JP2001199578A - Sheet feeder and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of feed failures due to sheets of different rigidity, in a sheet feeder using a separation inclined surface. SOLUTION: Sheets carried by a feed roller 18 are separated one by one by a separation inclined surface 33. When a sheet to be fed has a large rigidity, a separation roller 24 which is mounted so as to enable pressing the sheet between the feed roller 18 and the separation inclined surface 33 is moved off the sheet to allow the sheet to be largely deflected to minimize a driving force. When a sheet with a small rigidity is to be fed, the separation roller 24 presses the sheet to insure a separation by deflecting the sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding device provided in an image forming apparatus such as a printer for feeding sheets.

[0002]

2. Description of the Related Art Conventionally, as a sheet feeding apparatus used in an image forming apparatus such as a printer or a copying machine, there is a so-called slope separation type in which separation is performed using a separation slope. In the sheet feeding apparatus of this separation type, the stacked sheets are sent out by a sheet feed roller and abutted against a separation slope to separate and separate the sheets one by one.

[0003] In this sheet feeding apparatus of the slope separation type,
No complicated separating means such as a separation pad and a reverse roller is required, and no mechanism such as a lifter mechanism or a spring-biased pressure plate for maintaining the sheet at a predetermined height is required. There is an advantage that the configuration of the feeding device can be simplified.

[0004]

However, in the sheet feeding apparatus of the slope separation type, sheets of relatively various thicknesses and different stiffnesses can be separated and fed, but very thin sheets and small stiffness are provided. In the case of a sheet, since the sheet is easily bent, the sheet is not sufficiently separated when abutting against the separation slope, so that double feeding is likely to occur. Therefore, it is conceivable to prevent the double feeding by arranging the position of the sheet feeding roller near the separation slope to largely bend the sheet between the separation slope and the sheet feeding roller to increase the sheet separating force. However, in the case of a very thick sheet or a sheet having a high rigidity, there is a problem in that the sheet is hard to bend and stops when the sheet abuts on the separation slope to cause a feeding failure.

Therefore, it is conceivable to feed a highly rigid sheet with a large feeding force. However, it is necessary to drive the sheet feeding roller with a larger driving torque, which causes a problem that the driving mechanism becomes expensive and becomes large. Occurs.

[0006] Further, when the leading edge of the stacked sheets is curled, double feeding or defective feeding may occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has been made in consideration of the above-described problems. It is an object to provide a sheet feeding device.

[0008]

According to the present invention, there is provided a sheet stacking surface for supporting a sheet, sheet feeding means for feeding a sheet in contact with an upper surface of the sheet supported on the sheet stacking surface, A separating slope for separating the sheets fed by the feeding means one by one, and a rotatable roller for pressing the upper surface of the sheet fed by the sheet feeding means between the separating slope and the sheet feeding means. And a switching unit for switching the separation roller between a position where the upper surface of the sheet to be fed is pressed and a position where the separation roller is separated from the upper surface of the sheet to be sent.

The switching means positions the separation roller at a position separated from the upper surface of the sheet to be fed when feeding a sheet with high rigidity, and feeds the separation roller when feeding a sheet with low rigidity. The switching is performed so that the upper surface of the sheet to be pressed is positioned at a position where the sheet is pressed.

The separation roller located at the position for pressing the sheet is largely bent by pressing the sheet bent by the separation slope.

The separation roller is supported by swingable roller support means, and the switching means is engaged with the roller support means, and manually switches the position of the separation roller by swinging the roller support means. Characterized in that it has the following operation member.

[0012] It is characterized in that there is provided fixing means for fixing the position of the separation roller in a state of being switched by the switching means.

According to the present invention, there is provided a sheet loading surface for supporting a sheet, sheet feeding means for feeding the sheet supported on the sheet loading surface and feeding the sheet, and a sheet fed by the sheet feeding means. A separating slope for separating one sheet at a time, a rotatable separating roller for pressing an upper surface of a sheet fed by the sheet feeding means between the separating slope and the sheet feeding means, and the sheet feeding means Switching means for automatically switching the separation roller between a position where the separation roller is pressed against the upper surface of the sheet and a position where the separation roller is separated from the upper surface of the sheet according to the bending rigidity of the sheet which is sent out and bent by the separation slope, It is characterized by having.

The switching means positions the separation roller at a position separated from the upper surface of the sheet to be fed when feeding a sheet having a large bending rigidity, and the switching roller when feeding a sheet having a low bending rigidity. Is automatically switched so as to position the upper surface of the fed sheet at a position where the upper surface is pressed.

The switching means includes a detecting means for detecting a load applied to the separation roller based on a bending rigidity of the sheet fed by the sheet feeding means and bent by the separation slope, and a means for moving the separation roller. Separating roller operating means, based on the detection of the detecting means, presses the separating roller to a position where the separating roller is separated from the sheet when the load is large, and presses the separating roller to the sheet when the load is small It is moved to a position by the separating roller operating means.

The separating roller is supported by a swingable roller supporting means, and the separating roller operating means separates the separating roller from the sheet by pressing the sheet by swinging the roller supporting means. It is characterized by selectively moving to a position.

The detecting means is a load cell for detecting a load applied to the separating roller, the separating roller operating means is a solenoid for swinging the roller supporting means, and ON / OFF control of the solenoid is performed by detecting the load cell. Is performed.

