JP2002046884A - Paper feeding device and picture image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper feeding device and a picture image formation device capable of sequentially and certainly carrying out separation motion of sheets from the top sheet and carrying out stable paper feeding even in the case when a friction coefficient between the loaded sheets is largely different. SOLUTION: A first sheet storage part (paper feeding device) 2 furnished with a paper feeding roller 12 to feed the sheets on a paper feeding tray 7 to a picture image writing part 5 and a fixing part 6 (picture image formation part) constitutes its characteristic feature of being furnished with an auxiliary roller 13 to separate and displace the sheet on the top level of the paper feeding tray 7 upward. It is possible to separate and displace the sheet upward by pressing the sheet on the top level on a slippage regulating wall 37 on the one end side of the paper feeding tray 7 by rotation of the auxiliary roller 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper feeder and an image forming apparatus, and more particularly, to a paper feeder and an image forming apparatus for feeding paper sheets in a paper storage unit one by one to an image forming unit by a paper feed roller. Related to the device.

[0002]

2. Description of the Related Art An image forming apparatus, for example, a copier-type copying machine, a facsimile, a printer, or a combination of these functions, and digitally processes image information required for writing processing in each of these functions. Paper used in a digital copier or the like is usually stored in a paper storage section of the apparatus main body. The paper storage unit has a paper feed tray for storing a large number of papers in a stacked state, and uses a paper feed roller provided in the paper feed tray, so that the uppermost roller-facing paper is formed one by one in the apparatus. Transported to the department.

[0003] When paper sheets stacked and stored in a paper feed tray are fed one by one to the image forming section by a paper feed roller in order from the top one, a plurality of sheets are simultaneously overlapped due to a difference in friction between the sheets. It is easy to be sent out in a state. That is, the sheets stored in the sheet tray in a stacked state are not limited to a single kind, and sheets of various materials may be used in a mixed manner. In particular, for the purpose of saving resources in consideration of the environment, transfer paper with an image recorded on one side is stacked on the paper feed tray again, and furthermore, due to insufficient paper loading by the operator or the effect of curl of the paper itself, The coefficient of friction between sheets may differ for each sheet. In such a case, the sheet bundle above the roller-facing sheet receiving the feed force from the feed roller and the sheet located below and having the lowest friction coefficient among a plurality of sheet groups to which the same feed force is transmitted are weighted. May be fed, causing a paper feed failure. Therefore, by a sheet separating mechanism provided at the leading end of the sheet feeding tray, for example, it is performed to feed a lower layer sheet and feed only the uppermost sheet, and as a configuration for giving this resistance, A paper separation mechanism employing a friction pad separation method or a corner claw separation method is generally known.

[0004]

However, the conventional paper separating mechanism may cause a double feed in which two sheets are fed in a state of being overlapped or a non-feed in which no sheet is fed. Various ideas have been devised. For example, JP-A-7-
The paper separating mechanism disclosed in Japanese Patent Publication No. 315608 discloses that, when a large number of paper bundles are sent out to a paper supply separation unit at the leading end of a paper supply tray, the bundle is limited to a small number of sheets before reaching the separation unit. The sheet is sent out to the separation unit, and at the time of separation, both the sheet pickup roller and the holding filler are operated to retract from the sheet feed path to release the sheet restriction operation, so that the sheet separation operation is performed reliably. ing.

[0005] However, in the conventional apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 7-315608, there is a limit in exhibiting a sufficient function for preventing double feed due to a large difference in sheet friction coefficient for each sheet. However, the problem that the paper located above the paper portion having a low friction coefficient is sent out in a bundle is not sufficiently solved, and improvement is desired. Based on the above-mentioned problem, the present invention ensures that even if the coefficient of friction between the stacked sheets is significantly different, the sheet separating operation is sequentially and reliably performed from the top sheet, and stable sheet feeding is performed. It is an object of the present invention to provide a paper feeder and an image forming apparatus.

