JP2000318853A - Sheet supply device, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet supply device and an image forming device capable of reducing sheet feeding timing irregularity, and shortening an interval between sheets in simple constitution. SOLUTION: This device comprises a sheet stacking means 1 to stack sheets P, a sheet retracting means 2 to get in contact with the sheets P stacked on the sheet stacking means 1 to feed the sheets P, a sheet separating means 3 to separate the sheets P fed by the sheet retracting means 2 one by one to be fed downstream further, and a drive source 5 to supply driving power to the sheet retracting means 2 and the sheet separating means 3, the sheet retracting means 2 and the sheet separating means 3 are driven as the sheets P are carried even after a supply of the driving power from the drive source 5 is disconnected, and the sheet retracting means 2 is driven by interlock with drive as the sheets P are carried by the sheet separating means 3.

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 stacked sheets one by one, and an image forming apparatus using the same, such as a printer, a copying machine, and a facsimile.

[0002]

2. Description of the Related Art In an image forming apparatus such as a printer, a copying machine, a facsimile, etc., paper or OHP is generally used in order to form an image in an image forming section using an electrophotographic system or the like.
A sheet (paper), which is a recording material such as a sheet, is transported from a paper feed tray or a paper feed cassette loaded with the sheet to an image forming unit, and further, a sheet on which an image is formed is transported to an output port. A series of sheet transport devices are provided.
In these sheet conveying apparatuses, double feeding is prevented and 1
It is necessary to convey the sheets one by one, and to accurately convey the sheets to an image forming unit that forms an image on the sheet at a transfer timing.

Here, when a sheet is pulled in from a sheet feed tray or the like on which a plurality of sheets are stacked by a sheet drawer,
The adhesion between the sheets greatly changes depending on the type of sheets, environmental conditions such as temperature and humidity during conveyance, the method of stacking sheets by an operator, etc., and sometimes sheets are pulled in regularly one by one, and sometimes several sheets are put together. And is sent out to the sheet handling section. This sheet separating section essentially has a function of separating such a plurality of sheets one by one, and there is a problem in that the sheets separated one by one are sent to the downstream sheet conveying path. However, the interval between the sheets greatly differs depending on the state of the sheet being retracted by the sheet retracting unit. Here, if there is a large variation in the sheet interval, it is necessary to set the sheet conveyance timing in consideration of the variation, and there has been a problem that productivity in image formation is reduced.

In order to solve such a problem, Japanese Utility Model Laid-Open Publication No. 1-134633 discloses that a feed roller for drawing in paper and a pair of feed rollers having a separating function are independently driven to rotate. Regardless of the number of papers sent out simultaneously from the rollers, the paper is once aligned at the position where the leading edge of the paper abuts between the paper feed rollers, and the paper feed rollers are rotated at a predetermined timing to rotate the paper feed rollers. A technique is disclosed in which a start position of a sheet fed from between is always aligned in front of a sheet feeding roller.

[0005]

However, the technique disclosed in Japanese Utility Model Laid-Open Publication No. 1-164633 requires a sensor and an actuator for detecting that the leading edge of the sheet is positioned between the pair of sheet feeding rollers, which is not practical. . Further, it is premised to control the rotation of the attracting roller and the sheet feeding roller independently, which limits the mechanical structure and directly increases the cost.

Further, after the sheets are pulled in from a sheet feeding tray or a sheet feeding cassette, the sheets are separated and sent out one by one.
There is a so-called pre-feeding technique that suspends the sheet immediately after this feeding and then re-conveys the sheet to make the sheet conveyance timing uniform. If this pre-feeding technique is adopted, it is possible to solve the above-mentioned conveyance trouble. It is. However, in order to perform such pre-feed, it is necessary to separately provide a sheet sensor for detecting the leading edge of the sheet from the necessity of accurately detecting the leading edge position of the sheet, and there is no transport roll immediately after feeding. In the case of a so-called short paper pass,
Feed feed clutch before and after standby to feed
Times, and the required life of the feed clutch needs to be doubled.

Further, if the sheet interval is extremely different, the re-feeding timing by the pre-feed cannot be properly set, and the unstable sheet interval is absorbed to stop the sheet at the time of the pre-feed until there is no error in the sheet conveyance. In such a case, the sheet feeding speed becomes extremely slow, and it is impossible to increase the number of sheets on which an image can be formed within a predetermined time. Further, if the sheet interval varies greatly, it is necessary to set the sheet conveyance timing in consideration of the variation. Also, when a sheet having a slightly longer feed length than a standard size sheet is conveyed (for example, a letter size for A4 size), a sheet conveyance timing is required to obtain a sheet interval necessary for maintaining conveyance. It has been required to make a space corresponding to this, and there has been a problem that productivity in image formation is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above technical problems, and it is an object of the present invention to reduce variations in sheet feeding timing and to shorten the interval between sheets with a simple configuration. The present invention relates to a sheet feeding apparatus and an image forming apparatus that can perform the sheet feeding.

