JPH11255355A - Sheet feeding device and image forming device equipped with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To feed certainly recording paper (sheets) of any size without bringing about cost increase or an increase in the number of part items. SOLUTION: A plurality of sucking means 2A, 2B, 2C to attract a sheet P by the suction force given to the inside of a recess are held at moving means 3 and 3A and abutted on the sheet P by moving the means 3 and 3A when the sheet is to be attracted. The sheet sucking means 2C abutting on the sheet selectively in accordance with the sheet size is given a suction force from a suction force generating means 11 by a suction force giving means only at the time of abutting, and no suction force should be given at the time out of abutting. This precludes air from flowing into the suction force generating means 11 from the sheet sucking means 2C at the time of unabutting, and an attracting force required to make suction attachment is given to the other sheet sucking means 2A and 2B abutting on 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 apparatus and an image forming apparatus having the same, and more particularly to a sheet feeding apparatus in which sheets are suctioned one by one by sheet suction means.

[0002]

2. Description of the Related Art Conventionally, a copying machine, a printing machine, and other image forming apparatuses include a sheet feeding device of an air suction type as a sheet feeding device for a sheet such as a recording material or a thin plate material. Examples of such a sheet feeding device include, for example, Japanese Patent Application Laid-Open Nos.
Nos. 9417 and 6-127718, a suction pad as a sheet suction means, a moving means for supporting and moving the suction pad, and a continuous means for applying a suction force to the suction pad. And a suction force generating means for generating a negative pressure, and the sheet is fed by moving the suction pad which has sucked the sheet by the moving means.

[0003]

However, such a conventional sheet feeding apparatus has the following problems.

That is, Japanese Unexamined Patent Publication No. H05-058503 discloses a method in which four suction pads (suckers) are used as sheet suction means evenly over substantially the entire width of a sheet to be used from one end of the sheet to the other. At the end,
In this structure, if a sheet smaller in size than the sheet described in the apparatus of the embodiment in the publication is used, the suction pads at both ends do not come into contact with the sheet.

When the suction pad does not come into contact with the sheet as described above, when the recording paper is to be sucked, air is easily and largely generated from the suction pad which does not come into contact with the sheet. Flow into suction pump. And
When the air flows into the suction pump in this manner, it is difficult to obtain a negative pressure required for suction when the suction pump is single and connected to all the suction pads, so that the sheet is suctioned and conveyed. It becomes difficult.

As a countermeasure, it is conceivable to provide a plurality of suction pumps or to provide a suction pump having a considerably large capacity. However, any of these countermeasures causes an increase in the number of parts or an increase in cost. There is.

In Japanese Patent Application Laid-Open No. 05-289417, five suction pads (suckers) are provided as sheet suction means evenly over substantially the entire width of a sheet to be used, from near one end to the other end. There are migrants, and the problems are the same as described above.

In Japanese Patent Application Laid-Open No. 06-127718, the number of suction pads is two, and the number of suction pads is set near one end and almost the other end of substantially the entire width of a sheet to be used. If an attempt is made to use a sheet smaller in size than the sheet described in the apparatus of the embodiment in the publication, at least one of the suction pads does not contact the sheet, and the sheet is sucked and conveyed in the same manner as described above. It becomes difficult.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to reliably feed recording paper (sheets) of any size without increasing the number of parts and increasing the cost. An object of the present invention is to provide a feeding device and an image forming apparatus including the same.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a sheet feeding apparatus for adsorbing and feeding sheets stacked on sheet stacking means capable of stacking sheets of different sizes. A plurality of sheet adsorbing means for adsorbing the sheet by an adsorbing force provided therein, and a movable member provided above the sheet stacking means,
Moving means for holding the sheet suction means and moving the sheet suction means to contact the sheet during sheet suction, and suction force for generating the suction force applied in the recess of the sheet suction means Generating means, wherein at least one of the plurality of sheet suction means selectively contacts the sheet according to a sheet size, and the suction force generating means only when the sheet is in contact with the sheet. , Which is characterized in that a suction force is applied to the substrate.

According to another aspect of the present invention, there is provided a sheet feeding apparatus for sucking and feeding sheets stacked on sheet stacking means capable of stacking sheets of different sizes, wherein the sheet feeding apparatus has a concave portion on a bottom surface and is provided in the concave portion. A plurality of sheet suction means for sucking the sheet by a suction force, movably provided above the sheet stacking means, holding the sheet suction means, and moving at the time of sheet suction to move the sheet suction means. A moving unit that abuts the sheet, an attraction force generating unit that generates the attraction force applied in the recess of the sheet attraction unit, and at least one sheet attraction unit of the plurality of sheet attraction units, A suction force applying means for selectively abutting the sheet according to a sheet size and applying the suction force from the suction force generating means only at the time of the contact; It is characterized in that there.

Further, the present invention includes a communication path for communicating the suction force generating means with the concave portion for applying the suction force, wherein the suction force applying means connects the communication path only at the time of the contact. It is characterized in that it is opened to apply the suction force to the inside of the concave portion.

In the present invention, the suction force applying means is provided in the recess so as to close the communication path, and is moved by being pressed by the sheet at the time of the contact. The moving member is configured to open the opening.

Further, the present invention is characterized in that the sheet suction means selectively contacting the sheet according to the sheet size is arranged outside one or both of the other sheet suction means.

According to the present invention, there is provided a sheet feeding apparatus for sucking and feeding a sheet stacked on a sheet stacking means, and an image forming section for forming an image on the sheet fed by the sheet feeding apparatus. In the image forming apparatus provided, the sheet feeding device is the one according to any one of claims 1 to 5.

Further, as in the present invention, a plurality of sheet adsorbing means having a concave portion on the bottom surface and adsorbing a sheet by an adsorbing force provided in the concave portion are provided movably provided above the sheet stacking means. When the sheet is attracted, the moving means is moved so that the sheet attracting means is brought into contact with the sheet. Then, at least one of the plurality of sheet suction means, which selectively abuts the sheet according to the sheet size, is attracted from the attraction force generating means by the attraction force applying means only at the time of contact. By applying force and not applying suction force during non-contact, air is prevented from flowing from the sheet suction means to the suction force generating means during non-contact, and other sheets that are in contact with the sheet are attracted. The means can be provided with a suction force required for suction.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of a copying apparatus which is an example of an image forming apparatus provided with a sheet feeding apparatus according to a first embodiment of the present invention. It is. The copying apparatus 50 includes a paper cassette 55 which is a sheet stacking unit capable of stacking recording sheets P, which are sheets of different sizes.
After the recording paper P loaded on the recording paper P is fed by the sheet feeding device 1A to the pair of paper feeding rollers 15 and 16, a pair of registration rollers 63a and 63a having a function of correcting the inclination of the recording paper P is provided.
Process cartridge 5 serving as an image forming unit through 63b
2 is transported.

The recording paper P on which an image has been formed by the process cartridge 52 is further transported by a transport belt 73.
The image is fixed by being guided to a fixing device 75 via a pre-fixing guide 74, and thereafter discharged from a discharge port 78 downstream of the fixing device 75 and placed on a discharge tray 79.

Here, the process cartridge 52
Is constituted by a photosensitive drum 68, a developing sleeve 67, a cleaning blade 69 of the photosensitive drum, a toner (not shown), a stirring mechanism thereof, and a waste toner container. A transfer charger 70 is provided at a position facing the photosensitive drum 68.

On the other hand, the transport belt 73 has rollers 71, 7
2 and rotatably supported by rollers 72
Are driven by driving means (not shown). The transport belt 73 is given an appropriate tension by a tensioner (not shown) of the roller 72.

The fixing device 75 includes a heat roller 76 having a built-in heater and a pressure roller 77.
Thermal fixing of the toner printed on the recording paper P is performed in the nip portions 6, 77. The pressure roller 77 is pressed against the heat roller 76 by a spring (not shown).

In FIG. 1, reference numeral 80 denotes an original table glass on which an original is placed. Below the original table glass 80, an illumination lamp 81, an image forming lens 85, and mirrors 82 and 8 are provided.
An optical system including 3, 84, and 86 is provided, and the optical system irradiates a predetermined position of the photosensitive drum 68 with reflected light 87 from the document.

Reference numeral 91 denotes a pressure plate which is disposed on the original platen glass 80 so as to be openable and closable, and which presses an original appropriately.
Reference numeral 1 is provided with a pressure contact sheet 90 made of a sponge-like member having an appropriate hardness on the original contact surface side. Reference numeral 96 denotes a manual paper feed port, and the manual paper feed port 96 is used when recording paper which is difficult to feed from a cassette such as thick paper or thin paper is used. The recording paper from the manual paper feed port 96 is transported by rollers 97 and 98.

FIG. 2 shows the sheet feeding apparatus 1A.
FIG. 3 is a sectional view of the sheet feeding device taken along line AA, and FIG. 4 is a sectional view of the sheet feeding device taken along line BB.

2 to 4, reference numeral 1 denotes a main frame of the sheet feeding device 1A, and the following members constituting the sheet feeding device 1A are fixed to the main frame 1.
Or it is engaged.

Reference numerals 2A, 2B and 2C denote first, second and third suction pads which are sheet suction means, and 3, 3A are provided so as to be able to swing (move) above the paper cassette 55 and have a first end at one end. While the first suction pad 2A and the second and third suction pads 2B, 2C are rotatably held within a predetermined range, the suction pads 2A, 2B, 2C are swung (moved) when the recording paper is sucked. First and second swing arms, which are moving means for making contact with the recording paper P.

Here, these three suction pads 2A, 2A
B and 2C are formed of an elastic member such as rubber,
A concave portion 2a having a substantially conical shape is formed on the bottom surface. When the recording paper is fed, a negative pressure serving as an attraction force is applied to the concave portion so that both ends of the recording paper P, which has been cut into a predetermined size in the feeding direction, can be suctioned. Has become.

By the way, these three suction pads 2A,
2B and 2C, the first suction pad 2A and the second suction pad 2B are located on the feed direction side of the recording paper P ′ having the minimum width among the recording papers that can be used by the copying apparatus 50 shown in FIG. The first and second swing arms 3 and 3A are respectively held at intervals that can suck both ends. Note that, in the present embodiment, the recording paper P 'is held at intervals of about half the width of the minimum width recording paper P'.

On the other hand, the third suction pad 2C is
Is held by the second swing arm 3A at a position where one end of the recording paper P having the largest width among the recording papers that can be used is sucked. That is, when the recording paper P having the maximum width is fed, the first suction pad 2A is located at the other end of the recording paper P and the second suction pad 2B is located at the center of the recording paper P as shown in FIG. , The third suction pad 2C is sucked to one end of the recording paper P.

Further, in the recess of the third suction pad 2C, there is provided a piston 3 which is a moving member serving as suction force applying means.
0 is slidably provided. Here, the piston 30 opens a communication path S that communicates a suction pump 11 and the concave portion 2a, which will be described later, in a contact state with the recording paper P, and applies a negative pressure generated in the suction pump 11 to the concave portion 2a. It has a communication hole 30a for giving as a. Further, a contact member 31 is vertically provided on the bottom surface of the piston 30, and the piston 30 moves downward in a non-contact state with the recording paper P due to the weight of the contact member 31.

By the way, the piston 30 having such a configuration is used.
When the third suction pad 2C comes into contact with the recording paper P, it is pressed by the recording paper P via the contact member 31 and moves upward. And like this, piston 3
When 0 rises, the communication hole 30a moves to a position where the communication passage S is opened, whereby the negative pressure generated in the suction pump 11 is applied to the concave portion 2a.

When the third suction pad 2C does not come into contact with the recording paper P, as shown in FIG.
In this state, the piston 30 closes the communication passage S and shuts off the negative pressure from the suction pump 11. The contact member 31 is
As described later, when a negative pressure is applied to the concave portion 2a, the piston 30 has such a weight that the piston 30 does not rise due to the negative pressure.

On the other hand, the first and second swing arms 3 and 3A are swingably supported by the movable base 5 via the pins 3a, and are also supported by the tension coil springs 7 mounted between the movable base 5 and the movable base 5. The suction pads 2A, 2B, and 2C are urged in a direction in which the end 3b (hereinafter, referred to as the other end) that does not hold the suction pads 2A, 2B, and 2C is pulled up, that is, the suction pads 2A, 2B, and 2C are brought into contact with the recording paper. .

The moving table 5 has a part of the bracket 5.
By engaging the groove portion 5a 'of "a" with a not-shown notch of the main frame 1, it is slidably held by the main frame 1 and recorded by a tension coil spring 6 having one end fixed to the main frame 1. The paper P is urged in the feeding direction.

Reference numeral 4 denotes a recording paper presser. The recording paper presser 4 is rotatably supported by swinging arms 3 and 3A via pins 4a, and is urged downward by a compression spring 40. It is stopped at a predetermined position by a stopper 4b.

Reference numeral 8 denotes a drive shaft connected to a motor (not shown). The drive shaft 8 rotates the first cam 9, the second cam 10, and the third cam 13. The first cam 9 contacts the other end 3b of the swing arm 3 from above to swing the swing arm 3. Further, the second cam 10 comes into contact with the contact portion 5b formed at the end (hereinafter referred to as the other end) of the movable base 5 opposite to the side on which the tension coil spring 6 is attached, from the inside,
This is for moving the movable table 5 in parallel with the tension coil spring 6.

The third cam 13 is for driving the suction pump 11 by rotating a link 12 for driving the suction pump 11 which is a suction force generating means around a rotation shaft 12a as a fulcrum. . Here, this suction pump 11
Are fixed to the main frame 1 by brackets 11a. The suction pump 11 is configured to generate a negative pressure during an upward operation of a vertically movable partition (not shown) provided therein, and the negative pressure is generated by the suction pump 11 and the suction pad. Tubes 14 and 14a which form a communication path S with the recess 2a of 2A, 2B and 2C can reach the recess 2a of the suction pads 2A, 2B and 2C. Then, the suction pads 2A, 2B, and 2C can suck the recording paper P by the negative pressure.

The link 12 has two substantially L-shaped arms 121 and 122, and is attached to the main body of the sheet feeding device so as to be swingable about the rotation shaft 12a. In addition, one arm 1 of this link 12
The third cam 1 is biased by biasing means (not shown).
3 and the other arm 122 is connected to the suction pump 1
1 is engaged with the upper end of the movable portion 11b of the suction pump 11 so as to drive the suction pump 1.

On the other hand, reference numeral 20 denotes a separation claw.
Numeral 0 is for suppressing a plurality of sheets of recording paper P from being sucked up by the suction pads 2A, 2B and 2C, and for separating only one uppermost sheet. The feed roller pairs 15 and 16 described above are urged by urging means (not shown) in a direction approaching each other, and are driven by a motor (not shown) to convey the recording paper P. R indicates the rotation direction of the drive shaft 8 and the first to third cams 9, 10, and 13.

In the above configuration, FIGS. 3, 5 to 7
The operation of the present embodiment will be described with reference to FIG. In addition,
FIGS. 3, 5 to 7 show a case where the recording paper P having the largest width among the recording papers that can be used by the copying apparatus 50 is fed.

FIG. 3 shows a standby state before paper feeding. In this state, the first cam 9 has the largest part of its radius abutting on the other end 3b of the swing arm 3, 3A from above, whereby the swing arm 3, 3A keeps a substantially horizontal state, The suction pads 2A, 2B, 2C are separated from the recording paper P (see FIG. 11). In addition, the second cam 10 has the largest radius portion in contact with the contact portion 5b of the movable base 5, whereby the movable base 5 is stopped at the left end position of its movable range.

Further, the recording paper retainer 4 includes a compression spring 40.
, And is stopped at a predetermined position by the stopper 4b, and is separated from the recording paper P. Further, the third cam 13 is in contact with the first arm 121 of the link 12 in a state before the movable portion 11b of the suction pump 11 is pulled up, so that the suction pump 11 does not generate a negative pressure. It is in a state.

FIG. 5 shows a state in which the suction pad 2 tries to suck the recording paper P. This state is different from the state of FIG.
The first cam 9, the second cam 10, and the third cam 13 have started rotating together with the drive shaft 8 in the direction of arrow R. Here, the first cam 9 is separated from the other end 3b of the swing arm 3 or 3A by the rotation of the first cam 9 by this rotation. Swings downward by the force of the suction pads 2A, 2A.
The other ends of B and 2C come into contact with the recording paper P.

At this time, the piston 30 of the third suction pad 2C comes into contact with the recording paper P and rises together with the contact member 31. When the piston 30 rises, the communication hole 30a moves to a position where the communication passage S is opened, and the suction pump 11 and the recess 2a are in communication with each other.

The recording paper presser 4 is urged downward by the compression spring 40 to abut the recording paper P and press the recording paper P. At this time, the second cam 10 has the largest radius portion still in contact with the contact portion 2b of the movable base 5, whereby the movable base 5 stops at the left end position of its movable range. I have.

On the other hand, the third cam 13 gradually comes into contact with the link 12 at its maximum radius, and pulls the movable portion 11b of the suction pump 11 upward through the link 12. As a result, the suction pump 11 generates a negative pressure, and the negative pressure is generated by the suction pads 2A, 2B, 2 by the tubes 14, 14a.
It reaches the concave portion 2a of C. Then, the suction pads 2A, 2B, and 2C start suctioning the recording paper P by the negative pressure (see FIG. 12).

FIG. 6 shows a state where only the uppermost recording paper P1 of the sucked recording paper P is separated. In this state,
The first cam 9 has an intermediate radius portion between the maximum radius and the minimum radius of the first cam 9 abuts on the other end 3b of the swing arm 3, whereby the swing arm 3 is slightly shifted from the state shown in FIG. Then, the suction pads 2A, 2B, and 2C move upward, and the uppermost recording sheet P1 is pulled upward. The recording paper holder 4 is urged downward in the figure by a compression spring 40, and the uppermost recording paper P1
And presses the recording paper P1.

Here, the second sheet from the top has a weaker attraction force than the uppermost recording sheet P1, and is thus held down by the separation claw 20 and the recording sheet retainer 4 to the weaker attraction force. The rigidity of the recording paper in the middle overcomes, and there is also a frictional force due to the pressing force from the recording paper retainer 4, so that the second and subsequent sheets are separated from the uppermost recording paper P1.

On the other hand, the second cam 10 has the largest radius in contact with the moving table 5 and stops at the left end position of its movable range. The third cam 13 is still in contact with the link 12 at its maximum radius. This allows
The suction pump 11 continues to generate a negative pressure, and as a result, the suction pads 2A, 2B, and 2C maintain the state in which the recording paper P1 is suctioned.

FIG. 7 shows a state in which the sucked recording paper P1 is sent out toward the pair of paper feed rollers 15, 16.

In this state, the largest part of the radius of the first cam 9 abuts against the other end 3b of the swing arm 3, whereby the swing arm 3 returns to a substantially horizontal state. Further, since the second cam 10 has a minimum portion of the radius abutting on the moving table 5, the moving table 5 moves in the arrow X direction by the spring force of the extension coil spring 6.

By the way, this recording paper P1 is
When the recording paper is fed toward the recording papers 5 and 16, the recording paper retainer 4 is stopped at a predetermined position similar to the position shown in FIG. 3, so that there is some contact with the recording paper P1, but the pressing force is not applied. And the frictional force is extremely small, so that the conveyance of the recording paper is not hindered.

The position of the third cam 13 in contact with the link 12 returns to the state before the movable portion 11b of the suction pump 11 is pulled upward, and the suction pump 11 does not generate a negative pressure. Thus, the suction force of the unnecessary suction pads 2A, 2B, 2C after the transfer to the sheet feed roller pairs 15, 16 is not generated.

After that, the recording paper P1 delivered to the paper feed roller pair 15, 16 is applied to the paper guide plate 6 shown in FIG.
Registration roller pair 63a, 63 while being guided by 5, 66
By b, it is transported to the process cartridge 52.
On the other hand, the image information of the original (not shown) is illuminated by an illumination lamp 81 below the original platen glass 80, reflected by an imaging lens 85 and mirrors 82, 83, 84, and 86, and becomes reflected light 87. Irradiation is performed at 68 predetermined positions.

The image formed on the photosensitive drum 68 is developed by the developing sleeve 67 and is transferred to the conveyed recording paper P1 by the transfer charger 70.
Further, the recording paper P1 is transferred to the fixing device 75 by the transport belt 73.
Sent to Then, the toner printed on the recording paper P1 is thermally fixed by the heat roller 76, and thereafter,
The sheet is placed on the discharge tray 79 via the discharge port 78, and the recording is completed.

By the way, the case where the recording paper P having the maximum width among the recording papers which can be used by the copying apparatus 50 has been described, but the recording paper P ′ having the minimum width is supplied next. Will be described.

FIG. 8 is a diagram showing a state in which the recording paper P ′ (see FIG. 4) having the minimum width among the recording papers that can be used by the copying apparatus 50 is sucked.

In the case of adsorbing such a recording sheet P ', for example, as described above, the first cam 9, the second cam 10, and the third cam 13 rotate together with the drive shaft 8, and swing by such rotation. When the suction pad side of the arm 3 swings downward, the first
And the second suction pads 2A and 2B are pressed against the recording paper P ', but since the recording paper P' does not exist below the third suction pad 2C (see FIG. 4), the contact member 31 is shown in FIG. As described above, it remains in a state of protruding from the third suction pad 2C.

If the contact member 31 remains in the protruding state as described above, the piston 30 remains in the closed state of the communication passage S, so that air is supplied from the third suction pad 2C to the suction pump 11. And does not affect the negative suction pressure of the other suction pads 2A and 2B.

As described above, when the recording paper is sucked, the recording paper P ′
2a of the suction pad 2C that does not come into contact with
1 and the other suction pads 2A, 2
By not affecting the suction negative pressure of B, the recording paper P ′ can be reliably sucked and fed.

By the way, when the recording paper P having the maximum width has been sucked up to now, the first suction pad 2A is placed at the other end of the recording paper P, the second suction pad 2B is placed at the center of the recording paper P, 3
Although the sheet feeding apparatus having the configuration in which the suction pad 2C is suctioned to one end of the recording paper P has been described, the present invention is not limited to this, and includes a fourth suction pad having the same configuration as the third suction pad 3C. To absorb a large amount of recording paper P,
The first and second suction pads 2A and 2B may be suctioned at the center of the recording paper P, and the third suction pad 3C and the fourth suction pad may be suctioned at both ends of the recording paper P.

Next, such a second embodiment of the present invention will be described.

FIG. 9 is a schematic perspective view of a sheet feeding device 1A according to the present embodiment, and FIG.
It is -B sectional drawing. 9 and 10, the same reference numerals as those in FIGS. 2 and 4 indicate the same or corresponding parts.

In the figure, 2D is a third suction pad 2C.
The fourth suction pad 2D has the same configuration as that of the fourth suction pad 2D. The fourth suction pad 2D is located at a position where one end of the recording sheet P having the maximum width can be sucked by the first swing arm 3 and has a predetermined range. Are rotatably supported. That is, in the present embodiment, when the recording paper P having the maximum width is used,
As shown in the drawing, the first and second suction pads 2B are sucked at the center of the recording paper P, and the third and fourth suction pads 2C and 2D are sucked at both ends of the recording paper P. .

Then, with this configuration,
When the recording paper P having the maximum width is fed, the recording paper P can be sucked by the four suction pads 2A, 2B, 2C, and 2D.

On the other hand, the distance between the first and second suction pads 2B can suction both ends of the recording sheet P 'having the minimum width in the feeding direction, as in the first embodiment. Interval. Accordingly, when the recording paper P ′ having the minimum width is placed in the paper cassette 55 as shown in FIG.
The recording paper P ′ is sucked by the first and second suction pads 2B.

The third and fourth suction pads 2C, 2D
Are arranged at positions deviated from the recording sheet P ′ having the minimum width as shown in FIG. And the third and fourth
By arranging the suction pads 2C and 2D, the third and fourth suction pads 2 are used to feed the recording paper P ′ having the minimum width.
Even if C and 2D move downward due to the swing of the swing arm 3 as shown in FIG.

For this reason, the contact member 31 remains in the state of protruding from the third suction pads 2C and 2D. If the contact member 31 remains in the protruding state, the piston 30 establishes the communication path S. Since it remains closed, air does not flow into the suction pump 11 from the third and fourth suction pads 2C, 2D, and does not affect the suction negative pressure of the other suction pads 2A, 2B. In addition, other configurations,
The operation is the same as in the first embodiment, and a description thereof will be omitted.

As described above, when the recording paper is sucked, the recording paper P ′
The suction pump 11 does not communicate with the recess 2a of the suction pads 2C and 2D that do not contact the suction pads 2C.
By not affecting the suction negative pressure of A and 2B, the recording paper P ′ can be reliably sucked and fed.

The present invention is not limited to the first and second embodiments described above, and the negative pressure from the suction pump 11 when the suction pads 2C and 2D do not come into contact with the recording paper P '. A configuration that does not extend may be another configuration without departing from the gist of the present proposal. For example, the suction force applying means may be operated by an electric signal, and the recording paper size may be electrically detected, and the control unit may determine whether or not suction is possible.

The piston 30 for opening and closing the communication passage S in the above embodiment maintains the closed state by utilizing the weight of the contact member 31, but the closed state is maintained. An elastic member such as a spring may be used.

The suction pads 2A, 2B, 2C, 2D
Is not limited to the number (three or four) shown in the above embodiment, but may be increased or decreased according to the width or rigidity of the recording papers P and P ′. Further, the number of the swing arms 3 and 3A is not limited to the number (two) shown in the above-described embodiment, but may be different depending on various circumstances such as the width of the recording sheets P and P ′ used in the sheet feeding device. The number may be increased or decreased, for example, by integrating them into one.

[0074]

As described above, according to the present invention, the sheet attracting means which selectively contacts the sheet according to the sheet size does not apply the attracting force when the sheet attracting means does not contact the sheet. The other sheet suction means contacting the sheet can be provided with a suction force required for suction.
As a result, even when a single suction force generating means is used, the number of parts increases for any size sheet,
Feeding can be performed reliably without increasing the cost.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a copying apparatus as an example of an image forming apparatus including a sheet feeding device according to a first embodiment of the present invention.

FIG. 2 is a schematic perspective view of the sheet feeding device.

FIG. 3 is a sectional view of the sheet feeding device taken along line AA.

FIG. 4 is a sectional view of the sheet feeding device taken along line BB.

FIG. 5 is a diagram showing a state when the sheet feeding device starts a recording paper suction operation.

FIG. 6 is a diagram showing a state in which only the uppermost recording paper is separated from the recording paper sucked by the recording paper suction operation.

FIG. 7 is a diagram showing a state in which the sucked recording paper is sent out to a pair of paper feed rollers.

FIG. 8 is a diagram illustrating a state in which the sheet feeding apparatus sucks a recording sheet having a minimum width among recording sheets that can be used by a copying apparatus.

FIG. 9 is a schematic perspective view of a sheet feeding device according to a second embodiment of the present invention.

FIG. 10 is a sectional view of the sheet feeding apparatus taken along line BB.

FIG. 11 is a diagram illustrating a state in which a suction pad of the sheet feeding device is separated from a recording sheet.

FIG. 12 is a diagram showing a state when the suction pad starts suctioning recording paper.

[Explanation of symbols]

 1A Sheet feeding device 2A, 2B, 2C, 2D Suction pad 2a Recess 3, 3A Swing arm 11 Suction pump 14, 14a Tube 30 Piston 30a Communication hole 50 Copying device 55 Paper cassette P, P ', P1 Recording paper S continuous aisle

Claims (6)

[Claims] 1. A sheet feeding apparatus for sucking and feeding sheets stacked on sheet stacking means capable of stacking sheets of different sizes, comprising a concave portion on a bottom surface and a suction force applied to the concave portion. A plurality of sheet adsorbing means for adsorbing the sheet, movably provided above the sheet stacking means, holding the sheet adsorbing means, and moving at the time of sheet adsorbing to move the sheet adsorbing means to the sheet; A moving means to be brought into contact with, and an attraction force generating means for generating the attraction force applied in the concave portion of the sheet attraction means, wherein at least one of the plurality of sheet attraction means is a sheet attraction means, The sheet is selectively brought into contact with the sheet according to the sheet size, and the suction force from the suction force generating means is applied only at the time of the contact. Sheet feeding apparatus according to claim. 2. A sheet feeding apparatus for adsorbing and feeding sheets stacked on sheet stacking means capable of stacking sheets of different sizes, wherein the sheet feeding device has a concave portion on a bottom surface and a suction force applied in the concave portion. A plurality of sheet adsorbing means for adsorbing the sheet, movably provided above the sheet stacking means, holding the sheet adsorbing means, and moving at the time of sheet adsorbing to move the sheet adsorbing means to the sheet; A moving unit to be brought into contact with, a suction force generating unit that generates the suction force applied in the recess of the sheet suction unit, and at least one sheet suction unit of the plurality of sheet suction units is set to a sheet size. A suction force applying means for selectively contacting the sheet in accordance with the suction force and applying the suction force from the suction force generating means only at the time of the contact. Sheet feeding apparatus according to claim. 3. A communication path for communicating the suction force generating means with the concave portion for applying the suction force, wherein the suction force applying means opens the communication path only at the time of the contact. 3. The sheet feeding apparatus according to claim 2, wherein the attraction force is provided in the recess. 4. The attraction force applying means is provided in the recess so as to close the communication path, and at the time of the contact, is moved by being pressed by the sheet to open the communication path. 4. The sheet feeding device according to claim 3, wherein the moving member has a configuration. 5. The sheet suction means according to claim 1, wherein the sheet suction means selectively contacting the sheet according to the sheet size is disposed outside one or both of the other sheet suction means. A sheet feeding device according to any one of the above. 6. An image forming apparatus comprising: a sheet feeding device that sucks and feeds a sheet stacked on a sheet stacking unit; and an image forming unit that forms an image on the sheet fed by the sheet feeding device. The image forming apparatus according to claim 1, wherein the sheet feeding device is the one according to claim 1.