[0006]

According to a first aspect of the present invention, there is provided a sheet feeding apparatus having a sheet feeding roller for feeding a sheet in a sheet storing section to an image forming section. And an auxiliary roller for separating and displacing the uppermost sheet of the sheet upward. In this manner, the rotation of the auxiliary roller causes the uppermost sheet to be separated upward and displaced, thereby reducing the coefficient of friction between the sheet and the lower sheet. It is possible to realize stable paper feeding performance. Preferably, after the rotation of the auxiliary roller reduces the coefficient of friction between the sheets, the sheet feeding roller may start the sheet conveyance operation. In this case, the double feeding of the sheet can be prevented more reliably.

According to a second aspect of the present invention, in the paper feeder according to the first aspect, the uppermost sheet is pressed against a displacement regulating wall on one end side of the sheet storage portion by rotation of the auxiliary roller.
It is characterized by being displaced upward. In this way, the rotating auxiliary roller presses the uppermost sheet against the displacement regulating wall of the sheet storage section to separate and displace it upward, thereby reducing the coefficient of friction between the sheet and the lower sheet and then feeding the sheet. Since the paper feed operation is started by the paper roller, double feeding of the paper by the paper feed roller can be easily prevented, stable paper feed performance can be realized, and a simple configuration can be adopted.

According to a third aspect of the present invention, in the paper feeder according to the first aspect, the uppermost sheet is rotated by the auxiliary roller while the paper feed roller applies a shift regulating force to the uppermost sheet. It is characterized by being displaced upward. In this way, the uppermost sheet in the state where the sheet feeding roller is applied with the deviation regulating force is displaced upward by rotating the auxiliary roller, thereby reducing the coefficient of friction between the sheet and the lower sheet. Then, the sheet feeding operation is started by the sheet feeding roller, so that double feeding can be more reliably prevented, and stable sheet feeding performance can be realized. According to a fourth aspect of the present invention, in the paper feeder according to the first aspect, the rotation of the auxiliary roller is controlled for a time during which the uppermost sheet is displaced upward. In this manner, the auxiliary roller is rotated and stopped only during the time when the uppermost sheet causes the upward separation displacement, and the sheet feed roller starts to convey the sheet. Feeding can be prevented, and paper jam due to excessive upward displacement can be easily prevented by time control.

According to a fifth aspect of the present invention, in the paper feeder according to the first aspect, when a displacement sensor provided opposite to the paper storage unit detects that the separation displacement of the uppermost paper is a predetermined amount. The rotation of the auxiliary roller is controlled to be stopped. In this manner, when the displacement sensor detects that the uppermost sheet has a predetermined amount of upward displacement, the rotation of the auxiliary roller is stopped, and the sheet feed roller starts to convey the sheet. It is possible to reduce the number of sheets to prevent double feeding, and it is possible to easily prevent a paper jam caused by an excessive upward displacement by simply using a displacement sensor.

According to a sixth aspect of the present invention, in the paper feeder according to the first aspect, a fan is provided opposite to the paper storage section and sends air to a gap between the uppermost sheet and a lower sheet of the same sheet. It is characterized by doing. In this way, by feeding air with the fan provided in the paper storage unit, the coefficient of friction between the uppermost paper and the lower paper of the same paper is more reliably reduced, and the paper is transported by the paper feed roller. Therefore, more stable paper feeding performance can be realized.

According to a seventh aspect of the present invention, an image forming apparatus includes any one of the sheet feeding devices according to the first to sixth aspects. As described above, the image forming apparatus selectively employs the sheet feeding device according to claims 1 to 6, so that the image forming apparatus similarly has the function and effect equivalent to each adopted sheet feeding device, and Productivity as an image forming apparatus can be improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a paper feeder and an image forming apparatus having the same according to an embodiment of the present invention will be described. The image forming apparatus shown in FIG. 1 is a printer 1. The printer 1 includes a first paper storage unit 2 as a paper feeding device at a lower portion of an apparatus main body (a base frame assembly not shown), and a second paper storage unit at a left side. A storage section 3 is provided, a transport path R extends upward from both of the paper storage sections, and an upper end thereof is connected to a paper discharge tray 4 provided at an upper end of the apparatus main body. The image writing unit 5 and the fixing unit 6 are arranged.