The switching means has a belt-like member provided in a rotation transmission path for transmitting rotation to the sheet feeding means, and a tension member for applying tension to the belt-like member. The belt-like member expands and contracts in accordance with the load applied to the separation roller due to the bending rigidity of the sheet that is sent out by the feeding means and bent by the separation slope, and the belt-like member expands and contracts in accordance with the movement of the tension member due to the expansion and contraction of the belt-like member. The separation roller is moved.

The separating slope is provided rotatably, and takes the first position when the separating slope is in a position where the separating roller presses the upper surface of the sheet in conjunction with the switching of the position of the separating roller. When the separation roller is located at a position separated from the upper surface of the sheet, a rotating means for rotating so as to take a second position which is at an obtuse angle with respect to the sheet stacking surface at the time of the first position is provided. Features.

The pivoting means includes an urging means for urging the rotatable separating slope toward one of the first and second positions, and a urging force against the urging force of the urging means. A separation slope operating means for rotating the separation slope is provided at the other position.

The sheet stacking surface is fixed, and the sheet feeding means is a sheet feeding roller which is swingably supported so as to be lowered in accordance with a decrease in the number of sheets due to sheet feeding. I do.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment of the present invention will be described with reference to the drawings. First, an outline of the image forming apparatus 1 including the sheet feeding device of the present invention will be described.

First, the overall configuration of the image forming apparatus 1 will be described with reference to FIG. The image forming apparatus 1 includes a sheet feeding device 2 for storing and feeding a sheet for forming an image, an image forming unit 3 for forming an image on a sheet fed from the sheet feeding device 2, and an image forming unit 3. The discharge unit 4 includes a discharge unit 4 that discharges a sheet on which an image is formed by the forming unit 3 and a sheet stacking unit 5 that stacks the discharged sheets.

The image forming section 3 irradiates a light image based on the target image information from the optical system 6 by an exposure means (not shown, such as a slit image projection means for a document image, a laser scanning exposure means, etc.). A latent image is formed on the photosensitive drum 7 which is a toner image, and the latent image is visualized with a developer (hereinafter, referred to as toner) to form a toner image.

Then, a sheet is fed from the sheet feeding device 2 in synchronization with the formation of the toner image, and the toner image formed on the photosensitive drum 7 is transferred to the fed sheet by a transfer roller 8 as a transfer means. Transcribe by The toner image is fixed on the sheet to which the toner image has been transferred by a fixing unit 9 including a fixing rotator 9a having a built-in heater and a driving roller 9b pressed against the fixing rotator 9a.

The image forming section 3 includes a rotating photosensitive drum 7 having a photosensitive layer, and a charging roller 1 serving as a charging unit for uniformly charging the surface of the photosensitive drum 7 by applying a voltage.
0, developing means 11 for developing the surface of the photosensitive drum 7 on which the light image from the optical system 6 is exposed to form a latent image, and after the toner image is transferred to the sheet by the transfer roller 8 A process cartridge 13 integrally provided with a cleaning unit 12 for scraping off toner remaining on the surface of the photosensitive drum 7 is provided.

Next, a sheet feeding apparatus 2 according to the present invention will be described with reference to FIG.

The sheet feeding device 2 has an automatic sheet feeding section 14 for sequentially feeding stacked sheets and a sheet feeding tray section 15 for stacking sheets to be fed. The automatic paper feed unit 14 for feeding out the sheets stored in the paper feed tray unit 15 includes a paper feed unit 16 and a transport unit 17.

The paper feed section 16 includes a paper feed roller 18 that rotates integrally with the paper feed gear 18a, an idler gear A19 that meshes with the paper feed gear 18a, an idler gear B20 that meshes with the idler gear A19, and a drive gear 21 that meshes with the idler gear B20. , A drive shaft 22 mounted to rotate integrally with the drive gear 21, a feed roller 18, an idler gear A19, an idler gear B20, and a drive gear 21.
Are supported rotatably, and are rotatably mounted on the drive shaft 22.
It is composed of

The driving force of a driving source such as a motor (not shown) is transmitted to the driving shaft 22, and the driving shaft 22 transmits the gears 21 and
The rotation is transmitted to the paper feed roller 18 via 0, 19, 18a. The sheet is sent out by the rotation of the sheet feeding roller.

The paper feed roller 18 includes gears 18a, 19,
20, 21 and the weight of the paper feed holder 23 and the paper feed roller 1
Although it is provided so as to be in pressure contact with the sheet due to the weight of the sheet 8 itself, the pressure contact may be performed using a biasing means such as a spring for separately biasing the sheet.

The paper feed tray section 15 is provided with a separation slope 33 for separating the sheet fed by the paper feed roller 18. The separation slope is 33, which will be described in detail later.
The sheet fed from the sheet feed tray unit 15 by the sheet feed roller 18 is conveyed in a bent state, and the sheets are separated at this time by separating the sheets one by one.

A separation roller 24 is provided between the separation slope 33 and the paper feed roller 18, and the separation roller 24 is arranged at a position where it comes into contact with the leading end side of the stacked sheets. The separation roller 24 is rotatably supported by a tip of a separation roller arm 25, and the other end of the separation roller arm 25 is rotatably supported by the drive shaft 22.

The separation roller arm 25 is urged in the counterclockwise direction in FIG.
Is pressed against the leading end side of the loaded sheet. Further, the separation roller arm 25 includes a push-down arm 25a on the side opposite to the separation roller 24 with respect to the drive shaft 22.

