JPH0742053B2 - Document feeder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document feeder used in a copying machine, and more particularly to an automatic document feeder having a double-sided document front / back reversing mechanism.

[Background of the Invention]

Conventionally, a document is configured so that a document is drawn onto the document glass by a conveyor belt that rotates forward and backward on the document glass and then is conveyed in reverse to bring the rear end of the document into contact with a step portion of a stopper plate provided at the edge of the document glass. A carrier was provided (Japanese Patent Laid-Open No. 58-21).
762, Japanese Patent Laid-Open No. 61-229741).

In the case of this type of document feeder, only one document placed on the tray of the document feeder is sent out in the feeder, and is pressed against the document glass by the transport belt traveling in the forward direction. It is fed and stopped at a predetermined position. Here, the first surface (front surface side) of the document is scanned and exposed to form a copy image on the recording paper.

The original that has completed the copying process on the first side is moved on the original glass by the forward running of the conveying belt and is sent to the paper discharge reversing unit.

When the second side (back side) of the original is continuously copied, the original is reversed inside the discharge reversing unit, and is fed again from the front end of the original onto the original glass surface. Then, the conveyance belt switched to the reverse running by the reverse rotation of the reversible motor and the driving roller transfers the original in the opposite direction on the original glass surface. When the leading edge of the original comes into contact with the stepped portion of the stopper plate provided on the edge of the original glass, the feeding of the original is stopped.

After reaching the original stop position, the second surface of the original is scanned and exposed to form a copy image on the recording paper.

After that, the transport belt is switched to the forward direction, the document is transported in the forward direction on the glass surface of the document, and is delivered to the external tray through the delivery opening through the delivery reversing unit delivery path.

[Problems to be solved by the invention]

When a document is transported in the forward and reverse directions by the document transport device described above, slippage occurs between the drive roller that winds and drives the transport belt and the transport belt when the transport belt is switched from running in the reverse direction to running in the forward direction. Cause This is because when the document stop control is performed by the pulse count from the reverse rotation switching by the encoder provided on the rotary shaft of the reversible motor that rotates the drive roller, the slip of the conveyance belt causes a shortage of the document conveyance movement, and The leading edge does not reach the stopper plate step provided on the edge of the original glass. Therefore, the original does not stop at a predetermined stop position, that is, a copy positioning position, and correct copying cannot be performed.

[Means for solving problems]

The present invention is intended to solve the above problems, and it is an object of the present invention to always realize a correct document stop position irrespective of slippage of a conveyor belt.

In order to achieve the above object, the document feeder according to the present invention comprises a sheet feeding unit which is adjacent to a document glass and feeds placed double-sided documents one by one to the document glass side, and an upper surface of the document glass. Traveling in the forward and reverse directions,
It has a transport unit including a transport belt that slides and transports a fed document on the document glass surface, and a reversing unit that reverses the document surface after the transported document passes through the document glass surface. In a document feeding device for a two-sided document in which a document size is detected by a detection sensor provided between the paper feeding unit and the transport unit, a document pulled from the paper feeding unit onto the document glass is stopped at a predetermined position. After detecting this stop state, the conveyance belt starts to run in the reverse direction, one end of the original is brought into contact with the stopper plate step portion provided on the edge feeding side of the original glass, and then the conveyance belt is moved. A document is conveyed to the reversing unit side by traveling in the forward direction, and a signal detected by the sensor installed in the reversing unit at the end of the document and a size detection signal of the document. The basis, is characterized in that to control the document feed amount so as to abut the end of the original has been reversed in the stopper Itatan unit.

〔Example〕

Next, the present invention will be described based on an embodiment shown in the accompanying drawings. FIG. 1 is an external perspective view of a copying machine equipped with a document feeder. In the figure, 1 is a copying apparatus main body, and 5 is a document feeder. The document feeder 5 is installed on the document glass 2 on the copying apparatus main body 1.

FIG. 2 is a sectional view of the document feeding device 5 showing the document feeding path. FIG. 3 is a perspective view showing a drive system of the document feeder 5.