The printer 1 is provided with a side opening 8 on the right side of the apparatus main body, and accommodates an insertable drawer-type sheet feeding tray 7 forming the first sheet storage section 2 in the side opening 8. A side opening 9 is provided on the left side of the apparatus main body, and a manual paper feed tray 11 of the second sheet storage unit 3 is inserted into the side opening 9 and mounted. The paper feed tray 7 stores paper P (a frequently used paper such as A4 size or B5 size) in a stacked state. The paper in the paper feed tray 7 is separated one by one by a paper feed roller 12 and an auxiliary roller 13 which will be described later, and the lower end of a transport path R formed between the transport roller 14 and the first and second vertical guide walls 15a and 15b. The sheet is sent out to the site, and is further conveyed by the conveying roller 14 toward the registration roller pair 16.

The manual paper feed tray 11 is provided so that special paper P 'such as a postcard can be fed. The manual feed tray 11 has a tray body 17 attached to the side opening 9 via a tray receiving member (not shown), and a shaft 18 attached to the tray body 17.
And a coil spring 21 that constantly urges the paper placed on the bottom plate 19 upward.

On the free end side of the bottom plate 19, a manual feed roller 22 pivotally supported by the apparatus main body and a friction pad 23 are provided. The friction pad 23 is supported by a holding fitting 24, and the holding fitting 24 is pin-coupled to the apparatus main body side, and a rotating end side where the friction pad 23 is located is urged upward by a spring (not shown). The paper placed on the bottom plate 19 is separated one by one by a paper feed roller 22 and a friction pad 23 pressed and urged by the same roller, and passes through a branch path r between a pair of branch side guide members 25 to register. The sheet is conveyed to the roller pair 16, joins the conveyance path R at the same portion, and is sent to the image writing unit 5 in the same manner as the sheet from the sheet feed tray 7.

The image writing section 5 includes a photosensitive drum 26. The photosensitive drum 26 is uniformly charged in advance, and based on image information read from an original image reading unit (not shown), an optical system writing unit (not shown) is used. The electrostatic latent image is formed by the means, and the electrostatic latent image is developed into a toner image by the developing means 27. The registration roller pair 16 disposed near the transfer position of the photosensitive drum 26 temporarily stops the conveyed sheet to create slack, corrects the skew of the sheet, and fixes the toner on the photosensitive drum 26 as an image carrier. The sheet is sent to the transfer unit after the position of the image is aligned with the leading end position of the image.

The sheet fed by the registration roller pair 16 at a predetermined timing is transferred to a transfer roller 28 as a transfer unit.
As a result, the toner image on the photosensitive drum 26 is transferred. The sheet on which the toner image has been transferred is sent between the heating roller 29 and the pressure roller 30 of the fixing unit 6, where the toner image is fixed as a permanent image on the sheet by heat and pressure. The fixed sheet is discharged to the discharge tray 4 by the discharge roller pair 31. The paper feed tray 7 used in the above-described first paper storage unit 2 includes a substantially dish-shaped box-shaped base frame 32, and is provided at the outer end (right end in FIG. 1) of the right side of the apparatus body. A lid 33 capable of closing the opening 8 is integrally formed, and the conveyance path R on the opposite back side is formed.
A shift regulating wall 37 described later is formed on the side opposite to the end.

A guide member 10 is formed at the lower part of the apparatus main body and extends to the area farther (left side) than the side opening 8, along which a base frame 32 is slidably inserted and mounted.
More paper can be replenished and taken out. The base frame 32 has a bottom plate 35 placed thereon. The bottom plate 35 has a pin portion 351 protruding from the lid portion 33 side, and is pin-connected to the bottom plate mounting portion 34 on the base frame side via the pin portion 351. Paper P is stacked on the bottom plate 35, and the end of the bottom plate 35 facing the transport path R, which is the free end (left side in FIG. 1), is urged upward by the coil spring 36 together with the paper P to be placed.

