JP3251741B2 - Sheet feeding device and sheet physical property detecting device - Google Patents

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 in an image forming apparatus such as an electrophotographic copying machine, and more particularly, to a sheet feeding device using a suction force of air to convert a sheet bundle stacked on a sheet tray. And a sheet feeding apparatus that separates and conveys the sheets one by one.

[0002]

2. Description of the Related Art Conventionally, a sheet feeding device in an image forming apparatus such as an electrophotographic copying machine has a system in which a sheet stacked on a sheet tray is conveyed downstream by rotation of a sheet feeding roller. In general, a roller sheet feeding device is used. In this conventional roller sheet feeding device, the roller surface is made of an elastic body such as rubber, and the performance largely depends on the friction coefficient of the roller surface. Therefore, changes in the outer shape of the roller due to wear, changes over time in the material of the roller,
There were drawbacks in that the paper feeding performance was not stable due to a change in the friction coefficient of the roller surface due to the adhesion of paper powder, and it was not possible to cope with various sheets having different surface properties.

[0003] In view of the above-mentioned problems, there has been proposed an air sheet feeding device that sucks and conveys a sheet by using an air suction force. FIG. 6 shows a typical air feeder proposed in the past. Sheet tray 1 loaded with sheets
Above 01, a sheet transport unit 100 is arranged. The sheet conveyance unit 100 includes a sheet suction unit 102, a conveyance belt 103 having a plurality of suction holes 103a,
03a and a blower 104 that sucks air through the sheet suction unit 102. In the vicinity of the front end of the sheet, there is a nozzle 1 for jetting air to float the sheet.
05, a nozzle 106 for blowing air onto the second and subsequent sheets to separate only one sheet is provided. The nozzles 105 and 106 are connected to a blower 107 and supplied with air.

[0004] This device operates as follows.

[0005] First, air is ejected from the nozzle 105 by the action of the blower 107 to float several sheets on the sheet tray. Then, the uppermost sheet is attracted to the transport belt 103 by the action of the blower 104. Next, the transport belt is driven to transport the sheet to the downstream side. At this time, air is blown from the nozzle 106 to the sheet front end by the action of the blower 107, and the multi-fed sheet is blown back and separated. Then, one sheet is conveyed to the next conveying roller pair 108. <Prior art 2> Conventionally, a sheet feeding device in an image forming apparatus such as an electrophotographic copying machine is generally a roller sheet feeding device that conveys a sheet stacked on a sheet tray to a downstream side by rotation of a sheet feeding roller. It is a target. In this conventional roller sheet feeding device, the roller surface is made of an elastic body such as rubber, and the performance largely depends on the friction coefficient of the roller surface. Therefore, the paper feeding performance is not stable due to the change in the roller outer shape due to wear, the aging of the roller material, the change in the coefficient of friction of the roller surface due to the adhesion of paper dust, etc. There was a disadvantage that there was no.

In view of the above problems, there has been proposed an air sheet feeding device that sucks and conveys a sheet by using an air suction force. FIG. 17 shows a typical air feeder proposed in the past. Above the sheet tray 101 on which sheets are stacked, a sheet transport unit 100 is arranged. The sheet conveyance unit 100 includes a sheet suction unit 102, a conveyance belt 103 having a plurality of suction holes 103a,
03a and a blower 104 that sucks air through the sheet suction unit 102. In the vicinity of the front end of the sheet, there is a nozzle 1 for jetting air to float the sheet.
05, a nozzle 106 for blowing air onto the second and subsequent sheets to separate only one sheet is provided. The nozzles 105 and 106 are connected to a blower 107 and supplied with air.

This device operates as follows. First,
Air is blown from the nozzle 105 by the action of the blower 107 to float several sheets on the sheet tray. Then, the uppermost sheet is attracted to the conveyor belt 103 by the action of the blower 104. Next, the transport belt is driven to transport the sheet to the downstream side. At this time, air is blown from the nozzle 106 to the sheet tip by the action of the blower 107,
The multi-fed sheet is blown back and separated. Then, one sheet is conveyed to the next conveying roller pair 108.

What is important in the above-mentioned double feed separation method is to blow air between the first sheet to be conveyed and the second sheet to be separated.

As shown in FIG. 18A, when air is blown between the first sheet S1 and the second sheet S2, this portion becomes positive pressure and is separated into the second sheet. A downward force is generated that assists In addition, an upward force is generated in the first sheet so as to assist the suction on the conveyance belt. Therefore, the first sheet and the second sheet are naturally separated.

As described above, in the above-mentioned conventional example, the first sheet S1 to be conveyed and the second sheet S2 to be separated are separated.
If there is any gap at the leading end of the air, air can enter between the sheets and separate the second sheet. However, when the leading edge of the first sheet and the second sheet are in close contact with each other due to burrs caused by entanglement of the fiber of the sheet or defective cutting of the sheet, as shown in FIG. Air does not enter between the first sheet S1 and the second sheet S2, and the lower side of the second sheet is in a positive pressure state.

In this case, the air is blown up from the lower side of the second sheet, and a force is applied to help the first sheet and the second sheet adhere to each other. In the case of a particularly thin sheet, the first sheet and the second sheet are attracted by the suction force of the air from the suction holes of the transport belt. As described above, there is a drawback that double feeding cannot be sufficiently prevented for a sheet whose leading end is completely adhered.