The document feeding device 5 includes a feeding unit 20 having a feeding belt 21 capable of reversing forward and backward on the upper surface of the original glass 2, a paper feeding unit 10 at one end of the original glass 2, and the other end of the original glass 2. Paper output reversing unit 40 on the upper side
20 and a discharge tray portion 80 above. A frame 11 holding the paper feeding unit 10 is screwed to the copying apparatus main body 1 and is covered with an exterior frame 12. The transport unit 20 and the discharge reversing unit 40 are accommodated and held in another housing 22, and the housing 22 is supported by the frame 11 and a hinge or the like, and has a structure that can be opened counterclockwise by holding a handle 22A on the right side in the drawing. However, in the case of the figure, the transport unit 20 and the paper discharge reversing unit 40 are tilted to the right, and the document transport belt 21 presses the document glass 2 placed on the upper part of the copying apparatus main body 1. There is.

The document feeder 5 according to the present invention is capable of automatically feeding a document by a feeding mechanism described below.
Further, it also has a function as an ordinary platen cover by opening and closing the entire document feeder 5 by means.

The paper feed unit 10 supplies a first paper feed section for separating and sending out the originals D on the original tray 13 one by one from the upper layer, and the originals sent by the first paper feed section to a conveyor belt 21. It is composed of a second sheet feeding section.

First, a stack of originals to be copied is loaded on the original tray 13 with the first side (first side) of the first page facing down.

Next, when the copy button is pressed, the motor drive relay in the document feeder is turned on, and the motor M starts to rotate normally. By this motor drive, the separating belt 15, the paper feed roller 17, and the transport belt 21 all start forward rotation (counterclockwise travel). At the same time, the sheet feeding solenoid is operated, and the movable guide plate 14 of the first sheet feeding portion bounces up, and the documents D stacked on the movable guide plate 14 are pressed against the separating belt 15. The separating belt 15 starts to rotate in the direction of the arrow, whereby the manuscript D is squeezed by the rotating separating belt 15 and the separating roller 16 so that only the uppermost one of the accumulated document bundle is sent out. Be done. When the leading edge of the original reaches the vicinity of the paper feed roller 17 of the second paper feed unit that rotates in the direction of the arrow, the paper feed solenoid is turned off by the detection signal of the sensor 18, and the movable guide plate 14 descends. The feeding of the subsequent originals is stopped, and only the originals are conveyed by the paper feed roller 17.

The original D conveyed by the paper feed roller 17 has its leading end passing through the sensor 18 and above the stopper plate (scale plate) 3 for positioning the trailing end of the original D, and then the copying machine. A document glass 2 fixed above the main body 1,
The conveyance belt 21 of the conveyance unit 20 reaches the pressure contact position, and further the conveyance is continued by the frictional force of the rotating conveyance belt 21.

When the trailing edge of the document D passes through the sensor 18, the size of the document D is automatically detected by the leading edge detection signal and the trailing edge detection signal, and at the same time, the document D in this conveyance path is detected.
A paper jam (jam) is detected.

The conveyor belt 21 includes a driving roller 23 rotatably supported by bearing plates fixed to both side wall portions of the housing 22.
It is stretched between the driven roller 24 and the intermediate rollers 25A and 25B, and can be rotated forward and backward by the reversible motor M. The upper running surface of the conveyor belt 21 is pressed by tension rollers 26A, 26B adjustably supported by the bearing plate, and the lower running surface thereof is pressed rollers 27A, 27B supported by bearing members mounted on the bearing plate. , Belt presser roller 2
8 and the separation roller 38.

4, 5, and 6 are a cross-sectional view, a plan view, and a perspective view showing the main part in the vicinity of the drive roller 23 of the document feeder 5.

Of the rollers, a bearing member that supports a belt pressing roller (swing back roller) 28 near the drive roller 23.
29 is a position near the step portion 3a of the stopper plate (scale plate) 3 where the roller 28 is fixed to the end portion of the original glass 2 on the sheet feeding side, and to the right of this position, that is, in front of the sheet feeding direction. It is configured so that it can move substantially horizontally between the position (FIG. 4) and the running of the conveyor belt 21.

FIG. 7 is an exploded perspective view showing the shapes of the belt pressing roller 28, the bearing member 29, and the restraining member, and FIGS. 8 and 9 show the details of the shaft end portion 28a of the belt pressing roller 28. It is an expanded sectional view.

As shown in FIGS. 6 and 7, the bearing member 29 has notched oval grooves 29a, respectively, and the shaft end 28a of the belt pressing roller 28 is fitted into the grooves 29a so that the groove 29a It is movable in the long axis direction.

