JP2002145469A - Paper feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a wrinkle and breakage to a next waiting paper sheet 81a even when a paper tray 51 is drawn out, in a paper feeding device to perform preliminary paper feed to suppress the occurrence of unevenness in a paper forward end position and to realize shortening of a paper feed time when sheet-form papers 81 loaded and stored in a removable paper tray 51 are taken out, in order, and fed. SOLUTION: A first pair of paper feed rollers form a drive roller 84 and a separation roller 85. By bringing a pick up roller 83 into contact with the upper surface of a paper sheet 81 once, the paper sheet 81 is taken out (in Figs 5 (a)-(c)). The pick up roller 83 is brought into contact with the rear end side of the paper sheet 81 and a next paper sheet 81a is taken out (in Figs 5 (d)-(f)). In this case, a double feed by the separation roller 85 does not occur and the next paper sheet 81a is waited without biting in a gap between the rollers 84 and 85. Thus, in pull out of the paper tray 51, the occurrence of wrinkles and breakage to the next paper sheet 81a can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feeder mounted on an image forming apparatus such as a printer, a facsimile, a copying machine, etc., for feeding sheet-like paper, and more particularly to a paper feeder for an image forming section. Before performing a pre-feed to a predetermined position.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer, as shown in FIG. 7, a sheet feeding device is provided with a sheet tray 2 for accommodating the sheet-shaped sheet 1 for one or a plurality of sizes. 7, one is provided for the sake of simplicity of the drawing).
Takes out the sheets 1 one by one and makes a pair of sheet feed rollers 4.5.
And supplies the paper to the paper transport path of the main body device having the image forming unit in synchronization with the image forming timing. On the other hand, recently, in an image forming apparatus having a relatively large number of sheets to be processed, which is used in a business office or the like, as shown in FIG.
The front loading method of drawing out from the front side of the apparatus as shown in the paper tray 14 is mainly used because of the ease of paper supply and the like.

In the front loading method, the sheets 1 stored in the sheet trays 13 to 16 are fed in order from the upper side, with the right end being the leading end in the sheet feeding direction. Correspondingly, a vertical transport path for transporting the paper 1 to the upper image forming unit is provided on the right side in the apparatus main body 12, and the paper is fed from the paper trays 13 to 16. The fed sheet 1 is introduced into a transport path on the apparatus body 12 side by a pair of transport rollers.

In such an image forming apparatus,
With reference to FIG.
At the time of taking out the uppermost sheet 1 indicated by a, the next sheet 1 indicated by reference numeral 1b may be rubbed, and the leading end may fly out of the sheet tray 2. For example, as shown by reference numerals 1a and 1c, the amount of protrusion varies, and the next sheet 1 is synchronized with the image forming timing.
Even when the removal of the image is started, the timing of reaching the image forming unit varies, and a problem occurs that a formed image is lost. In addition, there is a problem that the sheet conveyance distance from the sheet tray 2 to the image forming unit is long, and the time from when the sheet 1 is fed to when the image is formed is long.

A typical prior art for solving these problems is disclosed in, for example, JP-A-3-95043.
In the publication, the pickup roller 3 preliminarily takes out the paper 1 from the paper tray 2 and uses a paper detection sensor or the like provided in a conveyance path in the paper feeding device to reserve the paper 1 on standby during the conveyance. By performing paper feeding, variation in the leading end position of the paper 1 is suppressed, and the paper feeding time is shortened.

[0006]

In the above-mentioned prior art,
When the paper 1 is made to stand by in the conveyance path in the paper feeding device, the paper 1 taken out by the pickup roller 3
Is held in a state of being held between a pair of paper feed rollers 4 and 5 located forward in the transport direction in the paper feeder. For this reason, even if the biting force between the paper feed rollers 4 and 5 is small, when the paper tray 2 is pulled out for additional supply of the paper 1 into the paper tray 2 or the like, the paper 1 that has been preliminarily fed is
There is a problem that wrinkles and breakage occur on the image, making it unusable for image formation.

Here, Japanese Patent Application Laid-Open No. 11-227964 discloses that the leading end position of the sheet 1 by the preliminary sheet feeding is stopped between the sheet feeding rollers 4 and 5 and the conveying roller, so that the sheet tray 2 Although it is shown that the leading end of the sheet 1 does not interfere with the main body frame indicated by reference numeral 17 in FIG.
Is sandwiched between the feed rollers 4 and 5, and it is clear that the same problem as described above occurs.

An object of the present invention is to provide a paper feeder capable of reliably preventing wrinkles and breakage of the paper 1 when performing preliminary paper feed.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a sheet feeding apparatus according to the present invention is designed to sequentially take out and supply sheet-like sheets stacked and stored in a detachable sheet tray. At the time of feeding a sheet, in a sheet feeding device configured to perform preliminary sheet feeding in which the next sheet is conveyed and kept on standby until the leading end thereof reaches a predetermined position downstream in the conveying direction, the predetermined position is set as It is set immediately before the nip portion of the first pair of paper feed rollers.

[0010] According to the above configuration, in performing the preliminary sheet feeding for suppressing the variation in the position of the leading edge of the sheet and shortening the sheet feeding time, the next sheet is fed by the first pair of sheet feeding rollers. Stop and wait just before the nip.

Therefore, the next sheet waiting is not caught between the first pair of paper feed rollers.
Even if the paper tray is pulled out, the next sheet in the waiting state is not wrinkled or damaged, and it is possible to reliably prevent a problem that the next sheet cannot be used for image formation. it can.

Further, in the paper feeding apparatus of the present invention, in order to solve the above-mentioned problems, the first pair of paper feeding rollers includes a driving roller that contacts the upper surface of the paper and conveys the paper, and a driving roller that contacts the lower surface of the paper. It is characterized in that it is constituted by a separating roller which is in contact with and rotates following the predetermined rotational torque.

According to the above construction, even if the front end of the next sheet is rubbed against the rear end of the previous sheet and is to be caught between the first pair of paper feed rollers, the conveyance of the next sheet is performed. The torque is only due to the slight friction torque rubbed against the previous sheet, the separating roller cannot be rotated, and the next sheet is caught in the nip portion of the first pair of sheet feeding rollers. I will wait just before

Therefore, the present invention can be reliably stopped just before the nip portion of the first pair of paper feed rollers without double feed of the next paper without complicated paper position detection and control.