The conveying section 17 conveys the fed sheet in a predetermined direction, a lower guide 26 for guiding the lower face of the fed sheet, an upper guide 27 for guiding the upper face of the fed sheet, and the like. Roller 28, a rotatable transport roller 29 disposed opposite to the transport roller 28,
A roller holder 30 rotatably supporting the transport roller 29 and rotatably supported by the upper guide 27, and a roller holder 3 for pressing the transport roller 29 against the transport roller 28.
And a transport spring 31 that urges 0.

The transport unit 17 sequentially transports the sheets separated one by one by the separation slope 33 toward the image forming unit 3.

The paper feed tray section 15 is composed of a paper feed tray 32 for supporting stacked sheets, and a separation slope 33 for separating the sheets sent out by the paper feed section 16. In the present embodiment, the sheet feed tray 32 and the separation slope 33 are formed integrally, but may be provided separately. Then, when the plurality of sheets sent out by the sheet feeding roller 18 are bent along the separation slope 33 and moved, the sheets are separated and separated one by one. The angle of the separation slope 33 is appropriately set.

Next, switching means for selectively switching between a position where the separation roller 24 is pressed against the sheets stacked on the sheet feeding tray 32 and a position where the separation rollers 24 are separated from the sheets will be described.

A lever 34 as a manual operation member for switching to the apparatus main body 1a is rotatably supported. The lever 34 includes a flag portion 34a and an arm portion 34b, and the arm portion 34b has a projection 34c in a direction perpendicular to the plane of the drawing. Flag section 34a
Is provided so as to be able to engage with the press-down arm 25a of the separation roller arm 25, and by engaging the press-down arm 25a to rotate the separation roller arm 25 clockwise in FIG. It can be moved to release the pressure contact.

Here, a description will be given of fixing means for fixing the separation roller at a position where the separation roller is pressed against the sheet and a position where the separation roller is separated from the sheet.

A torsion coil spring 35, one end of which is fixed to the apparatus main body 1a, is provided near the lever 34. The torsion coil spring 35 is provided with an extended portion that is bent in the middle at the end. . The extension portion has a first extension portion 35a on the free end side and a second extension portion 35b on the fixed side, and each extension portion 35a, 35b has an arm portion 34b.
Are configured to be engageable.

When switching by operating the lever 34,
At each switching position, the protrusion 34 c elastically engages with the torsion coil spring 35. Therefore, the lever 34 is urged in the rotational direction by the elastic force of the torsion coil spring 35 at the switching position. That is, when the projection 34c is engaged with the first extension 35a of the coil spring 35,
The lever 34 is urged clockwise in FIG.
When c is engaged with the second extension, the lever 34 is biased counterclockwise in the drawing. Then, the device body 1a
The rotation of the lever 34 is suppressed by the upper stopper 36 and the lower stopper 37 provided on the side, so that the lever 34 is fixed at a fixed position.

The operation of the sheet feeding apparatus having the above configuration will be described.

When feeding a sheet having high rigidity (for example, a sheet having a large thickness), the arm portion 34b of the lever 34 is used.
To the upper position (the position indicated by the two-dot chain line in FIG. 1). With this operation, the lever 34 rotates about its rotation axis, and the flag portion 34a of the lever 34 pushes down the push-down arm 25a of the separation roller arm 25. The separation roller arm 25 rotates around the drive shaft 22 in the clockwise direction in the figure, and the separation roller 24 moves to a position separated from the sheets stacked on the sheet feed tray 32. This separation roller 24
Are set at positions where they do not come into contact with the sheet fed by the paper feed roller 18 (the position indicated by the two-dot chain line in FIG. 1).

The lever 34 is the second of the torsion coil springs 35.
The separation roller arm 25 is also pressed against the upper stopper 36 by the extension 35b of the
The separation roller 24 is fixed in a state where it is pushed up against the elastic force of. Therefore, the separation roller 24 is connected to the paper feed tray 3
2 is fixed at a position separated from the sheets stacked on the sheet 2.

When a sheet having a high rigidity is fed in this state, the fed sheet does not come into contact with the separation roller 24 as shown in FIG.
Between the separation slope 33 and the separation roller 24, the bend is smaller (bend with a large curvature), so that it is easy to bend. Separated by driving force (torque)
Can be fed.

On the other hand, when feeding a sheet having low rigidity (for example, a thin sheet), the lever 34 is operated to the position indicated by the solid line. By this operation, the lever 34 rotates about its rotation axis, and the flag portion 34a of the lever 34 moves to a position separated from the push-down arm 25a of the separation roller arm 25. The lever 34 is pressed and fixed to the lower stopper 37 by the torsion coil spring 35 (the position indicated by the solid line in FIG. 1).

The separation roller arm 25 separated from the push-down arm 25a is urged by an urging spring 26, and the separation roller 24 presses the sheet stacked on the sheet feed tray 32 between the separation slope 33 and the sheet feed roller 18. . When a sheet with low rigidity is fed in this state, when the sheet feeding roller 18 rotates and the fed sheet is separated by the separating slope 33, the separation roller 24 is separated from the separating slope 33 and the sheet feeding roller 1.
Since the sheet is pressed between the positions 8, separation and feeding can be reliably performed without double feeding.

This is because when the sheet having a low rigidity is fed, the separation roller 24 presses the sheet sent between the separation slope 33 and the sheet feeding means. Separation slope 33 and separation roller 2
Bent between four. Since the distance between the separation slope 33 and the separation roller 24 is small, the sheet is largely bent (bent with a small curvature). Therefore, the sheets can be easily handled, and can be reliably separated and fed without double feeding.

With the above configuration, the following effects can be obtained.