A shaft support portion 29b that rotatably supports the shaft end portion 28a of the belt pressing roller 28 to prevent the shaft end portion 28a from falling down is projected from one end below the groove portion 29a. On the other hand, the other lower end of the groove 29a is cut out to form an opening 29c.
Shaft end 28a of belt pressing roller 28 fitted in groove 29a
When moved to the vicinity of the above opening, this opening 29c
It is possible to descend from.

Next, a stepped portion 28b having a slightly smaller diameter is formed at two places in the intermediate portion near the shaft end portion 28a of the belt pressing roller 28, and the stepped portion 28b has a recessed portion at the tip of the swing arm 30. 30a
Can be fitted and removed freely.

The other ends of the two rocking arms 30 are rocking shafts having a prismatic shape.
It is fixed by screws near both ends of 31. Both shaft end portions 31a of the swing shaft 31 are fitted into the holes of the hinge member 32 and are rotatably supported.

A link plate 33 is fixed near the center of the swing shaft 31 as shown in FIG. At the other end of the link plate 33,
An elongated hole 33a is provided, and a shaft portion 34a at one end of an L-shaped swing lever 34 is swingably fitted into the elongated hole 33a.

The rotation center shaft portion 34b of the swing lever 34 has an integral shape protruding to both sides, and is fitted into the through holes of both side plates of the box-shaped holding plate 36 for fixedly holding the electromagnetic solenoid 35 and rotatably held. Has been done. A torsion spring 37 is wound around the rotation center shaft portion 34b, and one end of the spring 37 is a swing lever.
The swing lever 34 is hooked by the 34 and the holding plate 36, and is biased by a spring in one direction.

An elongated hole 34c is provided at the upper end of the swing lever 34, and a fixed pin 35B planted at the tip of the plunger 35A of the electromagnetic solenoid 35 is slidably fitted into the elongated hole 34c. .

Next, the operation of the belt pressing roller 28 will be described with reference to partial sectional views of FIGS. 8 (A), (B), 9 (A) and (B).

One sheet of the document D sent out from the sheet feeding unit 10 passes through an entrance formed by a gap between the transport belt 21 of the transport unit 20 and the stopper plate 3, and is further separated between the document glass 2 and the transport belt 21. After reaching the press contact position, the conveyance is continued by the rotational frictional force of the conveyance belt 21.

In this document feeding and conveying process, when the conveying belt 21 rotates counterclockwise (forward rotation), the belt pressing roller 28
Is held in a state where it is not gripped by the swing arm 30 (state shown in FIG. 4) and is movable, but it slides into contact with the traveling of the conveyor belt 21 and shifts to the right,
Move away from the step 3a of the stopper plate 3. That is, the shaft end portion 28a of the belt pressing roller 28 rolls to the right along the groove portion 29a of the bearing member 29 while being driven to rotate in the counterclockwise direction, contacts the right end surface of the groove portion 29a, and stops shifting to the right. However, driven rotation is still performed.

FIG. 4 and FIG. 8 (A) show this state, in which the shaft end portion 28a of the belt pressing roller 28 is fitted into and supported by the shaft supporting portion 29b of the bearing member 29, and the conveyor belt 21 does not descend downward.
It rotates in contact with.

Next, a double-sided document conveying operation by the document conveying device having the belt pressing roller 28 will be described with reference to the flowchart of FIG.
A detailed description will be given based on the timing chart of the figure and the block diagram of FIG.

Subsequently, the document D being slid to the right on the document glass 2 by the transport belt 21 and transported, the trailing edge of the document D passes through the sheet trailing edge detection sensor 18, and the trailing edge of the document D is stopped by the stopper plate 3. After passing through, the transport belt 21 is further rotated in the forward direction to be transported to the right on the original glass 2 and fed to the paper discharge reversing unit 40.

The discharge reversing unit 40 includes a discharge path for the document D and a document D.
And a document reversing path for reversing the front and back sides of the document.

The paper discharge reversing unit 40 includes a feed passage 41 formed of a guide plate and the like, an anti-transfer entrance passage 42, reversing passages 43 and 44, a paper discharge roller pair 46, a reversing roller pair 47, and a document conveyance switching member 50.
And a paper front end detection sensor (paper discharge sensor) 48A and a rear end detection sensor (reversed paper sensor) 48B.

