JPH08225166A - Sheet feeder and image forming device - Google Patents

Abstract

PURPOSE: To provide a sheet feeder by which sheets can be stably conveyed in long term use. CONSTITUTION: A circumferential speed VR2 of an extracting roller pair 110 is set to be higher than a processing speed VP and to be higher than a circumferential speed VR1 of conveying rollers 106. In addition, a circumferential speed of a register roller pair 26 is set to be equal to the processing speed VP. In this way, a conveying speed VS1 of a sheet fed from the conveying rollers 106 does not exceed a conveying speed VS2 of the sheet at the extracting roller pair 110 even if the conveying speed VS1 is increased, so that the sheet is stably conveyed between the conveying rollers 106 and the extracting roller pair 110 while surely undergoing tension.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding apparatus for feeding a recording sheet to an image forming apparatus such as a copying machine, a printer or a facsimile.

[0002]

2. Description of the Related Art In an image forming apparatus, a sheet feeding apparatus for feeding a sheet to an image forming section needs a function of separating the sheet and a function of conveying the sheet at an appropriate speed.

As a sheet feeding device, for example, a conveying roller that rotates in the sheet conveying direction, and a separating roller that rotates in the opposite direction to the sheet conveying direction in order to separate the sheets one by one in cooperation with the conveying roller. Some include a roller, a drawing roller that conveys the sheet separated by the separation roller, and a registration roller arranged downstream of the drawing roller.

The sheets are separated one by one between the conveying roller and the separating roller, and the separated sheets are conveyed to the registration rollers by the pull-out roller. The pull-out roller is provided to compensate for the lack of the sheet conveying force of the separation roller, and the registration roller is provided to correct the skew of the sheet and to send the proper timing sheet to the image forming unit. There is.

In such a sheet feeding device, there is a technique disclosed in Japanese Utility Model Laid-Open No. 60-69260 as a technique for conveying the sheet at an appropriate speed without damaging the sheet.

As shown in FIG. 10, the peripheral speed VR1 of the conveying roller B is pulled out in consideration of the loss of the conveying force of the sheet P in the separating portion S composed of the conveying roller B and the separating roller C in advance, as shown in FIG. It is set higher than the peripheral speed VR2 of D, VR1> VR2 ... And the sheet conveying speed VS by the pull-out roller pair D
2 is set to be higher than the sheet conveying speed VS1 by the separating unit.

VS2 ≧ VS1 ...

As a result, the separating portion and the pull-out roller pair D
The sheet is conveyed with a proper tension between and so that the sheet is not damaged.

[0009]

However, in the above-mentioned conventional sheet feeding apparatus, the frictional force R on the separating roller C becomes small due to abrasion or the like, or the separating roller C and the conveying roller B are made smaller.
If the pressure contact force N with and is decreased, the sheet conveying speed VS1 by the separating portion may be increased, and VS2 <VS1 may be satisfied. In such a state, the sheet may sag between the separating portion and the pull-out roller pair D, and the sheet may be folded or the like. That is, there has been a problem that the condition of the sheet conveying speed changes due to long-term use, and stable sheet feeding cannot be performed.

In order not to change such conveyance conditions, the separation roller must always be set and managed so as to satisfy the above expressions and, but this is very difficult.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a sheet feeding apparatus capable of stably conveying a sheet even when it is used for a long period of time.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a sheet feeding device for feeding a sheet to an image forming section, which cooperates with a sheet conveying rotating body which rotates in the sheet conveying direction. And a pull-out rotating body for conveying the sheets separated by the friction separating means, and the peripheral speed of the pull-out rotating body is set to the process speed of the image forming unit. It is characterized in that it is set faster than the peripheral speed of the sheet conveying rotary body.

The present invention is characterized in that a resist rotator is arranged on the downstream side of the drawing rotator and the peripheral speed of the resist rotator is set to the same speed as the process speed.

