JP2614951B2 - Document feeder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document feeder which is mounted on a copying machine and automatically feeds a document to be copied to an exposure section of a copying machine main body.

[0002]

2. Description of the Related Art Conventionally, in a copying machine capable of duplex copying of a document, a document feeder 50 as shown in FIG. In such a document transport device 50, as shown in FIGS. 3 and 4, a plurality of transport rollers 51 and a transport belt 52 move a document P placed on a document table 53 to a reversing roller 54 side. After being conveyed, as shown in FIGS. 5 to 7, the document P inverted by the reversing roller 54 is arranged at a predetermined position on the exposure glass 61 shown in FIG.
In this state, light scanning of the document P passing through the exposure glass 61 is performed by light emitted from a light source (not shown).

Next, the original P on which the above-described optical scanning has been performed is again inverted by the inverting roller 54 as shown in FIG. 9, and thereafter, as shown in FIGS. By the rotation of 52, it is arranged at a predetermined position on the exposure glass 61 shown in FIG. At this time, the original P is
In the previous arrangement state shown in FIG.

Then, in the arrangement state of the document P shown in FIG. 12, after the light scanning of the document P is performed again by the light emitted from the light source (not shown), the reversing roller 54 shown in FIG.
14, the document P is discharged to a discharge tray 55 located on the transport belt 52, as shown in FIG.

[0005]

However, in the conventional document feeder 50, when the document P is copied on both sides, the document P
, Feed → transport → reverse → reverse transport → copy (back side) → reverse →
Double-sided copying is performed in the reverse transport → copy (front) → discharge process. For this reason, a number of processes including two reversal operations must be performed from the time when the original P is placed on the original mounting table 53 to the time when double-sided copying is performed.
The document P must be stopped at a predetermined position on the exposure glass 61, which has a problem in that the speed of the processing time required for duplex copying is greatly hindered.

[0006]

According to a first aspect of the present invention, there is provided a document feeder for irradiating a document passing through an exposure window with light emitted from a light source to perform optical scanning. An exposure transport unit that transports the document to the exposure unit to perform, and a reverse transport unit that reverses the document that has been optically scanned by the exposure unit and transports the document to the exposure transport unit. The following measures are taken in a document feeder that enables the following.

That is, the reversing conveyance section has a loop-shaped reversing conveyance path, and the reversing guide member forming the outer peripheral wall of the reversing conveyance path is moved forward and backward in accordance with the size of the document, so that the path length of the reversing conveyance path is increased. Is variably provided.

According to a second aspect of the present invention, there is provided a document feeder according to the first aspect of the present invention.

That is, the reverse transport section has a first reverse transport roller upstream of the reverse transport path, has a second reverse transport roller downstream of the reverse transport path, and rotates the first reverse transport roller. To transport the original into the reverse transport path,
The document in the reversing conveyance path is conveyed to the exposure conveyance section by the rotation of the second reversing conveyance roller, and when the leading end of the document reaches the second reversing conveyance roller,
When the rear end of the document has not reached the first reverse transport roller, the rotation of the second reverse transport roller is stopped, and
The reversing guide member advances and moves at a speed slightly higher than the speed at which the first reversing conveyance roller conveys the document into the reversing conveyance path.

Further, in order to solve the above-mentioned problems, the original conveying apparatus according to the third aspect of the present invention employs the following means in the original conveying apparatus according to the second aspect.

That is, when the document in the reversing conveyance path is conveyed to the exposure conveyance section by rotation of the second reversing conveyance roller, the reversing conveyance section retreats the reversing guide member at a speed slightly lower than the conveyance speed of the document. It is supposed to.

[0012]

According to the configuration of the first aspect, the reversing conveyance section for reversing the original optically scanned by the exposure section and conveying the original to the exposure conveyance section is capable of reversing guide that can advance and retreat according to the size of the original. It is formed from a reversing conveyance path having a section. For this reason,
Since the path length of the reversing conveyance path can be made variable according to the size of the document, there is no need to convey the reversal document in the reversing conveyance section into an extra path, and an appropriate document corresponding to the document size can be used. Can be reversed, and the processing speed in double-sided copying of a document can be improved.