On the other hand, when the trailing edge of the document D has finished passing the leading edge detecting sensor 48A installed near the pair of discharge rollers 46, after a predetermined count has passed from the detection signal from the leading edge detecting sensor 48A, the motor is driven. The relay operates to temporarily stop the normal rotation of the motor M. As a result, the forward running of the conveyor belt 21 is also temporarily stopped. Even after this motor stop signal is input, the motor drive shaft slightly rotates due to inertia, and the encoder E directly connected to the drive shaft counts the inertial pulse until the stop. The conveyor belt 21 is temporarily stopped for a predetermined short time (for example, 100 ms) from when the interval of the inertial pulse due to the decrease in the rotational speed of the drive shaft exceeds 10 ms. After the lapse of the predetermined short time, the reverse rotation ON signal is input to the motor M, and the reverse rotation is started.

As a result, the conveyor belt 21 rotates clockwise (reverse rotation).
Is switched to. The path length of the reversing portion from the leading edge detecting sensor 48A to the trailing edge detecting sensor 48B is set to be sufficiently longer than the maximum length of various documents D used in advance.

Immediately before the reverse transfer of the conveyor belt 21 is started, after the document trailing edge is detected by the sensor 48A, the electromagnetic solenoid 35
A signal is input to. As a result, the plunger 35A is sucked, and the fixed pin 35B of the plunger 35A engages with the elongated hole 34c of the swing lever 34 to swing the swing lever 34 clockwise around the fixed center shaft portion 34b. .

At the same time, the shaft portion 34a at the other end of the rocking lever 34 is engaged with the elongated hole 33a of the link plate 33. The moving shaft 31 and the swing arm 30 are swung counterclockwise about both shaft end portions 33a. By this counterclockwise swinging, the recess 30a of the swinging arm 30 is fitted into and gripped by the stepped portion 28b of the belt pressing roller 28, restricts the lateral movement of the belt pressing roller 28, and rotatably holds it.

FIG. 6 and FIG. 9 (A) are a perspective view and a partial cross-sectional view of the document feeder showing this state.

When the double-sided copy mode of the document D is set, a predetermined number of counts elapse after the sensor 18 detects the trailing edge of the document, and then the solenoid is energized to interlock with the document conveyance switching member.
As shown in FIG. 2, 50 is oscillated counterclockwise to close the discharge passage 45 side, and the lower surface of the switching member 50 has a pair of discharge rollers.
The document D conveyed from the upper press contact position of 46 is guided to the lower left. The original D is sent to the reversing path 43, and makes a U-turn again by the reversing roller pair 47, passes through the reversing path 44, passes through the downward pressure contact position of the discharge roller pair 46, and reverses the inserting path 42.
Is sent out in the direction of the original glass 2.

In this way, during reverse rotation of the conveyor belt 21,
The belt pressing roller 28 is hooked by the swing arm 30 and rotates at a position away from the stopper plate 3, and the conveyor belt 21 does not come into slidable contact with the stopper plate 3.
Does not rub or break.

The document D is turned upside down by passing through the reversing path of the sheet discharge reversing unit 40, and is sent out onto the document glass 2 with its back surface, that is, the second surface facing the upper surface of the document glass 2, and further conveyed by the conveyor belt 21. Transported.

When the trailing edge of the document D passes through the trailing edge detection sensor 48B, the trailing edge detection signal activates the motor driving relay to temporarily stop the reverse rotation of the motor M. As a result, the reverse rotation of the conveyor belt 21 is temporarily stopped, so that the belt pressing roller 28, which is in sliding contact with the conveyor belt 21 and is driven to rotate, is also stopped. (Refer to Fig. 6, 8 (A), 9 (A)) After the belt pressing roller 28 stops rotating, the solenoid 35
A drive signal is input to and the axial position regulation of the belt pressing roller 28 is released.

The belt pressing roller 28 before the restriction is released is shown in FIG. 8 (A).
As shown in the drawing, at the upper position where the shaft end portion 28a is placed on each shaft support portion 29b of the bearing member 29, the conveyor belt 21 is driven to rotate. Therefore, the lower surface of the conveyor belt 21 that is in pressure contact with the belt pressing roller 28 is separated from the upper surface of the original glass 2 with a slight gap g below the pressure contact position. That is, the conveying belt 21 pressed against the upper surface of the original glass 2 by the pressing rollers 27A and 28B and the separating roller 38 is
Since the belt pressing roller 28 in the vicinity of the stopper plate 3 is in the non-contact state, the leading edge of the document D conveyed in the direction of the stopper plate 3 due to the reverse rotation of the conveying belt 21 is conveyed. Stopper plate 3 due to excessive pressing force
It strongly hits the stepped portion 3a and does not cause troubles such as the folding of the original, the occurrence of wrinkles, and the improper positioning of copying.