The uppermost sheet P among the sheets P stacked on the bottom plate 19 is regulated in height by contacting the auxiliary roller 13, and the leading end of the uppermost sheet P is attached to the base frame 32. It is adjusted so as to come into contact with the uppermost edge e of the displacement regulating wall 37 which is a vertical wall on the end side facing the conveyance path R. A paper feed roller 12 pivotally supported by the apparatus main body is provided above the base frame 32 on the side of the conveyance path R, and the rotation of the paper feed roller 12 is controlled by a rotation drive system (not shown). As shown in FIGS. 1 and 2A, the paper feed roller 12 has a notch circular cross section, and the notch faces the uppermost sheet P at a reference rotation position as shown by a solid line in FIG. Set to work. For this reason, as shown in FIGS.
The sheet P is separated from the sheet P in the rotation range of the idle rotation angle θ1 / 2, and comes into contact with the sheet P in the rotation range of the feed rotation angle θ2 to perform the feeding operation.

Here, the uppermost sheet P in the base frame 32 is regulated in position in the vertical direction by abutting on the auxiliary roller 13. In some cases, as shown by a two-dot chain line in FIG. A vertical position regulating piece 38 supported on the 32 side may be provided, so that the leading end of the uppermost sheet may be adjusted so as to contact the uppermost edge e of the displacement regulating wall 37. The auxiliary roller 13 is pivotally supported by a roller support means 39 attached to the apparatus main body, is timely controlled by the control means 46, and is supported so as to be able to switch its vertical position between a separation operation position d1 and a retreat position d2. . The roller supporting means 39 is provided on the base frame 3.
A pair of right and left (only the back side is shown in FIG. 1) pair is provided outside the sliding area of No. 2. Each roller support means 39 has a vertically-oriented guide frame 41 and a movable frame 4 which can slide up and down and move up and down.
2 and a separation operation position d1 in which the movable frame 42
And a retractable position d2, an electromagnetic actuator 43 for switching and moving, a movable arm 42 having one end pin-coupled and a free end pivotally supporting the auxiliary roller 13; And a spring 45 that urges against pressure.

A position sensor 47 that contacts the base frame 32 and outputs an ON signal to the control means 46 is provided at an end of the guide member 10 on the side of the conveyance path R. The control means 46, which receives the output of the position sensor 47, switches the auxiliary roller 13 to the retracted position d2 when the signal is off, and switches to the separation operation position d1 when the signal is on. In the separation operation position d1, the pressing arm 44 can contact the stopper 421 formed on the movable frame 42 side. At this time, the auxiliary roller 13 pivotally supported at the leading end contacts the uppermost sheet P, and The position can be regulated in the up-down direction, that is, in this case, the position can be regulated so that the leading end of the uppermost sheet P comes into contact with the uppermost edge e of the displacement regulating wall 37 of the base frame 32.

The uppermost edge e of the displacement regulating wall 37 of the base frame 32
As shown in FIG. 3A, the uppermost sheet P is formed over the entire area in the width direction Y of the transport path R, and the auxiliary roller 1
When pressed by the rotation of No. 3, as shown in FIG.
The paper P is allowed to bend upward, that is, to be separated and displaced. Note that the uppermost edge e is provided over the entire width direction Y of the transport path R.
Instead of forming the uppermost edge e1 only at the center in the width direction Y, as shown in FIG. 3B, or as shown in FIG. The uppermost edge e2 may be formed only at the left and right ends. In these cases, when the paper P is pressed at the positions of the respective uppermost edges e1 and e2, the paper P easily bends upward. Separation displacement can be facilitated.

Further, a fan 48 driven and controlled by the control means 16 is provided at a position facing the base frame 32 at the lower part of the apparatus main body. When the uppermost sheet of the sheets P stacked on the base frame 32 bends above the lower sheet, that is, when the fan 48 separates and displaces as shown in FIG. It functions to send the airflow f, promote separation, and reduce the friction coefficient between sheets more reliably. Next, the operation of the printer 1 will be described.

The printer 1 shown in FIG. 1 is driven to maintain a standby state by turning on a main switch (not shown). Here, when the paper feed tray 7 is pulled out from the side opening 8 in order to additionally replenish the paper P (a frequently used paper such as A4 size or B5 size), the position sensor 47 is initially pulled out.
Is turned off, and the control means 46 switches and holds the movable frame 42 and the auxiliary roller 13 to the retracted position d2 via the electromagnetic actuator 43 according to the off signal. As a result, the back side portion of the paper feed tray 7 is pulled out without interfering with the auxiliary roller 13, and can be easily inserted and mounted after replenishing the paper. When the sheet feeding tray 7 is returned into the side opening 8 and the position sensor 47 is turned on, the control means 46 switches and holds the movable frame 42 and the auxiliary roller 13 to the separation operation position d1, and thereby the stopper 421 The auxiliary roller 13 on the pressing arm 44 whose upward displacement is restricted regulates the position of the uppermost sheet P in the vertical direction.