[0009]

That is, as shown in FIG. 1, a sheet feeding apparatus according to the present invention contacts a sheet stacking means 1 for stacking sheets P and a sheet P stacked on the sheet stacking means 1. A sheet pull-in means 2 for feeding out the sheet P; and a sheet pull-down means 2 provided downstream of the sheet pull-in means 2 in the sheet conveying direction. Before the sheet separating means 3 to be sent out and the rear end of the conveyed first sheet P1 pass through the sheet separating means 3, the first sheet P1
And a driving means 4 for driving the sheet retraction means 2 so as to send out the second sheet P2 following the second sheet P2.

The driving means 4 does not necessarily have to coincide with a driving source 5 such as a motor for driving the sheet drawing means 2 and the sheet separating means 3. In addition, sheet retraction means 2
If a pull-in roll (pick-up roll) for pulling a sheet is used and a supply roll (feed roll) is used as a driving portion of the sheet separating means 3, the pull-in roll can be configured to follow the rotation of the supply roll. . At this time, if the supply roll is rotated by the conveyance force of the sheet after the driving of the draw-in roll and the supply roll from the drive source 5 is cut off, the draw-in roll is further rotated based on the rotation of the supply roll. It can be configured to accompany.

The sheet conveying force of the sheet retracting means 2 driven by the driving means 4 is equivalent to the sheet separating means 3.
The second sheet P2 is configured to be set at a level that prevents the second sheet P2 from being over-ridden and conveyed with respect to the remaining first sheet P1, and is set to be smaller than the conveying force of the sheet separating means 3, for example, to prevent sheet damage at the leading end of the sheet, This is preferable because double feeding, in which two or more sheets are sent out at a time, can be prevented and the quality of conveyance can be maintained. This overriding conveyance is performed for the second sheet P
2 is supplied, for example, on the rear portion of the first sheet P1. The level of preventing the over-conveyance includes the sheet separating force of the sheet separating unit 3 and the sheet blocking of the sheet separating unit 3. It is preferable to make the sheet conveying force of the sheet retraction means 2 smaller than the force.

Further, if the driving means 4 drives the sheet retraction means 2 with a certain sliding action, for example, the conveying force of the sheet retraction means 2 with respect to the conveying force of the sheet separating means 3 The force is naturally adjusted in accordance with the sheet conveyance state, which is effective in that a change in the gap between sheets can be prevented with a simple configuration. In particular, it is preferable that the sheet conveying force is set to be weak particularly when the sheet has already penetrated into the vicinity of the nip portion of the sheet separating means 3, and when the drive transmission using friction is used. It is preferable to adopt a structure in which the frictional force is weakened or the sheet is slid so as to be weaker than the separating reaction force of the sheet separating means 3 at the time of overriding conveyance. Specifically, there is a case where a ring-shaped member capable of allowing slippage is provided between the rotation shafts, or a case where frictional transmission is performed by rubbing a knurled surface having a jagged angle.

It is preferable that the driving means 4 be configured to drive the sheet retraction means 2 in conjunction with the movement of the sheet separating means 3, since the gap between sheets can be reduced and the productivity can be improved. In order to interlock with the movement of the sheet separating means 3, when a rotating supply roll is used as the sheet separating means 3 and a drawing roll is used as the sheet drawing means 2, the drawing roll is rotated along with the rotation of the supply roll. What is necessary is just to configure. For this purpose, for example, a simple connecting member such as a ring-shaped member or a belt member hung on the rotation axis of the feed roll and the rotation axis of the pickup roll can be used in addition to the drive transmission by gears.

Further, the image forming apparatus of the present invention
Stacking means 1 for stacking sheets, and the sheet stacking means 1
Sheet pull-in means 2 which comes out of contact with the sheets P stacked on the sheet P, and is provided downstream of the sheet pull-in means 2 in the sheet conveying direction. A sheet separating means 3 for feeding the sheet to the downstream side and a driving source 5 for supplying a driving force to the sheet retracting means 2 and the sheet separating means 3;
The sheet retracting means 2 and the sheet separating means 3 are provided with a driving source 5
The sheet pulling means 2 is driven in conjunction with the driving of the sheet P by the sheet separating means 3 while being driven with the conveyance of the sheet P even after the supply of the driving force is stopped. Features.