The approach of the leading edge of the document D to the stepped portion 3a is detected in advance by setting a predetermined count based on the document passage signal and the document size detection signal of the trailing edge detection sensor 48B. Based on this document approach signal,
A signal is input to the electromagnetic solenoid 35 and the plunger 35A protrudes after the reverse rotation of the conveyor belt 21 is temporarily stopped by the motor reverse rotation temporary stop and the driven rotation of the belt pressing roller 28 is stopped. As a result, the swing lever 34 swings counterclockwise about the rotation center shaft portion 34b and engages with the link plate.
Since the swing arm 30 is swung clockwise around the swing shaft 31 via the 33 and is flipped up, the recesses 30a of the swing arm 30 are engaged with the stepped portion 28b of the belt pressing roller 28. Is released, the axial position regulation of the belt pressing roller 28 is released, and the belt pressing roller 28 becomes movable.

While the reverse rotation of the conveyor belt 21 is temporarily stopped due to the motor reverse rotation temporary stop, the restriction of the belt pressing roller 28 is released,
After a short time, the motor drive relay is activated again, the reverse rotation of the motor M is restarted, and the conveyor belt 21 starts reverse rotation again.

The roller surface 28c of the belt pressing roller 28, which is in sliding contact with the inner surface of the conveyor belt 21 traveling in the reverse direction, is movably driven to rotate in the clockwise direction, and the shaft end portion 28a has a bearing member 29.
Each of the grooves 29a rolls while being guided, and is pulled to the left to approach the vicinity of the left end surface of the groove 29a.

When the belt pressing roller 28 is moved to the left, the shaft end 28a of the belt pressing roller 28 separates from each groove 29a of the bearing member 29 and falls into the lower opening 29c, so that the position as shown in FIG. Move to.

FIG. 9B is a partial cross-sectional view of the document feeder showing this state. In the illustrated state, the conveyor belt 21 is pressed from the back surface by the roller surface 28c of the belt pressing roller 28, and the surface side of the conveyor belt 21 is lightly pressed against the step portion 3a of the stopper plate 3 to close the gap g. However, the leading edge of the document conveyed in the reverse direction surely comes into contact with the stepped portion 3a of the stopper plate 3 and stops, and does not enter the sheet feeding unit side. After one end of the document D contacts the stopper plate 3, the motor drive is stopped, the reverse rotation of the conveyor belt 21 is stopped, and the document D is stopped.

The original placed at this accurate stop position is pressed onto the original glass 2 by the conveyor belt 21 under the pressure of the plurality of pressing rollers 27A and 28B, and the exposure of the second side (back side) is started. After that, a known process is performed to form an image and transfer it to a recording sheet to complete one-sided copying. At this time, the image position on the recording paper and the original image position of the document are accurately held.

After the exposure of the back surface of the document D is completed, the transport belt 21 is rotated in the forward direction, and the document D is fed into the paper discharge reversing unit 40 from the feed passage 41, and as described above, the paper discharge roller pair 46 is reversed. Reversing insertion passage 42 through passages 43, 44 and reversing roller pair 47
Is conveyed in reverse from the original glass 2. The reverse rotation of the conveyor belt 21 is performed here, and the belt pressing roller 28
Is regulated by solenoid 35. Further, the temporary stop and the release of the regulation of the belt pressing roller 28 just before the end of the reverse transfer line are performed in the same manner as described above.

Thus, the document D, which has been conveyed onto the document glass 2 and has its tip abutted against the step portion 3a of the stopper plate 3 and stopped at a predetermined position,
The second surface (back surface) of the original is exposed, and the exposure is performed in the main body of the copying apparatus in the image forming process. When the exposure of the back surface of the document D is completed, the transport belt 21 is rotated in the forward direction, and the document D is sandwiched by the discharge roller pair 46 from the delivery passage 41, and the document transport switching member with the reversing passage closed. After passing the upper surface of 50, it is sent out onto the discharge tray portion 80 through the discharge passage 45, and the original documents D are sequentially stacked as the copy is repeated.

FIG. 13 (A) is a diagram showing the document feeding path, and the alternate long and short dash line shows the path. According to this transport device, the bundle of documents D is placed on the document receiving tray 13 of the feeding unit 10 as the first document
Place the front side (second side) D1A of the page (D1) face down. The document D is fed from the last page (for example, D6), the reverse side D6B of the document D6 is copied after reversing, and then the reversal reversal is followed by the front side D6A of the document D6 on the discharge tray 80.
Is placed upwards.