According to the second aspect of the present invention, the first reverse transport roller is provided upstream of the reverse transport path forming the reverse transport section, and the second reverse transport roller is provided downstream. The document in the reversing conveyance path is conveyed in reverse by the rotation of each of the first and second reversing conveyance rollers. Further, when the leading end of the document has reached the second reverse conveying roller and the rear end of the document has not yet reached the first reverse conveying roller, the rotation of the second reverse conveying roller is stopped. And the reversing guide member advances and moves at a speed slightly higher than the speed at which the document is transported,
The path length of the reverse transport path is increased according to the size of the document. For this reason, the document is guided by the reversing guide member and is conveyed into the reversing conveyance path without bending.

According to the third aspect of the present invention, the second
When the document in the reversing conveyance path is conveyed to the exposure conveyance section by the rotation of the reversing conveyance roller, the reversing guide member is moved backward at a speed slightly lower than the conveyance speed of the document. Therefore, the document conveyed from the reversing conveyance path to the exposure conveyance section is guided by the reversing guide member and does not bend as in the case of being conveyed into the reversing conveyance path. Will automatically return the reversing guide member to its original position.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 1. In addition, for convenience of description, the arrangement positions of various constituent members are up, down, left and right in FIG. Are described below as the positional relationship.

The document feeder 10 according to the present embodiment has a configuration shown in FIG.
As shown in FIG.
An exposure glass 2 as an exposure window is provided at an upper portion of the copying machine main body 1. A light source (not shown) and an optical system member that guides light R emitted from the light source to an exposure point A on the exposure glass 2 are provided below the document conveying device 10 in the copying machine main body 1.

In the copying machine main body 1, the light R emitted from the light source passes through the exposure glass 2 and passes through the exposure point A.
Is provided with an exposure unit 3 for optically scanning the document P.

The reflected light from the original P after the optical scanning by the exposure unit 3 is again taken into the optical system member and guided to a photosensitive drum (not shown) so that the photosensitive drum is exposed. Has become. The surface of the photosensitive drum is uniformly charged prior to exposure, and an electrostatic latent image corresponding to the image of the document P is formed on the surface by the above-described exposure, and then developed to become a toner image. It is designed to be transferred to transfer paper.

The document conveying device 10 includes a supply placing portion 11 on which a plurality of documents P to be supplied to the exposing portion 3 of the copying machine main body 1 are placed, and a document P of the supply placing portion 11 which is exposed and conveyed. 1
A transport unit 12 that transports the original P to the exposure unit 3; an inverting transport unit that reverses the original P optically scanned by the exposure unit 3 and transports the original P to the exposure transport unit 13. 1
4 and the original P scanned by the exposure unit 3
And a discharge placement unit 16 on which a document P to be discharged after light scanning in the exposure unit 3 is completed is placed.
By reversing the original P with the reversing transport unit 14, the double-sided optical scanning of the original P in the exposure unit 3 of the copying machine body 1 is enabled.

The supply transport section 12 includes a supply transport path 21
, First supply / conveyance rollers 22a / 22b, second supply / conveyance rollers 23a / 23b, a drive motor 24, a first document detection sensor 25, and a change lever 26.

The supply / conveyance path 21 forms a communication path connecting the supply / placement section 11 and the exposure / conveyance section 13. Downstream of the supply / conveyance path 21, bifurcated branch paths 21a and 21b are formed. I have. The outlet of the branch path 21a is disposed in the vicinity of a contact portion between a left pressing roller 28 and the document supporting drum 27, which will be described later, while the outlet of the branch path 21b is connected to a later-described outlet. It is arranged near a contact portion between the right pressing roller 29 and the document supporting drum 27.

The first supply / conveyance rollers 22a and 22b are disposed in the supply / conveyance path 21 on the supply placement portion 11 side in a contact state, and the rotation shaft 22a 'of the first supply / conveyance roller 22a. The drive of the drive motor 24 is transmitted by suspending the connection belt 24b between the drive shaft 24a and the drive shaft 24a of the drive motor 24. The second supply / conveyance rollers 23a and 23b are disposed in the supply / conveyance path 21 downstream of the first supply / conveyance rollers 22a and 22b in a contact state.

The first document detection sensor 25 is disposed in the supply conveyance path 21 downstream of the second supply / conveyance rollers 23a and 23b, and detects a leading end of the document P. And the document support drum 27 is controlled.