Further, if the sheet retraction means 2 is driven by the frictional contact mechanism 4 in conjunction with the driving of the sheet separating means 3 accompanying the conveyance of the sheet P, for example, expensive electric parts, etc. This is effective in that the succeeding second sheet P2 can be sent out with a simple component configuration without using. When a pull-in roll is used as the sheet pull-in means 2 and a supply roll is used as the sheet separating means 3, such a frictional contact mechanism is made of a rubber material or the like that connects the shaft of the supply roll and the pull-in roll. It is also possible to employ a mechanism for connecting the rolls by rubbing a ring-shaped member such as an O-ring, a belt-shaped member, or a friction surface having a knurl shape or the like.

Next, the operation of the above technical means will be described. In response to a sheet supply signal from a control unit (not shown), the drive source 5 drives the sheet retraction unit 2 and the sheet separation unit 3, and the sheet P loaded on the sheet stacking unit 1 by the sheet retraction unit 2 is removed from the upper surface thereof. First, picked up, sent out, and separated one by one by sheet separating means 3
The sheet P1 is transported further downstream. 1st sheet P1
Is held by a transport roll (not shown) on the downstream side and the transport force of the first sheet P1 is secured, and upon receiving a signal from the control unit, the drive source 5 drives the sheet pull-in means 2 and the sheet separating means 3 Cut off transmission. At this time, the first sheet P1 is still in contact with the sheet retracting means 2 and in a state sandwiched by the sheet separating means 3, and the first sheet P1
And the sheet separating means 3 rotates with the conveyance of the first sheet P1. Thereafter, when the first sheet P1 is further conveyed to the downstream side, the first sheet P1 is separated from the contact of the sheet retraction unit 2 and is still held by the sheet separating unit 3. At this time, the sheet separating means 3 rotates with the first sheet P1, but the sheet retracting means 2 does not rotate with the first sheet P1. However, sheet retracting means 2
Is configured to be able to be driven in conjunction with the sheet separating means 3 using, for example, a friction contact mechanism, so that the sheet retraction means 2 is continuously driven and the second sheet subsequent to the first sheet P1 is driven. Picking up P2 and handling sheet 3
Side can start sending out.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. First Embodiment FIG. 2 shows a first embodiment of an image forming apparatus to which the present invention is applied. The image forming apparatus 21 includes an apparatus main body 22 that forms an image on a sheet (paper) P, and an image reading apparatus (IIT) 23 that reads a document image. This device body 2
2 has an image forming unit 24 for directly forming an image on the paper P, and in FIG.
26 is a laser exposure device for forming an electrostatic latent image on the photosensitive drum 25 based on a signal output from an image processing device (IPS) 29, and 27 is a laser exposure device for forming the electrostatic latent image formed on the photosensitive drum 25. A developing device 30 for visualizing the image with a developer such as toner; a transfer device 30 for transferring an unfixed toner image onto the paper P by a transfer roll facing the photosensitive drum 25;
Reference numeral 1 denotes a fixing device for fixing an unfixed toner image formed on the paper P by the transfer device 30. A fixing roller is brought into contact with a heating roll and a pressure roll at an appropriate pressure, and the paper P
And fixed. In the present embodiment, the photosensitive drum 25 and the developing device 27 are integrated into a cartridge 28 that can be attached to and detached from the device main body 22, and the cartridge 28 also serves as a tank for storing the developer. , And this developer is used as a developing roll 27a.
Is supplied to the photosensitive drum 25 via the Further, the image processing device (IPS) 29 is based on image information output from the IIT 23 as an electronic copier,
As X, conversion to image information that can be formed by the device main body 22 is performed based on image information from an external device.

The apparatus main body 22 is provided with a plurality (four in the present embodiment) of paper feed trays 32 for accommodating paper P by size or paper feed direction, which are detachably provided at the upper and lower tiers. In these paper feed trays 32, a large number of papers P are stacked and stored on a bottom plate 33 provided therein, so that they can be inserted from the front side of the apparatus main body 22 (the surface side shown in FIG. 2). It is configured. The device body 22
, Paper feed rolls 34 for feeding the paper P toward the image forming unit 24 one by one from the upper surface of the paper P stacked on each paper feed tray 32 are provided. The paper feed roll group 34 includes a pick-up roll (Pick Up Roll) 35 that comes into contact with the upper surface of the stacked paper P lifted by raising the bottom plate 33 and pulls in the paper P, and a paper taken out of the pickup roll 35. Feed roll (Fee), which is a pair of rolls constituting the paper separating means for separating P
d Roll) 36 and a retard roll 37.

A sheet transport path 38 is formed on the left side of the apparatus main body 22 on the downstream side of the feed roll 36 and the retard roll 37, and has a plurality of transport rolls 39 disposed therein. . The paper P supplied from the lowermost paper feed tray 32 is transported along the entire length of the paper transport path 38, and the paper P supplied from the other upper paper feed tray 32 is transported halfway through the paper transport path 38. The sheets are merged and conveyed to the image forming unit 24. This image forming unit 24
A registration roll 40 is provided in front of the sheet P. The sheet P is fed into the image forming unit 24 after the conveyance posture and the conveyance timing of the paper P are matched.