If the lever 34 is rotated upward when feeding a sheet having high rigidity such as a thick sheet, the separation roller 24 is fixed at a position separated from the sheet to be fed, so that a smaller driving torque is required. Can feed the sheet.

When feeding a sheet having low rigidity such as a thin sheet, the lever 34 is rotated downward, and the separation roller 24 causes the sheet to be fed to separate the separation slope 33.
And the paper feed roller 18, the separation and feeding can be reliably performed without double feeding.

Further, usually, for example, a sheet having a small rigidity such as a thin sheet is likely to be curled at the front end.
When a sheet having low rigidity is fed, since the separation roller 24 is located at a position where the leading end of the sheet is pressed, an effect of holding down the curl and preventing poor separation and double feed at the time of feeding is also achieved.

As described above, according to this embodiment, when a sheet having a small rigidity is fed, the separation roller 24 can reliably separate and feed the sheet without double feeding without impairing the function. When a sheet having a large value is fed, a sheet feeding device capable of feeding the sheet with a smaller driving torque can be realized.

In this embodiment, the lever 34 and the coil spring 35 are used to move the separation roller 24. However, the present invention is not limited to this, and a switchable structure such as a toggle switch is used. Should be fine.

(Second Embodiment) A second embodiment according to the present invention will be described with reference to FIGS. Note that the schematic configuration of the image forming apparatus 1 is the same as that of the above-described first embodiment, and will not be described, and the sheet feeding apparatus will be described in detail. In the sheet feeding device, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

As shown in FIG. 3, a solenoid A38 as a separating roller operating means is installed near the pressing arm 25a of the separating roller arm 25 supporting the separating roller 24, and the pressing arm 2 of the separating roller arm 25 is provided.
5a has a connecting portion 25 for connecting to the solenoid A38.
b is provided integrally. And solenoid A3
When the switch 8 is turned on, the solenoid A 38 and the connecting portion 25 b are connected to rotate the push-down arm 25 a clockwise, so that the separation roller 24 can be lifted via the separation roller arm 25.

As shown in FIG. 4, the feed roller holder 23
Is provided with a contact plate 39 rotatably.
It is in contact with 2. A load cell 40 that detects a force when pressed against a surface of the contact plate 39 opposite to the surface that is in contact with the drive shaft 22 is installed so as to be in contact. When the load cell 40 detects a force larger than a predetermined value, the solenoid A38 is turned on, and when the load cell 40 detects a force smaller than a predetermined value, the solenoid A38 is controlled by a control means (not shown) so as to be turned OFF. .

The operation of the present embodiment will be described.

A sheet having high rigidity (for example, a thick sheet)
Is fed, the separation roller 24 presses the sheet stacked on the sheet feed tray 32 between the separation slope 33 and the sheet feeding roller 18, so that the bending rigidity between the separation roller 24 and the separation slope 33 is increased. Attempting to bend large sheets greatly increases feeding force. The paper feed roller 18 receives the reaction force and is pushed to the side opposite to the transport direction. The paper feed roller holder 23 is pushed by the paper feed roller 18 to push the drive shaft 22. The load cell 40 includes a paper feed roller holder 23 and a drive shaft 22.
Pressing force is detected.

When the feeding force is increased, the sheet feeding roller 18 feeds the sheet with a larger sheet feeding force, and the sheet feeding roller 18 receives the reaction force, and applies a larger force to the sheet feeding roller holder 23. To press. Paper feed roller holder 23
Presses the drive shaft 22 with a larger force.

When the load cell 40 detects a force equal to or greater than a predetermined value, the solenoid A38 is turned on,
The solenoid A38 is connected to the connecting portion 25b of the push-down arm 25a of the separation roller arm 25. The separation roller arm 25 rotates against the urging force of the urging spring 26, and the separation roller 24 separates from the sheet being fed (the position indicated by the two-dot chain line in FIG. 3).

Since the sheet can be bent between the sheet feeding roller 18 and the separation slope 33, the sheet can be fed if it is bent slightly, and the sheet can be fed with a smaller feeding force.
The driving torque decreases.

A sheet having a small rigidity (eg, a thin sheet)
Is fed, the paper feed roller 18 rotates and the paper feed tray 3
2 is fed, the sheet feeding roller 18
Receives the reaction force of the feeding force, and pushes the paper feed roller holder 23 so that the paper feed roller holder 23 pushes the drive shaft 22.

However, when feeding a sheet having a small bending rigidity, the sheet is easily bent greatly and can be fed with a small feeding force. Therefore, the force for pushing the drive shaft 22 by the sheet feeding roller holder 23 is small, and the load cell 40 The detecting force is smaller than a certain value. Therefore, the solenoid A38
Remains in the OFF state, and the separation roller 24 is separated and fed while pressing the sheet (the position indicated by the solid line in FIG. 3). Since the separation roller 24 keeps pressing the sheet stacked on the paper feed tray 32 between the separation roller 33 and the paper feed roller 18 and bends a sheet having a small rigidity between the separation roller 24 and the separation roller 33, Sheets can be easily handled, no double feeding occurs, and the sheets can be separated and fed reliably.

With the above configuration, the following effects can be obtained.

When a sheet having high rigidity such as a thick sheet is fed, the force by which the sheet feed roller holder 23 presses the drive shaft 22 increases, and the load cell 40 for detecting the force is used.
When the value exceeds a certain value, the separation roller 2
4 is moved to a position away from the sheet being fed, so that the sheet is not bent at the position of the separation roller 24,
Since the sheet is bent at the position of the sheet feeding roller 18, the sheet can be fed with a smaller torque.