Subsequently, the next original D5 is conveyed and copied, and is placed on the original D6 on the discharge tray 80.

Thus, all the originals that have been copied are output to the output tray 80.
The first page (D1) is page-aligned and stacked with the front surface (D1A) facing upward.

The document feeder of the present invention can also be set to the copy mode for only the first side of the document. FIG. 13 (B) is a diagram showing the document feeding path in this case, and the alternate long and short dash line is the document passing path. Further, the inside of the circular broken line is a partially enlarged view for explaining the document accumulation state.

The original stack placed on the original receiving tray 13 of the paper feeding unit 10 is placed with the first page as the lowermost layer and the first page (front side) as the lower side.
And then discharged to the discharge tray section 80. At this time, the document D does not pass through the reversing passages 43, 44 and the reversing insertion passage 42, but goes from the delivery passage 41 to the paper ejection roller pair 46 to the paper ejection passage 45 to the ejection tray portion 80. Further, the belt pressing roller 28 at the entrance of the transport unit 20 has a swing arm formed by the solenoid 35.
The regulating operation of 30 does not operate, and the roller 28 is slidably driven by the forward / reverse rotation of the conveyor belt 21, and can be moved left and right by the forward / reverse rotation and the bearing member 29.

The document D being slid to the right on the document glass 2 by the conveyor belt 21 has its trailing edge passed through the paper trailing edge detection sensor 18, and then the trailing edge of the document D has passed through the stopper plate 3. After that, it overruns slightly and then stops. This is based on the rear end detection signal generation by the sensor 18,
It is determined by counting up the clock pulse value set according to the length of the detected document size.

At this point, the drive signal for the normal rotation of the motor M is turned off, and then the start signal for driving the reverse rotation is applied to the motor.

When the motor M is started to rotate in the reverse direction, the conveyor belt 21 starts to rotate in the reverse direction to reverse the overrun original D, and after the motor M is rotated by a predetermined pulse in the reverse direction, the rear end of the original D is a stopper plate. The conveyance belt 21 stops running after coming into contact with the stepped portion 3a of No. 3.

When the conveyor belt 21 travels in the reverse direction, the belt pressing roller 28, which is capable of moving the shaft end, is driven to rotate clockwise by the frictional pulling force of the circumscribing conveyor belt 21, while the shaft end portion 28a has a bearing member. Rolling to the left along the groove 29a of 29. And the roller 28c of the belt pressing roller 28
However, when it is positioned above and closest to the stepped portion 3a of the stopper 3, the shaft end portion 28 of the belt pressing roller 28 comes into contact with the left end surface of the groove portion 29a of the bearing member 29, and only the driven rotation occurs. At the left end position, the belt pressing roller 28 comes into light contact with the step portion 3a of the stopper plate 3 via the conveyor belt 21 to close the gap g.

The traveling front end of the document D traveling in the reverse direction surely hits the vicinity of the stepped portion 3a of the stopper in this closed state, and the traveling of the transport belt 21 stops the document D at an accurate stop position. That is, the document D is completely prevented from entering the sheet feeding unit 10 side through the gap.

The original placed at this accurate stop position is pressed onto the original glass 2 by the conveyor belt 21 under the pressure of the plurality of pressing rollers 27A and 28B and the separating roller 38, and the first surface (front surface) is exposed. After the start, a known process is performed to form an image and transfer it to a recording sheet to complete the one-sided copying. At this time, the image position on the recording paper and the original image position of the document are accurately held.

Original D, which has completed the copying process on the first side, is conveyed by the conveyor belt.
By the forward rotation of 21, the document glass 2 is moved to the right on the original glass 2 and sent to the paper discharge reversing unit 40.

The document D enters the delivery passage 41 from the right end of the document glass 2 by the conveyance force of the conveyance belt 21 and ascends, makes a U-turn, is pressed and pinched at a position above the discharge roller pair 46, and the left discharge passage 45.
Is discharged outward from the sheet and placed on the document discharge tray 80 with the first surface thereof facing upward. At this time, the document conveyance switching member 50 is lowered and enters the side of the paper discharge central roller 46A to guide the document D to the paper discharge passage side.