The present invention is characterized in that the peripheral speed of the sheet conveying rotary member is set to the same speed as the process speed.

[0015]

According to the above construction, the peripheral speed of the pull-out rotary member is set higher than the peripheral speed of the sheet transport rotary member. Since the sheet conveying speed is always higher than that of the sheet conveying sheet, the sheet does not sag between the sheet conveying rotary body and the pulling rotary body.

If the peripheral speed of the resist rotator is set to the process speed, the sheet is conveyed in a state in which a loop is formed between the resist rotator and the pull-out rotator, so that the resist rotator does not move. Stable sheet conveyance can be performed without applying back tension from the sheet.

[0017]

FIG. 1 shows the overall structure of an image forming apparatus to which the present invention is applicable.

First, the overall schematic structure of the image forming apparatus will be described along the flow of sheets.

In FIG. 1, a document (not shown) is automatically fed from the automatic document feeder (ADF) 3 to the platen glass 5 on the main body 2 of the copying machine 1 as an image forming apparatus. The original is scanned by the optical system 6 to form an image forming unit 7.
To form a latent image on the photosensitive drum 9. By developing this latent image, a toner image is formed on the photosensitive drum 9.

A plurality of right sheet feeding decks 10A and a plurality of left sheet feeding decks 10 capable of accommodating a large number of sheets P are provided in the apparatus main body 2.
B are respectively provided, and the paper feed rollers 11A and 11B, the transport rollers 12A and 12B,
Paper feed units 8lA and 81 including separation rollers 13A and 13B
Paper is fed one by one by B.

Sheets P fed from the respective paper feed decks 10A and 10B are fed to the right deck path 14 and the left deck path 5 respectively.
0, resist introduction path 1 through double-sided path 15 respectively
6 is transported to each. Paper feed deck 10A, 10
B is re-guided by the deck guide rail 17 and is a front loading device that can be pulled out from the front of the apparatus main body 2. The double-sided path 15 is guided by a double-sided guide rail 18 and can be pulled out to the front side of the apparatus main body 2.

Below the paper feed decks 10A and 10B, an upper paper feed cassette 19A and a lower paper feed cassette 19 for storing a small number of sheets are provided.
B are respectively provided, and the paper feed rollers 20A, 20
B, transport rollers 21A, 21B, separation rollers 22A, 2
The sheet P is conveyed to the resist introducing bus 16 one by one by 2B. This paper feed cassette 19
A and 19B are also front-loaded by the cassette guide rail 24.

A pre-registration guide 25 for guiding the sheet P conveyed from the resist introducing path 16 and a pair of resist rollers 26 are provided on the downstream side of the resist introducing path 16.

On the side surface of the apparatus main body 2, there is provided a multi-sheet feeding section 100 capable of feeding various sizes from postcards to A4 size sheets.

The multi-sheet feeding unit 100 supports a sheet, a multi-tray 102, a sheet-feeding roller 104 that sends out the sheet supported by the multi-tray 102, and a sheet that is fed out by the sheet-feeding roller 104. The conveyance roller 106, a separation roller 108 that is press-contactable with the conveyance roller 106, and separates the sheets one by one by reversing, and the conveyance roller 1 that separates the separated sheets.
06 and a separation roller pair 110 for extracting the separation roller 108 from the nip.

The image forming section includes an upper image forming section 7 including the photosensitive drum 9, a transfer / separation charging section 27, a conveying section 28,
The image forming unit 30 on the lower side is formed by integrating the fixing unit 31 and the discharge path 37. The image forming unit 30 is
Front loading is performed on the apparatus main body 2 by a main body guide rail 34.

The sheet P sent from any of the paper feed decks 10A and 10B, the paper feed cassettes 19A and 19B, and the paper feed unit 100 and conveyed by the registration rollers 26 is
The toner image is transferred from the photosensitive drum 9 by the transfer / separation charging unit 27 to form an image, and the conveying unit 28 fixes the fixing unit 31.
And is fixed by the fixing roller 29.