Further, in order to prevent double feed, the nozzle 10
If the air ejection from the nozzle 6 is strengthened, the problem of blowing back to the first sheet to be conveyed occurs.

As described above, in the conventional paper feeding apparatus, it is not possible to realize stable paper feeding without a paper feeding defect and without a change in paper feeding performance with time.

In view of the above points, the following excellent devices have been proposed. FIG. 19 shows the improved air feeding device.

Reference numeral 1 denotes a sheet tray on which a plurality of sheets can be stacked.
It is loaded so that it can be hit against. Reference numeral 3 denotes a sheet conveying unit. Reference numeral 4 denotes a first sheet suction unit, which includes a substantially flat bottom surface 5 facing the sheet bundle stacked on the sheet tray 1, an air suction opening 6 opened in the substantially flat bottom surface 5, and a suction chamber 7. ing.

Reference numeral 8 denotes a second sheet suction portion, which is disposed downstream of the first substantially flat bottom surface 5 in the sheet conveying direction and forms a predetermined angle with the first substantially flat bottom surface 5. Second substantially planar bottom surface 9 displaced upward, second substantially planar bottom surface 9
The air suction opening 10 and the suction chamber 11 are provided. The first sheet suction unit 4 and the second sheet suction unit 8 are each provided with an air suction blower 12A.
And the blower 12B. The suction of the blower 12A and the blower 12B can be turned on / off by the valve 13A and the valve 13B, respectively.

A transport belt 14 is stretched over the surfaces of the first sheet suction unit 4 and the second sheet suction unit 8. The conveyor belt 14 has a plurality of suction holes 14a.
Has been opened. The conveyor belt 14 includes rollers 15, 1
6, 17 and 18, and are intermittently driven in the direction of arrow A by driving means (not shown) to convey the sheet. The roller 15 is disposed at a position where the first substantially planar bottom surface 5 and the second substantially planar bottom surface 9 intersect,
It functions as a displacement fulcrum 15a for displacing the sheet so as to be convex downward.

Reference numeral 19 denotes a nozzle for ejecting air to float the sheet, and reference numeral 20 denotes a nozzle for ejecting air to separate one sheet. The nozzles 19 and 20 are connected to a blower 21 for ejecting air. Nozzle 19, 2
The ejection of air from 0 can be selectively switched by the valve 22. Reference numeral 23 denotes a pair of conveying rollers for conveying the conveyed sheet further downstream.

Next, the operation of the above-described air feeding device will be described.

First, the valve 22 is switched to the position "a" by switching means such as a solenoid (not shown), the blower 21 is operated, and air is blown from the nozzle 19 toward the front end of the seat. Then, several sheets are blown up and float. The valve 13A and the valve 13B are switched to positions c and f, respectively, by switching means such as a solenoid (not shown), the blowers 12A and 12B are operated, and the air is passed through the suction openings 6, 10 and the intake holes 14a. Is sucked.

As a result, the uppermost sheet S1 is sucked by the first and second sheet suction portions 4 and 8, and is brought into close contact with the transport belt 14. More specifically, as shown in FIG. 19, the vicinity of the center of the sheet is sucked by the first sheet suction unit 4, and the vicinity of the leading end of the sheet is sucked by the second sheet suction unit 8. At this time, since the suction force of the first and second sheet suction portions 4 and 8 is set to be sufficiently high, the sheet bends around the displacement fulcrum portion 15a against the stiffness of the sheet, and the sheet is bent. tip,
The central portion is in close contact with the conveyor belt 14.

That is, the sheet S1 has substantially flat bottom surfaces 5, 9
In accordance with the shape of the fulcrum, a downwardly protruding “ku” is formed with the displacement fulcrum 15a as a fulcrum. At this time, it is assumed that the second sheet S2 is in close contact with the sheet S1. In this case, sheet S
The vicinity of the central portion of No. 2 is substantially similar to the sheet S1. However, since the surface of the second sheet suction unit 8 is covered with the sheet S1, no suction force works near the leading end of the sheet S2.

Accordingly, the stiffness of the sheet prevails, and the sheet S2 maintains a flat shape without bending using the displacement fulcrum 15a as a fulcrum, the leading end of the sheet is separated, and a gap e is formed between the sheets. Thereafter, the transport belt 14 is driven by a driving unit (not shown), and the sheet S1 is transported in the direction of arrow A. At the same time, the valve 22 is switched to the position b, and air is blown from the nozzle 20 into the gap e between the sheet S1 and the sheet S2, and the sheet S2 is stably separated as described with reference to FIG. Therefore, only the sheet S <b> 1 is conveyed downstream, and is passed to the conveying roller pair 23. <Prior Art 3> Conventionally, in an image forming apparatus such as an electrophotographic copying machine, a transfer voltage, an air feeding suction force, and a roller feeding retard roller depend on the type of sheet, particularly the stiffness (thickness) of the sheet. It is known that various optimum conditions for image formation, such as the retard pressure and the fixing temperature at the time of fixing, change.