The sheet P having an image formed on the first surface after passing through the fixing device 31 via the image forming section 24 is
In the case of single-sided printing, the image-formed first surface is discharged by a first discharge roll 41 onto a discharge tray 42 formed on the upper surface of the apparatus main body 22 with the first surface facing downward. In the case of double-sided printing, the paper P is once sent to the paper output tray 42 side,
When the rear end of the paper P reaches the position where it is held by the first paper discharge roll 41, the gate 43 is switched, and the first paper discharge roll 41 is rotated in the reverse direction. The sheet P is turned over with the end of the sheet P as the leading end, and is sent from the second sheet discharging roll 44 to the automatic duplex unit 45.

The automatic double-sided unit 45 includes
The outer shell is constituted by a relatively thin casing having a depth slightly smaller than 2, the support unit 47 of the manual feed tray 46 is fixed to the apparatus main body 22, and the automatic duplex unit 45 is located at the lower end. Are hingedly connected to the support unit 47, and the upper side is a free end, which is configured to be openable and closable with respect to the apparatus main body 22. Further, a circulating transport path 48 for double-sided printing is provided in the automatic duplex unit 45, and a plurality of transport rolls 49 are provided in the circulating transport path 48. The circulating transport path 48 is connected to a paper transport path of the apparatus main body 22, and has an opening at one end facing the second paper discharge roll 44 and an opening at the other end at the paper transport path 38.
Is opposed to the upper end. First side for double-sided printing
The paper P on which the (front side) is printed is sent from the second paper discharge roll 44 to the circulation transport path 48, transported downward by the transport roll 49, and supplied again to the paper transport path 38 of the apparatus main body 22. Thereafter, the conveyance timing is adjusted by the registration roll 40, and the second
An image is formed on the surface (back surface). Then, after the second surface is fixed via the fixing device 31, the sheet is discharged onto the sheet discharge tray 42 with the second surface facing downward.

Next, the paper feed tray 32 and the paper feed roll group 3
4 will be described in detail. FIG. 3 shows the paper feed tray 32 in a perspective view. Bottom plate 33 shown in FIG.
Is configured such that sheets P can be stacked, an end opposite to the sheet feeding direction is hinged to the bottom of the sheet feeding tray 32, and the sheet feeding direction is configured to be rotatable. The feed direction side of the bottom plate 33 is the lift-up motor 5.
5 rotates the lift lever 5 through the joint 54.
3 to raise the paper P in the transport direction,
It comes into contact with the lower peripheral surface of the pickup roll 35. As shown in FIG. 3, the apparatus main body 22 includes, for each paper feed tray, a paperless sensor 56 for detecting the presence / absence of paper P in the paper feed tray 32, a size and a storage direction of the stored paper P. Size sensor 57 that detects
And a face control sensor 58 for detecting whether or not the uppermost sheet P has come into contact with the pickup roll 35 when the bottom plate 33 is lifted, and information detected by these sensors is 2
The display is displayed on an operation panel (not shown) provided at the second or the like, and the user can check the supply state of the paper P, select the paper feed tray 32, and check a paper feed error or the like by looking at the display.

Next, the structure and operation of the paper feed roll group 34 will be described with reference to FIGS. Here, FIG. 4 is a perspective view showing the paper feed roll group 34 and its driving structure from the back side (rear side) of the apparatus main body 22, and FIG. 5 is for describing the paper feed roll group 34 in more detail. It is a perspective view of. Each of the rolls 35, 36 of the paper feed roll group 34,
Reference numeral 37 denotes rolls having the same shape and the same size as each other. As shown in FIG. 5, both ends in the axial direction are slightly larger in diameter than the center part by an elastic body such as rubber on the surface. 35b, 36b, and 37b are configured to come into contact with and act on the paper P. As shown in FIG. 4, the pickup roll 35 having the pickup roll shaft 35 a as an axis is cantilevered by an arm 67 that rotates about a feed roll shaft 36 a that is the axis of the feed roll 36. A drive gear 61 connected to a feed roll shaft 36a is mounted via a feed clutch 62 at the far end of the machine frame 60 that supports the feed roll 36 in a cantilever manner. The drive gear 61 is connected to a feed motor (not shown) via an intermediate gear 63. The power of the feed motor is transmitted from the intermediate gear 63 to the drive gear 61, and in the connected state of the feed clutch 62, the feed roll 36 rotates in the forward direction to feed the paper P via the feed roll shaft 36a. Gears 65 and 66 are fixed to the pickup roll shaft 35a and the feed roll shaft 36a, respectively.
is rotated, the gear 66 on the feed roll shaft 36a side is rotated.
The rotation of the pickup roll shaft 35 through the intermediate gear 64
a, the pickup roll 35 rotates together with the feed roll 36. The gear 66 has a built-in one-way clutch for the pickup roll 35 to prevent the pickup roll 35 from rotating in the reverse direction.