The change lever 26 is provided on the downstream side of the supply conveyance path 21 so as to be rotatable in the B ₁ -B ₂ directions.
The change lever 26 receives a one-sided copy mode by a key input means on an operation panel (not shown) provided on the copying machine main body 1 side, and the first document detection sensor 25 detects the leading end of the document P. Once detected, is oN in accordance with this, B ₂ showing the rotation state of the B ₁ direction in the OFF state (shown in Figure 1 solid lines) by a broken line in FIG. 1
, And the communication on the downstream side of the supply conveyance path 21 is switched to the branch path 21a. On the other hand, when the mode of duplex copying is input by said key input means, even if the tip end of the original P by the first document sensor 25 is detected, the change lever 26, B ₁ direction in the OFF state And the downstream side of the supply conveyance path 21 communicates with the branch path 21b.

The exposure transport section 13 includes the original supporting drum 2
7 and left and right pressing rollers 28 and 29.

The document supporting drum 27 is connected to the branch paths 21a and 2
1b is provided between the downstream side of the supply conveyance path 21 where the supply conveyance path 21 is formed and the exposure unit 3, and the outer peripheral surface thereof is provided in contact with the exposure point A on the exposure glass 2. Also,
The document support drum 27 is rotatably provided on the C ₁ -C ₂ direction, when the first document sensor 25 at one side copy mode detects the leading edge of the document P is rotated in the C ₂ direction while it adapted to be driven, when the first document sensor 25 detects the leading edge of the document P at duplex copy mode, is adapted to be rotated in the C ₁ direction.

The left pressing roller 28 is provided in contact with the outer peripheral surface of the document supporting drum 27 located at the paper exit of the branch path 21a, and the right pressing roller 29 is connected to the branch path 2a.
The document supporting drum 27 is provided in contact with the outer peripheral surface of the document supporting drum 27 located at the paper output port 1b.

The reverse transport section 14 includes a reverse transport path 30.
, Left delivery roller 31, first reversing conveyance roller 32a
32b, the second reverse conveyance rollers 33a and 33b, and the second
A document detection sensor 34 and a third document detection sensor 35 are provided.

The reversing conveyance path 30 has a loop shape, and its paper entrance is arranged near the left side of the exposure glass 2, while the paper exit is located at the original supporting drum 27 and the left pressing roller 2.
8 is disposed in the vicinity of the contact portion. The outer peripheral wall of the reversing conveyance path 30 is formed as a reversing guide 30a as a reversing guide member. This reversing guide 30
a is provided so as to move forward and backward in the D ₁ -D ₂ direction in response to the detection of the document P by the second and third document sensor 34, 35 will be described later, when regression movement in the D ₂ direction ( FIG.
The medium indicated by the solid line), while the shortest path length of the reverse conveying path 30, with the advancing movement in the D ₁ direction (shown in Figure 1 the broken lines), the path length of the reverse conveying path 30 It is growing.

The left delivery roller 31 is disposed at the entrance of the reversing conveyance path 30 and guides the document P passing through the exposure point A of the exposure unit 3 from the right side into the reversing conveyance path 30. I have.

The first reversing transport rollers 32a and 32b are disposed on the upstream side of the reversing transport path 30 in a contact state, and the second reversing transport rollers 33a and 33b are in contact with each other. In this state, it is disposed downstream of the reverse conveyance path 30. Then, the first reversing conveyance rollers 32a and 32
b and the second reverse conveyance rollers 33a and 33b are controlled in rotation by respective second and third document detection sensors 34 and 35 described later.

The second document detection sensor 34 is disposed in the reverse conveyance path 30 downstream of the first reverse conveyance rollers 32a and 32b, and the third document detection sensor 35 is
Reverse transport path 3 downstream of reverse transport rollers 33a and 33b
It is arranged in 0. When the third original detection sensor 35 detects the leading end of the original P in a state where the rear end of the original P is not detected by the second original detection sensor 34, the third reverse conveyance Rollers 33a and 33
b stops the rotation of, so as to advance the movement in the D ₁ direction in slightly faster speed than the conveying speed of the document P in the reverse guide 30a in the reverse conveying path within 30. Also,
The second document detection sensor 34 is provided with the reversing guide 3 as described above.
In advancing movement state of the D ₁ direction 0a, when detecting the trailing end of the original P, along with this, the second reversing conveyance rollers 33a
-While the rotation drive of 33b is restarted, the reversing guide 30
adapted to regress moved D ₂ direction at a slightly slower speed than the conveying speed of a document P.

The discharge / conveyance section 15 includes a discharge / conveyance path 36
, Right delivery roller 37, and first discharge / conveyance roller 38a
38b, second discharge / conveyance rollers 39a / 39b,
A document detection sensor 40 is provided.