When a sheet having a small rigidity such as a thin sheet is fed, the force by which the feed roller holder 23 pushes the drive shaft 22 is small, and the value of the load cell 40 for detecting the force is larger than a predetermined value. Is small, the separation roller 24 separates the fed sheet from the separation slope 33 and the sheet feeding roller 1.
8, the paper can be separated and fed without double feeding.

Further, similarly to the first embodiment, curl at the leading end of a sheet having low rigidity can be suppressed, and poor separation and double feed due to sheet curl can be prevented.

Depending on the value of the load cell 40, the separation roller 2
4 automatically switches between pressing the sheet being fed by the paper feed roller 18 and separating the sheet from the fed sheet, so that the sheet fed by the user is a sheet having high rigidity or a sheet having low rigidity. Since there is no need to judge whether or not, there is no hassle. In addition, reliable switching can be performed without erroneous determination and erroneous operation.

As described above, according to the present embodiment, when a sheet having low rigidity is fed, the function of reliably separating and feeding without double feeding by the separation roller 24 can be achieved without impairing the function. When a large sheet is fed, a sheet with high rigidity can be fed with a smaller driving torque, and switching between feeding a rigid sheet and feeding a non-rigid sheet can be performed. Since the sheet feeding can be performed automatically, a sheet feeding device that does not cause an erroneous operation can be realized.

In this embodiment, a solenoid is used as the separating roller operating means, but other means such as a motor may be used to move the separating roller.

(Third Embodiment) A third embodiment according to the present invention will be described with reference to FIG. Note that the schematic configuration of the image forming apparatus 1 is the same as that of the above-described first embodiment, and will not be described, and the sheet feeding apparatus will be described in detail. In the sheet feeding device, the same components as those in the first and second embodiments are denoted by the same reference numerals, and detailed description is omitted.

As in the second embodiment, the separation rollers 24
Arm 2 of separation roller arm 25 supporting
A solenoid A38 is installed in the vicinity of 5a, and the press-down arm 25a of the separation roller arm 25 is integrally provided with a connecting portion 25b with the solenoid A38.

As shown in FIG. 4 of the second embodiment, a contact plate 39 is rotatably provided on the sheet supply roller holder 23 and is in contact with the drive shaft 22. Contact plate 3
The load cell 40 for detecting a force when the surface is in pressure contact with the surface opposite to the surface in contact with the drive shaft 22 of No. 9 is installed so as to abut. When the load cell 40 detects a force larger than a predetermined value, the solenoid A38 is turned on, and when the load cell 40 detects a force smaller than a predetermined value, the solenoid A38 is controlled to be OFF.

Next, the movable separation slope which is a feature of the present embodiment will be described. The paper feed tray section 15 includes a paper feed tray 32, a movable separation slope 41, and a movable conveyance surface 42. The rotating means for rotating the movable separation slope 41 is constituted by a pressing spring 43 as biasing means, a slope stopper 44, and a solenoid B45 as separation slope operating means. The movable separation slope 41 and the movable transfer surface 42 are rotatably attached to the main body, and are arranged so that the movable separation slope 41 overlaps the movable transfer surface 42 when viewed from the transfer direction.

The pressing spring 43 urges the movable transfer surface 42. When the movable transfer surface 42 pushes the movable separation slope 41, the movable separation slope 41 is moved at a predetermined angle with respect to the stacking surface of the sheet feed tray 32. It is biased so as to be θ1 (this is called the first position in the state shown by the solid line in FIG. 5). The biased movable separation slope 41 has a predetermined angle θ.
The slope stopper 44 is arranged so as to be fixed in the state of 1.

Near the movable separation slope 41, a solenoid B
When the movable separation slope 41 is connected to the solenoid B45, the movable separation slope 41 rotates so that the angle of the movable separation slope 41 with respect to the loading surface of the sheet feed tray 32 becomes a predetermined angle θ2 (the two-dot chain line in FIG. 5). This is referred to as a second position in the state shown in FIG. That is, the solenoid B45 is turned on.
Is reached, the movable separation slope 41 is connected to the movable separation slope 41 against the urging force of the pressing spring 43, and is turned to the second position at a predetermined angle θ2. Here, the angle θ2
Is set to an angle larger than the angle θ1.

The solenoid B45 is connected to the load cell 4 described above.
When the load cell 40 detects a force larger than a predetermined value, the solenoid B45 is turned on, and the load cell 40 detects a force smaller than the predetermined value. Has a solenoid B45
Is turned off by control means (not shown).

The operation of the present embodiment will be described.

When a sheet having a high rigidity is fed, the separation roller 24 presses the sheet stacked on the sheet feeding tray 32 between the separation slope 33 and the sheet feeding roller 18. A larger driving torque is required because the rigid sheet is bent between 33.
When the paper feed roller 18 rotates and pushes the sheet in the transport direction, the paper feed roller 18 receives the reaction force and is pushed to the opposite side to the transport direction. The paper feed roller holder 23 is pushed by the paper feed roller 18 to push the drive shaft 22. The load cell 40 detects the force by which the paper feed roller holder 23 presses the drive shaft 22.

When the torque for driving the paper feed roller 18 is increased, the paper feed roller 18 presses the sheet with a larger force, and the paper feed roller 18 receives the reaction force, and the paper feed roller holder 23 is made larger. We come to push with power. The feed roller holder 23 pushes the drive shaft 22 with a larger force.

