 …… Original set Knowledge sensor PS3 ...... document passing detection sensor PS4 ...... document discharge sensor PS5 ...... inverted document passing detection sensor (original passage synchronization sensor) v ₁ ...... fast transport mode, v ₂ ...... low speed feed mode

Claims (1)

(57) [Claims] 1. A plurality of sheet-shaped originals are sequentially conveyed to an image exposure unit, the originals are stopped at the image exposure unit, an optical system is moved to perform scanning exposure, and the originals are discharged after the exposure. In the automatic document feeder that carries out to the table, the original size detection unit that detects the size of the sheet original on the original table, and the feeding of the subsequent sheet original before the exposure operation of the preceding sheet original is completed Feeding means, a detection sensor for detecting the passage of a succeeding sheet-like document, and after a predetermined time elapses based on the detection sensor signal, the succeeding sheet-like document being conveyed is temporarily stopped in the conveying path. An automatic document feeder having a stop means for waiting until a sheet-shaped document starts to be discharged from an exposure position, wherein a temporary stop position stopped by the stop means is a document size detected by the document size detection means. Based on the detection signal, at least two or more stop positions that differ depending on the document size are provided, and the stop position is such that the stop position of a document with a small document size is on the downstream side of the stop position of a large document with respect to the document feeding direction. The distance from the leading edge of the subsequent original stopped by the stop means to the leading edge of the preceding original stopped at the image exposure unit is greater than the distance from the trailing edge of the preceding original to the discharge position of the discharge means. An automatic document feeder characterized by being set long.