The stacking order of the stack of documents stacked on the document receiving tray 13 and the stacking order of the documents discharged onto the discharge tray unit 80 are the same as those in the double-sided document copying mode described above.

〔The invention's effect〕

As described above, according to the present invention, after the original is drawn onto the original glass by the conveyor belt that travels in the forward direction on the original glass, the original is conveyed in the reverse direction and the leading end of the original comes into contact with the stopper plate stepped portion provided at the original glass end. In the document transporting device configured to operate, the reverse traveling is started after detecting the stop of the traveling of the transport belt in the forward direction, and it is detected that the rear end of the document transported by the backward traveling has passed a predetermined position. Since the document conveyance is controlled by the signal detected by the sensor and the document size signal so that the leading end of the document is brought into contact with the step portion of the stopper plate, the document can be positioned accurately and reliably. .

In particular, since the document stop position is controlled by the document trailing edge detection means, the document moving distance from the time of this detection until the document leading edge reaches the stopper plate step portion is relatively small. Therefore, the conveyance belt travels by pulse control. The control is accurately performed, and it is prevented that the document does not stop at a predetermined position due to overrun or insufficient running.

Further, a defective conveyance of the document due to a slip between the drive roller and the conveyance belt which occurs when the motor is switched between the forward and reverse directions is eliminated by the temporary stop of the conveyance belt and the document rear end detection control.

[Brief description of drawings]

FIG. 1 is an external perspective view of a copying machine equipped with a document feeder according to the present invention. FIG. 2 is a cross-sectional view of the document feeding device showing the document feeding path. FIG. 3 is a perspective view showing a drive system of the document feeder. 4, 5, 6, and 7 are a cross-sectional view, a plan view, a perspective view and an exploded perspective view showing a main part near the drive roller of the document feeder. 8A and 8B are enlarged sectional views showing details of the shaft end portion of the belt pressing roller. 9 (A) and 9 (B) are partial cross-sectional views for explaining the regulation / release state of the belt pressing roller. 10 and 11 are a flowchart and a timing chart for explaining the document conveying process, and FIG. 12 is a block diagram showing the control of the document conveying device. FIGS. 13 (A) and 13 (B) are diagrams showing the conveyance paths for double-sided originals and single-sided originals. 1 ... Copying device main body, 2 ... Original glass 3 ... Stopper plate, 3a ... Step part 5 ... Original document feeder, 10 ... Paper feeding unit 20 ... Transport unit, 21 ... Transport belt 23 ... Drive rollers 27A, 27B …… Pressing roller 28 …… Belt pressing roller 28a …… Shaft end, 28c …… Roller surface 29A, 29B …… Bearing member, 29a …… Groove 29b …… Shaft support, 29c …… Opening 30A, 30B …… swing arm, 30a …… recess 31 …… swing shaft, 32A, 32B …… hinge shaft 33 …… link plate, 34 …… swing lever 35 …… electromagnetic solenoid, 36 …… holding plate 38: Separation roller 40: Paper ejection reversing unit 46: Paper ejection roller pair, 47: Reversal roller pair 48A: Front edge detection sensor (paper ejection sensor) 48B: Rear edge detection sensor (reversal paper sensor) ) 50 ... Original transport switching member, 80 ... Ejection tray section D, D1, D2, D3, D4, D5, D6 ... Original, g ... Gap

Claims (2)

[Claims] 1. A paper feed unit which feeds a placed double-sided original adjacent to the original glass one by one to the original glass side; and a forward and reverse direction on the upper surface of the original glass,
It has a transport unit including a transport belt that slides and transports a fed document on the document glass surface, and a reversing unit that reverses the document surface after the transported document passes through the document glass surface. In a document feeding device for a two-sided document in which a document size is detected by a detection sensor provided between the paper feeding unit and the transport unit, a document pulled from the paper feeding unit onto the document glass is stopped at a predetermined position. After detecting this stop state, the conveyance belt starts to run in the reverse direction, one end of the original is brought into contact with the stopper plate step portion provided on the edge feeding side of the original glass, and then the conveyance belt is moved. A document is conveyed to the reversing unit side by traveling in the forward direction, and a signal detected by the sensor installed in the reversing unit at the end of the document and a size detection signal of the document. The basis, document feeder and controls the original feeding amount so as to abut the end of the original has been reversed in the stopper Itatan unit. 2. The document feeder according to claim 1, wherein the sensor installed in the reversing unit detects passage of the trailing edge of the document.