When the load cell 40 detects a force equal to or greater than a predetermined value, the solenoid A 38 and the solenoid B 4
5 is turned on, and the connecting portion between the solenoid A38 and the push-down arm 25a of the separation roller arm 25 is connected.
The separation roller arm 25 rotates against the urging force of the urging spring 26, and the separation roller 24 separates from the sheets stacked on the paper feed tray 32. Further, the solenoid B45 and the movable separation slope 41 are connected to each other, and the movable separation slope 41 is set to the first position so that the angle with respect to the loading surface of the sheet feed tray 32 is increased.
From the second position to the second position against the urging force of the pressing spring 43.

The sheet is bent between the sheet feeding roller 18 and the separation slope 33, and further, the movable separation slope 41 is bent.
Is tilted at a large angle θ2, the sheets can be separated with a smaller feeding force than in the second embodiment, and the driving torque is further reduced.

When a sheet having low rigidity is fed, the sheet feeding roller 18 rotates and pushes the sheets stacked on the sheet feeding tray 32 in the conveying direction. When the roller holder 23 is pushed, the paper feed roller holder 23 pushes the drive shaft 22.

However, when a sheet having a low rigidity is fed, the sheet can be separated and fed with a small driving torque. Therefore, the force for pushing the drive shaft 22 by the sheet feeding roller holder 23 is small, and the force detected by the load cell 40 is a certain value. Less than the value given. Therefore, the solenoids A38 and B45 remain in the OFF state, and the separation roller 24 is separated and fed while pressing the sheet. The separation roller 24 presses the sheet stacked on the sheet feed tray 32 between the separation slope 33 and the sheet feeding roller 18, and the sheet having small rigidity is bent between the separation roller 24 and the separation slope 33. Can be easily separated, no double feed occurs, and separation and feeding can be reliably performed.

With the above configuration, the following effects can be obtained.

For example, when a sheet having high rigidity such as a thick sheet is fed, the force by which the paper feed roller holder 23 presses the drive shaft 22 becomes large, and the value of the load cell 40 for detecting the force is determined. When the value exceeds the value, the separation roller 24 is moved to a position separated from the sheet stacked on the sheet feeding tray 32, so that the sheet is not bent at the position of the separation roller 24 but is bent at the position of the sheet feeding roller 18. And
Further, since the movable separation slope 41 falls with respect to the stacking surface of the sheet feed tray 32, sheets can be fed with a smaller torque.

For feeding a sheet having a small rigidity such as a thin sheet, for example, the force by which the sheet feed roller holder 23 presses the drive shaft 22 is small, and the load cell 4 for detecting the force is used.
Since the value of 0 is smaller than a predetermined value, the separation roller 24 keeps pressing the sheet loaded on the sheet feeding tray 32 between the separation slope 33 and the sheet feeding roller 18, so that the sheet is not fed twice. Separation and feeding can be performed reliably.

Depending on the value of the load cell 40, the separation roller 2
4 automatically switches between pressing the sheet stacked on the paper feed tray 32 and separating the sheet from the sheet.
Whether the sheet fed by the user is thick and rigid
Since there is no need to judge whether the sheet is thin and rigid,
No hassle. In addition, reliable switching can be performed without erroneous determination and erroneous operation.

As described above, according to the present embodiment, when a sheet having a small rigidity is fed, the function of reliably separating and feeding the sheet without double feeding by the separation roller 24 can be achieved without impairing the function. When a large sheet is fed, the separation roller 24 is separated from the sheet stacked on the sheet feed tray 32, and the separation slope 33 is tilted, so that a sheet having high rigidity can be fed with a smaller driving torque. Further, it is possible to realize a sheet feeding apparatus capable of automatically switching between feeding a sheet having high rigidity and feeding a sheet having low rigidity.

In this embodiment, the solenoid is used as the separation roller operating means, but other means such as a motor may be used to move the separation roller. Further, although the solenoid is used as the separating slope operating means for rotating the separating slope, other means such as a motor may be used.

In this embodiment, the movable separation slope 4
A rotating means for rotating the first 1 between the first position and the second position urges the movable separation slope 41 to the first position by the pressing spring 43 and rotates to the second position by the solenoid B45. Although the configuration is adopted, the configuration may be reversed. Further, other means such as a motor may be used instead of the solenoid.

(Fourth Embodiment) In the second embodiment, the load cell 40 detects the force by which the paper feed roller holder 23 presses the drive shaft 22 to determine whether to feed a highly rigid sheet. Although the switching when feeding a sheet having a small size is performed, another method may be used.

The feed roller 18 is driven by the gear belt 46 to switch between feeding a sheet having high rigidity and feeding a sheet having low rigidity.
The following shows a method using the difference in the magnitude of the tension.

A fourth embodiment according to the present invention will be described with reference to FIGS. Note that the schematic configuration of the image forming apparatus 1 is the same as that of the above-described first embodiment, and a description thereof will be omitted. Hereinafter, the sheet feeding device will be described. In the sheet feeding device, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

The paper feed section 16 includes a paper feed roller 18 that rotates integrally with a paper feed gear 18 a, a drive gear 21 integrally mounted on a drive shaft 22, a paper feed roller 18 and a drive gear 21.
A roller belt 23 rotatably supported and rotatably mounted on the drive shaft 22, and a gear belt for transmitting drive through a paper feed gear 18 a and a drive gear 21. 46, a tension roller 47 for pressing the gear belt 46 to apply tension to the gear belt 46, a tension roller holder 48 for rotatably supporting the tension roller 47, and urging the tension roller holder 48 to apply tension to the gear belt 46. And a tension spring 49 for hooking.