In the discharge conveyance path 36, the paper entrance is arranged near the right side of the exposure glass 2, while the paper exit is arranged in the discharge placement section 16, and the light scanning in the exposure section 3 is performed. It is formed as a communication path for transporting the completed document P to the discharge placement unit 16.

The right delivery roller 37 is disposed at the paper entrance of the discharge conveyance path 36, and guides the document P, which has passed the exposure point A of the exposure unit 3 from the left side, into the discharge conveyance path 36. I have.

The first discharge / conveyance rollers 38a and 38b are disposed on the upstream side of the discharge / conveyance path 36 in a contact state, and the second discharge / conveyance rollers 39a and 39b are in contact with each other. In this state, it is disposed downstream of the discharge conveyance path 36.

The fourth document detection sensor 40 includes a first discharge / conveyance roller 38a / 38b and a second discharge / conveyance roller 39a / 3.
9b, and is disposed in the discharge conveyance path 36 on the downstream side between
By detecting the rear end of the document P, the discharge
The ejection of the document P upward is detected.

In the above configuration, the process of transporting the document P in each mode of single-sided copying and double-sided copying of the document P in the document transporting device 10 of the present embodiment will be described below.

First, in the one-sided copy mode of the document P, a plurality of documents P are set on the
A copy mode (one-sided document, number of copies, copy density, etc.) is input by key input means on an operation panel (not shown). When the print switch on the operation panel is operated, the first motor is driven by the driving motor 24 of the supply / transportation unit 12.
The supply conveyance rollers 22a and 22b feed only one document P located on the uppermost surface of the documents P...

Next, the original P fed as described above
When the leading end of the first document reaches the first document detection sensor 25, the first
With in the document detecting sensor 25 is ON, is rotated change lever 26 is turned ON in the B ₂ direction, the downstream side of the supply conveyance path 21 is switched to the branch passage 21a, also, the document support drum 27 is C It is driven to rotate in _two directions.
Then, after the document P is guided by the side surface of the change lever 26 and passes through the branch path 21 a, the document P is sandwiched between the document support drum 27 and the left pressing roller 28, and A predetermined time is counted from the ON timing, and the feeding is temporarily stopped.

Next, the irradiation timing of the emitted light R to the exposure unit 3 is measured, and the feeding of the document P to the exposure point A on the upper surface of the exposure glass 2 is started again. Then, the leading end of the document P is pressed against the document supporting drum 27, and the document supporting drum 27 and the exposure glass 2 are not bent.
Pass through the exposure point A, which is the contact point with the left side.

The original P after scanning which has passed through the exposure point as described above is sent to the right output roller 37 side,
The sheet is discharged to the discharge placement section 16 through the discharge transfer path 36 by the first discharge transfer rollers 38a and 38b and the second discharge transfer rollers 39a and 39b. At this time, the document P is discharged onto the discharge placing portion 16 by the fourth document detection sensor 40 disposed between the first discharge and conveyance rollers 38a and 38b and the second discharge and conveyance rollers 39a and 39b. Is detected.

The process of one-sided copying of the document P as described above is repeated for each document P.
When a document detection sensor (not shown) provided in the printer 1 detects that the document P is no longer present on the supply tray 11, the one-sided copying of the document P is completed. When the original P is repeatedly copied as described above, the next original P is
The document is fed from the feeder 11 at the timing when the rear end of the previous document P passes through the exposure point A.

Next, in the double-sided copy mode of the original P, a plurality of originals P are set on the
A copy mode (double-sided document, number of copies, copy density, etc.) is input by key input means on an operation panel (not shown). When the print switch on the operation panel is operated, the first motor is driven by the driving motor 24 of the supply / transportation unit 12.
The supply conveyance rollers 22a and 22b feed only one document P located on the uppermost surface of the documents P...

Next, the original P fed as described above
When the leading end of the first document reaches the first document detection sensor 25, the first
With in the document detecting sensor 25 is turned ON, the document support drum 27 is rotated in the C ₁ direction. At this time, the change lever 26 is in the OFF state, and the branch path 21b is in a state in which the downstream side of the supply conveyance path 21 is opened. The document P is guided by the side surface of the change lever 26 and passes through the branch path 21b.
7 and the right pressing roller 29, the first
A predetermined time is counted from the ON timing of the document detection sensor 25, and the feeding is temporarily stopped.