On the other hand, a retard gear 68 is fixed to the retard roll shaft 37a, which is the axis of the retard roll 37, on the inner side of the machine frame 60. Also, as shown in FIG.
The retard roll shaft 37a is rotatably supported around a transport roll shaft 39a via a supporter 71, and the retard gear 68 meshes with a gear having the same center as the axis of the transport roll shaft 39a. The structure is such that the pressure of the retard roll 37 increases with the rotation of 36. Further, a torque limiter 69 is provided on the retard roll shaft 37a, and when there is no paper P, the retard roll 37 overcomes the limit force of the torque limiter 69 and moves along with the feed roll 36 because the frictional force (μ) is large. When the paper P rotates around, that is, rotates in the paper feeding direction at the contact portion, and the two or more sheets P are conveyed, the frictional force (μ) between the sheets is small, and the torque limiter 69 stops at the contact portion. The feed roll 36 and the retard roll 37 stop the second and subsequent sheets of paper P that have been multi-fed, and as a result,
Are transported one by one to the downstream side.

The feed roll shaft 36b has a joint 70 with a built-in one-way clutch for the feed roll.
Is provided, and only forward rotation is permitted, and reverse rotation is prohibited. Accordingly, for example, in a case where the paper P is stopped by the registration roll 40 to form a loop, when the feed roll 36 rotates in the reverse direction, the loop is elongated, and a problem such as insufficient registration adjustment occurs. Preventing. Even when the feed clutch 62 is disengaged and the driving force from the feed motor is cut off by the one-way clutch for the feed roll provided on the joint 70, the one-way clutch is rotated in the sheet conveying direction along with the conveyance of the sheet P. This rotation by the feed roll 36 is not linked to the gear 66. On the other hand, since the gear 66 has a built-in one-way clutch for the pickup roll 35, the pickup roll 35 rotates in the sheet conveyance direction with the conveyance of the sheet P even when the driving force from the feed motor is cut off. It is possible. Here, if the connection by the gear is continued, since the feed roll 36 is being rotated by the paper P when the first sheet P is pulled out of the pickup roll 35, the pickup roll 35 When the second and subsequent sheets P are already in the nip portion of the feed roll 36 and the second and subsequent sheets are already in the nip portion, the second and subsequent sheets are multi-fed (overloading). Transport). for that reason,
In the present embodiment, the rotation by the feed roll 36 is not linked to the gear 66.

On the other hand, in the present embodiment, as shown in FIG. 5, a feed roll shaft 36a of the feed roll 36,
Pickup roll shaft 35a of pickup roll 35
Are connected by a ring-shaped member 80. In the present embodiment, an O-ring made of synthetic rubber is used as the ring-shaped member 80, and the elasticity of the ring-shaped member 80 made of the O-ring is used. The pick-up roll shaft 35a is configured to be hooked on both shafts of the joint 70 of the shaft 36b and the pickup roll shaft 35a. Since the ring-shaped member 80 is hooked on both shafts, the ring-shaped member 80 may connect the feed roll 36 and the pickup roll 35 while sliding on the shaft in some cases. That is, the ring-shaped member 80 has a form in which the rotational force generated by the rotation of the feed roll 36 is weakened, that is, has a function of transmitting the driving force of the pickup roll 35 with a weak conveyance force.

In the conventional state without the ring-shaped member 80, the supplied paper P is nipped by the transport roll on the downstream side.
When the pinch is nipped, the feed clutch 62 is disengaged, the power from the drive source is cut off, and the pickup roll 35 and the feed roll 36 are allowed to idle in the paper transport direction, and each of them was idle independently. In other words, while the paper P being transported is present in each roll, the paper P rotates, but stops when the paper P being transported comes off the roll. That is, first, when the sheet P has passed through the pickup roll 35 on the upstream side, the pickup roll 3
5 is stopped, and then the downstream feed roll 36
The feed roll 36 was stopped at the time when the paper P came off the sheet. In this conventional state, even if the pickup roll 35 conveys a plurality of sheets to the feed roll 36 in a state where the power from the first drive source is applied, one state is obtained.
Since the pickup roll 35 stops when the second sheet P exits the pickup roll 35, the second sheet P is not conveyed immediately after exiting. Therefore, while the first sheet P is being conveyed, the second and subsequent sheets are not overloaded and conveyed (double feed), so that a trouble of feeding the sheet P can be prevented. However, on the other hand, when the first sheet is fed by the pickup roll 35, the second and subsequent sheets P are already conveyed to the nip portion of the feed roll 36, and the second sheet P is not conveyed and is stacked. In some cases, the conveyance start position of the second sheet is different. As a result, paper conveyance troubles occur, and in order to prevent such troubles, sensors and the like are increased to complicate the conveyance control, It was necessary to sacrifice productivity by delaying the feed timing.