Therefore, there is an apparatus in which a user or a service person determines the stiffness (thickness) of a sheet based on human senses such as sight and touch, and manually changes the above-described conditions optimal for image formation. Proposed. <Prior Art 4> Conventionally, a sheet feeding device in an image forming apparatus such as an electrophotographic copying machine is generally a roller sheet feeding device that conveys a sheet stacked on a sheet tray to a downstream side by rotation of a sheet feeding roller. It is a target. In this conventional roller sheet feeding device, the roller surface is made of an elastic body such as rubber, and the performance largely depends on the friction coefficient of the roller surface. Therefore, the paper feeding performance is not stable due to the change in the roller outer shape due to wear, the aging of the roller material, the change in the coefficient of friction of the roller surface due to the adhesion of paper dust, etc. There was a disadvantage that there was no.

In view of the above problems, there has been proposed an air sheet feeding device that sucks and conveys a sheet by using an air suction force. FIG. 29 is an example of a conventionally proposed air sheet feeding device. Reference numeral 201 denotes a sheet tray on which a plurality of sheets can be stacked, and the sheets are stacked such that the leading ends thereof abut against the sheet alignment guide plate 202. 203 is a sheet conveying unit. Reference numeral 204 denotes a first sheet suction unit, which has a substantially planar bottom surface 205 and a substantially planar bottom surface 20 facing the sheet bundle stacked on the sheet tray 201.
5, air suction opening 206, suction chamber 2
07.

Reference numeral 208 denotes a second sheet suction unit,
Of the first substantially flat bottom surface 2 at a predetermined angle θ.
05, which is displaced above the second bottom surface 209,
Air suction opening 21 opened in the substantially planar bottom surface 209 of FIG.
0, constituted by a suction chamber 211. The first sheet suction unit 204 and the second sheet suction unit 208 are connected to an air suction blower 212. Blower 21
2 can be turned on / off by a valve 213.

The conveyor belt 214 covers the surfaces of the first sheet suction unit 204 and the second sheet suction unit 208.
Has been passed over. The transport belt 214 has a plurality of suction holes 214a. The conveyor belt 214
Rollers 215, 216, 217, and 218 are supported by a predetermined tension, and are driven by an arrow A by driving means (not shown).
Driven intermittently to convey the sheet. Roller 2
Reference numeral 15 is disposed at a position where the first substantially planar bottom surface 205 and the second substantially planar bottom surface 209 intersect, and functions as a displacement fulcrum 215a for displacing the sheet so as to be convex downward.

Reference numeral 219 denotes a nozzle for ejecting air to float the sheet, and reference numeral 220 denotes a nozzle for ejecting air to separate one sheet. Nozzles 219, 22
0 is connected to a blower 221 for blowing air. The ejection of air from the nozzles 219 and 220 can be selectively switched by a valve 222. Reference numeral 223 denotes a pair of conveying rollers for conveying the conveyed sheet further downstream.

Next, the operation will be described. The valve 222 is switched to the position a by switching means such as a solenoid (not shown), the blower 221 is operated, and air is blown from the nozzle 219 toward the front end of the sheet. Then, several sheets are blown up and float. And
The valve 2 is switched by switching means such as a solenoid (not shown).
13 is switched to the position c, the blower 212 is operated, and air is sucked through the suction openings 206 and 210 and the suction hole 214a. Then, the top sheet S1 is sucked by the first and second sheet suction units 204 and 208,
It adheres closely to the conveyor belt 214.

More specifically, as shown in FIG. 29, the vicinity of the center of the sheet is suctioned by the first sheet suction unit 204, and the vicinity of the leading end of the sheet is suctioned by the second sheet suction unit 208. In this way, the sheet is bent with the displacement fulcrum 215a as a fulcrum against the stiffness of the sheet,
The central portion is in close contact with the transport belt 214. That is, the sheet S1 follows the substantially planar bottom surfaces 205 and 209, and has a downwardly convex "ku" shape with the displacement fulcrum 225a as a fulcrum. At this time, it is assumed that the second sheet S2 is in close contact with the sheet S1.

In this case, since the angle θ is set in advance to the above angle, the second sheet S2 is
A flat shape is maintained without bending around the fulcrum 25a, the leading end of the sheet is separated, and a gap e is formed between the sheets. Thereafter, the transport belt 214 is driven by a driving unit (not shown),
Sheet S1 is transported in the direction of arrow A. At the same time,
The valve 222 is switched to the position b, air is blown from the nozzle 220 into the gap e between the sheet S1 and the sheet S2, and the sheet S2 is stably separated. Therefore, only the sheet S1 is transported downstream, and the transport roller pair 223
Passed to.

[0032]

[Problems to be Solved by the Invention] Problems to be Solved by the First Invention However, when feeding various types of sheets, if the distance from the uppermost sheet of the sheet bundle to the transport belt is set long (fixed), the distance from the nozzle 105 is increased. Since the distance between the uppermost sheet raised by the air and the conveyor belt is long, the result is as follows.

When thin (light) paper is fed, the sheet is completely attracted to the sheet attracting portion 102. However, when thick (heavy) paper is supplied, the sheet is attracted to the sheet attracting portion 102 due to insufficient suction force. And the stability of paper feeding is hindered.

