JP2001146329A - Paper feeding device, and image forming device or image reading device provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the paper feeding control corresponding to speedup of the printing speed with the simple structure in a paper feeding device for feeding the sheets while being brought in pressure-contact or separated with/from the sheets. SOLUTION: Moving time A to be required for moving a pickup roller 2 from the initial position that the roller is separated from a sheet to a pressure- contact position for feeding the sheet and the time B to be required for passing a rear end of the sheet through a separating position of a pair of separating rollers 3 after a tip of the sheet is detected by a sensor 11 are respectively computed, and when the time (B-A) is passed since the tip of the fed sheet is detected by the sensor 11, a CPU 12 turns on a solenoid 9 so that the pickup roller 2 waiting at the initial position is brought in pressure-contact with the following sheet be fed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feeding device such as a copying machine, a printer, a facsimile and the like, and an image forming apparatus or an image reading device having the same.

[0002]

2. Description of the Related Art A paper feeder in an image forming apparatus such as a copying machine or a printer or an image reading apparatus such as a facsimile machine includes a separating unit for separating stacked sheets one by one, and a feeding unit for feeding the sheets to the separating unit. It is broadly divided into sending means and various methods are available.

In a recent paper feeder, a pickup roller is configured so as to be able to contact and separate from the stacked and supported sheets, and a pickup roller that contacts and feeds the sheet and a sheet that is sent by the pickup roller is separated into one sheet. After that, a retard separation method using a pair of separation rollers for transporting a sheet further downstream is increasing.

A normal paper feeding operation in such a paper feeding device configuration will be described using a printer as an image forming apparatus.

In the standby state of the sheet feeding operation, the pickup roller is at an initial position separated from the sheet supported by sheet supporting means such as a sheet feeding cassette or a sheet feeding tray. When the image forming operation is started, driving of an image forming unit such as a photoreceptor or a laser scanner for forming an image (toner image) on a sheet or a fixing unit for fixing an image on a sheet is started, and the image forming operation of the image forming unit is started. , The sheet feeding operation is started.

With the start of the sheet feeding operation, the pickup roller waiting at the initial position moves in the sheet direction and comes into contact with the stacked and supported sheets. When rotational driving is transmitted to the pickup roller in that state, the sheet that is in contact with the roller is sent out toward the image forming unit. The fed sheet is fed to the nip of a separation roller pair including a feed roller that rotates in the sheet conveyance direction and a retard roller that is pressed against the feed roller and transmitted with a drive in a direction opposite to the conveyance direction. Here, the sheet sent out by the pickup roller is separated into one sheet, and is conveyed in the direction of the image forming means by a pair of conveying rollers further downstream of the pair of separating rollers in the sheet conveying direction.

The pick-up roller that has sent out the sheet retreats to the initial position again at a predetermined timing from the start of feeding, and comes into contact with the sheet at the timing of feeding the next sheet to be fed. Normally, such control is provided on the downstream side of the separation roller pair in the sheet conveyance direction, and is performed by a sensor that detects the leading edge and the trailing edge of the sheet. When a sufficient time has passed to be pinched by the pair of conveying rollers, the pickup roller retracts from the sheet, and when the rear end of the sheet passes through the sensor or the pair of conveying rollers,
The pickup roller starts to descend on the sheet so as to abut the next sheet to be fed.

[0008] In this manner, the sheet feeding operation of the sheet feeding method using the pickup roller is performed.

[0009]

However, the following problems have occurred in the sheet feeding system using the pickup roller.

Normally, in the case of a paper feeding system using a pickup roller, the drive source (motor) for driving the pickup roller to rotate and the drive source (motor) for driving the feed roller, the retard roller, and the transport roller pair to rotate are the same. In many cases, it is often used as a sheet feeder of an image forming apparatus having a low printing speed and a low printing speed. Therefore, after the trailing edge of the sheet sent out by the pickup roller passes through the sensor and the pair of conveyance rollers, the pickup roller starts moving from the retreat position to a position where it comes into contact with the sheet in order to feed the next sheet. The above-described control sequence was able to satisfy the required print speed.

However, in recent years, there has been a demand for an image forming apparatus having a low cost and a high print speed performance.
With one driving source and control sequence as described above, the interval between sheet feeding operations becomes large, and it has not been possible to cope with high speed. For this reason, it has been tried to cope with high speed by increasing the number of motors or providing a large number of clutches.
With such a configuration, the product cost has risen and it has not been possible to meet the needs of the market.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a paper feeding apparatus capable of achieving both high printing speed and low cost, and an image forming apparatus or an image reading apparatus having the same. The purpose is to provide.

[0013]

According to the present invention, there is provided a sheet feeding means for feeding sheets stored in a sheet storage section, and a separating means for separating the sheets fed by the sheet feeding means into one sheet. Holding the sheet feeding means,
Moving means for moving the sheet feeding means so as to be separated from the sheet stored in the sheet storing means after the sheet feeding means has sent out the sheet, and control means for controlling the operation of the moving means. Having the control means,
When the trailing end of the sheet sent to the sheet feeding means passes through the separating position of the separating means, the operation of the moving means is controlled so that the sheet feeding means is pressed against the next sheet. And

Further, the sheet feeding means moves between an initial position separated from the sheet and a pressing position for pressing the sheet stored in the sheet storing section by the operation of the moving means. And

Further, a detection means for detecting the passage of the leading edge and the trailing edge of the sheet is provided downstream of the separating means in the sheet conveying direction.

Further, the control means detects the movement time of the sheet feeding means in which the sheet feeding means moves from the initial position to the pressure contact position and the leading end of the sheet fed by the sheet feeding means by the detection means. The sheet moving time from when the sheet trailing edge passes through the separating position of the separating means to the time when the sheet leading edge is detected by the detecting means is stored. When a time obtained by subtracting the moving time of the feeding means has elapsed, the moving means is operated to perform control for starting the movement of the sheet feeding means from an initial position.

Further, the control means has a calculating means for calculating a moving time of the sheet feeding means in which the sheet feeding means moves from the initial position to the pressing position, and the sheet fed by the sheet feeding means is provided. The time obtained by subtracting the sheet feeding means moving time measured by the measuring means from the sheet moving time from when the leading end is detected by the detecting means to when the sheet rear end passes through the separating position of the separating means. When the time has elapsed, the moving means is operated to perform control for starting the movement of the sheet feeding means from the initial position.

Further, the calculating means has a distance detecting means for detecting a distance between a sheet surface stored in the sheet storing portion and the initial position, and the calculating means detects the distance by the distance detecting means. The moving distance of the sheet feeding unit is calculated by dividing a distance by the moving speed of the sheet feeding unit.

Further, the calculating means includes a contact detecting means for detecting a contact between the sheet surface stored in the sheet storing portion and the sheet feeding means, and the calculating means is configured to detect the contact from the initial position. The sheet feeding means moving time is calculated by measuring a time from the start of movement of the sheet feeding means to the detection of contact by the contact detecting means.

Further, the control means recognizes the length of the sheets stored in the sheet storage section in the feed direction and performs control for switching the sheet moving time according to the length of the sheets. It is characterized by.

Further, the sheet feeding means, the separating means, and the moving means are driven by one motor whose driving is controlled by the control means.

Further, the motor is a stepping motor whose driving can be controlled by inputting a pulse signal, and the control means manages the operation timing of the moving means by the number of pulses.

The moving means includes a swing arm for holding the sheet feeding means, a cam for moving the swing arm, a gear for holding the cam, and a control unit for controlling rotation of the gear. A solenoid operated by the control means.

Further, the separating means includes a feed roller for conveying the sheet sent from the sheet feeding means further downstream, and a rotational force for pressing the feed roller to rotate in a direction opposite to the feed roller. And a set retard roller.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus provided with a paper feeder embodying the present invention will be described in detail with reference to the drawings. In the present embodiment, an explanation will be given based on an electrophotographic printer as an image forming apparatus. However, the present invention is not limited to this, and is not limited to an image forming apparatus such as a copying machine or a facsimile, and is used for reading an original. The present invention can also be applied to the document feeder of the image reading device described above.

FIG. 1 schematically shows a drive path of a sheet feeding apparatus embodying the present invention and a transmission path of a control signal. In FIG. 1, a thick oblique dashed line indicates drive transmission, and a thin solid line indicates a control signal transmission path. First, the configuration of the sheet feeding device will be described.

Reference numeral 1 denotes a paper feed tray as a sheet storage unit, which supports and supports sheets for forming images. A swing arm 10 as a moving means having a swing fulcrum is provided above the paper feed tray 1, and an end of the arm 10 is in contact with the uppermost sheet supported by the paper feed tray 1. A pickup roller 2 is provided as a sheet feeding unit that rotates in a sheet feeding direction.

The pickup roller 2 is swung by the swing arm 10 to contact the sheet on the sheet feeding tray 1 and feed the sheet, and a retracted position separated from the sheet (hereinafter, this position is referred to as an initial position). ) And can be displaced.

On the downstream side of the pickup roller 2 in the sheet feeding direction, a feed roller 4 for conveying the fed sheet further downstream, and pressed against the feed roller 4 to rotate the sheet in the direction of returning the sheet to the paper feed tray 1 side. Roller pair 3 is provided as a separating means including a retard roller 5 to which a driving force is transmitted, and the sheet sent out from the pickup roller 2 is nipped by the nip portion of the separation roller pair 3 and conveyed. The sheet is separated into one sheet.

On the downstream side of the separation roller pair 3 in the sheet conveyance direction, there is provided a conveyance roller pair 6 for conveying the separated sheet to the image forming unit. Note that all these rollers are configured to rotate by receiving the drive from one motor 7. The transport roller pair 6 has a configuration in which only a gear (not shown) is interposed between the transport roller pair 6 and the motor 7.
When it is driven, it rotates in the transport direction.

The drive is transmitted to the retard roller 5 via a torque limiter (not shown) so as to rotate in the direction opposite to the sheet conveying direction. The feed roller 4 pressing the retard roller 5 is pressed. By rotating in the sheet conveying direction, the retard roller 5 is given a torque in the sheet conveying direction. Since the set torque of the torque limiter is set to a value smaller than the torque applied from the feed roller 4 to the retard roller 5, the retard roller 5
Receives the rotation of the feed roller 4 and rotates in the sheet conveying direction.

When two or more sheets are fed to the separation roller pair 3 by the feeding operation by the pickup roller (this state is called double feeding), the coefficient of friction between the sheets is larger than the coefficient of friction between the rollers and the sheets. The retard roller 5 to which the drive in the direction opposite to the sheet conveying direction is transmitted by the action of the torque limiter rotates in the direction opposite to the sheet conveying direction, and the multi-fed sheets other than the top sheet are fed to the sheet feed tray 2. In the direction of As a result, the sheets can be conveyed one by one to an image forming unit as an image forming unit.

The sheet sent to the image forming unit is a photosensitive drum for forming a toner image, an image forming means (not shown) such as a laser scanner for optically writing image information to be formed on the photosensitive drum, or a photosensitive drum. By a transfer unit (not shown) for transferring the toner image formed on the sheet,
The toner image is transferred to the sheet surface, and the toner image is semi-permanently fixed on the sheet by a fixing unit (not shown) provided downstream of the transfer unit. The sheet on which the image has been fixed is discharged and stacked on a sheet discharge unit (not shown) provided outside the apparatus or the like.

Feed roller 4 and pickup roller 2
The drive from the motor is transmitted through the clutch 8 so as to rotate in the sheet conveying direction. In addition, a one-way clutch (not shown) that regulates the rotation direction of the feed roller 4 only in the sheet conveyance direction is provided on a shaft that supports the feed roller. This is because the clutch 8 is disengaged and the motor 7
Is not transmitted to the feed roller 4, the feed roller 4 rotates in the direction opposite to the transport direction due to the rotation of the retard roller 5 in the reverse direction,
This is a configuration for preventing occurrence of sheet conveyance failure.

The pickup roller 2 is moved up and down by the operation of a solenoid 9 as a moving means and an oscillating arm 10 oscillated by a pickup cam (not shown), and comes into contact with and separates from the sheets stacked on the sheet feed tray 1. It is possible to do.

The operations of the motor 7, the clutch 8, and the solenoid 9 are managed by a CPU 12 as control means. Further, in order to detect the passage of the leading edge and the trailing edge of the sheet, the operation is controlled based on the detection of a sensor 12 as a detecting means provided downstream of the separation roller pair 3 in the sheet conveying direction. The CPU 12 of the sheet feeding device is managed by a main CPU 13 that controls the entire image forming apparatus, and controls a sheet feeding operation according to a sheet feeding command from the main CPU 13.

Next, referring to FIG. 2, moving means for moving the pickup roller 2 serving as the feeding means from the initial position to the pressing position where the sheet is fed by contacting the uppermost sheet on the sheet feeding tray 1 with the sheet. Will be described. A pickup cam 14 has a stopper 15 for stopping the cam 14 that has made one rotation at a predetermined position, and a toothless gear 16. The driving force of the motor 7 is transmitted to the pickup cam 14 by the gear 17 provided at a position where the gear 17 can mesh with the missing gear 16 meshes with the missing gear 16.

The swing arm 10 supports the pickup roller 2 at its end, and swings by rotating the pickup cam 14. The drive from the motor 7 is transmitted to the pickup roller 2 via the clutch 8 as described above, and the pickup roller 2 rotates in the sheet conveying direction. Before the sheet feeding operation starts, the pawl 18 is engaged with the stopper 15 of the pickup cam 14. At this time, even if the motor 7 is rotating, the drive is not transmitted to the toothless gear 16 because the toothless gear 16 is at a position where it does not mesh with the gear 17, and the pickup cam 14 does not rotate. Therefore, the swing arm 10 is raised, and the pickup roller 2 is at an initial position separated from the sheet on the sheet feed tray 1 (FIG. 2A).
State).

In this state, when the solenoid 9 is turned on, the engagement between the pawl 18 and the stopper 15 is released, the gear 17 and the toothless gear 16 are engaged, and the pickup cam 14 starts rotating. The solenoid 9 only needs to be turned on for a time during which the engagement between the claw 18 and the stopper 15 is surely released. When the rotating pickup cam 14 pushes up the end of the swing arm 10, the end supporting the pickup roller 2 moves in the direction of the sheet feed tray 1, and the pickup roller 2 contacts the sheet surface. Touch

At this time, when the clutch 8 is turned on, the drive from the motor 7 is transmitted to rotate the pickup roller 2, and the pickup roller 2 rotates to feed the uppermost sheet of the sheet feed tray 1 in contact with the separation roller pair 3. I do. When the pickup cam 14 further rotates, the pickup roller 2 starts moving toward the initial position again. At this time, since the solenoid 9 is already in the OFF state, the claw 18 engages with the stopper 15, and the pickup cam 14 makes one rotation and stops. By this operation, the pickup roller 2 returns to the initial position.

The shape and rotation speed of the cam 14 are set so that a series of operations as described above are performed during one rotation of the pickup cam 14.