When the image formation on the sheet P is in the single-sided mode, the sheet P after the toner image is fixed is the inner discharge roller pair 3
2. A switching member 36 serving as a transport path switching unit,
The sheet is discharged onto the discharge tray 35 by the discharge path 37 including the outside discharge roller 33.

Below the image forming section 30, the intermediate tray 4 is provided.
A double-sided unit 42 including 3 is arranged. The double-sided unit 42 has a guide rail 83 with respect to the apparatus body 2.
Is front loading.

When the image forming mode is the double-sided mode or the multiplex mode, the sheet P after fixing is fed to the inner paper discharge roller 3
2. The sheet is sent to the reversing path 38 by the switching member 36, and is discharged onto the intermediate tray 43 by the pair of transport rollers 40 and 41.

The sheets P temporarily stacked on the intermediate tray 43 are fed from the lowermost sheet by the paper feed roller 44, and separated and fed one by one by the conveyance roller 45 and the separation belt 46.

The sheet feeding roller 44, the conveying roller 45, and the separation belt 46 constitute a sheet refeeding section from the sheet feeding roller 44.

Sheet P re-fed from the intermediate tray 43
In the double-sided mode, the sheet is conveyed to the double-sided path 15 by the sheet re-feeding path 49 including the pair of conveying rollers 47 and the switching member 48 as a switching section for the conveying path. The re-fed sheet P has a double-sided pass 15 and a resist introduction pass 16
The image is conveyed to the image forming units 7 and 30 via the sheet, and is discharged to the discharge tray 35 after the image is formed again.

Next, a conveyance control method for feeding paper from the left paper feed deck 10B will be described.

In FIG. 3, the double-sided path 15 includes a pair of conveying rollers 51, 52, 53, 54 and a double-sided guide 55. A detection member 56 for the sheet P is provided immediately upstream of the pair of transport rollers 53. And the left paper feed deck 10
When the user selects the sheet feeding from B and the image forming operation is started, the CPU (control unit) 90 controls
The sheet feeding roller 11B rotates to feed the sheet P from the left sheet feeding deck 10B. The sheet P is transported in the double-sided path 15 by the transport roller pair 53 as shown in FIG.

At this time, the leading end of the sheet P in the carrying direction is
The detection member 56 detects the detection means 5 earlier than a predetermined time T _1.
6 is not detected, or if the trailing end of the sheet P in the conveying direction is not detected earlier than the predetermined time T ₂ , it is determined that a jam has occurred, and the control unit 90 of the image forming apparatus causes the image forming operation of the apparatus 2. To stop.

Further, when the time from the detection member 56 detecting the sheet P until the image forming operation is stopped is shorter than a predetermined time, the sheet P is conveyed by a predetermined amount from the position where the sheet P is stopped. It is controlled by the CPU 90 as described above.

In FIG. 1, as will be described in detail later, a structure that blocks the front surface of the double-sided path 15 between the pair of transport rollers 53, the transport roller 12B, and the separation roller 13B, and the front side of the left paper feed deck path 50. Transport roller 12 that blocks the
The structure supporting B is not arranged.

FIG. 2 shows the double-sided path 15 or the left paper feed deck 1.
It is a figure which shows the structure which releases | releases the clamping pressure of the conveyance roller 12B and the separation roller 13B in interlocking with the pulling-out operation of 0B.

The arm 57 is rotatably supported by the shaft 57A and presses the rotatably supported separation roller 13B against the conveying roller 12B by the elasticity of the tension spring 58. One end of the release arm 62 pivotally supported by the shaft 62A is pressed against the other end 57B of the arm 57 by the elastic force of the tension spring 63.

The deck grip 59 is rotatably supported by the left paper feed deck 10B with a shaft 59A as a fulcrum, and when the left paper feed deck 10B is set in the apparatus main body 2, a projection integral with the deck grip 59 is formed. The portion 59 </ b> B engages with the locking member 60 fixed to the device body 2 by the elasticity of the tension spring 61, and is locked to the device body 2. Further, the inner end 59C of the deck handle 59 rotates the release arm 62 in the clockwise direction against the force of the tension spring 63 to separate it from the arm 57.

Next, the deck handle 59 is pulled by a tension spring 61.
When it is rotated against the force of the
When it goes out of 0, the left paper feed deck 10B is ready to be pulled out. At the same time, the release arm 62 moves the tension spring 63.
Is rotated counterclockwise to separate the separation roller 13B from the conveyance roller 12B against the tension spring 58, or reduce the holding pressure between the conveyance roller 12B and the separation roller 13B.

The double-sided handle 64 is rotatably supported by the shaft 64A and has a projection 64B which engages with the locking member 65 of the apparatus main body 2 in the same manner as the deck handle 59, and further has a tension spring. 66, release arm 67, tension spring 6
8, the double-sided path 15 is locked to the apparatus main body 2 and the holding pressure between the transport roller 12B and the separation roller 13B is increased and released.

Here, the procedure for removing the sheet P remaining in the double-sided path 15, the left paper feed deck 10B, and the deck path 50 when the image forming operation is stopped during paper feed from the left paper feed deck 10B explain.

First, when the detecting means 56 does not detect the sheet P while the operation of the apparatus 2 is stopped, that is, as shown in FIG. 3, the sheet P is held only by the conveying roller 12B and the separating roller 13B. If so, the control means 90 displays “Please pull out the left paper feed deck” on the display provided on the apparatus main body 2.

Then, when the deck grip 59 of the left paper feed deck 10B is rotated and then the left paper feed deck 1OB is pulled out, as described above, the conveying roller 12B and the separating roller 13B.
Holding pressure is released, and the left paper feed deck 10 is on the front side.
Since there is no structure that prevents the B sheet from being pulled out, the jammed sheet P is not accompanied by a structure such as a side regulating plate or a rear side plate (not shown) that is arranged on the rear side in the pulling direction of the left paper feed deck 10B. Since it is pulled out, the jammed sheet P can be easily removed.

Next, when the detecting means 56 detects the sheet P, that is, as shown in FIG. 4, the sheet P is on both the conveying roller 12B, the separating roller 13B and the conveying roller pair 53, or is illustrated. If there is no sheet, but the sheet is held only by the pair of transport rollers 53, the control means 90 displays "Please pull out the double-sided path".

When the double-sided handle 15 is pulled out and the double-sided path 15 is pulled out, as described above, the conveying roller 12 is moved.
B, the holding pressure of the separation roller 13B is released, and since the structure is not arranged on the front side, the jammed sheet P is pulled out together with the double-sided path 15 so that the jammed sheet P can be easily removed. Can be removed.

Further, in the operation stopped state of the apparatus, when the time from the detection means 56 detecting the leading end of the sheet P in the conveying direction to the apparatus 2 being stopped is shorter than the predetermined time t _1. That is, when there is a possibility that the sheet P is not nipped by the transport roller 53, the control means 90 causes the transport roller 12B, the separation roller 13B, and the transport roller pair 5 to operate.
3 is rotated for a predetermined time t ₂ so that the sheet P is securely held by the pair of transport rollers 53. As a result, since the sheet P is reliably sandwiched by the pair of transport rollers 53 and "Please pull out the double-sided path" is displayed, more reliable jam processing is possible.

Next, the structure of the sheet feeding section 81B for feeding the sheet from the left sheet feeding deck 10B will be described in detail with reference to FIGS. 5 is a front view and FIG. 6 is a side view.

Reference numeral 120 is a right front side plate formed of sheet metal, and 122 is a left front side plate formed by aluminum die casting. The right front side plate 120 is provided with a sheet feeding portion 81A (not shown in FIG. 5), and the left front side plate 122 is provided with a sheet feeding portion 81B.

As shown in FIG. 6, the conveying roller 12B and the separating roller 13B of the sheet feeding section 81B are supported by a bracket 124 fixed to the right front side plate 120 and the left front side plate 122. The paper feed roller 11B is the transport roller 12B.
It is swingably attached to the shaft 12C by a mechanism (not shown). The front side of the bracket 124 is the front plate 12.
It is fixed to 0 and 122, and the rear side is a back plate 126 of the apparatus main body 2.
It is positioned by a pin 124A.

The right front side plate 120 is supported by the side plate 2A of the apparatus main body 2 and the partition plate 2B, and is formed of sheet metal because it has relatively high rigidity. As described above, the left front side plate 122 needs to form a gap X between the right front side plate 120 and the left front side plate 122 in order to pull out the jammed sheet together with the left sheet feeding deck 10B, and as shown in FIG. It is fixed in a cantilevered manner only to the side plate 2B of. Therefore, it is formed by aluminum die casting, which has high rigidity.

In this embodiment, as shown in FIG. 1, a double-sided guide rail 18 for guiding the double-sided path 15 so that it can be pulled out to the front side (leftward in FIG. 6) is held above the left front side plate 122. However, since the left front side plate 122 has a structure that cannot be connected to the right front side plate 120 at the upper side, the left front side plate 122 is supported in a cantilever state.
The same structure will be obtained even if another configuration such as 0 that can be pulled out to the front side is arranged on the upper portion of the left front side plate 122. The left front side plate 122 may be made of a material having high rigidity such as synthetic resin other than aluminum die casting.

One of the pair of deck guide rails 17 for guiding the loading / unloading of the left paper feed deck 10B is the right front side plate 120.
And a back plate 126, and the other is a side plate 2B of the apparatus main body 2.
Supported by.

Although the left front side plate 122 is made of a material having a large rigidity, it is easily supported by a cantilever, so that it is easily deformed, and particularly vertically deformed. So, this front left side plate 1
In order to perform the positioning of No. 22, the left paper feed deck 10B is provided with positioning pins 128 and 128 which are fitted into the positioning holes 122A and 122B formed in the left front side plate 122. As a result, when the left paper feed deck 10B is attached to the apparatus main body 2, the positioning pins 128 and 128 are positioned in the positioning holes 12.
2A and 122B are fitted and positioning is performed accurately. Although the positioning holes 122A and 122B provided in the left front side plate 122 and the positioning pins 128 and 128 provided in the left paper feeding deck 10B are used as the positioning means, conversely, the positioning holes 122A and 122B are provided in the left paper feeding deck 10B.
Is provided, and positioning pins 128, 128 are provided on the left front side plate 122.
May be provided.

In this way, the left front side plate 1 in the cantilever state
Since 22 is accurately positioned, the paper feeding portion 81B supported by it is also accurately positioned, and the occurrence of separation defects and conveyance defects can be reduced.

In the above embodiment, the positioning pin 12 is used.
8 and 128 are fitted into the positioning holes 122A and 122B to position the left front side plate 122. However, when the positional accuracy deteriorates only in the vertical direction, the left paper feed deck 10B is indicated by a broken line in the figure. Such a cam 130 may be provided, and the left front plate 122 may be lifted by the cam 130 for positioning.

Next, the sheet feeding in the multi-sheet feeding section 100 will be described in detail. FIG. 7 shows the paper feed roller 10.
4 shows a drive transmission mechanism for transmitting drive to each of the transport roller 106, the separation roller 108, and the pull-out roller pair 110. FIG. 7A is a side view thereof, and FIG. 7B is a developed view thereof. .

Drive from a drive source (not shown) on the apparatus main body 2 side is input to the input gear 132, and the drive is transmitted from the input gear 132 to the shaft 108A of the separation roller 108 via the gear 134. A pulley 136 provided on the shaft 108A
The drive is transmitted from the shaft 108A to the shaft 106A by a belt 142 that is wound around a pulley 140 to which a clutch 138 provided on the shaft 106A of the transport roller 106 is connected, and further, the pulley 14 provided on the shaft 106A.
4 and a pulley 146 provided on the shaft 104A of the paper feed roller 104, the shaft 1
Drive from 06A is transmitted to shaft 104A.

The drive is transmitted in this way, and the separating roller 108, the conveying roller 106, and the paper feeding roller 104 rotate. Further, by turning the clutch 138 on and off, the drive is transmitted to and cut off from the shaft 106A of the conveying roller 106. Further, the input gear 132 to the gear 150
Drive is transmitted to the shaft 110 </ b> A of the pull-out roller pair 110 via the to rotate the pull-out roller pair 110.

A torque limiter 152 is provided on the shaft 108A of the separation roller 108. When the load applied to the separation roller 108 by the torque limiter 152 is smaller than a predetermined value (limit value), the separation roller 108 is provided.
The drive is transmitted to and the drive is cut off when the drive becomes large.

The paper feed roller 104 is provided so as to be movable up and down by an elevator mechanism (not shown).
02, the sheet P is lowered and abutted against the sheet P to be fed out, and the fed sheet is lifted at a predetermined timing after being bitten by the pull-out roller pair 110 to raise the sheet P.
Away from.

The clutch 138 may be an electromagnetic clutch or a spring clutch controlled by a solenoid.

The sheet conveying operation in the structure of the multi-sheet feeding unit 100 will be described.

The multi-tray 10 by the paper feed roller 104
The sheet P on the second sheet is sent out and sent to the nip portion between the transport roller 106 and the separation roller 108 that is in pressure contact with the transport roller 106. When there are two or more sheets sent to the nip portion, the separating roller 108 rotating in the reverse direction sequentially returns the sheets on the separating roller 108 side and sends out only one sheet. When only one sheet is sandwiched in the nip portion, the drive is shut off by the torque limiter 152 and the separation roller 108 rotates following the sheet.

The separated sheet is pulled out by a roller pair 11
0 is further conveyed and sent to the registration roller pair 26. Then, the registration roller pair 26 sends the sheet to the image forming unit 7 at a predetermined timing.

The multi-sheet feeding unit 100 has a designation mode for designating the size of the sheet to be fed and a free size mode for not designating the size. In the designated mode,
When the trailing edge of each size sheet passes through the nip portion between the transport roller 106 and the separation roller 108, the clutch 1
38 is turned off to stop the drive rotation of the paper feed roller 104 and the transport roller 106.

In the free size mode, since the size of the sheet to be sent cannot be detected, the clutch 138 is turned off at the timing when the trailing edge of the minimum size sheet passes through the nip portion between the conveying roller 106 and the separating roller 108, and the sheet feeding roller 104 is connected. The driving rotation of the transport roller 106 is stopped. At this time, the separation roller 108 is continuously driven and the separation operation is continued because the drive transmission is not interrupted.
As a result, double feeding of sheets is reliably prevented even in the free size mode.

When the trailing edge of the sheet leaves the pull-out roller pair 110, the rotation of the pair of pull-out rollers 110 is stopped, and at the same time, the rotation of the separation roller 108 is also stopped.

The control of these operations is performed by the CPU 90 (shown in FIG. 1) which is a control means.

Next, a description will be given of a structure for preventing the skew feeding correction of the sheet from occurring in the registration roller pair 26. In addition, here, the sheet P from the multi-feed unit 100 is used.
Will be described as an example.

First, referring to FIG.
The sheets P stacked on the sheet are sent out by the sheet feeding roller 104, and separated one by one by the conveying roller 106 and the separating roller 108. The separated sheet is conveyed by the pull-out roller pair 110 and is sent to the registration roller pair 26, the tip of the sheet is abutted against the nip portion of the registration roller pair 26, and a loop is formed on the sheet to correct skew.

The peripheral speed VR1 of the conveying roller 106 is set to the same speed as the process speed VP in the image forming section 7, and the peripheral speed VR2 of the pull-out roller pair 110 is set to a speed higher than the process speed VP. . Also,
The peripheral speed VR3 of the registration roller pair 26 is set to the same speed as the process speed VP.

VR2> VR1 = VP (1) VR3 = VP (2) Here, the peripheral speed of each roller may be set by the gear ratio of the gear of the drive transmission mechanism, or the roller diameter. It may be set according to the size of. Alternatively, the gear ratio and the roller diameter may be set in combination. In this embodiment, the peripheral speed VR2 of the pull-out roller pair 110 is 13 / the process speed VP.
A good result can be obtained by setting it at about 12.

As a result, the sheet sent out by the conveying roller 106 and the separating roller 108 is separated by the separating roller 10.
Since the sheet is conveyed at a speed VS1 slower than the process speed VP due to the loss caused by 8, and the sheet is conveyed at a speed VS2 higher than the process speed VP by the pull-out roller pair 110, the sheet is conveyed while being pulled. This can prevent the seat from buckling.

If the friction coefficient of the separation roller 108 decreases due to wear or the like or the force N for pressing the separation roller 108 against the conveying roller 106 becomes small due to long-term use, the sheet conveying speed VS1 by the conveying roller 106 becomes small.
However, if it is set as in the above equations (1) and (2), the sheet conveying speed V of the pull-out roller pair 110 must be set.
It becomes smaller than S2, and the sheet is conveyed in a pulled state between the conveying roller 106 and the pull-out roller pair 110, and the sheet is not damaged.

Further, the pull-out roller pair 110 rotates after the registration roller pair 26 starts to rotate and sends out the sheet. At this time, the pull-out roller pair 110 conveys the sheet at a speed VS2 faster than the process speed VP, and the registration roller pair 26 conveys the sheet at the same speed VS3 as the process speed VP (VS2 ≧ VS3).
= VP), the sheet is always in a looped state between the pull-out roller pair 110 and the registration roller pair 26 even while the sheet is being conveyed. Therefore, a load due to the back tension of the sheet is not applied to the registration roller pair 26, and stable image formation can be performed without causing an image shift.

Next, a configuration for effectively correcting skew when the distance between the pull-out roller pair 110 and the registration roller pair 26 is short will be described with reference to FIG. In addition,
Also here, the case where the sheet P is supplied from the multi-sheet feeding unit 100 will be described as an example.

In FIG. 9, the sheet P sent out by the paper feed roller 104 and separated by the carrying roller 106 and the separating roller 108 is further carried by the pulling roller pair 110 and sent to the registration roller pair 26. The registration roller pair 26 is stopped until the sheet P conveyed by the pull-out roller pair 110 forms a loop, and the skew of the sheet P is corrected by forming the loop. Then, the registration roller pair 26 starts rotating at a predetermined timing and sends the sheet P to the image forming unit 7.

The pull-out roller pair 110 is arranged at a position substantially corresponding to the center in the left-right direction of the sheet, and the length of the roller (the length in the width direction of the sheet) is set short. In this embodiment, the sheets that can be sent out from the multi-sheet feeding unit 100 are postcards (width 100 mm) to A4 size sheets (width 297 mm), and the roller length is 4 mm.
It is set to 4 mm.

With the above structure, the pull-out roller pair 11
When the skew is corrected by the registration roller pair 26 after being sent by 0, the skew of the sheet P is so large that a loop cannot be completely formed between the pull-out roller pair 110 and the registration roller pair 26 and skew correction is performed. Even if you can't do it,
By rotating the pull-out roller pair 110, the sheet P can be rotated in the direction shown by the arrow in FIG. 9B to perform skew correction.

This is because one corner portion P1 of the skewed sheet P fed by the pull-out roller pair 110 contacts the nip NP of the registration roller pair 26, and the pull-out roller pair 1
When 10 further rotates, the sheet P rotates about one corner P1 thereof, and the leading edge of the sheet P is brought into contact with the nip NP of the registration roller pair 26 to perform skew correction. As a result, skew feeding can be surely corrected even for a sheet conveyed in a large skewed state in which skew feeding cannot be corrected only by a loop.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment.

[0085]

As described in detail above, the present invention provides
Since the peripheral speed of the pull-out rotating body is set to be faster than the peripheral speed of the sheet conveying rotating body, even if the conveying speed of the fed sheet increases due to abrasion of the friction separating means, etc. The sheet is large and the sheet does not sag between the sheet conveying rotary body and the pulling rotary body. This makes it possible to stably supply the sheet for a long period of time without damaging the sheet and improve maintainability.

Further, if the peripheral speed of the resist rotating member is set to the process speed, the sheet is conveyed to the image forming section in a state where a loop is formed between the resist rotating member and the pulling rotating member. Stable sheet conveyance can be performed without applying back tension from the sheet to the resist rotation body. As a result, it is possible to prevent the image from being stretched in the image forming section, and to improve the image quality.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an example of an image forming apparatus provided with a sheet feeding apparatus of the present invention.

FIG. 2 is a side view showing a pressure release mechanism of a conveyance roller of a left paper feed deck in the image forming apparatus shown in FIG.

FIG. 3 is a diagram showing a state in which a sheet is fed from a left paper feed deck in the image forming apparatus shown in FIG.

FIG. 4 is a diagram showing a state in which a sheet is fed from a left paper feed deck in the image forming apparatus shown in FIG.

5 is a front view showing a mounting portion of a paper feed deck of the image forming apparatus shown in FIG.

6 is a sectional view taken along line VI-VI in FIG.

7 is a diagram showing a drive transmission mechanism of a multi-sheet feeding unit in the image forming apparatus shown in FIG.

8 is a diagram showing the speed of each roller of the multi-feed unit in the image forming apparatus shown in FIG.

9 is a diagram showing a configuration for correcting skew of sheets in a multi-sheet feeding unit in the image forming apparatus shown in FIG.

FIG. 10 is a schematic view showing an example of a conventional sheet feeding device.

[Explanation of symbols]

 7 Image Forming Unit 26 Registration Roller Pair (Registration Rotating Body) 106 Conveying Roller (Sheet Conveying Rotating Body) 108 Separation Roller (Friction Separation Means) 110 Pulling Roller Pair (Pulling Rotating Body)

Claims (5)

[Claims] 1. A sheet feeding device for feeding a sheet to an image forming unit, wherein a sheet conveying rotating body that rotates in a sheet conveying direction and a sheet separating one by one in cooperation with the sheet conveying rotating body. And a pulling-out rotary body that conveys the sheet separated by the frictional separating means, and sets the peripheral speed of the pulling-out rotary body higher than the process speed of the image forming unit, and A sheet feeding device, wherein the peripheral speed of the sheet conveying rotating body is set to be higher than the peripheral speed. 2. The sheet feed according to claim 1, wherein a resist rotator is arranged on the downstream side of the drawing rotator, and the peripheral speed of the resist rotator is set to the same speed as the process speed. Sending device. 3. The sheet feeding apparatus according to claim 1, wherein the peripheral speed of the sheet conveying rotary member is set to the same speed as the process speed. 4. The sheet feeding device according to claim 1, wherein the friction separating means is a separating roller that rotates in a direction opposite to a sheet conveying direction. 5. A sheet feeding device according to claim 1, and an image forming unit for forming an image on a sheet fed from the sheet feeding device. Image forming apparatus.