Next, the irradiation timing of the emitted light R to the exposure unit 3 is measured, and the feeding of the document P to the exposure point A on the upper surface of the exposure glass 2 is started again. Then, the leading end of the document P is pressed against the document supporting drum 27, and the document supporting drum 27 and the exposure glass 2 are not bent.
Passes through the exposure point A, which is the contact point with the right side, from the right side.

The original P after scanning that has passed through the exposure point A as described above is sent to the left exit roller 31 side, and then passes through the inside of the reverse conveyance path 30 by the first reverse conveyance rollers 32a and 32b. Is transported to the third document detection sensor 35 side.

When the leading end of the document P reaches the third document detection sensor, the third document detection sensor is turned on. At this time,
When the trailing end of the document P is detected by the second document sensor 34, with the regression movement in the D ₂ direction reversing guide 30a is held, the second reversing conveyance rollers 33a
The document P is transported from the inside of the reverse transport path 30 to the exposure transport section 13 by the rotation of 33b. On the other hand, when the trailing end of the original P by the second document sensor 34 is not detected, the rotation drive of the second reverse conveying rollers 33a · 33b is stopped, reversing guide 30a is advanced to the D ₁ direction By being moved, the document P is fed into the reverse conveyance path 30 without bending the rear end side. On the other hand, the front end side of the document P
The sheet is sandwiched between the second reverse conveyance rollers 33a and 33b and the feeding is stopped.

[0049] Then, in the advanced moving state of the D ₁ direction reversing guide 30a as described above, when the trailing end of the original P by the second document sensor 34 is detected, the second reverse conveying rollers 33a · 33b the driving of the rotation is resumed, reversing guide 30a is regressive moving in the D ₂ direction at a slightly slower speed than the conveying speed of the document P, the document P is conveyed from the reverse conveying path 30. in the exposure transport unit 13 .

Next, the irradiation timing of the emitted light R to the exposure unit 3 is measured, and the feeding of the document P to the exposure point A on the upper surface of the exposure glass 2 is started again. Then, the leading end of the document P is pressed against the document supporting drum 27, and the document supporting drum 27 and the exposure glass 2 are not bent.
Passes through the exposure point A, which is the contact point with the right side, from the right side.

At this time, the document P is in a state where the front and back are reversed with respect to the previous optical scanning.

The process of double-sided copying of the document P as described above is repeated for each document P.
The double-sided copying of the document P is completed when it is detected by the document detection sensor (not shown) provided on the sheet supply unit 11 that the document P has disappeared.

As described above, in the original transporting apparatus 10, the reverse transport section 14 is provided with the reverse transport path 3 provided with the reverse guide 30a.
0, and the reversing guide 30a
Are provided so as to be able to advance and retreat in the D ₁ -D ₂ directions according to the size of the document P. For this reason, the path length of the reversing conveyance path 30 for reversing the document P is variably provided according to the size of the document P, and the reversing conveyance unit 14 can appropriately reverse the document P according to the size of the document P. Since the operation can be performed, the processing speed in double-sided copying of the document P can be improved.

The speed of the reversing guide 30a, which makes the length of the reversing conveyance path 30 variable as described above, is set to be slightly faster than the conveyance speed of the original P while moving forward. The speed at the time of movement is set slightly lower than the transport speed of the document P.

For this reason, the reversing guide 30a is moved forward when the original P is conveyed into the reversing conveyance path 30, or when the reversing movement is performed, that is, when the original P is conveyed to the reversing conveyance path 30.
When the document P is transported to the exposure transport unit 13, the document P is appropriately guided according to the time.
Regardless of the size, the original P can be conveyed in the reverse conveyance path 30 without bending.

[0056]

As described above, in the document conveying apparatus according to the first aspect of the present invention, the reverse conveying section has a loop-shaped reverse conveying path, and the reverse guide member forms an outer peripheral wall of the reverse conveying path. Are moved forward and backward in accordance with the size of the document, and the length of the reverse conveyance path is variably provided.

As a result, it is not necessary to transport the original to be inverted by the inverting and transporting unit in an extra path, and the original can be appropriately inverted according to the size of the original. There is an effect that the processing speed can be improved. It should be noted that such an effect of improving the processing speed in double-sided copying can be further enhanced with an increase in the number of processed originals.