Next, upon receiving the read image information from the image reading device (not shown) and receiving the image forming command C, the printer 1 starts an image forming cycle S1 as shown in FIG. Here, it is assumed that the control means 46 selects the paper in the paper feed tray 7 according to the image forming command C.
In this case, the process of transporting the top sheet of the paper feed tray 7 and
A process of forming a toner image corresponding to the read image information included in the image forming command C by the image writing unit 5 and a process of heating and fixing the toner image on the paper P by the fixing unit 6 are sequentially executed along a predetermined image forming cycle S1. .

In this case, as shown in FIG. 4, the paper feed roller 12 and the auxiliary roller 13 are simultaneously rotated by the image forming command C, and the fan 48 also starts blowing air to the base frame 32. The paper feed roller 12 is held in a non-contact state with the sheet P in a rotation range of the idle rotation angle θ1 / 2, rotates at the feed rotation angle θ2 after the rotation angle θ1 / 2 elapses, and moves the uppermost sheet P to the registration roller pair. It is transported toward 16. The image writing unit 5 and the fixing unit 6 are driven in a predetermined mode in response to the image forming command C. The rotation of the registration roller pair 16 at a predetermined timing causes the paper P to be aligned with the toner image on the photosensitive drum 26. After that, the toner image is transferred, and the toner image on the same sheet is fixed as a permanent image by heat and pressure in a fixing unit 6, discharged to the discharge tray 4, and subjected to one image forming cycle S 1.
Is completed.

At the beginning of the image forming cycle S1, as shown in FIG.
Receiving the paper, the paper feed roller 1 that does not contact the paper
2 enters the rotation of the idle rotation angle θ1 / 2 (see FIG. 3A), and at the same time, the auxiliary roller 13 in contact with the sheet P rotates. The auxiliary roller 13 moves the sheet P toward the transport path R. At this time, since the leading end of the sheet is opposed to the uppermost edge e of the displacement regulating wall 37 of the base frame 32, the leading end is immediately When the auxiliary roller 13 continues to rotate while being in contact with the upper edge e, the rear side of the sheet P is bent upward from the intermediate portion, that is, separated and displaced as shown in FIG. Due to the separation displacement of the uppermost sheet P, a gap is formed between the uppermost sheet P and the sheet below the sheet P, and as shown in FIG. It is accelerated quickly and sufficiently reduces the coefficient of friction between the paper and the lower paper.

By the way, the control means 46 controls the image forming command C
The roller timer and the fan timer (not shown) are driven at the same time as the
1. The fan drive time T2 is counted, and the rotation of the auxiliary roller 13 is stopped after the lapse of the separation time T1. After the fan drive time T2 has elapsed, the fan 48 is stopped. Here, the separation time T1 is appropriately set as a time at which the uppermost sheet P reliably causes an upward separation displacement.

Although the rotation range of the auxiliary roller 13 for the separation time T1 partially overlaps the rotation range of the feed roller 12 for the feed rotation angle θ2, the overlapping range t1 may be eliminated. Further, the fan drive time T2 is set longer than the separation time T1, and when the feed roller 12 is driven in the region of the feed rotation angle θ2, the coefficient of friction between the lower sheet and the lower sheet is sufficiently reduced. The paper feed roller 12 which is transported at a feed rotation angle θ2 on which the uppermost sheet P is reliably separated can be sent out to the transport path R. As described above, the first paper storage unit 2 as a paper feeding device used by the printer 1 of FIG.
Performs time control in which the auxiliary roller 13 is rotated for a separation time T1, which is a predetermined time during which the uppermost sheet P undergoes upward separation displacement, thereby preventing a paper jam due to excessive upward separation displacement. it can. In addition, the printer 1 having such a first paper storage unit 2 can realize a stable paper feeding performance and can adopt a simple configuration.
Has the same function and effect as the first paper storage unit 2, and can also improve the merchantability of the printer.