Here, the movement (operation in the present embodiment) of the sheet P when the ring-shaped member 80 in the present embodiment is used will be described with reference to FIGS. 6 (a) to 6 (c). 6 (a) to 6 (c), P1 is 1 in paper P.
The second sheet, P2, indicates the second sheet following the first sheet P1, and FIG. 6A shows an initial state of feeding the first sheet P1. First, when the feed roll 36 rotates in response to a feed signal from a control unit (not shown), the driving force from the driving source is applied to the gears 66, 64, 65.
And the pickup roll 35 rotates together. With the rotation of the pickup roll 35, first, the first sheet P1 is fed to the feed roll 3 serving as a sheet separation unit.
6 and the nip portion of the retard roll 37. Thereafter, the first sheet P1 sent out is transported toward the downstream transport roll (for example, the transport roll 39) by the transport force of the feed roll 36.

After that, as shown in FIG. 6B, the first sheet P1 is nipped by the downstream transport roll (for example, the transport roll 39), and the transport of the paper by the feed roll 36 and the retard roll 37 is unnecessary. , The power from the drive source is cut off in response to a stop signal from a control unit (not shown), and the pickup roll 35 and the feed roll 36 can idle in the paper transport direction by a one-way clutch built in the gear 66 and the joint 70. In this state, the pickup roll 35 and the feed roll 36 come into contact with the first sheet P1 to rotate in the sheet transport direction based on the transport force generated by the downstream transport roll. In FIG. 6B,
This shows a state in which the second sheet P2 slightly protrudes due to the rotation of the pickup roll 35 due to the driving force from the initial driving source, and is conveyed in an overlapping manner.

Thereafter, the first sheet P1 is further conveyed, and the contact with the pickup roll 35 is first released. In this state, the feed roll 36 is still nipping the first sheet P1, and the feed roll 36 is rotating with the conveyance of the first sheet P1. In the prior art, the pickup roll 35 stops in this state and waits for the next drive start, but in the present embodiment, the ring-shaped member 80 is connected to the feed roll shaft 36.
Since the joint 70b and the pick-up roll shaft 35a are connected with a weak force, the joint 70 rotates together with the first sheet P1 on the feed roll 36.
The pickup roll 35 rotates with a smaller force than the rotation of the feed roll 36. This pickup roll 35
, The conveyance of the second sheet P2 is started before the driving force from the driving source is obtained.
Since the pre-conveyance by the pickup roll 35 is a weak conveyance force, the second sheet P2 is replaced with the first sheet P1.
The second sheet P2 is regularly conveyed while maintaining a narrow interval with the first sheet P1, as shown in FIG. 6C. In particular, the pickup roll 35 is driven by the drive from the initial drive source.
When the first sheet P1 is pulled up and conveyed, even if the second sheet P2 has already reached the vicinity of the nip portion of the sheet separating section, the separating force by the feed roll 36 and the retard roll 37 ( Since the conveyance force due to the rotation of the pickup roll 35 is set to be weaker than the sheet prevention force), the second sheet P2 is not transported over the first sheet P1.

As described above, according to the present embodiment, the feed roll 36 and the pickup roll 35 are connected by the ring-shaped member 80. Pickup roll 35 in conjunction with the rotation by 36
Can rotate, and advance conveyance of the second sheet P2 is possible. Further, since the ring-shaped member 80 is selected within a range in which the second sheet P2 can prevent the first sheet P1 from being over-ridden and conveyed, the second sheet P2 is the first sheet P2. It is possible to prevent a transport trouble caused by getting over the sheet P1. Here, in order to select within a range in which the overriding conveyance can be prevented, the ring-shaped member 80 is required.
The ring-shaped member 80 may be appropriately selected in consideration of the size, thickness, frictional force depending on the surface state, the amount of stretching, the adhesion between papers, environmental conditions, and the like. It is preferable to select a proper one.

In this embodiment, the feed roll 3
Although a ring-shaped member 80 such as an O-ring is used to connect the drive of the pickup roll 6 and the pickup roll 35, the cross-sectional shape is not necessarily circular, but may be a square or a D-shaped cross-sectional shape. May be provided. It is preferable to use a ring having a square or D-shaped cross section in that the torsion or the like can be prevented. Further, the material is not necessarily rubber, and can be appropriately selected as long as it can transmit the driving force in a state where it can slide with a certain force or more between the shaft and the shaft. .