Further, in order to solve the above-mentioned problems, in the paper feeder of the present invention, a pickup roller sequentially takes out sheet-like paper stacked and stored in a detachable paper tray, and further passes through the paper feed roller. In the paper feeding device, when the previous paper is supplied, the next paper is conveyed and kept in a standby state until the leading end thereof reaches a predetermined position downstream in the conveyance direction. Of the paper feed rollers, the first pair of paper feed rollers is
A drive roller that contacts the upper surface of the sheet and conveys the sheet, and a separating roller that contacts the lower surface of the sheet and rotates by a rotation torque equal to or more than a predetermined rotational torque, and moves the pickup roller toward and away from the sheet, and drives the pickup roller. The operation control means for controlling the connection and disconnection of the driving force from the source to the pickup roller and the paper feed roller comprises: once bringing the pickup roller into and out of contact with the paper to take out the previous paper; The pickup roller is brought into contact with the rear end side of the sheet for a predetermined time again to take out the next sheet.

According to the above configuration, even if the leading edge of the next sheet is rubbed against the trailing edge of the previous sheet and bites between the first pair of sheet feeding rollers, the next sheet is rolled by the separating roller. The paper is on standby just before being caught in the nip portion of the first pair of paper feed rollers. Utilizing this, the operation control means causes the pickup roller to once come into contact with and separate from the sheet so that the previous sheet is ejected, and then contacts the rear end side of the preceding sheet again for a predetermined time. As a result, the frictional force between the previous sheet and the next sheet increases, and the leading end of the next sheet can be fed between the first pair of sheet feed rollers.

Therefore, even if there is a variation in the amount of the next sheet ejected from the sheet tray when the pickup roller is once brought into contact with or separated from the sheet, the predetermined time is set to a sufficient length. Thus, the next sheet can be reliably stopped immediately before the nip portion of the first pair of sheet feeding rollers. Thus, complicated paper position detection and control can be eliminated.

Further, in the paper feeding apparatus of the present invention, in order to solve the above-mentioned problem, the operation control means is configured to use a paper leading edge detection signal from a paper detecting means provided on a downstream side in a paper conveying direction as a reference. It is characterized by controlling each unit.

According to the above configuration, the pickup roller is brought into and out of contact with the sheet, and the timing of connection and disconnection of the driving force from the driving source to the pickup roller and the sheet supply roller is fed and conveyed. By controlling based on the leading edge detection signal of the paper, it is possible to control the paper at a certain timing even if there is unevenness or slippage of the paper, and to stop the next paper just before the pair of paper feed rollers. Can be put on standby.

In order to solve the above-mentioned problems, the sheet feeding apparatus of the present invention sequentially takes out sheet-like sheets stacked and stored in a detachable sheet tray and supplies the sheets via a sheet feeding roller. At the time of feeding a sheet, in a sheet feeding device configured to perform a preliminary sheet feeding in which the next sheet is conveyed and kept waiting until the leading end thereof reaches a predetermined position downstream in the conveying direction, the predetermined position is initially set to The pre-nip sheet detecting means for detecting the leading end of the next sheet is set at the predetermined preliminary sheet feeding position which is set immediately before the nip portion of the pair of sheet feeding rollers.

According to the above arrangement, by providing the pre-nip paper detecting means at the predetermined preliminary paper feeding position, the pre-nip paper detecting means detects the leading edge of the next paper and moves to the predetermined preliminary paper feeding position. Sheets can be made to wait.

Therefore, the next sheet that has been pre-fed is
The paper does not go too far downstream in the transport direction from the predetermined preliminary paper feed position, and always stops at the predetermined preliminary paper feed position for the next paper, that is, immediately before the nip portion of the first pair of paper feed rollers.

As a result, even when the paper tray is pulled out, the next waiting paper is not bitten by the paper feed roller. For this reason, the trouble that the next sheet becomes wrinkled or damaged and cannot be used for the next image formation does not occur. Further, since the next sheet is always kept on standby immediately before the sheet feeding roller, quick sheet feeding can be performed.

Further, in order to solve the above-mentioned problems, in the paper feeder of the present invention, a pickup roller sequentially takes out sheet-like paper stacked and stored in a detachable paper tray, and further passes through the paper feed roller. In feeding, when feeding a previous sheet, in a sheet feeding device that performs a preliminary sheet feeding in which the next sheet is conveyed and held until the leading end thereof reaches a predetermined position downstream in the conveying direction, Operation control means for controlling the contact of the pickup roller with the paper and the transmission of driving force from the drive source to the pickup roller and the paper feed roller are provided, and the operation control means is arranged at a predetermined preliminary paper feed position. A sheet detection signal of the pre-nip sheet detecting means for detecting the leading edge of the next sheet,
The control is performed based on a sheet detection signal of a sheet detection unit of a conveyance unit provided in a sheet conveyance direction downstream of the sheet feeding roller.

According to the above arrangement, for example, when the leading end of the previous sheet is detected by the sheet detecting means in the conveying section, the pickup roller separates from the previous sheet being conveyed.
Next, at the timing when the trailing edge of the previous sheet passes through the pickup roller, the pickup roller is brought into direct contact with the next sheet. Further, when the leading edge of the next sheet is detected by the pre-nip sheet detecting means, the pickup roller separates from the next sheet, and the pickup roller and the sheet feeding roller stop.

Therefore, the transmission of the power of the drive motor,
The interruption and the contact / separation between the pickup roller and the sheet can be controlled at a reliable timing by a leading edge detection signal of the sheet being fed and conveyed.

Therefore, even if there is uneven conveyance or slippage of the sheet, the next sheet can be reliably stopped at a predetermined preliminary sheet feeding position, that is, immediately before the nip portion of the first pair of sheet feeding rollers, and made to stand by. It becomes possible. Further, since the first pair of paper feed rollers are completely stopped, the next sheet is not bitten by the paper feed rollers.

Further, in order to solve the above-mentioned problem, the paper feeding apparatus of the present invention is provided with a clutch means for connecting and disconnecting the driving force in a transmission path of the driving force from the driving source to the paper feeding roller and the pickup roller. In addition, the clutch means is capable of disconnecting the driving force from the drive source to the paper feed roller and the pickup roller when the pre-nip paper detection means detects the leading edge of the next paper.