In the above description, when the fan 48 is used, more reliable sheet feeding performance can be realized. However, in order to simplify the control, the fan 48 may be continuously driven during the image forming cycle S1, In some cases, the fan 48 may be omitted to simplify the apparatus. As described above, the first paper storage unit 2 of the printer 1 of FIG. 1 stops the rotation of the auxiliary roller 13 after the control unit 46 counts the separation time T1, and the rotation of the auxiliary roller 13 is prolonged. Although the paper P is prevented from being excessively separated and displaced upward and jammed, instead of this, the uppermost position is detected by using a displacement sensor 51 as shown in FIGS. 5 (a) to 5 (c). The rotation of the auxiliary roller 13 may be stopped when the deflection amount (height) of the sheet P reaches a certain amount.
The first paper storage unit 2 here is a modified example of the first paper storage unit 2 in FIG. 1, and at least the roller counter is eliminated from the control system, and the first paper storage unit 2 is displaced to an input port (not shown) of the control unit 46. Except for the configuration in which the sensor 51 is connected, the same configuration is adopted, and thus redundant description is omitted.

The paper feed tray 7 used in the first paper storage section 2 is provided with a paper feed roller 12 opposed to the uppermost edge e of the displacement regulating wall 37 of the base frame 32 so as to face the paper feed tray 7. The auxiliary roller 13 is provided at the center of the roller 32, and the displacement sensor 51 is provided at an intermediate position between the two rollers. The displacement sensor 51 is supported on the apparatus body side via a bracket 52, and has a movable contact piece 53.
Is disposed at the center in the width direction Y of the transport path R (in the direction perpendicular to the paper surface, see FIG. 3A). As a result, in the initial stage of the image forming cycle S1, the paper feed roller 12 starts to rotate at the idle rotation angle θ1 / 2, and at the same time, the auxiliary roller 13 in contact with the paper P rotates. Abuts against the uppermost edge e of the displacement regulating wall 37 of the base frame 32, and the auxiliary roller 13 continues to rotate, whereby the rear side of the sheet P is bent upward from the middle part, that is, as shown in FIG. Is displaced as follows. Due to the separation displacement of the uppermost sheet P, a gap is formed between the uppermost sheet P and the lower sheet, and as shown in FIG. 5C, an airflow f flows from the fan 48, and the separation between the two sheets is promoted. , The coefficient of friction between the paper and the lower paper is sufficiently reduced.

Next, when the upward displacement amount of the uppermost sheet P reaches a predetermined value h1, the displacement sensor 51 is turned on as shown in FIG. Stops the rotation of the auxiliary roller 13. As described above, when the upward separation displacement of the uppermost sheet P reaches the predetermined value h1, the displacement amount control of stopping the auxiliary roller 13 is performed. Jams can be reliably prevented, and stable paper feeding performance can be realized. In the above description, the printer 1 has been described as an image forming apparatus. However, the present invention is not limited to this, and a facsimile machine or a facsimile machine, or a combination of these functions, and writing with these functions is performed. Japanese inventions such as a digital copying machine for digitally processing image information required for processing may be applied. In these cases, the same operation and effect can be obtained.

[0033]

As described above, according to the first aspect of the present invention, the uppermost sheet is separated and displaced upward by rotating the auxiliary roller, and the coefficient of friction between the lower sheet and the lowermost sheet is reduced. In addition, since the sheet feeding operation is started by the sheet feeding roller, double feeding of the sheet by the sheet feeding roller can be easily prevented, and stable sheet feeding performance can be realized.

According to the second aspect of the present invention, the rotating auxiliary roller presses the uppermost sheet against the leading end wall of the sheet storing portion to separate and displace upward, thereby reducing the coefficient of friction between the sheet and the lower sheet. In addition, since the paper feed roller starts to convey the paper, double feeding of the paper by the paper feed roller can be easily prevented, stable paper feed performance can be realized, and a simple configuration can be adopted. .

According to a third aspect of the present invention, the uppermost sheet in a state where the deviation is regulated by the sheet feeding roller or the like is separated upward by the rotation of the auxiliary roller, and the friction between the sheet and the lower sheet is increased. Since the sheet feeding operation is started by the sheet feeding roller after the coefficient is reduced, double feeding can be more reliably prevented, and stable sheet feeding performance can be realized.