Second Embodiment FIGS. 7 and 8 show a second embodiment to which the present invention is applied. In the present embodiment, instead of the ring-shaped member 80 in the first embodiment, a knurled member having a jagged angle on a predetermined surface is brought into contact with the pickup roll 3 from the feed roll 36 by using the contact force at the contact portion.
5 is transmitted. Note that components similar to those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted.

FIG. 7 is a perspective view for explaining the sheet feed roll group 34 in the present embodiment, and FIG. 8 is an explanatory view schematically showing the structure of the feed roll 36. As shown in FIG. In the present embodiment shown in FIG. 7, a knurled joint 81 is used instead of the ring-shaped member 80 shown in FIG. 5.
And a gear 82. This joint 81
Built-in one-way clutch for feed roll,
The rotation of the feed roll 36 in the paper transport direction is permitted and the reverse rotation thereof is prohibited, and the feed roll 36 can be separated from other parts and can be carried around by transporting the paper P. Further, as shown in FIG. 8, the joint 81 has a knurled portion 81a in which an end surface in the axial direction is processed with a jagged angle. On the other hand, the gear 82 has a built-in one-way clutch for the pick-up roll, which allows the pick-up roll 35 to rotate forward in the sheet conveying direction and prohibits reverse rotation.
Can be separated and the paper P can be carried around by being transported. Further, this gear 82 has a joint 81
Knurled portion 8 facing knurled portion 81a
2a, and the knurled portion 82a is formed with a jagged edge of a predetermined size.

The shape, size, and direction of the jagged corner processing in the knurled portions 81a and 82a are not such that both the joint 81 and the gear 82 are firmly fastened. It is set to a level that allows the vehicle to spin past the jagged corners. Therefore, the shape and size of the jagged angle are preferably relatively small. In the present embodiment, a knurl having a predetermined height is employed. In the present embodiment, a coil spring 83 is provided between the supporter 71 and the gear 82. The coil spring 83 does not have a high spring constant. By pressing the coil spring 83 against the joint 81, that is, the knurl portion 82a of the gear 82 and the knurl portion 81a of the joint 81 are brought into contact with a predetermined pressure. Let me. As a result of adopting such a contact method, unlike a connection by a gear or the like, a connection by a weak force that allows a certain amount of slip can be performed.

Next, the operation of this embodiment will be described. In the same manner as in the first embodiment, the first sheet P1 is nipped by
When the conveyance of the paper by the retard roll 37 becomes unnecessary, the power from the driving source is shut off, and the pickup roll 35 and the feed roll 36 can be idled in the paper conveyance direction by the one-way clutch built in the gear 66 and the joint 70, Pickup roll 3
The feed roll 5 and the feed roll 36 are each brought into contact with the first sheet P1 to rotate in the sheet transport direction based on the transport force generated by the downstream transport roll.
Thereafter, the first sheet P1 is further conveyed. When the first sheet P1 comes into contact with the pickup roll 35 first, the pickup roll 35 does not receive the conveying force from the sheet P1, while the feed roll 36 still has one sheet. The first sheet P1 is nipped, and the feed roll 36 is still in a state of being rotated along with the conveyance of the first sheet P1.

Here, in the present embodiment, the knurled portion 82a of the gear 82 and the knurled portion 81a of the joint 81 and the coil spring 8 for pressing them are provided.
3 are used to connect the feed roll 36 and the pickup roll 35 to each other. Therefore, the pickup roll 35 rotates in conjunction with the rotation of the feed roll 36 with the first sheet P1. However, the connection at this time is based on the knurled contact as described above, and is a very weak connection. Therefore, the pickup roll 35 rotates with a smaller force than the rotation force of the feed roll 36. Since the conveyance force is applied before obtaining the driving force from the driving source, the conveyance of the second sheet P2 can be started in advance. The pre-conveyance by the pick-up roll 35 is a weak conveyance force, so that the second sheet P2 does not ride over the first sheet P1 and is conveyed. The sheet is conveyed regularly while keeping a small interval with the eye sheet P1. If this weak conveyance force is used, even if the second sheet P2 has already reached the vicinity of the nip portion of the sheet separating section, the feed roll 36 and the retard roll 37 are used.
And the second sheet P2 is not transported over the first sheet P1.

As described above, according to the present embodiment, the second sheet P2 can be transported in advance before the driving force is obtained from the driving source for the pickup roll 35.
The paper interval can be shortened and made substantially uniform. Furthermore, 2
Even when the second sheet of paper P2 has already reached the vicinity of the nip of the sheet handling section, the knurls 81a and 82
Since a slip occurs between a and a, it is possible to prevent damage due to excessive transport. In the present embodiment, the knurl portion 8 is formed by using the coil spring 83.
Although 1a and 82a are in pressure contact, there is no problem if the knurls 81a and 82a are brought into contact only by positioning and fixing the joint 81 and the gear 82 without using a coil spring. In short, the knurled portion 81a is designed to prevent damage due to excessive transport.
The specific method can be arbitrarily selected as long as the bonding force of the steps 82a and 82a is set.

[0039]

As described above, according to the present invention,
In the sheet supply, it is possible to reduce the variation in the timing of feeding with a simple configuration, and it is possible to improve the sheet conveyance performance by shortening the interval between the sheets.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an outline of an apparatus according to the present invention.

FIG. 2 is an explanatory diagram illustrating an outline of the image forming apparatus according to the first embodiment;

FIG. 3 is a perspective view illustrating a sheet feed tray according to the embodiment.

FIG. 4 is a perspective view showing a paper feed roll group and a drive structure thereof according to the embodiment.

FIG. 5 is a perspective view for explaining the sheet feed roll group in the present embodiment in further detail.

FIGS. 6A, 6B, and 6C are explanatory diagrams for explaining the movement of a sheet in the present embodiment.

FIG. 7 is a perspective view for describing in detail a sheet feed roll group according to a second embodiment.

FIG. 8 is an explanatory diagram illustrating a drive transmission structure according to a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sheet loading means, 2 ... Sheet retraction means, 3 ... Sheet separating means, 4 ... Driving means / friction contact mechanism, 5 ... Driving source,
21 image forming apparatus, 22 apparatus main body, 23 image reading apparatus (IIT), 24 image forming section, 25 photosensitive drum, 26 laser exposure apparatus, 27 developing apparatus, 28
Cartridge, 29: Image processing device (IPS), 30: Transfer device, 31: Fixing device, 32: Feed tray, 33: Bottom plate, 34: Feed roll group, 35: Pickup roll, 36: Feed roll, 37 ... Retard roll, 38 ... Paper transport path, 39 ... Transport roll,
40 registration roll, 41 first discharge roll, 42 discharge tray, 53 lift lever, 54
Joint, 55: Lift-up motor, 56: No paper sensor, 57: Size sensor, 58: Face control sensor, 61: Drive gear, 62: Feed clutch, 63: Intermediate gear, 64: Intermediate gear, 65, 66
… Gear, 67… arm, 68… retard gear, 69… torque limiter, 70… joint, 71… supporter, 8
0: ring-shaped member, 81: joint, 81: knurl part, 82: gear, 82a: knurl part, 83: coil spring, P: sheet (paper), P1: first sheet, P2: second sheet Paper.

Claims (6)

[Claims] 1. A sheet stacking unit for stacking sheets, a sheet retraction unit that contacts a sheet stacked on the sheet stacking unit and feeds out the sheet, and is provided downstream of the sheet retraction unit in a sheet conveyance direction; The sheet sent out by the sheet pull-in means is 1
A sheet separating unit that separates the sheets one by one and sends the sheet further downstream, and a second sheet that follows the first sheet before the rear end of the conveyed first sheet passes through the sheet separating unit. A sheet feeding device comprising: driving means for driving the sheet drawing means. 2. A sheet conveying force of the sheet retraction unit driven by the driving unit is a level at which the second sheet is prevented from being over-ridden and conveyed to the first sheet remaining in the sheet separating unit. 2. A sheet feeding apparatus according to claim 1, wherein said sheet feeding apparatus is set to be smaller than a conveying force of said means. 3. The sheet feeding apparatus according to claim 1, wherein said driving means has a predetermined sliding action to drive said sheet retraction means. 4. The sheet feeding apparatus according to claim 1, wherein the driving unit drives the sheet pull-in unit in conjunction with the movement of the sheet separating unit. 5. A sheet stacking means for stacking sheets, a sheet retraction means for contacting a sheet stacked on the sheet stacking means and feeding the sheet, and a sheet rewinding means provided downstream of the sheet retraction means in a sheet conveying direction. The sheet sent out by the sheet pull-in means is 1
A sheet separating unit that separates each sheet and sends the sheet to the downstream side, and a driving source that supplies a driving force to the sheet retracting unit and the sheet separating unit, wherein the sheet retracting unit and the sheet separating unit include: After the supply of the driving force from the driving source is stopped, the sheet is driven in accordance with the conveyance of the sheet, and the sheet retraction unit is driven in conjunction with the driving of the sheet in accordance with the conveyance of the sheet by the sheet separating unit. Characteristic image forming apparatus. 6. The image forming apparatus according to claim 5, wherein the sheet retraction unit is driven in conjunction with driving of the sheet releasing unit accompanying conveyance of a sheet by using a friction contact mechanism.