In the paper feeder having such a configuration, in order to realize high-speed printing, it is necessary to shorten the paper feed interval as much as possible, that is, to start the next paper feed operation as soon as possible after sending out the previous sheet. Therefore, it is conceivable to start the feeding operation of the next sheet while feeding the sheet before the feeding. However, the previous sheet is conveyed by the conveying roller pair 6 and is still nipped by the nip portion of the separation roller pair 3, that is, the rear end of the previous sheet is located upstream of the separation roller pair 3 (toward the pickup roller 2). Sometimes,
Even if the clutch 8 is off, the sheet pulling force of the conveying roller pair 6 is received, and the feed roller 4 and the pickup roller 2 are driven to rotate in the sheet conveying direction.

In this state, if the solenoid 9 is turned on to lower the pickup roller 2 on the next sheet in order to perform the next sheet feeding, the pickup roller 2 is driven to rotate together with the feed roller 4 because of the following rotation. Even if the clutch 8 is not turned on, the next sheet is fed. However, since the next sheet fed in is not advanced beyond the separation roller pair 3 due to the rotation of the retard roller 5 in the reverse direction, the pickup roller 2 and the retard roller 5
The sheet is crushed and buckled between (separation roller pair 3).

Therefore, in order to feed the next sheet, the trailing edge of the previous sheet passes through the separation roller pair 3 and the separation roller pair 3
It is necessary at least to bring the pickup roller 2 into contact with the sheet surface after the previous sheet no longer exists in the nip portion. In order to feed the next sheet at the earliest timing, the rear end of the previous sheet is
The pickup roller 2 may be brought into contact with the sheet surface at the moment when the pickup roller 2 passes. Hereinafter, a paper feed control sequence for realizing the above paper feed timing will be described.

(First Embodiment) FIG. 3 shows a timing chart of a paper feed control sequence in the present embodiment. This is a drawing of the above-described paper feed timing. Based on this, the present control will be described in detail. Before starting the sheet feeding operation, it is assumed that the size of the sheet to be fed is detected by the CPU 12 or recognized by a user setting. Even if the sheet size is not known, the CPU 12 is configured to set a fixed sheet size that can satisfy the main sheet feeding control in advance.

Before the start of the sheet feeding operation, the pickup roller 2 is at an initial position separated from the sheet. Main CPU
The CPU 12 that has received the sheet feed command from 13 drives the motor 7 to turn on the solenoid 9. As a result, the missing gear 16
The swing arm 10 is displaced by the engagement of the gear 17 with the gear 17, and the pickup roller 2 comes into contact with the uppermost sheet surface supported by the sheet feed tray 1. Here, A is a time as a sheet feeding means moving time from when the solenoid 9 is turned on to when the pickup roller 2 comes into contact with the sheet surface. The moving time A is a value calculated and stored in advance by the control means from the moving speed of the pickup roller 2 and the distance between the initial position and the sheet surface.

The moving time A of the pickup roller 2
The distance between the initial position and the sheet surface is not always constant because the number of stacked sheets supported by the sheet feed tray 1 changes. Therefore, the moving time A is not constant, but the moving time in a state where the sheet is fully loaded on the sheet feeding tray 1, that is, a state where the distance between the initial position of the pickup roller 2 and the uppermost sheet is the shortest is set. Keep it.

After the pickup roller 2 is pressed against the sheet surface, the clutch 8 is turned on, so that the pickup roller 2
Is transmitted to start feeding. After the leading edge of the fed sheet is detected by the sensor 11, the sheet reaches the nip of the conveying roller pair 6. Here, the clutch 8 is turned off to release the drive transmission between the feed roller 4 and the pickup roller 2. However, as described above, while the sheet is held between the nip portions of the separation roller pair 3, the feed roller 4 and the pickup roller 2 are driven to rotate because the conveyance force of the conveyance roller pair 6 is transmitted via the sheet. I have. At this point, the pickup roller 2 starts moving to the initial position after being separated from the sheet surface by the rotation of the cam 14.

The CPU 12 turns on the sensor 11 at the leading edge of the sheet and then passes through the separation roller pair 3 based on the size of the sheet to be fed and the sheet conveying speed in the sheet feeding operation, which are recognized in advance. The sheet movement time up to is calculated. Let that time be B.

The time B required from the time when the sensor 11 detects the leading edge of the sheet to the time when the trailing edge of the sheet passes through the separation roller pair 3 varies depending on the sheet size. CPU as control means
12 is stored.

As described above, if the pickup roller 2 can abut the sheet surface to be fed next and turn on the clutch 8 at the moment when the trailing end of the sheet passes through the separation roller pair 3,
The sheet interval can be the distance between the sheet feed tray 1 and the separation roller pair 3. In other words, the time A from when the solenoid is turned on to when the pickup roller 2 contacts the sheet surface is reduced from the time B from when the sensor 11 detects the leading edge of the sheet to when the trailing edge of the sheet passes through the separation roller pair 3. The CPU 12 calculates the time (B−A), and the solenoid 9 is operated after (B−A) time after the sensor 11 detects the leading edge of the sheet.
Is turned on, the pickup roller 2 comes into contact with the sheet surface at the moment when the rear end of the sheet passes through the separation roller pair 3, and the clutch 8 can be turned on.

Next, FIG. 4 shows a flowchart of a paper feed control sequence in this embodiment.

The CPU 12 that has received the paper feed command from the main CPU 13 drives the motor 7 (step S101),
The solenoid 9 is turned on, the toothless gear 16 and the gear 17 mesh with each other to displace the swing arm 10, and the pickup roller 2 is brought into contact with the uppermost sheet surface supported by the sheet feed tray 1 (step S102). ).

When the time A during which the pickup roller 2 reaches the sheet surface has elapsed (step S103), the clutch 8
Is turned on (step S104), and sheet feeding is started. The leading end of the fed sheet is detected by the sensor 11 (step S105), and the leading end of the sheet
When the time to reach the nip portion elapses (step S1
06), the clutch 9 is turned off (step S107).

If the fed sheet is the last printed sheet, when the trailing end of the sheet has passed through the pair of transport rollers 6 (step S110), the drive of the motor 7 is stopped (step S111), and the sheet is fed in the printing operation. The operation ends.

When the sheet is not the last sheet, the time A (the time from when the leading edge of the sheet is detected by the sensor 11 until the trailing edge passes through the separation roller pair 3) to the time A (when the solenoid 9 is turned off) is calculated in advance. Pickup roller 2 after turning on
Sheet feeding means movement time until the sheet contacts the sheet surface)
After a lapse of time (step S109), the flow returns to step S102, and the same sheet feeding operation is controlled.

The above is the control of the sheet feeding operation in the image forming apparatus embodying the present invention. As described above, by detecting the leading edge of the sheet with the sensor and calculating in advance the timing of turning on the solenoid so that the pickup roller comes into contact with the sheet surface at the moment when the trailing edge of the sheet passes through the separation roller pair, one sheet can be obtained. Feed command for each CPU
, The paper feeder can automatically feed paper at the same timing. Therefore, the feeding operation of the next sheet can be performed at the earliest timing, and it is possible to cope with an increase in the printing speed.

Further, since the pickup roller 2, the separation roller pair 3, the conveyance roller pair 6, and the pickup cam 14 can be driven by one motor 7, even a simple apparatus configuration is faster than a conventional sheet feeding apparatus. Since the paper feed timing can be realized, it can greatly contribute to the cost reduction of the apparatus.

In the paper feeder of this embodiment, the main CPU 13 is used for the image forming apparatus, and another CPU 1 is used for the paper feeder.
2, but the present invention is not limited to such a configuration.

In the present embodiment, the control timing is controlled by time. However, if the motor 7 is a stepping motor driven by inputting a pulse, the control may be performed by the number of pulses input to the motor. Therefore, the same effect as in the present embodiment can be obtained.