According to a fourth aspect of the present invention, since the auxiliary roller is rotated and stopped for a time during which the uppermost sheet undergoes upward separation displacement, the sheet feeding operation is started by the sheet feeding roller. The coefficient can be reduced to prevent double feeding, and paper feed failure due to excessive upward displacement can be easily prevented by time control.

According to the fifth aspect of the present invention, when the displacement sensor detects that the uppermost sheet has been separated upward by a predetermined amount, the rotation of the auxiliary roller is stopped, and the sheet feeding operation by the sheet feeding roller is started. In addition, double feeding can be prevented by reducing the coefficient of friction between sheets, and paper feeding failure due to excessive separation displacement upward can be easily prevented only by using a displacement sensor.

According to a sixth aspect of the present invention, by feeding air with a fan provided in a paper storage section, the coefficient of friction between the uppermost paper and the lower paper of the same paper is more reliably reduced, and the paper is fed. Since the operation of transporting the paper by the rollers is started, more stable paper feeding performance can be realized.

According to a seventh aspect of the present invention, the image forming apparatus selectively employs the sheet feeding device according to any one of the first to sixth aspects. In addition, the merchantability of the image forming apparatus can be improved.

[Brief description of the drawings]

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

FIGS. 2A and 2B are diagrams illustrating a sheet feeding operation in a sheet feeding tray of the sheet feeding device of FIG. 1, wherein FIG. 2A illustrates a non-operating time, FIG. 2B illustrates a separating operation, and FIG. Indicates the start time.

FIGS. 3A and 3B show a paper feed tray shift regulating wall that can be used in the paper feeding device of FIG. 1; FIG. 3A shows a configuration adopted in the paper feeding device of FIG. 1; (C) shows a second modification.

FIG. 4 is an operation explanatory diagram of various rollers and a fan used in the sheet feeding device of FIG. 1;

5A and 5B are diagrams illustrating a sheet feeding operation in a sheet feeding tray of a printer according to another embodiment of the present invention, wherein FIG. 5A illustrates a non-operating state, FIG. 5B illustrates a separating operation, and FIG. This indicates the start of feeding roller driving.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printer (image forming apparatus) 2 1st paper storage part (paper feeder) 7 paper feed tray 5 image writing part (image forming part) 6 fixing part (image forming part) 12 paper feed roller 13 auxiliary roller 37 displacement control Wall 46 Control means 48 Fan 51 Displacement sensor e, e1, e2 Uppermost edge of displacement control wall R Transport path

Claims (7)

[Claims] 1. A sheet feeding device provided with a sheet feeding roller for feeding a sheet in a sheet storing section to an image forming section, wherein the uppermost sheet in the sheet storing section is disposed upstream of the sheet feeding roller in the feeding direction. A sheet feeding device comprising an auxiliary roller for separating and displacing the sheet. 2. The sheet feeding device according to claim 1, wherein the uppermost sheet is pressed against a shift regulating wall at an end in the feed direction of the sheet storage section by the rotation of the auxiliary roller, and is separated and displaced upward. Characteristic paper feeder. 3. The paper feeding device according to claim 1, wherein the uppermost paper is separated and displaced upward by rotation of the auxiliary roller in a state where the paper feed roller applies a displacement regulating force to the uppermost paper. A sheet feeding device, characterized in that: 4. The paper feeder according to claim 1, wherein the rotation of the auxiliary roller is controlled only for a time during which the uppermost sheet undergoes upward separation displacement. 5. The sheet feeding device according to claim 1, further comprising a displacement sensor provided opposite to the sheet storage unit, wherein the displacement sensor detects that the separation displacement of the uppermost sheet has reached a predetermined amount. A sheet feeding device for controlling the stop of the rotation of the auxiliary roller when the sheet feeding is performed. 6. The paper feeder according to claim 1, wherein a fan is provided opposite to the paper storage section and sends air to a gap between the uppermost paper and a lower paper of the same paper. Paper feeder characterized by being equipped. 7. An image forming apparatus having one of the paper feeders according to claim 1. Description: