JPH09216742A - Sheet carrying device, image reader and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize an interval between a preceding document and a following document, by increasing the carrying speed of a sheet due to separating means while the sheet receives action by the separating means. SOLUTION: While a preceding document Df is held between separating roller pairs and carried at a carrying speed Vs, the rotational driving of a feeding motor and the stepping motor of and the separating roller pairs, is controlled for a predetermined time tf2 through a motor driver by a CPU(central processing unit). The separating roller pairs and carrying rotor pairs are made to increase their speed to a predetermined carrying speed Vx (>Vs) for a predetermined time Tx. Before the separating action timing of a following document Db by the separating roller pairs comes, the rear end of the preceding document Df is slipped out from the separating roller pairs in its early stage. Thusly, after separating action by the separating roller paris is completed, carrying action by the tip of the document Df is started.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus such as a copying machine, a scanner and a printer, and an image forming apparatus, and more particularly to a sheet conveying apparatus equipped in these apparatuses.

[0002]

2. Description of the Related Art Conventionally, there is known an automatic document feeder which automatically conveys a document to a predetermined reading position for reading image information of the document. Also, when the image to be scanned is recorded on both sides of the original, the reverse side of the original is read by automatically reversing the original and refeeding the original to the reading position in the automatic document feeder. Is going.

In recent digital image forming apparatuses that combine digital reading, memory saving, etc., it is necessary to speed up the reading of images as the printing speed increases, and in order to solve this problem. It is necessary to improve the document feeding speed and minimize the interval between the conveyed documents.

When a plurality of originals stacked on the original placing table are separated one by one and fed to the reading position, the originals on the original placing table are fed out by the feeding means, and the fed out originals are separated by the separating means. Although the sheets are separated and conveyed one by one, in the feeding operation of the original by the feeding means and the separation operation by the separating means, the original conveyance speed may be delayed or varied, and the original may reach the reading position at a regular time. In order to solve this problem, the conveyance speed of the document that cannot reach the reading position at a predetermined timing is accelerated or decelerated so that the document can reach the reading position at a regular timing.

The separating means may be composed of a separating roller pair consisting of a roller rotating in the feeding direction and a roller rotating in the opposite direction to the feeding direction. Separation and conveyance operations by the separating roller pair. In this case, the leading end of the sheet-like document is separated and separated one by one, and then the separated one document is conveyed at a predetermined speed.

While the preceding document is separated into one sheet by the separation roller pair and the leading end of the following document cannot be accessed to the separation roller pair while passing through the nip portion of the separation roller pair, the preceding document cannot be accessed. The succeeding original document is in a standby state until the trailing edge of the original document passes through the nip portion of the separation roller pair.

The original separated into one sheet by the pair of separation rollers is conveyed while being sandwiched by the pair of separation rollers as it is, but the pair of separation rollers is rotationally driven by the motor.
A predetermined start-up time (usually, until the separation roller pair reaches a predetermined rotation speed and the document reaches a predetermined conveyance speed)
It takes about 10 ms (seconds).

Here, the conveying speed and the conveying timing of the preceding document Df and the succeeding document Db in the conventional example will be described with reference to FIG. In the graph of FIG.
The horizontal axis t represents time, the vertical axis X represents the position of the document D in the conveyance path, Xa is the position where the separation roller pair is arranged in the conveyance path, and Xb is the rear end of the document Db where the separation roller pair is arranged. At time tb2 when the document passes through (Xa), the original D
The position where the tip of b reaches is shown.

Further, V1f and V1b are the tip of the document Df,
The conveyance speeds of the rear end are shown, and V2f and V2b are the conveyance speeds of the front end and the rear end of the document Db, respectively. Here, the leading edge of the document Df,
Since the trailing edge and the leading edge and trailing edge of the document Db are transported at the same speed, the curves indicating the trailing edge transport speeds V1b and V2b correspond to the curves indicating the leading edge transport speeds V1f and V2f, respectively.

Td3 and Td4 are predetermined positions Xa and X on the conveying path.
In b, the time difference between the time when the trailing edge of the preceding document Df passes and the time when the leading edge of the succeeding document Db passes, that is, the interval time between the preceding document Df and the succeeding document Db is shown.

That is, Td3 is the time when the preceding document Df is separated and conveyed by the separation roller pair arranged at the position Xa of the conveying path, and the rear end of the document Df passes through the separation roller pair (Xa). The time difference between tf2 and the time tb0 at which the leading edge of the following document Db reaches the separation roller pair (Xa) and the separation / conveyance operation by the separation roller pair is started is shown.

Further, at Td4, the leading edge of the original document Db reaches at time tb2 when the succeeding original document Db is separated and conveyed by the separation roller pair and the rear end of the original document Db passes through the separation roller pair (Xa). The time difference between the time tf3 when the trailing edge of the preceding document Df passes the position Xb on the conveying path and the time tb2 is shown.

As for Tm, the originals Df and Db are time tf0,
At tb0, after entering the separation roller pair and separated into one sheet, the sheet is nipped and conveyed by the separation roller pair, and the specified conveyance speed Vs.
It is the start-up time until reaching (constant) (time tf1, tb1).

Here, in order to minimize the distance between the originals, as shown in FIG. 6, after the trailing edge of the preceding original Df passes through the separation roller pair (Xa), the leading edge of the succeeding original Db. Even if the timing Td3 for advancing the separation roller pair into the separation roller pair is set to the minimum timing, the start-up time T
The action of m causes the trailing edge of the succeeding document Db to pass through the separation roller pair (Xa) and to precede the preceding document D at time tb2.
Document interval time T between the trailing edge of f and the leading edge of the following document Db
d4 is generally larger than Td3.

[0015]

However, in order to minimize the distance between the preceding document Df and the following document Db, the document D sandwiched and conveyed by the above-mentioned pair of separation rollers is regulated to be conveyed. The rise time Tm required to reach the speed Vs is an obstacle.

That is, since the separation roller pair is generally driven by a motor, the start-up time Tm thereof (usually several tens of meters).
s (seconds)), and as shown in FIG. 6, when the start-up time Tm becomes long, the interval time Td4 between the trailing end of the preceding document Df and the leading end of the following document Db inevitably becomes long. However, it becomes difficult to improve the document transport efficiency by minimizing the distance between the document Df and the document Db.

For example, when the feeding time of the following document Db is advanced from tb0 in FIG. 6 to tb0 'in FIG. 7 with the start-up time Tm kept unchanged, as shown in F in FIG.
While the preceding document Df is being conveyed while being sandwiched by the separation roller pair, the leading edge of the following document Db enters the separation roller pair and the trailing edge of the preceding document Df and the leading edge of the following document Db. May interfere with each other, and the separation and conveyance operations of the documents Df and Db may not be performed properly.

The present invention is to solve the above-mentioned problems.
The purpose thereof is to increase the sheet conveying speed by the separating means at a predetermined timing to minimize the distance between the preceding sheet and the succeeding sheet, and to improve the sheet conveying efficiency. An object of the present invention is to provide a carrying device, an image reading device and an image forming device provided with the carrying device.

[0019]

A typical configuration according to the present invention for achieving the above object is a sheet placing means for placing a sheet, and a sheet placed on the sheet placing means. A sheet feeding unit for feeding and a separating unit for separating and conveying the sheets fed by the sheet feeding unit one by one, and the separating unit while the sheet is being acted on by the separating unit. The sheet conveying apparatus is configured to increase the conveying speed of the sheet by the means.

Since the present invention is configured as described above, the time during which the sheet separated by the separating means is passed through the separating means by increasing the conveying speed of the sheet while being acted on by the separating means. Can be accelerated.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION As an example of a sheet conveying apparatus according to the present invention, an image reading apparatus including the same, and an image forming apparatus, a document feeding apparatus having an image reading unit for reading image information of a document and a document feeding apparatus including the same are provided. An embodiment of the image forming apparatus will be specifically described. FIG. 1 is a cross-sectional explanatory view showing the configuration of a document feeding apparatus provided with a sheet conveying device according to the present invention, FIG. 2 is a block diagram showing the configuration of a control system for controlling the sheet conveying speed, and FIG. 3 is controlling the sheet conveying speed. 4 is a graph showing a sheet conveying speed and a sheet conveying timing, and FIG. 5 shows a sheet conveying apparatus according to the present invention, an image reading apparatus including the same, and an image forming apparatus including the same. FIG.

In FIG. 1, the document feeding device 9 has a document placing table 10 which serves as a sheet placing means for placing a plurality of sheet-like documents D made of paper, synthetic resin or the like. The document placing table 10 is provided with an abutting surface 10b which is formed on the lower side of the gently inclined document placing surface 10a in the inclination direction and abuts the leading end of the document D to align the leading end position of the document D.

The first surface of the document D, on which the image of the document D is recorded, is placed on the document table 10 so as to face upward. A sheet feeding roller 11 serving as a sheet feeding unit is disposed above the original placing table 10 on the abutting surface 10b side, and a predetermined pressing force is applied to the uppermost original D placed on the original placing table 10. Abuts on. Then, by rotating the feeding roller 11 in the direction of the arrow in the figure, the uppermost original D can be sequentially fed.

Document D fed by the feeding roller 11
Are separated and conveyed one by one by a separation roller pair 12 serving as separation means. The separation roller pair 12 is composed of a feed roller 12a that rotates in a direction for feeding the document D and a separation roller 12b that rotates in a direction opposite to the feeding direction.
Due to the cooperation of 12a and 12b, only the uppermost original D is separated and conveyed one by one, the double feeding of the original D is prevented, and one original D is prevented.
Only the pair of rollers is arranged further downstream and serves as a sheet conveying means, and is conveyed in the direction of arrow a in FIG. 1 in the first introducing path 2 by the conveying roller pair 13, 21, 22, 23, 24, 25.

Then, the skew (skew) of the document D is corrected by the registration roller pair 26 arranged at the terminal end of the first introduction path 2. A platen glass 3 arranged at a reading position B is provided downstream of the registration roller pair 26, and a reading optical system 1 constituting an image reading unit shown in FIG. 5 is arranged below the platen glass 3. ing.

Flappers 7a and 7b for switching respective conveying paths, which will be described later, are provided on both sides of the platen glass 3. The flapper 7a is arranged on the downstream side of the platen glass 3 in the direction of arrow a, and the flapper 7b is indicated by the arrow. It is arranged on the upstream side of the platen glass 3 in the a direction.

When the flappers 7a and 7b are in the positions (first positions) shown by the solid lines in FIG. 1, respectively, the first introduction path 2
The image information on the first side of the document D fed from
After being read by the reading optical system 1, the document D is guided to the first discharge path 5.

After the document D guided to the first discharge path 5 reaches the discharge / conveyance roller pair 6 serving as the sheet conveying means arranged on the upstream side of the first discharge path 5, the flapper 7a is moved to the first position. It moves to the position indicated by the broken line in FIG. 1 which is the position 2 and opens the second introduction path 8 to stand by.

The first discharge path 5 and the second introduction path 8 are connected via an annular reversing path 14, and the document D is the first
Sheet conveying means provided on the sheet discharging path 5 and conveying roller pair 29 and 30 also forming sheet conveying means provided on the reversing path 14 and the same sheet provided on the second introducing path 8. The document is sequentially transported by a pair of transport rollers 31 serving as a transport unit and a pair of registration rollers 27 that corrects skew of the document D, and proceeds in the directions of arrows b → c → d in FIG. Is reversed.

A flapper 19 is provided between the first discharge path 5 and the reversing path 14, and when the flapper 19 is located at the first position shown by the solid line in FIG.
When the flapper 19 is located at the second position shown by the broken line in FIG. 1, the first discharge path 5 and the reverse path 14 are cut off, The first discharge path 5 and the third discharge path 20 are connected. When the double-sided image of the document D is read, the flapper 19 is at the first position, which is shown by the solid line in FIG. 1, and the first discharge path 5 and the reversing path 14 are connected.

At the time when the trailing edge of the document D guided to the first discharge path 5 passes the flapper 7b, the flapper 7b moves to the second position.
1 to the position indicated by the broken line in FIG. 1 to shut off the first introduction path 2 and open the second discharge path 15 to stand by. Here, the fact that the trailing edge of the document D has passed the flapper 7b is detected by a document trailing edge sensor s4 described later.

When the flappers 7a and 7b are in the second position, which is indicated by the broken line in FIG. 1, the document D passes from the first discharge path 5 through the reversing path 14 and the second introducing path 8 and the document surface. 1 is reversed and is conveyed in the direction of the arrow d in FIG. 1, and after the image information recorded on the second surface of the document D at the reading position B is read by the reading optical system 1, the document D is transferred to the second discharge path. 15
It is led to.

Then, the document D is conveyed by the pair of conveying rollers 32, 33, 34 provided in the second discharge path 15 and the second discharge path.
After being sequentially conveyed by the pair of conveying rollers 17 and 18 provided in the third discharge path 20 connected to 15, and proceeding in the direction of arrow e in FIG. 1, the sheet is discharged and placed on the discharge tray 16.

Then, at the time when the trailing edge of the document D guided to the second discharge path 15 passes through the flapper 7a, the flapper 7
The a and 7b are switched to the first position, which is shown by the solid line in FIG. 1, and stand by for the introduction of the subsequent document D.
Here, the fact that the trailing edge of the document D has passed the flapper 7a is detected by a document trailing edge sensor s3 described later.

By repeating the above-described operation, a double-sided reading operation is performed on the document D on which a plurality of documents are stacked on the document placing table 10 and image information is recorded on both sides, and the minimum document interval is described in detail later. Can read continuously.

A plurality of sheets (for example, 2 sheets) are provided in the reversing path 14.
It is also possible to send the document D at intervals such that the (document) documents D are continuously sent. In this case, since two documents D that are continuously conveyed are sent in one set, the second surface of the second document D preceding the reverse path 14 through the second introduction path 8 After passing through the platen glass 3
The first surface of the third document D that follows through the introduction path 2 of 1. passes through the platen glass 3.

Further, in the document feeding device 9, when the document D having an image formed on only the first side of one side is read, the first side is faced up on the document placing table 10 as described above. The placed document D reaches the reading position B where the platen glass 3 is provided from the document table 10 through the first introduction path 2, and the reading optical system 1 reads the image information on the first surface.

Then, the document D is conveyed through the first discharge path 5, and at this time, the flapper 19 provided at the branch point of the first discharge path 5, the reversing path 14 and the third discharge path 20. 1 in advance from the first position shown by the solid line in FIG. 1 to the second position shown by the broken line in FIG.
The first discharge path 5 and the third discharge path 20 are connected to each other by blocking the discharge path 5 and the reverse path 14. As a result, the document D is conveyed from the first discharge path 5 to the third discharge path 20 and discharged and placed on the discharge tray 16.

In the above-mentioned first introduction path 2, the document leading edge sensor s1 serving as a sheet detecting means is arranged between the conveyance roller pair 13 and the conveyance roller pair 21, and the conveyance of the second introduction path 8 is performed. On the downstream side in the vicinity of the roller pair 31, a document leading edge sensor s2 also serving as a sheet detecting means is arranged. Further, on both sides of the platen glass 3, a document trailing edge sensor s3 serving as sheet detecting means is arranged on the flapper 7a side, and a document trailing edge sensor s4 is arranged on the flapper 7b side.

Next, the configuration of the control system for controlling the conveyance speed of the document D will be described with reference to FIG. In FIG. 2, arrival detection information at a predetermined position of each path of the document D detected by the document leading edge sensors s1 and s2 and the document trailing edge sensors s3 and s4 is transmitted to a CPU (central information processing unit) 4.

A storage unit and a counter unit for the CPU 4 to perform a predetermined operation are arranged in parallel in the CPU 4, and at least the first and second storage units provided in the document feeder 9 are provided in the storage unit. The time during which the document D is normally conveyed through the conveyance paths including the introduction paths 2 and 8, the first discharge path 5 and the reverse path 14 is stored in advance.

Further, the storage section stores the rotation speed information of the stepping motor 35b for rotating the separation roller pair 12 in correspondence with the original size of the original D to be used, and the original D of a predetermined size is original. When set on the mounting table 10, the conveyance speed of the document D conveyed by the separation roller pair 12 is accelerated and decelerated at a predetermined timing.

Further, the storage section stores the speed rising time T of the stepping motor 35b for increasing the conveying speed of the document D conveyed by the separation roller pair 12 to a predetermined speed.
m is stored, and the CPU 4 sets the startup time Tm.
The rotation speed of the stepping motor 35b is controlled so that the leading edge of the document D subsequently fed by the feeding roller 11 becomes shorter than the time when it reaches the separation roller pair 12.

Further, the counter section is provided at least in the first,
Sensors s1, s2, s3, s are set from predetermined timings for the transport time of the document D transported in the transport paths of the second introduction path 2, 8 and the first discharge path 5 and the reverse path 14.
The actual arrival time of the original document D at the predetermined position detected by 4 is counted.

Further, the counter section recognizes the conveyance timing of the document D passing through the separation roller pair 12 by counting the number of pulses of the stepping motor 35b which rotationally drives the separation roller pair 12, and the CPU 4 causes the CPU 4 to separate the separation roller pair.
An increase amount of the conveyance speed of the document D by 12 is calculated, and the rotation speed of the stepping motor 35b is increased to a predetermined speed via the motor driver 36.

Further, the counter section has a pulse number of a stepping motor 35a for rotationally driving the feeding roller 11 and a stepping motor 35b for rotationally driving the separation roller pair 12.
By counting the number of pulses, the distance between the preceding document Df and the following document Db in the vicinity of the separation roller pair 12 is measured.

Further, the CPU 4 compares the preset regular time when the conveyed document D reaches a predetermined position with the time when the actually conveyed document D reaches the same position. have.

Then, the CPU 4 controls the motor driver 36 in accordance with the above calculation information, and the motor driver 36 controls the stepping motors 35a, 35b, 35c, 35d so as to control the feed motor arranged in the first introduction path 2. The feed roller 11, the separation roller pair 12, the transport roller pair 13, 21, 22, 23, 24, 25 and / or the discharge transport roller pair 6, the transport roller pair 28, and the reversing path 14 arranged in the first discharge path 5. The conveyance speed of the document D is controlled by accelerating and decelerating the rotation speed of the conveyance roller pair 29, 30 arranged in the above and the conveyance roller pair 31 arranged in the second introduction path 8.

In the document feeder 9 described above, when the feeding roller 11 rotates and comes into contact with the uppermost document D placed on the document table 10 with a predetermined pressing force, the document D is fed. However, at this time, a slip may occur between the feeding roller 11 and the document D for some reason, and the document D may not be fed at a predetermined timing.

Also, in the separation roller pair 12 on the downstream side, the action of the separation roller 12b rotating in the direction opposite to the feeding direction in order to prevent double feeding causes the feeding roller 12a rotating in the feeding direction to move. It is known that the conveyance speed of the document D is lower than the rotation speed, and the document D may not be conveyed at a predetermined timing due to these factors.

On the other hand, if a sufficient conveying force is applied to the conveying roller pair 13, after the document D is separated by the separating roller pair 12,
Since the document D can be conveyed at a desired conveying speed on the downstream side of the conveying roller pair 13, the leading end of the original arranged near the conveying roller pair 13 where the conveying speed of the original D is stable as described above. By the sensor s1, the document D passes through the feeding roller 11 and the separation roller pair 12 which cause the delay,
Further, the arrival time of the document D is detected after passing through the pair of transport rollers 13.

In this case, the CPU 4 calculates the delay time from the preset regular arrival time. Here, the delay time is a preset time from the time when the rotation driving of the feeding roller 11 is started to the time when the document D normally reaches the position where the document leading edge sensor s1 is arranged, and an arbitrary time In, the time when the document D actually reaches the position where the document leading edge sensor s1 is arranged is counted from the time when the rotation driving of the feeding roller 11 is started, and the difference from the regular time is calculated.

When the conveyance time of the document D is delayed due to the detection information of the document leading edge sensor s1, the rotation speed of the separation roller pair 12 and the conveyance roller pairs 13, 21, 22, 23, 24, 25 is increased. The original D is conveyed at a higher speed, but the original D
Before reaching the registration roller pair 26 or the reading position B, the conveyance speed of the document D must be reduced to the regular reading conveyance speed. Is calculated by the CPU 4.

Then, based on the calculation result of the CPU 4, the motor driver 36 drives the stepping motor 35 as a drive source.
b, 35c by controlling separation roller pair 12 and conveyance roller pair
By accelerating and decelerating the rotational speeds of 13, 21, 22, 23, 24, and 25, the conveyance speed of the document D conveyed in the first introduction path 2 is adjusted, whereby the document D is paired with the registration roller pair. When the regular time is reached at 26 or the reading position B, the transport speed of the document D can be set to the regular read transport speed.

Thus, the passage time of the document D at a predetermined position after the document D is separated and conveyed is detected (see FIG. 3).
Step S1), the delay amount from the normal passage time at that position is calculated (see steps S2 and S3 in FIG. 3), and the rotational speed of the transport roller pair arranged downstream thereof is accelerated / decelerated (FIG. 3 (see step S4 in FIG. 3), the original document D can be passed at the correct position at the reading position B by returning the original document D to the conveyed state (step S5 in FIG. 3).
(Refer to FIG. 3), the image information of the document D can be accurately read, and the conveyance speed of the document D can be recovered to improve the reading processing efficiency.

Further, in step S2 in FIG. 3, when the arrival time is the same as the regular arrival time, the rotation speeds of the separation roller pair 12 and the conveyance roller pairs 13, 21, 22, 23, 24, 25 remain unchanged. The original D is conveyed by being rotationally driven at a constant speed (see step S6 in FIG. 3).

Next, the first discharge path 5 and the reverse path 14
The acceleration / deceleration control of the conveyance speed of the document D in the second introduction path 8 will be described. At the reading position B, the first
The document D from which the image information of the surface is read is guided to the first discharge path 5 and the image surface is reversed by the annular reversing path 14 as described above. There is a case in which the document D cannot reach the timing of reading the second surface of the document D at the reading position B because the predetermined transport speed cannot be obtained due to the load of the guides in the reversing path 14.

Therefore, when the document leading edge sensor s2 is arranged on the downstream side of the conveying roller pair 28, 29, 30, 31 in the conveying direction c, and the document D passes through the conveying roller pair 28, 29, 30, 31. The arrival time of is detected by the document leading edge sensor s2.

At this time, similarly to the above, the delay time from the regular arrival time is calculated by the CPU 4, and when the arrival time of the document D is behind the regular time, the motor driver 36 drives the stepping motor 35d. The speed of rotation of the discharging and conveying roller pair 6 and the pair of conveying rollers 28, 29, 30, 31 is controlled to increase the conveying speed of the document D.
If the conveyance speed is not increased from the time when the trailing edge of the document D moving from the introduction path 2 to the first discharge path 5 in the direction of the arrow b leaves the reading position B, the reading operation of the first surface of the document D is performed. Since a defect may occur, the timing at which the trailing edge of the document D guided from the first introduction path 2 leaves the reading position B is detected by the document trailing edge sensor s3.

Further, since the original D has to be decelerated to the regular reading speed before it reaches the registration roller pair 27 provided at the end of the second introduction path 8 or the reading position B, these are to be reduced. In consideration of this, the rotation speeds of the discharge / conveyance roller pair 6 and the conveyance roller pairs 28, 29, 30, 31 are accelerated and decelerated to control the conveyance speed of the document D.

In the flow chart of these control systems, in FIG. 3, the document leading edge sensor s1 in step S1 is designated as the document leading edge sensor s2, and the conveying roller pair 13, 21, 22, 23, 24, 25 and the separating roller pair in step S4. Twelve,
Conveying roller pairs 28, 29, 30, 31 and discharging conveying roller pair 6
If replaced with, it is the same as the above description and is omitted here.

The passing time of the original D being conveyed at a predetermined position after the original D being conveyed is inverted is detected, the delay amount from the normal passing time is calculated, and the conveying speed of the original D is increased. , The original document D is returned to the reading position B
Thus, the document D can be passed at the correct timing.

In the above embodiment, the transport speed of the document D is increased to return to the normal state in response to the delay from the regular passage time of the document D at the predetermined position.
As another configuration, the transport speed of the document D may be reduced to return to the normal state in accordance with the advance time from the regular time, and the same configuration can be performed with the above configuration.

The features of the present invention will be described in detail with reference to FIG. FIG. 4 is a diagram for explaining the conveyance speed and the conveyance timing of the preceding document Df and the succeeding document Db in the sheet conveying device according to the present invention.

In the graph of FIG. 4, the horizontal axis t represents time, the vertical axis X represents the position of the document D in the first introduction path 2 which is the transport path, and Xa is the separation roller pair 12 arranged in the transport path. The position Xb indicates the position where the leading edge of the document Db arrives at time tb3 when the trailing edge of the document Db that follows passes the position (Xa) where the separation roller pair 12 is disposed.

Further, V1f and V1b are the tip of the document Df,
The conveyance speeds of the rear end are shown, and V2f and V2b are the conveyance speeds of the front end and the rear end of the document Db, respectively. Here, the leading edge of the document Df,
Since the trailing edge and the leading edge and trailing edge of the document Db are transported at the same speed, the curves indicating the trailing edge transport speeds V1b and V2b correspond to the curves indicating the leading edge transport speeds V1f and V2f, respectively.

Td1 and Td2 are the preceding document Df at the predetermined positions Xa and Xb of the first introduction path 2 which is the conveyance path.
The time difference between the time when the trailing edge passes and the time when the leading edge of the succeeding document Db passes, that is, an interval time between the preceding document Df and the succeeding document Db is shown.

That is, in Td1, the preceding document Df is separated and conveyed by the separation roller pair 12 arranged at the position Xa of the first introduction path 2, and the trailing end of the document Df is separated by the separation roller pair 12 ( Xa) passing time tf3 and the succeeding document Db
Shows the time difference from the time tb0 when the tip of the roller reaches the separation roller pair 12 (Xa) and the separation and conveyance operations by the separation roller pair 12 are started.

Td2 is the time tb3 when the following document Db is separated and conveyed by the separation roller pair 12 and the trailing edge of the document Db passes through the separation roller pair 12 (Xa).
Time tf4 when the trailing edge of the preceding document Df passes the position Xb on the first introduction path 2 where the leading edge of the document Db reaches,
The time difference from the tb3 is shown.

As for Tm, the originals Df and Db are time tf0,
After entering the separation roller pair 12 at tb0 and separated into one sheet,
It is nipped and conveyed by the pair of separation rollers 12 and has a prescribed conveying speed V
It is the start-up time until s (constant) is reached (time tf1, tb1).

Here, although it depends on the size of the length of the document D in the document transport direction, when the trailing edge of the preceding document Df is nipped by the separating roller pair 12 and is transported, the following document Db is transported.
When the separation operation timing by the separation roller pair 12 comes, the document D is read as in the conventional example shown in FIG.
f and Db cannot be reliably separated and transported.

Since the separation roller pair 12 is rotationally driven by the stepping motor 35b, the rise time until the stepping motor 35b reaches a specified rotation speed and the conveyance speed of the document D reaches the specified conveyance speed Vs. Tm
Usually requires several tens of ms (seconds).

Therefore, in the present embodiment, as shown in FIG. 4, while the preceding document Df is being sandwiched by the separation roller pair 12 and being conveyed at the conveying speed Vs, at a predetermined time tf2, the CPU 4 causes the motor to move. By controlling the rotational driving of the stepping motors 35b and 35c via the driver 36, the separation roller pair 12 and the conveying roller pairs 13 and 21 to 25 are moved to a predetermined conveying speed Vx for a predetermined time Tx (from time tf2 to time tf3). (> Vs), and before the separation operation timing by the separation roller pair 12 for the subsequent document Db comes,
The trailing edge of the preceding document Df can be removed from the separation roller pair 12 early.

That is, in FIG. 4, the preceding document Df
At time tf0, the leading edge of the original document Df enters the separation roller pair 12, and after the separation operation by the separation roller pair 12 whose rotation is controlled by the CPU 4 through the motor driver 36 is completed, the leading edge of the original document Df. The part is nipped by the separation roller pair 12, and the conveying operation by the separation roller pair 12 is started.

Then, during the rising time Tm from time tf0 to time tf1, the stepping motor 35b that rotationally drives the separation roller pair 12 rises to a predetermined rotation speed, and from time tf1 to time tf2, the document Df is It is carried at a specified carrying speed Vs.

Then, at time tf2, the separation roller pair
The stepping motors 35b and 35c that rotationally drive 12 and the pair of conveying rollers 13 and 21 to 25 are accelerated, and during the acceleration time Tx from time tf2 to time tf3, the document Df has a predetermined conveying speed Vx (> Vs, In addition, it is transported at a constant rate.

Then, at time tf3, when the trailing edge of the preceding document Df passes the separation roller pair 12 (Xa), the stepping motor 35c is decelerated, and the conveyance roller pair disposed downstream of the separation roller pair 12 is decelerated. 13, 21 to 25 are maintained at the specified transport speed Vs, and the document Df is transported by the transport roller pair.
It is carried at a specified carrying speed Vs by 13, 21 to 25.

At the same time, the separation roller pair 12 is controlled in a predetermined rotation by the CPU 4 via the motor driver 36 and transits to the separation operation state.

The succeeding document Db is predetermined so that the front end of the document Db reaches the separation roller pair 12 (Xa) after time tf3 when the trailing end of the preceding document Df passes through the separation roller pair 12 (Xa). The sheet is fed by the feeding roller 11 at the timing.

Then, at time tb0 (> tf3), the leading edge of the original Db enters the separation roller pair 12, and the separation operation by the separation roller pair 12 controlled by the CPU 4 through the motor driver 36 in a predetermined rotation is completed. After that, the leading edge of the document Db is nipped by the separation roller pair 12, and the separation roller pair 12
The transport operation is started by and the transport roller pairs 13, 21-
Transported by 25.

That is, during the rising time Tm from time tb0 to time tb1, the stepping motor 35b that rotationally drives the separation roller pair 12 rises to a predetermined rotation speed, and from time tb1 to time tb2, the document Db is It is carried at a specified carrying speed Vs. Then, at time tb2, the stepping motors 35b and 35c that rotationally drive the separation roller pair 12 and the conveyance roller pairs 13 and 21 to 25 are accelerated, and the document Db is not fed during the acceleration time Tx from time tb2 to time tb3. The sheet is conveyed at a conveying speed Vx (> Vs and constant).

At time tb3, when the trailing edge of the succeeding document Db passes the separation roller pair 12 (Xa), the stepping motor 35c is decelerated, and the conveyance roller pair disposed downstream of the separation roller pair 12 is decelerated. 13, 21 to 25 are maintained at the specified transport speed Vs, and the document Df is transported by the transport roller pair.
It is carried at a specified carrying speed Vs by 13, 21 to 25.

Then, both the preceding document Df and the following document Db are conveyed while maintaining the document interval time Td2 after passing through the separation roller pair 12.

In the present embodiment, as shown in FIG. 4, the document interval time Td2 after both the preceding document Df and the following document Db have passed through the separation roller pair 12 is the trailing edge of the preceding document Df. Is a value relatively close to the document interval time Td1 when the leading edge of the following document Db reaches the separation roller pair 12 after passing through the separation roller pair 12, and the preset document interval can be maintained. I can.

Further, the document interval time Td2 is shorter than the document interval time Td4 shown in FIG. 6 of the conventional example described above, and thus the document transport efficiency can be improved. Further, unlike the conventional example shown in FIG. 7, the preceding document Df and the following document Db do not interfere with each other (FIG. 4).
See middle E).

With the above configuration, the interval time Td2 between the original document Df and the subsequent document Db on the downstream side of the separation roller pair 12 is shortened to minimize the interval time Td2 between the original document Df and the original document Db. It is possible to speed up the document transportation by using.

As shown in FIG. 5, the document feeding device 9 can be mounted on the apparatus main body A of an image forming apparatus such as a copying machine. In FIG. 5, 37 is an electrophotographic photosensitive drum, 38 is a transfer charger, 39 is a feeding cassette loaded with recording sheets made of paper or synthetic resin, 40 is a recording sheet feeding roller, and 41 is a recording sheet. A separation roller pair, 42 is a fixing device, and 43 is a double-sided path.

In the image forming apparatus, the latent image is formed by irradiating the surface of the uniformly charged photosensitive drum 37 with light corresponding to the image information of the document D to form a latent image, and the latent image is supplied from a toner supply device (not shown). A toner image is formed on the surface of the photosensitive drum 37 by the toner. Then, the recording sheet feeding roller 40 is driven in synchronization with the rotation of the photosensitive drum 37, and the recording sheet accommodated in the feeding cassette 39 is fed.

The recording sheet is conveyed to a position facing the photoconductor drum 37 while being prevented from double feeding by the recording sheet separating roller pair 41, and the toner image on the photoconductor drum 37 is transferred by the transfer charger 38. Then, the recording sheet on which the toner image is transferred is sent to the fixing device 42 and the toner image is fixed.

When recording images on both sides of the recording sheet, the recording sheet on which the toner image on the first side is fixed by the fixing device 42 passes through the double-sided path 43 again to the photosensitive drum 37 and the transfer charger 38 again. And a toner image is formed on the second surface. This toner image is fixed by the fixing device 42, and then discharged to the outside of the apparatus main body A.

In the above-described embodiment, the case where the sheet conveying apparatus according to the present invention is applied to the image reading apparatus has been described. However, as another configuration, the platen glass 3 and the reading optical system which constitute the image reading means in the above-described embodiment. Instead of No. 1 and the like, it is also possible to apply to an electrophotographic image forming unit forming an image forming unit, or an image forming apparatus equipped with an image forming unit including an inkjet head, a thermal head or the like.

For example, the recording sheet separating roller pair 41 shown in FIG.
May be configured to be controlled in the same manner as the separation roller pair 12 described above.

[0093]

Since the present invention has the above-described structure and operation, the conveying speed of the sheet separated by the separating means is increased, and the rear end of the sheet is extracted from the separating means at an early timing, It is possible to secure the start-up time for the subsequent sheet separation and conveyance operations, and it is possible to perform high-speed processing without lowering the predetermined image processing efficiency (image reading efficiency, image forming efficiency, etc.).

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing a configuration of a document feeding device including a sheet conveying device according to the present invention.

FIG. 2 is a block diagram showing a configuration of a control system that controls a sheet conveying speed.

FIG. 3 is a flowchart of a control system that controls a sheet conveying speed.

FIG. 4 is a graph showing a sheet conveyance speed and a sheet conveyance timing.

FIG. 5 is a cross-sectional explanatory view showing configurations of a sheet conveying device according to the present invention, an image reading apparatus including the same, and an image forming apparatus including the same.

FIG. 6 is a diagram illustrating a conventional example.

FIG. 7 is a diagram illustrating a problem of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reading optical system, 2 ... 1st introduction path, 3 ... Platen glass, 4 ... CPU, 5 ... 1st discharge path, 6 ... discharge conveyance roller pair, 7a, 7b ... flapper, 8 ... 2nd introduction Paths, 9 ... Original feeding device, 10 ... Original placing table, 10a ... Original placing surface, 10b ... Abutting surface, 11 ... Feed roller, 12 ... Separation roller pair, 12a ... Feed roller, 12b ... Separation roller, 13 ... conveying roller pair, 14 ... reversing path, 15 ... second discharging path, 16 ...
Discharge tray, 17, 18 ... Pair of transport rollers, 19 ... Flapper, 20
... Third discharge path, 21 to 25 ... Conveying roller pair, 26, 27 ... Registration roller pair, 28 to 34 ... Conveying roller pair, 35
a to 35d ... Stepping motor, 36 ... Motor driver,
37 ... Photosensitive drum, 38 ... Transfer charger, 39 ... Feed cassette, 40 ... Recording sheet feeding roller, 41 ... Recording sheet separating roller pair, 42 ... Fixing device, 43 ... Double-sided path, s1, s2 ... Document leading edge Sensors, s3, s4 ... Document rear end sensor, A ... Device body, B ... Reading position, D ... Document

Claims (7)

[Claims] 1. A sheet placing means for placing a sheet, a sheet feeding means for feeding a sheet placed on the sheet placing means, and a sheet fed by the sheet feeding means. Separating means for separating and conveying the sheets one by one, and the constitution is such that the conveying speed of the sheets by the separating means is increased while the sheets are being acted on by the separating means. Sheet transport device. 2. A speed rising time for increasing a conveying speed of a sheet conveyed by the separating means to a predetermined speed is set for a sheet fed subsequently to the sheet by the sheet feeding means. The sheet conveying apparatus according to claim 1, wherein the leading end is configured to be shorter than the time required to reach the separating means. 3. The sheet conveying apparatus according to claim 1, wherein the CPU calculates an increase amount of the conveying speed of the sheet conveyed by the separating means. 4. The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is configured so that the increase amount of the conveying speed of the sheet conveyed by the separating unit is changed according to the size of the conveyed sheet. 5. The separating means is driven by a stepping motor, and the sheet conveying speed by the separating means is increased by controlling the stepping motor. The sheet conveying device described. 6. A sheet conveying apparatus according to claim 1, further comprising an image reading unit for reading image information recorded on a sheet-like original conveyed by the sheet conveying apparatus. Characteristic image reading device. 7. An image forming unit comprising the sheet conveying device according to claim 1, further comprising an image forming unit for recording an image according to image information on a recording sheet conveyed by the sheet conveying device. An image forming apparatus having.