The feed roller holder 23 is provided with a guide 23a, and the tension roller holder 48 is
It is configured to move along 3a. further,
A separation roller 24 is disposed between the separation slope 33 and the sheet feeding roller 18, and the separation roller 24 is rotatably supported by a separation roller arm 25. The other end of the separation roller arm 25 is rotatably supported by the drive shaft 22, and the separation roller arm 25 is urged by an urging spring in a direction to press the separation roller 24 against the sheet. The arm 4 extending in a direction perpendicular to the paper surface of FIG.
8a, and is arranged to be always engageable from below the separation roller arm 25.

When a sheet having high rigidity is fed, the separation roller 24 presses the sheet fed between the separation slope 33 and the sheet feeding roller 18, and the separation roller 24 and the separation slope 3 are pressed.
Since the sheet having high rigidity is largely bent between the three positions, a larger feeding force is required, and the driving torque is further increased.

At this time, when a large driving torque is applied to the driving gear 21, a large tension is applied to the driving side 46 a of the gear belt 46, and the tension roller 47 is lifted against the urging force of the tension spring 49, and
6 tries to straighten. Then, the tension roller 47 and the tension roller holder 48 are lifted, and the arm portion 48a of the tension roller holder 48 engages with the separation roller arm 25 to lift. as a result. Separating roller 2
4 is separated from the sheet being fed (see FIG. 7).

As described above, since a sheet having high rigidity is bent between the sheet feeding roller 18 and the separation slope 33, the sheet can be separated with a smaller feeding force.
The driving torque is reduced.

When a sheet having a small rigidity is fed, the sheet can be separated with a small feeding force, so that the driving torque is small and the gear belt 46 is not subjected to a large tension. Therefore, the separation roller 24 keeps pressing the sheet fed between the separation slope 33 and the sheet feeding roller 18, and the sheet having low rigidity is greatly bent between the separation roller 24 and the separation slope 33, so that the sheet is separated. Since double feeding is not caused, separation and feeding can be reliably performed.

With the above configuration, the following effects can be obtained.

When a sheet having a large rigidity such as a thick sheet is fed, for example, as shown in FIG. 7, the tension of the gear belt 46 is increased, and the tension roller 47 is lifted against the urging force of the tension spring 49. Since the separation roller 24 is moved to a position separated from the sheet being fed, the sheet is not bent at the position of the separation roller 24 but is bent at the position of the paper feed roller 18 so that the sheet is supplied with a smaller torque. Can be sent.

For example, when feeding a sheet having a small rigidity such as a thin sheet, as shown in FIG. 6, the tension of the gear belt 46 is small, so that the gear belt 46 does not lift the tension roller 47 and the separation roller 24 is fed. Since the separated sheet is kept pressed between the separation slope 33 and the sheet feeding roller 18, separation and feeding can be reliably performed without double feeding.

Depending on whether the tension of the gear belt 46 lifts the tension roller 47 against the urging force of the tension spring 49, the separation roller 24 presses the sheet stacked on the sheet feed tray 32 or separates the sheet from the sheet. Is automatically switched, and it is not necessary to judge whether the sheet fed by the user is a sheet having a high rigidity or a sheet having a low rigidity. In addition, reliable switching can be performed without erroneous determination and erroneous operation.

As in the second embodiment, the load cell 4
An effect similar to that of the second embodiment can be obtained with an inexpensive configuration without using expensive components such as zeros and solenoids.

Although the fourth embodiment uses a gear and a gear belt, a pulley and a belt such as a flat belt may be used in combination.

Although the embodiments of the present invention have been described above, the configurations of the embodiments may be combined. For example, the configuration of the movable separation slope described in the third embodiment may be combined with the switching configuration of the separation rollers described in the first and fourth embodiments. In this case, for example, various configurations such as rotating the movable separation slope in response to the detection of the position of the separation roller arm, and rotating the movable separation slope by operating the operation member by a link mechanism or the like may be employed. it can.

[0110]

As described above, according to the present invention, the separation roller is moved between the position where the fed sheet is pressed and the position where the separated roller is separated from the fed sheet according to the rigidity of the fed sheet. In this case, it is not necessary to feed a sheet having a high rigidity with a large force, and an effect of reliably separating and feeding a sheet having a low rigidity is achieved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a sheet feeding device according to a first embodiment.

FIG. 2 is a schematic diagram of an image forming apparatus including a sheet feeding device according to the first embodiment.

FIG. 3 is a longitudinal sectional view of a sheet feeding device according to a second embodiment.

FIG. 4 is a sectional view of a main part of a sheet feeding apparatus according to a second embodiment.

FIG. 5 is a longitudinal sectional view of a sheet feeding device according to a third embodiment.

FIG. 6 is a longitudinal sectional view of a sheet feeding device according to a fourth embodiment.

FIG. 7 is a diagram illustrating the movement of a separation roller of a sheet feeding device according to a fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Sheet feeding apparatus 18 Paper feed roller (sheet feeding means) 22 Drive shaft 23 Paper feed roller holder 24 Separation roller 25 Separation roller arm (roller support means) 32 Paper feed tray (sheet loading surface) 33 Separation slope 34 Lever 35 Torsion coil spring (fixing means) 36, 37 Stopper (fixing means) 38 Solenoid A (separating roller operating means) 40 Load cell 43 Pressing spring (biasing means) 44 Movable separating slope 45 Solenoid B (separating slope operating means) 46 Gear belt 47 Tension roller 48 Tension roller holder

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiro Matsuo 3-30-2 Shimomaruko, Ota-ku, Tokyo 3F343 FA02 FB01 FC01 GA01 GB01 GC01 GD01 HA12 HB01 JA01 JD04 JD13 JD22 JD33 LA04 LA15 LC04 LC07 LC19 LD11 MA03 MA09 MA39

Claims (15)

[Claims] 1. A sheet loading surface for supporting a sheet, sheet feeding means for feeding a sheet in contact with an upper surface of the sheet supported by the sheet loading surface, and a sheet fed by the sheet feeding means. A separating slope for separating one sheet at a time, a rotatable separating roller for pressing an upper surface of a sheet fed by the sheet feeding means between the separating slope and the sheet feeding means, and the separating roller. And a switching unit for switching a position of pressing the upper surface of the fed sheet and a position of separating from the upper surface of the fed sheet. 2. The sheet feeding apparatus according to claim 1, wherein the switching unit is configured to position the separation roller at a position separated from an upper surface of a sheet to be fed when feeding a sheet having a high rigidity, and to switch the separation roller when feeding a sheet having a low rigidity. 2. The sheet feeding device according to claim 1, wherein switching is performed such that the position of the sheet is pressed to a position where the upper surface of the sheet to be fed is pressed. 3. The sheet feeding device according to claim 2, wherein the separation roller located at a position where the sheet is pressed is largely bent by pressing the sheet bent by the separation slope. 4. The roller is supported by a swingable roller supporting means, and the switching means is engaged with the roller supporting means, and swings the roller supporting means manually to set the position of the separating roller. The sheet feeding device according to claim 2, further comprising an operation member for switching. 5. The sheet feeding apparatus according to claim 2, further comprising fixing means for fixing the position of the separation roller by switching by the switching means. 6. A sheet stacking surface for supporting a sheet, sheet feeding means for sending the sheet in contact with an upper surface of the sheet supported on the sheet stacking surface, and one sheet fed by the sheet feeding means. A separating slope for separating the sheet feeding means, a rotatable separating roller for pressing an upper surface of a sheet fed by the sheet feeding means, between the separating slope and the sheet feeding means, and a sheet fed by the sheet feeding means. Switching means for automatically switching the separation roller between a position where the separation roller is pressed against the upper surface of the sheet and a position where the separation roller is separated from the upper surface of the sheet according to the bending rigidity of the sheet bent by the separation slope.
A sheet feeding device comprising: 7. The switching means, when feeding a sheet having a high bending rigidity, positions the separation roller at a position separated from an upper surface of a sheet to be fed, and when feeding a sheet having a low bending rigidity, the switching means is arranged to be separated from the upper surface of the sheet. 7. The sheet feeding apparatus according to claim 6, wherein the separation roller is automatically switched so as to be positioned at a position where the upper surface of the fed sheet is pressed. 8. The switching means includes a detecting means for detecting a load applied to the separation roller based on a bending rigidity of the sheet fed by the sheet feeding means and bent by the separation slope, and moving the separation roller. Separation roller actuation means for detecting, based on the detection of the detection means, when the load is large, at a position to separate the separation roller from the sheet, when the load is small, the separation roller to the sheet The sheet feeding device according to claim 7, wherein the separation roller operating means is moved to a position to be pressed. 9. The separating roller is supported by a swingable roller supporting means, and the separating roller operating means swings the roller supporting means so that the separating roller is pressed from a position where the sheet is pressed against a sheet. 9. The sheet feeding device according to claim 8, wherein the sheet feeding device is selectively moved to a position where the sheet is separated. 10. The detecting means is a load cell for detecting a load applied to the separating roller, the separating roller operating means is a solenoid for swinging the roller supporting means, and ON / OFF of the solenoid is detected by detecting the load cell. OF
The sheet feeding device according to claim 9, wherein F control is performed. 11. The switching means has a belt-like member provided in a rotation transmission path for transmitting rotation to a sheet feeding means, and a tension member for applying tension to the belt-like member. The belt-shaped member expands and contracts in accordance with the load applied to the separation roller due to the bending rigidity of the sheet sent out by the sheet feeding means and bent by the separation slope, and in accordance with the movement of the tension member due to the expansion and contraction of the belt-shaped member. The sheet feeding device according to claim 6, wherein the separation roller is moved by moving. 12. The separation slope is provided rotatably, and takes the first position when the separation slope is in a position where the separation roller presses the upper surface of the sheet in conjunction with the switching of the position of the separation roller. When the separating roller is located at a position separated from the upper surface of the sheet, a rotating means is provided for rotating so as to take a second position which is at an obtuse angle with respect to the sheet stacking surface at the time of the first position. The sheet feeding device according to claim 1, wherein 13. The urging means for urging the rotatable separation slope toward one of the first and second positions, and a biasing force against the urging force of the urging means. 13. The sheet feeding device according to claim 12, further comprising a separation slope operating means for rotating the separation slope at the other position. 14. The sheet stacking surface is fixed, and the sheet feeding means is a sheet feeding roller that is swingably supported so as to descend in accordance with a decrease in the number of sheets due to sheet feeding. The sheet feeding device according to claim 1 or 6, wherein 15. A sheet feeding apparatus according to claim 1, further comprising: an image forming apparatus for forming an image on a sheet fed by the sheet feeding apparatus. Image forming device.