According to a second aspect of the present invention, in the original transporting apparatus according to the first aspect, the reverse transport section has a first reverse transport roller upstream of the reverse transport path.
A second reverse transport roller downstream of the reverse transport path;
The document is transported into the reverse transport path by rotation of the reverse transport roller, and the document in the reverse transport path is transported to the exposure transport section by rotation of the second reverse transport roller.
Further, when the leading end of the document reaches the second reverse conveying roller and the rear end of the document has not yet reached the first reverse conveying roller, the rotation of the second reverse conveying roller is stopped, and The configuration is such that the reverse guide member advances and moves at a speed slightly higher than the speed at which the first reverse transport roller transports the document into the reverse transport path.

Thus, the document to be reversed by the reversing conveyance section is guided by the reversing guide member and conveyed into the reversing conveyance path without bending.

According to a third aspect of the present invention, in the document transport apparatus according to the second aspect, the reverse transport unit transports the document in the reverse transport path to the exposure transport unit by rotation of the second reverse transport roller. In this case, the reversing guide member is moved backward at a speed slightly lower than the speed at which the document is transported.

Thus, the document conveyed from the reversing conveyance path to the exposure conveyance section is guided by the reversing guide member and does not bend, similarly to the case where the document is conveyed into the reversing conveyance path. In addition, by performing the document guiding operation by the reversing guide member, the reversing guide member can be automatically returned to the original position.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a document feeder according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a document setting state in a conventional document feeder.

FIG. 3 is a vertical cross-sectional view showing a document feeding state in the document feeder.

FIG. 4 is a vertical cross-sectional view illustrating a state in which a document is transported in the document transport device.

FIG. 5 is a longitudinal sectional view showing a reversed state of the original in the original conveying apparatus.

FIG. 6 is a longitudinal sectional view showing a state in which a document is reversely conveyed in the document conveyance device.

FIG. 7 is a vertical cross-sectional view illustrating a state in which a document is transported in the document transport device.

FIG. 8 is a longitudinal sectional view showing a state in which copying of the back side of the original in the original conveying apparatus is stopped.

FIG. 9 is a longitudinal sectional view showing a reversed state of a document in the document feeder.

FIG. 10 is a longitudinal sectional view showing a state in which a document is reversely conveyed in the document conveyance device.

FIG. 11 is a vertical cross-sectional view illustrating a state in which a document is transported in the document transport device.

FIG. 12 is a longitudinal sectional view showing a state in which a front copy of a document is stopped in the document feeder.

FIG. 13 is a longitudinal sectional view showing a state in which a document is discharged in the document feeder.

FIG. 14 is a vertical cross-sectional view showing a state in which the discharge of a document in the document feeder is completed.

[Explanation of symbols]

 2 Exposure glass (exposure window section) 3 Exposure section 10 Document transport device 13 Exposure transport section 14 Reverse transport section 21 Supply transport path 30 Reverse transport path 30a Reverse guide (reverse guide member) 32a / 32b First reverse transport roller 33a / 33b Second reverse transport roller P Document R Emitted light

Claims (3)

(57) [Claims] 1. An exposure transport section for irradiating a document passing through an exposure window with light emitted from a light source to transport an original to an exposure section for optical scanning, and for reversing the document optically scanned by the exposure section. And a reverse transport unit that transports the document to the exposure transport unit, and enables a two-sided optical scanning of the document in the exposure unit.The reverse transport unit has a loop-shaped reverse transport path, and A document conveying device, wherein a reversing guide member forming an outer peripheral wall of a reversing conveyance path is moved forward and backward in accordance with a document size, and a path length of the reversing conveyance path is variably provided. 2. The reverse transport section has a first reverse transport roller upstream of the reverse transport path, has a second reverse transport roller downstream of the reverse transport path, and rotates the first reverse transport roller. To transport the original in the reverse transport path, and to rotate the second reverse transport roller to transport the original in the reverse transport path to the exposure transport section. If the rear end of the document has not yet reached the first reversing conveyance roller at the time of reaching the rollers, the rotation of the second reversing conveyance roller is stopped and the first reversing conveyance roller is stopped.
2. The document conveying apparatus according to claim 1, wherein the reverse conveying roller advances and moves the reverse guide member at a speed slightly higher than a speed at which the document is conveyed into the reverse conveying path. 3. The reversing conveyance section retreats a reversing guide member at a speed slightly lower than the conveyance speed of the document when the document in the reversing conveyance path is conveyed to the exposure conveyance section by rotation of a second reversing conveyance roller. 3. The document conveying device according to claim 2, wherein the document is conveyed.