According to the above configuration, the leading edge of the next sheet is
When the sheet reaches a position before the nip of the first pair of paper feed rollers, the driving force from the driving source to the paper feed roller and the pickup roller is cut off by the clutch means in accordance with the paper detection signal from the paper detection means before the nip.

Therefore, even if a slip occurs in the pickup roller, the clutch means is connected to the driving force from the driving source unless the leading end of the next sheet is detected by the pre-nip sheet detecting means. The sheet is reliably conveyed to a predetermined preliminary sheet feeding position. Therefore, there is no possibility that the next sheet stops short of the predetermined preliminary sheet feeding position and the feeding is insufficient. In particular, when the apparatus is used for a long period of time, the frequency of slippage of the pickup roller increases due to the adhesion of paper dust generated from the paper feeder, but even in such a case, it is possible to surely perform the original preliminary paper feeding. Thus, variations in the position of the leading edge of the sheet can be suppressed.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a cross-sectional view showing the overall configuration of a digital multifunction peripheral 30 equipped with a paper feeder 33 according to the embodiment. The digital MFP 30 can perform a copy operation, a printer operation, and a facsimile operation, and generally includes a scanner unit 31, an image forming unit 32, and a sheet feeding device 3.
3 and a post-processing device 34.

The scanner unit 31 is provided as an image input device in the digital multifunction peripheral 30 for reading a document image. In addition to the document table 35 made of transparent glass, a double-sided automatic document feeder (Recirculatin) is provided.
g Automatic Document Feeder (hereinafter abbreviated as RADF) 36 and a scanner unit 40. The scanner unit 31 sequentially reads an image from a document placed on the document table 35 one by one.

The RADF 36 conveys the documents set on the document tray 37 one by one to the document table 35. Then, after the document image is read by the scanner unit 40, the scanner unit 40 has a function of carrying the document image to a predetermined take-out position. The RADF 36 can also turn over the original after reading the original image by the scanner unit 40 and transport the original to the original mounting table 35 again.

The scanner unit 40 is configured as a document image reading unit that reads an image of a document conveyed to the document table 35 in units of scanning lines. The scanner unit 40 includes a first scanning unit 41 and a second scanning unit 41.
Scanning unit 42, optical lens 43 and CCD 44
have. The first scanning unit 41 exposes a document while moving at a constant speed V from left to right in FIG. 1 along the document table 35. Then, as shown in FIG. 1, a lamp reflector assembly 41a for irradiating light and a reflected light from the original
2 and a first reflection mirror 41b leading to the second reflection mirror 41b. Second
The scanning unit 42 moves at a speed of V / 2 following the first scanning unit 41. The second scanning unit 42 has second and third reflection mirrors 42 a and 4 for guiding the light from the first reflection mirror 41 b toward the optical lens 43 and the CCD 44.
2b. The optical lens 43 forms an image on the CCD 44 of the reflected light from the third reflecting mirror 42b. The CCD 44 converts the light imaged by the optical lens 43 into an electric signal.

The image forming section 32 is for forming an image on a sheet of paper based on image data, and includes a laser writing unit (LSU) 46, an electrophotographic processing section 47, a fixing device 49, and a paper feeder. An apparatus 33 is provided. The LSU 46 applies a signal to the photosensitive drum 48 of the electrophotographic process unit 47 based on image data read by the scanner unit 31 and image data externally input via a communication interface 65 shown in FIG. The laser beam is irradiated to form an electrostatic latent image on the photosensitive drum 48, and includes a semiconductor laser light source, a polygon mirror that deflects the laser light at a constant angular velocity, and an f-θ lens.

The electrophotographic process section 47 includes a photosensitive drum 48, and a charger, a developing device, a transfer device, a peeling device, a cleaning device, and a static eliminator provided around the photosensitive drum 48. ing. Then, the electrostatic latent image on the photosensitive drum 48 formed by the LSU 46 is developed to generate a toner image, which is electrostatically transferred to a sheet.

The paper feeder 33 supplies paper to the electrophotographic process section 47, and includes a transport path 50, paper trays 51, 52, 53, a manual paper feeder 54, a resupply path 56, and a duplex copying unit. 55.

The transport path 50 is provided in the electrophotographic processing section 4.
7, for transporting the paper from the paper trays 51 to 53, the manual paper feeder 54, or the re-supply path 56. The paper trays 51 to 53
Transfer paper is stored in a stacked state. The manual sheet feeding device 54 is a device for supplying sheets of an arbitrary size loaded by a user to the transport path 50. The resupply path 56 and the duplex copying unit 55 are for resupplying the sheet to the transport path 50 in order to form an image on the back side of the sheet after fixing the toner image.

The post-processing device 34 has a multi-stage paper discharge tray 38, performs post-processing such as stapling on the paper discharged from the paper discharge rollers 57, and discharges the paper to an arbitrary stage in an arbitrary order. Things.

FIG. 2 is a block diagram showing the electrical configuration of the digital multifunction peripheral 30 described above. An analog electric signal obtained by the CCD 44 is input to an image data input unit 6.
1 converts the image data into digital signal image data. This image data is stored in the memory 63 and the hard disk device 64 after being subjected to various types of image processing in the image processing unit 62, and is output to the LSU 46 in accordance with an output instruction of the central processing unit 60 described later. You.

In connection with the central processing unit 60 realized by a microcomputer or the like, an operation board unit 66 having an LCD, various operation keys, and the like is connected as a user interface. Central processing unit 60
Responds to the output of the user interface and various sensors in response to the load 67 related to the RADF 36, the load 68 related to the sheet feeding device 33, the load 69 related to the post-processing device 34, and the relationship related to the image forming unit 32. And the load 71 related to the scanner unit 31 are controlled.

FIGS. 3 and 4 are cross-sectional views for explaining the configuration of the sheet feeding device 33 of the present embodiment. This configuration is common to the drawer-type trays 51 to 53 as shown in FIG. 1 (see FIG. 8), and the paper tray 51 will be described as an example in FIGS. 3 and 4 show a standby state, FIG. 3 shows a state in which the paper tray 51 has been mounted after the supply of the paper 81 has been completed, and FIG. 4 shows a preliminary paper feed after image formation has been performed. Indicates a waiting state.

Near the end of the paper tray 51 on the downstream side in the transport direction of the paper 81, the ON / OFF of the paper feed solenoid 82 is set.
A pickup roller 83 that is displaced in contact with / separates from the sheet 81 by the OFF operation faces. The paper 81 picked up by the pickup roller 83 is introduced into the transport path 50 by a drive roller 84 and a separation roller 85, which are a pair of first paper feed rollers, and is nipped and transported by a pair of transport rollers 86 and 87. The sheet is conveyed to the image forming section 32. In the transport path 50, transport rollers 86
Immediately after 87, a transport paper sensor 88 that outputs a leading edge detection signal of the paper is provided as transport paper detection means.

The driving roller 84 comes into contact with the upper surface of the paper 81, and the separating roller 85 comes into contact with the lower surface of the paper 81 and is driven to rotate at a predetermined rotational torque or more. For this reason,
In the separating roller 85, a torque limiter 89 for preventing the rotation of the separating roller 85 up to the predetermined rotation torque is provided. The rollers 83, 84, 86 are driven to rotate by the driving force from the driving motor 90.

From the drive motor 90 to the transport roller 86
In the power transmission path from the drive motor 90 to the drive roller 84 and the pickup roller 83, a power transmission path to the power transmission path up to and including the transport clutch 91 is further provided with a paper feed clutch 92. . When the transport clutch 91 is turned on while the drive motor 90 is rotating, the transport roller 86 rotates, and the transport clutch 91 and the paper feed clutch 92
When N, the drive roller 84 and the pickup roller 83 rotate.

FIGS. 5A to 5G are cross-sectional views for explaining the operation of the sheet feeding device 33 of the present embodiment.
(A)-(f) is the timing chart. 5A to 5G, the state in which the rollers 83 and 84 are being rotationally driven by the driving force from the driving motor 90 is indicated by solid-line arrows indicating the direction of rotation. The state of being driven and rotated by the driving force due to the friction with the paper 81 is indicated by a dashed arrow indicating the rotation direction, and the state without the arrow is indicated by rollers 83 to 8.
5 indicates that it is stopped.

As shown in FIG. 6A, when a start signal of the paper feeding operation is generated at time t1, in response to the start signal, the drive motor 90 is driven as shown in FIG. 6B.
Is turned on, the paper feed solenoid 82 is turned on as shown in FIG. 6 (c), the paper feed clutch 92 is turned on as shown in FIG. 6 (d), and as shown in FIG. 6 (e), The transfer clutch 91 is turned on. As a result, as shown in FIG. 5A, the pickup roller 83 comes into contact with the upper surface of the sheet 81, and the sheet 81 is conveyed to the rollers 84 and 85.

As shown in FIG. 5 (b), the paper 81 is bitten into the nip between the rollers 84 and 85, is conveyed by the rollers 84 and 85, and the leading end thereof is shown in FIGS. When the sheet passes through the conveying rollers 86 and 87, as shown at time t2 in FIG. 6F, the passage of the leading end of the sheet 81 is detected by the sheet sensor 88 of the conveying section. At this time t2, the paper supply solenoid 82 is turned off as shown in FIG. 6C, and the pickup roller 83 separates from the upper surface of the paper 81 as shown in FIG. Further, at time t3 when a time W1 corresponding to the length of the sheet 81 in the transport direction elapses from the time t2, at time t3 in FIG.
As shown in (d), the paper feed clutch 92 is turned off. The time W1 is the time from the passing time t2 of the paper sensor 88 to the time when the rear end of the paper 81 is left by about 30 mm from the rollers 84 and 85 in order to prevent double feeding of the next paper 81a. The length is set in accordance with the length of the paper 81 in the transport direction that is detected in advance in accordance with the selection of 51 to 53 or the like.

It should be noted that, in the present embodiment, as shown in FIG. 6C, the sheet feeding solenoid extends from time t4 before time t3 to time t5 after time t3. 82 is turned on again. Therefore, between time t4 and time t3, as shown in FIG. 5D, the rotationally driven pickup roller 83 comes into contact with the upper surface of the paper 81 again, and the leading edge of the next paper 81a is ejected from the paper tray 51. Let it. When the paper feed clutch 92 is turned off at the time t3, as shown in FIG.
The rollers 83 and 84 are driven to rotate. After that, even if the leading edge of the next sheet 81a reaches between the rollers 84, 85, it stands by without being caught between the rollers 84, 85 by the action of the separating roller 85 described above.

The trailing end of the paper 81 is a pickup roller 83
As shown in FIG. 5F, the pickup roller 83 comes into contact with the upper surface of the next sheet 81a, and the drive roller 84 continues to rotate by the frictional force of the previous sheet 81, thereby causing the pickup roller 83 to rotate. The roller 83 is also driven to rotate. Further, the separating roller 85 is stopped after the leading end of the next sheet 81a reaches as described above.

Thus, the rear end of the previous sheet 81 is
As shown in FIG. 5 (g), the rollers 83 to 85 immediately stop after passing between 4.85. At this time, at time t5, the paper feed solenoid 82 is turned off, and the pickup roller 83 is separated from the upper surface of the next sheet 81a. Therefore, the next sheet 81a is not pushed out, and the next sheet 81a is not pushed out.
5A is returned to the state shown in FIG. In the case where the image formation is continuously performed on the next sheet 81a in the continuous processing, at time t6 when a predetermined time has elapsed from time t5.
Again, the feed solenoid 82 and the feed clutch 92
N, the next sheet 81a is started to be taken out, and the same operation is repeated thereafter.

As described above, the sheet feeding device 3 of the present embodiment
3, a pickup roller 83 sequentially takes out the papers 81 stored in the removable trays 51 to 53,
Further, when the paper is supplied via the rollers 84, 85, 86, and 87, the position of the preliminary sheet feeding is set to the first pair of rollers 84.
The next sheet 8 waiting just before the nip portion 85
1a is prevented from being caught between the rollers 84 and 85. Therefore, even if the trays 51 to 53 are pulled out, the next sheet 81a in the waiting state does not wrinkle or break. It is possible to reliably prevent a problem that the next sheet 81a cannot be used for image formation.

The first pair of rollers 84 and 85
Are a driving roller 84 that contacts the upper surface of the sheet 81 and conveys the sheet 81, and a separating roller 85 that contacts the lower surface of the sheet 81 and is driven to rotate at a predetermined rotation torque or more. Even if the edge of the next sheet 81a is rubbed by the edge and the leading edge of the next sheet 81a is caught between the rollers 84 and 85, the conveyance torque of the next sheet 81a is slightly increased due to the friction of the previous sheet 81. Due to only the torque, the separating roller 85 cannot be rotated, and the next sheet 81a waits just before being bitten by the nip portion of the first pair of rollers 84 and 85.

Therefore, once the pickup roller 83
Even if there is a variation in the amount of the next paper 81a ejected from the paper trays 51 to 53 at the time when the paper roller 81 is brought into contact with or separated from the paper 81, the pickup roller 83 is again moved to the paper 8 for a predetermined time.
By simply contacting the trailing edge of the first sheet 81, the next sheet 81a can be reliably stopped immediately before the nip portion of the rollers 84 and 85 without double feeding, and complicated sheet position detection and control are not required. be able to.

Further, the contact of the pickup roller 83 with the paper 81 is determined based on the detection signal of the leading end of the paper 81 being conveyed from the paper sensor 88 provided on the downstream side in the paper conveyance direction. In addition, since the timing of connection and disconnection of the driving force from the driving motor 90 to the pickup roller 83 and the driving roller 84 is controlled, even if there is uneven conveyance or slippage of the paper 81, it can be controlled with reliable timing. In addition, the next sheet 81a can be reliably stopped just before the pair of rollers 84 and 85 and kept in a standby state.

Second Embodiment Another embodiment of the present invention will be described below with reference to FIGS. For convenience of explanation, members having the same functions as those in the first embodiment are given the same member numbers, and their explanations are omitted.

In the paper feeder according to the first embodiment,
As shown in FIGS. 5A to 5G, preliminary paper feeding can be performed without nipping the next paper 81a between a pair of paper feeding rollers 84 and 85 located in front of the tray in the paper feeding direction. it can. Specifically, after the contact between the pickup roller 83 and the paper 81 is released in one paper supply cycle, the pickup roller 83 is brought into contact with the rear end of the paper 81 again. As a result, the transport roller 86 downstream of the paper feeding unit
The next sheet 81a is conveyed to a predetermined preliminary sheet feeding position and stopped by the frictional force of the contact portion between the back side of the sheet 81 and the surface of the next sheet 81a being pulled by 87. As a result, the next sheet 81a is fed to the pair of sheet feeding rollers 84
85 does not bite.

That is, the preliminary sheet feeding force by the above means depends on the frictional force of the contact portion between the back surface of the sheet 81 and the front surface of the next sheet 81a. Therefore, when slippage occurs in the pickup roller 83, sufficient frictional force is not generated in the contact portion, and the next sheet 81a may not be transported to a predetermined preliminary sheet feeding position.

In addition, in consideration of long-term use of the apparatus, the frequency of slippage generated on the pickup roller 83 due to the adhesion of paper dust generated from the paper sheet may increase. Therefore, if the device is used for a long time,
In some cases, the original intended preliminary sheet feeding cannot be performed reliably, and the effect of suppressing variations in the sheet leading edge position may be insufficient.

Therefore, in this embodiment, the paper 8
A sheet feeding device that can prevent wrinkles and breakage of the sheet feeding device 1 and reliably perform preliminary sheet feeding without being affected by slip of the pickup roller 83 will be described below. Although the sheet feeder of the present embodiment is configured in common with the drawer-type trays 51 to 53 and 55 as shown in FIG. 1, the sheet tray 51 will be described here as an example.

In the paper feeder 33, as shown in FIGS. 1, 9 and 10, the paper 81
The pickup roller 83 faces near the end on the downstream side in the transport direction of the pickup roller 83. The paper 81 picked up by the pickup roller 83 is introduced into the transport path 50 by a pair of paper feed rollers 84 and 85, and is introduced into a pair of transport rollers 86 and 85.
The paper is conveyed to the image forming section 32 by the squeeze 87. Here, the feed roller 84 is a driving roller, and the feed roller 85 is a separating roller. Further, the transfer path 50
In the figure, immediately after the transport rollers 86 and 87, a transport section paper sensor 88 as a transport section paper detecting means is provided. Further, a torque limiter 89 is provided in the paper feed roller 85. Further, the pickup roller 83, the paper feed roller 84, and the transport roller 86 are driven to rotate by a driving force from a driving motor 90.
In addition, in the present embodiment, the paper feed rollers 84.8
A pre-nip paper sensor 93 as a pre-nip paper detection unit is disposed at a preliminary paper feed standby position set immediately before the nip portion of No. 5. The pre-nip paper sensor 93 outputs a leading edge detection signal of the paper.

A power transmission path from the drive motor 90 to the transport roller 86 is provided with a transport clutch 91, and a power transmission path from the drive motor 90 to the paper feed roller 84 and the pickup roller 83 is The transport clutch 91 and the paper feed clutch 92 are interposed.

As shown in FIG. 9, when the paper tray 51 is mounted after the paper 81 is replenished, the leading ends of the paper 81 are all aligned. Here, when copying is started, the drive motor 90 is turned on, and when the transport clutch 91 is turned on, the transport roller 86 is driven. When the paper feed clutch 92 is turned on in this state, the paper feed roller 84 and the pickup roller 83 are driven. Further, when the paper supply solenoid 82 is turned on, the pickup roller 83 comes into contact with the surface of the paper 81, and the paper 81 is transported to the paper transport roller side one by one.

The operation of the sheet feeding device 33 having the above configuration will be described.
A description will be given based on the timing charts of FIGS. 11 (a) to 11 (f) and FIGS. 12 (a) to 12 (g). Note that FIG.
In (a) to (f), the pickup roller 83,
The state in which the sheet feeding roller 84 is driven to rotate by the driving force from the driving motor 90 is indicated by a solid line arrow indicating the rotation direction. Also, the state in which the pickup roller 83 and the paper feed rollers 84 and 85 are driven and rotated by the driving force due to the friction with the paper 81 is indicated by a dashed arrow indicating the direction of rotation, and the state in which no arrow is indicated is shown. This means that the pickup roller 83 and the paper feed rollers 84 and 85 are stopped.

First, as shown in FIGS. 12 (a) to 12 (g), when a start signal of the sheet feeding operation is generated at time t1, the driving motor 90,
The paper supply solenoid 82, the paper supply clutch 92, and the transport clutch 91 are turned on. As a result, FIG.
7, the pickup roller 83 comes into contact with the upper surface of the paper 81, and the paper 81 is conveyed to the paper feed rollers 84 and 85.

Next, as shown in FIG. 11B, the paper 81 is caught in the nip between the paper feed rollers 84 and 85. As a result, the paper 81 is nip-pressed and conveyed by the paper feed rollers 84 and 85.

Here, if two or more sheets of paper 81 try to bite into the feed rollers 84 and 85 at the same time,
Since the torque limiter 89 is mounted on the feed roller 5, the load on the paper feed roller 85 increases, and the paper feed roller 85 stops. Therefore, even if the next sheet 81a is taken by the sheet 81 and conveyed to the sheet feeding rollers 84 and 85, two or more sheets 81 are collectively
・ It is not sent to 85.

Further, the leading end of the paper 81 passes through the conveying rollers 86 and 87 shown in FIGS. 9 and 10. Then, the passage of the leading end of the paper 81 is detected by the paper sensor 88 of the transport unit. At this time, as shown in FIG. 12F, at time t2, the paper sensor 88 of the transport unit is turned on. Accordingly, as shown in FIG.
At time t2, the paper supply solenoid 82 is turned off.
Therefore, as shown in FIG. 11C, the pickup roller 83 separates from the upper surface of the paper 81.

Further, at time t3 when the time W1 corresponding to the length of the sheet 81 in the transport direction before time t2 elapses, the paper supply solenoid 82 is turned on as shown in FIG. That is, the time W1 is a time until the rear end of the paper 81 passes the position of the pickup roller 83, and corresponds to the length of the paper 81 in the transport direction detected in advance in response to selection of the paper trays 51 to 53, and the like. Is set. Therefore, as shown in FIG. 11D, the pickup roller 83 contacts the upper surface of the next sheet 81a after the rear end of the sheet 81 has passed, and conveys the next sheet 81a to the sheet feeding rollers 84 and 85. I do.

Further, when the pre-nip paper sensor 93 detects the leading edge of the next paper 81a, the paper supply solenoid 82 and the paper supply clutch 92 are turned off at the timing of t4.
That is, the pickup roller 83 and the paper feed roller 8
4 stops, and the conveyance of the sheet 81 is stopped.

At this time, the next sheet 81a is stopped immediately before the nip portion between the sheet feeding rollers 84 and 85 as shown in FIG. 10 or 11 (f).

If the next sheet 81a is fed along with the sheet 81, as shown in FIG.
If the paper has been fed up to just before the nip portion 85, the pre-nip paper sensor 93 detects that there is an excess paper. That is, if the pre-nip paper sensor 93 does not detect the front end of the next paper 81a at the timing when the rear end of the paper 81 passes the pre-nip paper sensor 93, the paper feed solenoid 82
Is turned off, and the pickup roller 83 is separated from the upper surface of the paper 81.

Therefore, the next sheet 81a is directly conveyed by the pickup roller 83 to a position immediately before the nip portion between the sheet feeding rollers 84 and 85, so that even if a slip occurs between the sheet 81 and the pickup roller 83, it is not affected. Is reliably transported to a predetermined preliminary sheet feeding position. That is,
Since the feed amount of the pickup roller 83 for performing the preliminary sheet feeding of the next sheet 81a does not depend on the frictional force of the sheet 81 to be pulled, even if the slip occurs, the sheet is reliably transported to a predetermined preliminary sheet feeding position without being affected. Is done.

On the other hand, the pre-nip paper sensor 93 detects the leading edge of the next paper 81a and
By controlling the above operation, the next sheet 81a can be reliably stopped at the predetermined preliminary sheet feeding position.

As a result, it is possible to suppress variations in the leading edge position of the next sheet 81a and to reliably perform preliminary sheet feeding. Moreover, if the device is used for a long time,
Although the pickup roller 83 may slip due to the adhesion of the paper dust, the effect of suppressing the variation in the leading edge position of the next sheet 81a can be sufficiently maintained.

Also, even when the paper tray 51 is pulled out, the next paper 81a waiting is not bitten by the paper feed rollers 84 and 85. Troubles that will not be used will not occur. Further, immediately before the paper feed rollers 84 and 85, the next paper 8
Since the printer 1a is always on standby, it is possible to perform quick paper feeding.

In this way, as shown in FIG. 11 (f), when the paper 81 has passed the paper feed rollers 84 and 85, the next paper 81a always stands by at the position immediately before the nip portion of the paper feed rollers 84 and 85. ing. That is, the next sheet 81
“a” is conveyed to the paper feed rollers 84 and 85 by the pickup roller 83 without time delay at the next paper feed timing.

Thereafter, by repeating the same operation,
Since the position of the leading edge of the preliminary paper feed is stable and the paper interval is constant, the variation between the paper tray 51 and the paper feed rollers 84 and 85 is absorbed, and the job speed can be increased accordingly. Further, after the paper tray 51 is mounted, the first copy can be shortened.

As described above, the sheet feeding device 3 of the present embodiment
Reference numeral 3 denotes a pre-nip paper sensor 9 at a predetermined preliminary paper feed position.
By providing 3, the pre-nip paper sensor 93 can detect the leading edge of the next paper 81a and make the next paper 81a stand by at a predetermined preliminary paper feed position.

Therefore, the next sheet 81 that has been
a does not go too far downstream in the conveying direction from the predetermined preliminary paper feed position, and always keeps the next paper 81a in the predetermined preliminary paper feed position, that is, the first pair of paper feed rollers 84.
Stops just before the 85 nip.

As a result, even when the sheet tray 51 is pulled out, the next sheet 81a on standby is not bitten by the sheet feeding rollers 84 and 85. For this reason, the trouble that the next sheet 81a becomes wrinkled or damaged and cannot be used for the next image formation does not occur. Further, since the next sheet 81a is always on standby immediately before the sheet feeding rollers 84 and 85, quick sheet feeding can be performed.

In the paper feeding device 33 of the present embodiment,
When the leading edge of the previous sheet 81 is detected by the sheet sensor 88 of the conveyance unit, the pickup roller 83 separates from the previous sheet 81 being conveyed. Next, at the timing when the rear end of the previous sheet 81 passes through the pickup roller 83, the pickup roller 83 is brought into direct contact with the next sheet 81a. Further, when the leading end of the next sheet 81a is detected by the pre-nip sheet sensor 93, the pickup roller 83
Is separated from the next sheet 81a, and the pickup roller 83 and the sheet feeding roller 84 stop. Therefore, the transmission and cutoff of the power of the drive motor 90 and the contact / separation between the pickup roller 83 and the sheet 81 or the next sheet 81a can be controlled at a reliable timing by the leading edge detection signal of the sheet being conveyed.

Therefore, even if there is unevenness in conveyance or slippage of the sheet 81, the next sheet 81a is reliably stopped at a predetermined preliminary sheet feeding position, that is, immediately before the nip portion between the first pair of sheet feeding rollers 84 and 85. It can be made to wait. Further, since the first pair of paper feed rollers 84 and 85 are also completely stopped, the next paper 81a is not bitten by the paper feed rollers 84 and 85.

Further, in the paper feeding device 33 of this embodiment, when the leading end of the next paper 81a reaches the nip between the first pair of paper feeding rollers 84 and 85, the paper detection from the paper sensor 93 before nip is performed. At the signal, the paper feed clutch 92
From the driving source, the sheet feeding roller 84 and the pickup roller 8
The driving force to 3 is cut off.

Therefore, even if a slip occurs in the pickup roller 83, unless the leading edge of the next sheet 81a is detected by the pre-nip sheet sensor 93, the sheet feeding clutch 92 is connected to the driving force from the driving source. So
The next sheet 81a is reliably conveyed to a predetermined preliminary sheet feeding position. Therefore, the next sheet 81a stops just before the predetermined preliminary sheet feeding position, and there is no shortage of feeding.
In particular, when the apparatus is used for a long period of time, the frequency of slipping of the pickup roller 83 increases due to the adhesion of paper dust generated from the paper feeding apparatus 33, but even in such a case, the original purpose of the preliminary paper feeding is surely performed. Therefore, it is possible to suppress variations in the position of the leading end of the sheet.

[0087]

As described above, the sheet feeding apparatus of the present invention takes out sheet-like sheets stacked and stored in a detachable sheet tray to suppress variations in the position of the leading end of the sheet and to shorten the sheet feeding time. In performing the preliminary paper feed for realizing the above, the leading edge of the next paper is stopped immediately before the nip portion of the first pair of paper feed rollers so that the next paper is not caught between the pair of paper feed rollers. Configuration.

Therefore, even if the paper tray is pulled out,
There is no wrinkling or breakage of the next sheet in the waiting state, and the effect that the next sheet cannot be used for image formation can be reliably prevented.

Further, as described above, in the paper feeding apparatus of the present invention, the first pair of paper feeding rollers are brought into contact with the driving roller for transporting the paper in contact with the upper surface of the paper and in contact with the lower surface of the paper. A separation roller that is driven and rotated with a rotation torque equal to or greater than a predetermined rotation torque, and even if the front end of the next sheet is rubbed against the rear end of the previous sheet and tries to be caught between the first pair of sheet feeding rollers, This is a configuration in which the separation roller prevents the separation.

Therefore, the present invention has the advantage that the stoppage can be reliably stopped immediately before the nip portion of the first pair of paper feed rollers without double feed of the next paper without complicated paper position detection and control. Play.

Further, as described above, the sheet feeding device of the present invention takes out sheet-like sheets stacked and stored in a detachable sheet tray to suppress variations in the position of the sheet leading end and to shorten the sheet feeding time. When performing the preliminary paper feed, the first pair of paper feed rollers are driven by a driving roller that contacts the upper surface of the paper and conveys the paper, and is driven by a rotation torque equal to or greater than a predetermined rotation torque by contacting the lower surface of the paper. The separation roller prevents the front end of the next sheet from being caught between the first pair of paper supply rollers by being rubbed against the rear end of the previous sheet. Utilizing this, once the pickup roller is brought into contact with and separated from the sheet to take out the previous sheet, the pickup roller is again brought into contact with the rear end side of the previous sheet for a predetermined time, and the next sheet Take out Done so, immediately before the nip portion of the pair of the paper feed roller tip of outermost first next sheet, which is configured to wait without being caught.

Therefore, even if there is a variation in the amount of the next sheet ejected from the sheet tray when the pickup roller is once brought into contact with or separated from the sheet, the predetermined time should be set to a sufficient length. Thus, the next sheet can be reliably stopped immediately before the nip portion of the first pair of sheet feed rollers, and the effect of eliminating complicated sheet position detection and control can be achieved.

Further, as described above, the sheet feeding apparatus of the present invention is configured to control each unit based on the leading edge detection signal of the sheet from the sheet detecting means provided at the downstream of the sheet conveying direction. is there.

Therefore, even if there is unevenness in conveyance or slippage of the sheet, it can be controlled at a certain timing, and the next sheet can be stopped and stopped just before the pair of sheet feeding rollers. It works.

As described above, the paper feeder of the present invention sets the predetermined position immediately before the nip portion of the first pair of paper feed rollers, and places the next preliminary paper in the predetermined preliminary paper feed position. This is a configuration in which pre-nip paper detection means for detecting the leading end is arranged.

Therefore, the pre-nip sheet detecting means for detecting the leading edge of the next sheet is disposed at the preliminary sheet feeding position. There is an effect that the next sheet is always stopped at a predetermined preliminary sheet feeding position, that is, immediately before the nip portion of the first pair of sheet feeding rollers, without excessively going downstream in the transport direction.

In the paper feeding apparatus of the present invention, as described above, the operation control means for controlling the contact of the pickup roller with the paper and the transmission of the driving force from the driving source to the pickup roller and the paper feeding roller. The operation control means is provided in a paper feed direction downstream of the paper feed roller, and a paper detection signal of a pre-nip paper detection means arranged at a predetermined preliminary paper feed position and detecting the leading edge of the next paper. The control is performed on the basis of the sheet detection signal of the conveyance unit sheet detecting means.

Therefore, based on the sheet detection signal of the pre-nip sheet detection unit and the sheet detection signal of the conveyance unit sheet detection unit, the transmission and cutoff of the power of the drive motor and the contact and separation of the pickup roller and the sheet are determined. In addition, there is an effect that control can be performed at a reliable timing by a leading edge detection signal of the sheet being conveyed and conveyed.

Further, in the paper feeding apparatus of the present invention, as described above, the clutch means for connecting and disconnecting the driving force is provided in the transmission path of the driving force from the driving source to the paper feeding roller and the pickup roller. The clutch means, when the pre-nip paper detection means detects the leading edge of the next paper,
In this configuration, the driving force from the driving source to the sheet feeding roller and the pickup roller can be cut.

Therefore, since the clutch means for connecting and disconnecting the driving force is provided in the driving force transmission path, even if the pickup roller slips, the leading end of the next sheet is not detected by the pre-nip sheet detecting means. As long as the clutch is engaged. For this reason, the next sheet is reliably conveyed to the predetermined preliminary sheet feeding position. Therefore, there is an effect that the next sheet stops just before the predetermined preliminary sheet feeding position, and there is no shortage of feeding.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an overall configuration of a digital multifunction peripheral equipped with a sheet feeding device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the digital multi-function peripheral shown in FIG.

FIG. 3 is a cross-sectional view illustrating a configuration of a sheet feeding apparatus according to the present invention in a state where a sheet tray is mounted after sheet supply is completed.

FIG. 4 is a cross-sectional view illustrating a configuration of the sheet feeding device of the present invention in a state where preliminary sheet feeding is being performed.

FIGS. 5A to 5G are cross-sectional views illustrating the operation of the paper feeding device.

FIGS. 6A to 6F are timing charts for explaining the operation of the paper feeding device.

FIG. 7 is a cross-sectional view illustrating a general configuration of a sheet feeding device.

FIG. 8 is a perspective view for explaining a front loading type paper tray.

FIG. 9 is a cross-sectional view illustrating a configuration of a sheet feeding apparatus according to another embodiment of the present invention in a state where a sheet tray is mounted after sheet supply is completed.

FIG. 10 is a cross-sectional view illustrating a state in which preliminary paper feeding is being performed for explaining the configuration of the paper feeding device.

FIGS. 11A to 11F are cross-sectional views for explaining the operation of the paper feeding device.

FIGS. 12A to 12G are timing charts for explaining the operation of the paper feeding device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 30 digital multifunction peripheral 31 scanner unit 32 image forming unit 33 paper feeding device 34 post-processing device 35 document table 36 double-sided automatic document feeder (RADF) 40 scanner unit 44 CCD 46 laser writing unit (LSU) 47 electrophotography process unit 48 Photoreceptor drum 49 Fixing device 50 Transport path 51, 52, 53 Paper tray 54 Manual feeder 55 Duplex copying unit 56 Resupply path 60 Central processing unit (operation control means) 61 Image data input unit 62 Image processing unit 63 Memory 64 Hard disk device 66 Operation board unit 67-71 Load 81 Paper (previous paper) 81a Next paper 82 Paper feed solenoid 83 Pickup roller 84 Drive roller (first pair of paper feed rollers) 85 Separation roller (first pair of paper feeds) Roller) 86 ・ 87 Carry Roller 88 conveying section sheet sensor (conveying portion paper detecting means) 89 torque limiter 90 the drive motor 91 conveying clutch 92 paper feed clutch 93 nip the preceding sheet sensor (pre-nip paper detecting means)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3F343 FA02 FB02 FB03 FB04 GA03 GB01 GC01 GD01 HB03 HD18 JA18 JD09 KB05 KB06 KB20 LD30 MC04 MC23

Claims (7)

[Claims] When successively taking out and feeding sheet-like sheets stacked and stored in a detachable sheet tray, the leading edge of the next sheet is set at a predetermined position downstream of the conveying direction when the preceding sheet is supplied. Wherein the predetermined position is set immediately before the nip portion of the first pair of paper feed rollers in a paper feed device which performs a preliminary paper feed in which the paper is transported and kept in a standby state until the paper reaches the paper feed roller. apparatus. The first pair of paper feed rollers comprises a drive roller for contacting the upper surface of the paper and transporting the paper, and a separation roller for contacting the lower surface of the paper and driven and rotated with a predetermined rotation torque or more. The sheet feeding device according to claim 1, wherein the sheet feeding is performed. 3. A pickup roller sequentially takes out sheet-like sheets stacked and stored in a detachable sheet tray, and further supplies the sheets via a sheet feed roller. In a paper feeding device configured to perform preliminary paper feeding in which the leading end thereof reaches a predetermined position downstream in the carrying direction and is kept in a standby state, the first pair of paper feeding rollers among the paper feeding rollers is a paper feeding roller. And a separation roller that contacts the lower surface of the paper and rotates following the predetermined rotation torque. The pickup roller contacts and separates from the paper, and is separated from the drive source. The operation control means for controlling the connection and disconnection of the driving force to the pickup roller and the paper feed roller temporarily moves the pickup roller toward and away from the sheet to take out the previous sheet. After paper feeding device only predetermined interval of time on the rear end side of the front of the paper in contact again the pick-up roller, characterized in that to perform the extraction of the next sheet. 4. The apparatus according to claim 3, wherein said operation control means controls each part based on a leading edge detection signal of the sheet from a sheet detecting means provided at a downstream side in a sheet conveying direction. Paper feeder. 5. When sequentially taking out sheet-like sheets stacked and stored in a detachable sheet tray and feeding them through a paper feed roller, the leading edge of the next sheet is conveyed when the preceding sheet is supplied. In a sheet feeding device configured to perform preliminary sheet feeding in which the sheet is conveyed and kept waiting until a predetermined position downstream in the direction is reached, the predetermined position is set immediately before the nip portion of the first pair of sheet feeding rollers, A sheet feeding device, wherein a sheet detection unit before nip for detecting the leading edge of the next sheet is arranged at the predetermined preliminary sheet feeding position. 6. A pickup roller sequentially takes out sheet-like sheets stacked and housed in a detachable sheet tray, and further supplies the sheets via a sheet feed roller. In a paper feeding device which carries out preliminary paper feeding in which the leading end thereof reaches a predetermined position downstream in the carrying direction and is kept in a standby state, the pickup roller comes into contact with and separates from the sheet, and the pickup roller comes from a driving source. And operation control means for controlling transmission of driving force to the paper feed roller, wherein the operation control means is disposed at a predetermined preliminary paper feed position and is provided with a pre-nip paper detection means for detecting the leading edge of the next paper. A sheet feeder configured to perform control based on a sheet detection signal and a sheet detection signal of a sheet detection unit provided in a conveyance unit provided in a sheet conveyance direction downstream of the sheet supply roller. 7. A clutch for connecting and disconnecting the driving force is provided in a transmission path of the driving force from the driving source to the sheet feeding roller and the pickup roller. 7. The sheet feeding device according to claim 6, wherein when the leading end of the sheet is detected, the driving force from the driving source to the sheet feeding roller and the pickup roller can be cut off.