(Second Embodiment) In the above-described first embodiment, the time A and the time B are calculated in advance, and the sheet feeding operation is controlled based on the calculated time. However, the present invention is not limited to this. For example, it is also possible to provide a timer for measuring time, measure time A and time B for each sheet feeding, and use the measurement result as the next sheet feeding timing. This is the second
An embodiment will be described below.

In the case of a sheet feeding device in which the distance between the initial position of the pickup roller 2 and the sheet surface gradually increases due to the decrease in the sheet stacking amount due to the sheet feeding, the moving time A also indicates the sheet stacking amount. Will gradually increase along with the decrease in. That is, there is a difference between the preset travel time A and the actual travel time A '(A <A'). When such a difference occurs, using the preset time A (B
-A) solenoid 9 to feed the next sheet in time
Even if is turned on, the time for the pickup roller 2 to contact the sheet surface actually takes A ', so that the sheet feeding interval gradually widens.

Therefore, the moving time A 'which changes according to the change in the distance between the initial position of the pickup roller 2 and the sheet surface.
Is constantly measured, and based on the measurement, the time when the CPU 12 turns on the solenoid 9 is set to the time (B-A '), whereby the sheet can always be fed at a constant timing.
This makes it possible to provide a more reliable sheet feeding device.

The measurement of the moving time A 'is performed by providing a sensor as a distance detecting means for detecting the distance between the sheet surface and the initial position, and dividing the distance by the moving speed of the pickup roller 2. Is possible. It is also possible to provide a sensor as contact detection means for detecting contact between the sheet surface and the pickup roller 2 and calculate the time from ON of the solenoid 9 to contact.
It should be noted that the present invention is not limited only to the method for measuring the movement time A ′ described in the present embodiment.

In the present embodiment, the moving time that changes in accordance with the change in the sheet stacking amount is determined by turning on the solenoid 9.
The control is shown such that the initial position and the sheet surface are always constant, that is, the control is performed such that the movement time A is always constant.
A) The control may be such that the time is always constant. For example, a sensor for measuring the distance between the above-described sheet surface and the initial position is provided, and the initial position of the pickup roller 2 is moved in the direction of the sheet surface by the sheet height of the reduced load amount according to the detection of the sensor. Alternatively, by performing control such as moving the paper feed tray 1 in the direction of the initial position, the moving time A can be kept constant even if the amount of stacked sheets changes.

Although the present invention has been described in detail in each of the embodiments, the present invention is not limited only to the above-described configuration.

In this embodiment, the separation roller pair is provided as the separation means. However, a separation pad which presses against the feed roller 4 may be used.

[0068]

As described above in detail, according to the present invention, the sheet interval at the time of continuous sheet feeding can be shortened in a simple apparatus configuration as compared with the conventional apparatus, and the cost of the apparatus can be reduced and the feeding speed can be increased. , And an image forming apparatus or an image reading apparatus having the same.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a sheet feeding device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an operation of a pickup roller according to the embodiment of the present invention.

FIG. 3 is a timing chart of sheet feeding control according to the first embodiment of the present invention.

FIG. 4 is a flowchart of a sheet feeding operation according to the first embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 paper feed tray (sheet storage section) 2 pickup roller (sheet feeding means) 3 separation roller pair (separation means) 7 motor 8 clutch 9 solenoid (moving means) 10 swing arm (moving means) 11 sensor (detection means) 12 CPU (control means)

Continued on the front page F term (reference) 2H072 AA14 AA22 AA24 AA29 AB09 BA03 BA19 JA02 3F343 FA02 FB02 FB03 FB04 JD09 KB05 LA04 LA14 LC11 LD10 LD11 LD24 LD26 MA03 MA23 MA33 MA36 MA53 MB03 MB14 MC04 MC08 MC17 MC18

Claims (14)

[Claims] A sheet feeding unit for feeding sheets stored in a sheet storage unit; a separating unit for separating the sheets fed by the sheet feeding unit into one sheet; and a sheet feeding unit. Holding means for moving the sheet feeding means so as to separate from the sheet stored in the sheet storing means after the sheet feeding means has sent out the sheet; and control for controlling the operation of the moving means. Means for controlling the sheet feeding means to press the sheet feeding means against the next sheet when the rear end of the sheet sent to the sheet feeding means passes through the separation position of the separating means. A sheet feeding device for controlling an operation of the moving means. 2. The sheet feeding means moves between an initial position separated from a sheet and a pressure position for pressing against a sheet stored in the sheet storage section by an operation of the moving means. The sheet feeding device according to claim 1, wherein 3. The sheet feeding device according to claim 1, further comprising a detection unit that detects passage of a leading end and a trailing end of the sheet downstream of the separating unit in the sheet conveying direction. 4. The control means detects the movement time of the sheet feeding means in which the sheet feeding means moves from the initial position to the pressure contact position and the leading end of the sheet fed by the sheet feeding means by the detection means. The sheet moving time from when the sheet trailing edge passes through the separating position of the separating means to the time when the sheet leading edge is detected by the detecting means is stored. When the time that reduced the transportation means travel time has elapsed,
4. The sheet feeding apparatus according to claim 3, wherein control is performed to start the movement of the sheet feeding means from an initial position by operating the moving means. 5. The control means has a calculating means for calculating a moving time of the sheet feeding means in which the sheet feeding means moves from the initial position to the pressing position, and the sheet fed by the sheet feeding means is provided. The time obtained by subtracting the sheet feeding means moving time measured by the measuring means from the sheet moving time from when the leading end is detected by the detecting means to when the sheet rear end passes through the separating position of the separating means. 4. The sheet feeding device according to claim 3, wherein when the time has elapsed, control is performed to start the movement of the sheet feeding means from the initial position by operating the moving means. 6. The apparatus according to claim 1, wherein the calculating unit includes a distance detecting unit that detects a distance between a sheet surface stored in the sheet storing unit and the initial position, and the calculating unit detects the distance between the sheet surface and the initial position. The sheet feeding device according to claim 5, wherein the sheet feeding unit movement time is calculated by dividing a distance by a moving speed of the sheet feeding unit. 7. The calculating means has a contact detecting means for detecting a contact between a sheet surface stored in the sheet storing portion and the sheet feeding means, and the calculating means is configured to detect the contact from the initial position. 6. The sheet feeding means moving time is calculated by measuring a time from the start of movement of the sheet feeding means to the detection of contact by the contact detecting means. Paper feeder as described. 8. The apparatus according to claim 1, wherein the control unit recognizes a length of the sheet stored in the sheet storage unit in a feeding direction, and performs control for switching the sheet moving time according to the length of the sheet. The sheet feeding device according to claim 4, wherein: 9. The sheet feeding means, the separating means, and the moving means are driven by one motor whose driving is controlled by the control means. Paper feeder. 10. The motor according to claim 9, wherein the motor is a stepping motor whose driving can be controlled by inputting a pulse signal, and wherein the control means manages the operation timing of the moving means by the number of pulses. Paper feeder as described. 11. The moving means includes: a swing arm that holds the sheet feeding means; a cam that moves the swing arm; a gear that holds the cam; and a control unit that controls rotation of the gear. 2. The sheet feeding device according to claim 1, further comprising a solenoid operated by the control unit. 12. The separation unit includes a feed roller that conveys the sheet sent from the sheet feeding unit further downstream, and a rotational force that presses against the feed roller and rotates in a direction opposite to the feed roller. The sheet feeding device according to claim 1, further comprising a set retard roller. 13. An image, comprising: the sheet feeding device according to claim 1; and an image forming unit for forming an image on a sheet fed from the sheet feeding device. Forming equipment. 14. A sheet feeding device according to claim 1, further comprising: image reading means for reading image information recorded on a sheet fed from said sheet feeding device. Image reading device.