On the other hand, when the distance from the uppermost sheet of the sheet bundle to the conveyor belt is set short (fixed), the nozzle 105
Since the distance between the uppermost sheet raised by the air from the conveyor belt and the transport belt is short, the result is as follows.

When thick (heavy) paper is fed, the sheet is completely attracted to the sheet attracting portion 102, but when thin (light) paper is fed, the first sheet is completely attracted to the sheet attracting portion 102. However, since the distance is short, the suction force also acts on the second sheet, and even the second sheet is adsorbed along with the first sheet and may be double-fed.
As described above, there has been an inconvenience that various types of sheets cannot be stably fed by one setting.

It is an object of the present invention to provide a sheet feeding apparatus which reliably separates and conveys a sheet in a sheet feeding apparatus using an air suction force. <Problem of the Second Invention> However, the above-described air feeding apparatus has the following disadvantages.

For example, consider the case where a very thick and stiff sheet is conveyed.

In this case, several sheets float by the action of air from the nozzle 19, and the top sheet S 1 is sucked by the first sheet suction unit 4 and the second sheet suction unit 8.
At this time, since the first sheet suction unit is closer to the sheet S1, the sheet S1 is first suctioned to the first sheet suction unit 4. Then, the portion behind the sheet S <b> 1 is restrained by the first sheet suction unit 4.

Here, since the sheet S1 has a strong stiffness, the sheet S1 is hard to bend with respect to the displacement fulcrum 15a and is hard to be sucked by the second sheet suction portion 8. Therefore, as shown in FIG. 20, the gap e between the sheets is not sufficiently obtained, and the air separating effect by the nozzle 20 is not sufficiently performed, so that poor sheet feeding, particularly double feeding, is likely to occur. .

An object of the present invention is to provide a sheet feeding apparatus in which the leading end of a sheet is reliably separated. <Problem of the Third Invention> However, in the above-described conventional example, in order to set the above conditions, a user or a service person needs to feel the stiffness (thickness) of the sheet, such as sight, feel, and the like. In this case, variations in judgment due to physical condition, emotions, etc. and variations in judgment due to individual differences occur at that time, and it is possible to reliably set various conditions such as paper feeding and transfer to the optimal state. could not.

An object of the present invention is to provide a sheet physical property detecting device which measures physical properties of a sheet and enables various conditions such as sheet feeding and image formation to be set in an optimum state based on the measurement results. It is assumed that. <Problem of the Fourth Invention> However, when feeding various types of paper, if the angle θ is fixed and conveyed, the suction force of the first sheet suction unit 204 and the second sheet suction unit 208 is set to be weak (fixed). In this case, when the sheet with a weak stiffness is fed, the sheet is completely attracted to the conveyance belt 214 and the separation state is good. As the first sheet S
1 does not project downward and inhibits the stability of separation (FIG. 3).
0).

On the other hand, when the suction force of the first sheet suction unit 204 and the second sheet suction unit 208 is set strong (fixed), when the sheet with strong stiffness is fed, only the first sheet is completely conveyed by the conveyor belt 214. It is adsorbed on and separated. However, when a sheet having low stiffness is fed, the first sheet is completely attracted to the conveyor belt 214, but the second sheet S2
Is sucked, and even the second sheet becomes convex downward with the displacement fulcrum portion 209a as a fulcrum along with the first sheet (FIG. 31), and a double feed may occur. . As described above, there is an inconvenience that various types of paper cannot be stably fed by one setting.

According to the present invention, when a sheet is attracted to the first and second sheet attracting portions, the angle of the leading end is set to an optimal angle according to the type of the sheet, thereby enabling stable sheet feeding. It is intended to provide a device.

[0044]

<Means of the First Invention> The present invention provides a sheet tray for stacking a plurality of sheets,
A sheet suction unit opposed to the stacked sheet bundle and having a plurality of air suction openings in a substantially planar bottom surface, and a sheet suction unit for sucking air by sucking air through the air suction openings of the sheet suction unit. , At least one air suction means, provided near the sheet suction unit,
Detecting means for detecting the stiffness of the sheet; changing means for changing the distance between the sheet tray and the sheet suction portion according to the stiffness of the sheet; control means for controlling the changing means; Feeding means for feeding.

According to the present invention, there is provided a sheet tray on which a plurality of sheets are stacked, a first sheet suction portion opposed to the stacked sheet bundle and having a plurality of air suction openings on a substantially planar bottom surface; A second sheet suction unit disposed downstream of the first sheet suction unit in the sheet conveyance direction and having a plurality of air suction openings in a substantially planar bottom surface; A displacement fulcrum disposed upstream of the second sheet suction unit for displacing the sheet sucked by the first and second sheet suction units in a downwardly convex shape; At least one air suction unit for sucking a sheet by sucking air through an air suction opening of the sheet suction unit, and a detection unit provided near the air suction unit and detecting a stiffness of the sheet And the sheet A variation unit that varies the distance between the ray and the first and second sheet suction units according to the stiffness of the sheet, a control unit that controls the variation unit, and a feeding unit that feeds the sheet. It is characterized by having. <Means of the Second Invention> The present invention provides a sheet tray on which a plurality of sheets are stacked,
A first sheet suction unit opposed to the stacked sheet bundle and having a plurality of air suction openings in a substantially planar bottom surface, and a first sheet suction unit disposed downstream of the first sheet suction unit in a sheet conveying direction; A second sheet suction unit having a plurality of air suction openings displaced upward with respect to the substantially planar bottom surface;
For displacing the sheet adsorbed by the first and second sheet adsorbing portions so as to be convex downward, which is disposed downstream of the sheet adsorbing portion and upstream of the second sheet adsorbing portion. A displacement fulcrum, at least one air blowing means for blowing air near the front end of the sheet bundle stored in the sheet tray, and a coil wound around at least the first and second sheet suction portions and the displacement fulcrum. A sheet having a plurality of suction holes on the surface thereof, and suctioning air through the suction holes of the conveyance belt and the air suction openings of the first and second sheet suction portions to attract the sheet to the conveyance belt. And a control means for independently performing suction of air from the first and second sheet suction units. When feeding the sheet, the control means controls suction so that air is first suctioned from the second sheet suction portion, and then air is suctioned from the first sheet suction portion. I do.

A sheet tray on which a plurality of sheets are stacked, a first sheet suction portion opposed to the stacked sheet bundle and having a plurality of air suction openings on a substantially planar bottom surface; A second sheet suction unit disposed on the downstream side in the sheet conveying direction with respect to the sheet suction unit and having a plurality of air suction openings displaced downward with respect to the substantially planar bottom surface;
The sheet, which is provided downstream of the first sheet suction unit and near the upstream side of the second sheet suction unit, displaces the sheet sucked by the first and second sheet suction units so as to be convex upward. A displacement fulcrum for causing the air to be blown near the front end of the sheet bundle stored in the sheet tray, and at least one of the first and second sheet suction portions and the displacement fulcrum. A conveying belt that is wound and has a plurality of suction holes on its surface, and that the sheet is conveyed by suctioning air through the suction holes of the conveyance belt and the air suction openings of the first and second sheet suction units. Sheet feeding device, comprising: at least one air suction means for sucking air into the sheet; and control means for independently sucking air from the first and second sheet suction portions. In the above aspect, at the time of feeding the sheet, control is performed by control means such that air is first suctioned from the second sheet suction portion, and then air is suctioned from the first sheet suction portion. And <Means of the Third Invention> The present invention provides a first sheet adsorbing section which faces a sheet to be measured and has at least one air suction opening on a substantially planar bottom surface; A second sheet suction unit having at least one air suction opening on the bottom surface of the plate, at least one air suction unit for sucking air through the air suction openings of the first and second sheet suction units, It is provided near the first sheet suction unit,
First detecting means for detecting that the sheet is attracted by the first sheet attracting portion, and a first detecting means provided near the second sheet attracting portion, wherein the sheet is provided by the second sheet attracting portion; A second detecting means for detecting that the sheet has been sucked, and a measurement for detecting a time from when the sheet is sucked by the first sheet sucking section to when the sheet is detected by the second sheet sucking section. Means.

Further, the first sheet is measured from the sheet to be measured.
Is different from the distance from the sheet to the second detecting means.

[0048] Further, there is provided a display means for displaying a signal measured by the measuring means. <Means of Fourth Invention> The present invention provides a sheet tray for stacking a plurality of sheets,
A first sheet suction unit opposed to the stacked sheet bundle and having a plurality of air suction openings in a substantially planar bottom surface;
And a plurality of air suction openings disposed on the substantially planar bottom surface with respect to the sheet suction portion.
And a sheet suction unit disposed downstream of the first sheet suction unit and upstream of the second sheet suction unit.
A displacement fulcrum for displacing the sheet sucked by the second sheet suction unit so as to be convex downward;
At least one air suction means for sucking a sheet by sucking air through an air suction opening of the sheet suction section, and a sheet suction section provided in the vicinity of the first sheet suction section; A protrusion that is movable by being pressed, and a detecting unit that detects a movement amount of the protrusion that is pressed and moved by the sheet when the sheet is sucked by the first sheet suction unit, An angle changing unit that changes an angle formed by the first sheet suction unit and the second sheet suction unit with the displacement fulcrum as an apex, and a feeding unit that feeds the sheet are provided. .

[0049]

The first sheet of the sheet bundle on the sheet tray is sucked by the feeding means by the suction force of the sheet suction means from which the air is sucked by the air suction means. The paper is fed by the rotation of the feeding means.

When the sheet is attracted by the sheet attracting means, the stiffness of the sheet is detected by detecting means for detecting the stiffness of the sheet, which is provided in the vicinity of the sheet attracting means. Moves the sheet tray to change the distance between the sheet tray and the sheet suction means.

Thus, the sheets can be stably fed with the same suction force even when feeding various kinds of fed sheets. <Operation of the Second Invention> The sheets stacked on the sheet tray are blown up, and the leading end of the first sheet is attracted to the transport belt by the second detection means which starts suction of air first. Is done. This sheet is attracted to the transport belt by the attraction force of the first detecting means that operates next, and the intermediate portion between the first and second sheet attracting portions is bent in a convex shape by the displacement fulcrum. As a result, the leading end of the first sheet can be reliably separated from the second sheet, and a stable sheet feeding apparatus that does not have a feeding defect such as a double feed and a change in sheet feeding performance with time is realized. can do. <Operation of Third Invention> When the air suction means operates, a suction force acts on the first and second sheet suction portions to suck the sheet. In the suction of the sheet, first, the sheet is sucked by the first sheet suction unit, the suction is detected by the first detection unit, and the sheet is sucked by the second sheet suction unit with a slight delay, and the second detection unit. Adsorption is detected.

The time from when the sheet is detected by the first detecting means to when the sheet is attracted to the second sheet attracting portion is measured by the measuring means, whereby the sheet such as stiffness and thickness of the sheet is measured. Since the physical properties can be detected, for example, the optimum conditions for forming the sheet feed image can be set for the sheet feeding apparatus or the image forming apparatus. <Operation of the Fourth Invention> The sheet on the sheet tray is sucked by the suction force of the first and second sheet suction portions, and bent at an angle at the displacement fulcrum portion in a convex shape. The detection protrusion is moved by the sheet sucked by the first and second sheet suction portions, and the amount of movement is detected by the detecting means, whereby the strength of the sheet is detected.

Based on the above detection result, the angle formed by the second sheet suction unit with respect to the first sheet suction unit is changed by the angle changing unit. This makes it possible to bend the sheet at an angle that is optimal for the stiffness of the sheet and to separate the leading end of the sheet, thereby enabling stable feeding of various types of sheets with the same suction force.

Reference numerals in parentheses are shown for reference to the drawings, and do not limit the configuration of the present invention.

[0055]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment of First Invention> An embodiment according to the first invention will be described below with reference to the drawings.

FIG. 1 shows an air feeding device of the electrophotographic copying machine.

Referring to FIG. 1, reference numeral 1 denotes a sheet tray on which a plurality of sheets S can be stacked, and the sheets are stacked such that the leading ends thereof abut against the sheet alignment guide plate 2. Reference numeral 3 denotes a sheet conveying unit. Reference numeral 4 denotes a first sheet suction unit, which includes a substantially flat bottom surface 5 facing the sheet bundle described on the sheet tray 1, an air suction opening 6 formed in the substantially flat bottom surface 5, and a suction chamber 7. ing.

Reference numeral 8 denotes a second sheet adsorbing portion, which is disposed downstream of the first substantially planar bottom surface 5 in the sheet conveying direction and forms a predetermined angle θ with the first substantially planar bottom surface 5. Substantially flat bottom surface 9 displaced upward from above, air suction opening 10 opened in second substantially flat bottom surface 9, suction chamber 11
It consists of.

The first sheet suction section 4 and the second sheet suction section 8 are connected to a blower 12 for sucking air. The suction of the blower 12 can be turned on / off by the valve 13. A conveyor belt 14 is stretched over the surfaces of the first sheet suction unit 4 and the second sheet suction unit 8. The transport belt 14 has a plurality of suction holes 14.
a is opened. The conveyor belt (feeding means) 14
The sheet is supported by rollers 15, 16, 17, and 18 with a predetermined tension, and is intermittently driven in a direction indicated by an arrow A by a driving unit (not shown) to convey the sheet. Roller 15 is the first
Is disposed at the position where the substantially planar bottom surface 5 and the second substantially planar bottom surface 9 intersect, and functions as a displacement fulcrum 15a for displacing the sheet so as to be convex downward.

Reference numeral 19 denotes a nozzle for ejecting air to float the sheet, and reference numeral 20 denotes a nozzle for ejecting air to separate one sheet. The nozzles 19 and 20 are connected to a blower 21 for ejecting air. Nozzle 19, 2
The air ejection from 0 can be selectively switched by the valve 22. Reference numeral 23 denotes a pair of conveying rollers for conveying the conveyed sheet further downstream.

Next, a mechanism for enabling the sheet tray 1 to be changed according to the sheet stiffness will be described.

Reference numeral 27 denotes a rack attached to the sheet tray 1, which is movable in the direction of arrow B in the figure by meshing with a pinion gear 28. Reference numeral 29 denotes a motor (variation means) for rotating the pinion gear 28. These are for setting the sheet tray 1 to a height that satisfies the following two conditions according to the sheet to be sent. The first is that only the top sheet S1 is the second sheet suction unit 8
Secondly, the second sheet S2 is not adsorbed at the same time as the first sheet S1.

The means for detecting the stiffness of the sheet will be described. Reference numeral 30 denotes a detection projection which is movable in the direction of arrow C in the figure. Reference numeral 31 denotes a font sensor that detects the position of the detection protrusion 30.

Next, the operation of the above-described air feeding device when the sheet has a strong stiffness will be described with reference to FIG. First, the sheet tray 1 is located at a position close to the transport belt 14 (FIG. 3). This is the home position. The valve 22 is switched to the position a by switching means such as a solenoid (not shown), the blower 21 is operated, and the nozzle 19
Air is blown out toward the front end of the seat. Then, several sheets are blown up and float. Then, the valve 13 is switched to the position c by switching means such as a solenoid (not shown), the blower 12 is operated, and air is sucked through the suction openings 6, 10 and the suction hole 14a.

As a result, the uppermost sheet S 1 is sucked by the first and second sheet suction portions 4 and 8, and comes into close contact with the transport belt 14. Specifically, as shown in FIG. 1, the vicinity of the center of the sheet is suctioned by the first sheet suction unit 4, and the vicinity of the leading end of the sheet is suctioned by the second sheet suction unit 8. Although a downward force due to its own weight is applied to the detection projection 30, the rear end of the sheet does not drop much with respect to the substantially planar bottom surface 5 because the sheet is strong, and the detection projection 30 is pushed upward by the sheet. The photo sensor 31 is turned on. The control means 37 having received the signal from the photo sensor 31 determines the thickness (weight) of the sheet.

In general, the stronger the stiffness of a sheet is, the heavier (thick) the sheet is, and the lower the stiffness is, the lighter (thin) the sheet is. In this case, the position of the sheet tray 1 may be kept close to the conveyor belt 14 because the sheet is heavy and is hardly attracted to the conveyor belt 14. Therefore, paper is fed as follows. The first sheet S <b> 1 comes into close contact with the first sheet suction unit 4 and the second sheet suction unit 8. That is, the sheet S1 follows the substantially planar bottom surfaces 5 and 9, and has a downwardly convex "ku" shape with the displacement fulcrum 15a as a fulcrum, and the second sheet S2 has the displacement fulcrum 15a. Maintain a flat shape without bending as a fulcrum,
The leading end of the sheet is separated, and a gap e is formed between the sheets.

Thereafter, the transport belt 14 is driven by a driving means (not shown), and the sheet S1 is transported in the direction of arrow A. At the same time, the valve 22 is switched to the position b, air is blown from the nozzle 20 into the gap e between the sheet S1 and the sheet S2, and the sheet S2 is separated stably. Therefore, only the sheet S <b> 1 is conveyed downstream, and is passed to the conveying roller pair 23. Thereafter, an image is formed by a known image forming apparatus.

FIG. 2 shows a setting in the case where the stiffness of the sheet is weak. Since a downward force is applied to the detection protrusion 30 by its own weight, when the paper is sucked, the rear end of the paper is substantially flat bottom surface 5.
Will fall. That is, the detection protrusion 30 is in a lowered state, and the photo sensor 31 is off. The control means 37 having received the signal from the photo sensor 31 determines the thickness (weight) of the sheet. In this case, since the sheet is a light sheet, if the position of the sheet tray 1 is high, the distance α between the first sheet S1 and the first sheet suction unit 4 is small, so the suction force is strong, and the first sheet S1 is Since the second sheet S2 is also easily sucked at the same time when sucked,
The following operation is performed to lower the position of the sheet tray 1.

The control means 37 moves the motor 29 to lower the rack 27 via the pinion gear 28, thereby lowering the sheet tray 1 so as to satisfy the above-mentioned conditions.
(FIG. 4) As a result, the distance β between the first sheet S1 and the first sheet suction portion 4 increases, and only the sheet S1 bends with the displacement fulcrum 15a as a fulcrum against the stiffness of the sheet. Both the leading end and the center of the sheet are in close contact with the transport belt 14. The subsequent steps are the same as those described in the case of a sheet having strong stiffness. Thereafter, when the sheet feeding operation is completed, the sheet tray 1 is moved so that the position of the uppermost sheet of the sheet is at the above-described home position.

In this embodiment, the measurement of the amount of movement of the detection projection 30 is described in only two steps. However, the present invention is not limited to this, and the measurement is performed in more steps using a slide volume or the like. It is easily conceivable that stable feeding can be performed for various kinds of sheets if the measurement is carried out or steplessly measured. Further, in the present embodiment, the detection protrusion attempts to fall downward by its own weight, but the present invention is not limited to this, and any device that generates a force in the opposite direction to the suction direction, such as using a spring, is effective. It is easy to imagine.

In this embodiment, the case where the stiffness is detected at the rear end of the sheet is shown. However, the present invention is not limited to this. Needless to say, a great effect can be obtained.

Further, in the present embodiment, the height of the sheet tray 1 is changed by the stiffness of the sheet. However, the height of the first sheet suction portion 4 may be changed, and the sheet tray 1 and the first It is easily conceivable that the method is effective as long as the distance from the sheet suction unit 4 is changed.

In the present embodiment, the sheet transport unit having the first and second sheet suction units is described. However, the present invention is not limited to this, and one sheet suction unit or a plurality of sheet suction units (FIG. 5) may be used. It is easy to think that it is effective.

In this embodiment, the sheet tray 1 returns to the home position close to the conveyor belt after the sheet feeding is completed, but it is apparent that the sheet tray 1 may be just before starting the sheet feeding. <Example 1 of second invention> Hereinafter, the present invention will be described in detail based on examples.

FIG. 7 is a diagram that best illustrates the present invention. Since the configuration itself is exactly the same as that of the above-described conventional example, the description is omitted.

Next, the operation of the present invention will be described (the operation is based on the timing chart of FIG. 9 and the block chart of FIG. 10).

First, the valve 22 is switched to the position a by a switching means such as a solenoid (not shown), the blower 21 is operated, and air is blown from the nozzle 19 toward the front end of the seat. Then, several sheets are blown up and float. Then, first, the blower 12A and the blower 12
B operates. Next, the valve 13B is switched to the position f by switching means such as a solenoid (not shown), and air is sucked through the suction opening 10 and the suction hole 14a.

Then, the uppermost sheet S 1 is sucked by the second sheet suction section 8 and comes into close contact with the transport belt 14. At this time, only the second sheet suction unit 8 is operating, and the portion behind the sheet S1 is not restrained, so that only the leading end of the sheet S1 is securely held in the second sheet suction unit 8
Is adsorbed. Therefore, it becomes easy to separate and convey only the sheet S1. Thereafter, the valve 13A is switched to the position c by switching means such as a solenoid (not shown), and air is sucked through the suction opening 6 and the suction hole 14a. Then, the sheet is bent around the displacement fulcrum 15a as a fulcrum against the stiffness of the sheet,
The central portion is in close contact with the conveyor belt 14.

More specifically, as shown in FIG. 8, the vicinity of the center of the sheet is sucked by the first sheet suction unit 4, and the vicinity of the leading end of the sheet is sucked by the second sheet suction unit 8. That is, the sheet S1 follows the substantially planar bottom surfaces 5 and 9, and has a downwardly convex “ku” shape with the displacement fulcrum 15a as a fulcrum. At this time, it is assumed that the second sheet S2 is in close contact with the sheet S1. In this case, the vicinity of the central portion of the sheet S2 is substantially similar to the sheet S1. However, since the surface of the second sheet suction unit 8 is covered with the sheet S1, no suction force works near the leading end of the sheet S2.

Accordingly, the stiffness of the sheet prevails, and the sheet S2 maintains a flat shape without bending using the displacement fulcrum 15a as a fulcrum, the leading end of the sheet is separated, and a gap e is formed between the sheets (FIG. 8). . Thereafter, the transport belt 14 is driven by a driving unit (not shown), and the sheet S1 is transported in the direction of arrow A. At the same time, the valve 22 is switched to the position b, and air is blown from the nozzle 20 into the gap e between the sheet S1 and the sheet S2, and the sheet S2 is stably separated as described with reference to FIG. Therefore, only the sheet S <b> 1 is conveyed downstream, and is passed to the conveying roller pair 23.

Then, after a predetermined time (the sheet is
3), the valves 13A and 13B are at the positions d and g, respectively, and the blowers 12A and 12B also stop. After a further predetermined time (after the sheet has passed through the roller pair 23), the transport belt 14 and the blower 21 are stopped, the valve 22 is also at the position a, and the sheet feeding operation ends.

As described above, if the suction of the sheet suction portion on the sheet front end portion is performed first, even a thick and stiff sheet can be reliably sucked to the first and second sheet suction portions, and the sheets can be reliably separated. Can be transported. <Second Embodiment of the Second Invention> Next, another embodiment will be described.

Parts similar to those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

FIG. 11 shows a second embodiment of the present invention.

Reference numeral 40A denotes a second sheet suction section. Second
The sheet suction unit 40 </ b> A is disposed downstream of the first sheet suction unit 4 in the sheet conveyance direction. The second sheet suction unit 40A includes a hollow suction roller 41A having a plurality of suction holes 41a on its surface, a suction chamber unit 42, and a suction roller 4A.
Cover 43 that covers almost the portion other than the portion for sucking the 1A sheet
Consisting of Reference numeral 44 denotes a displacement fulcrum that bends the sheet S in a convex shape downward. Since the surface of the suction roller 41A that adsorbs the sheet has a curvature, it is substantially the first surface.
(Above the substantially flat bottom surface 5).

The first sheet suction section 4 and the second sheet suction section 40A are connected to the blower 12. The transport belt 14 is stretched around the first sheet suction unit 4 and the second sheet suction unit 40A so as to cover the surfaces thereof. The transport belt 14 is supported by rollers 40A, 16, 17, and 18 with a predetermined tension, and is driven intermittently in the direction of arrow A by drive means (not shown) to transport the sheet.

Also in this embodiment, the same effect as in the first embodiment can be obtained by sucking air from the second sheet suction portion 40A before the first sheet suction portion 4. . <Third Embodiment of the Second Invention> Next, a third embodiment will be described with reference to FIG. This embodiment is an application of the above-described embodiment to a lower separation sheet feeding (a method in which stacked sheets are separated and fed one by one from the lowermost sheet).

The configuration is the same as that of the first embodiment except that the top and bottom are reversed, and sheets are stacked on the first sheet suction unit and its vicinity, and function as the sheet tray 1. Further, the sheet blowing nozzle 19 is eliminated. The operation of the other parts is exactly the same as that of the first embodiment, and the description is omitted because the top and bottom are only reversed.

Next, the operation of this embodiment will be described (the operation is based on the timing chart of FIG. 15).

First, the blowers 12A and 12B operate. Next, the valve 13B is switched to the position f by switching means such as a solenoid (not shown), and air is sucked through the suction opening 10 and the suction hole 14a. Then, the lowermost sheet S <b> 1 is attracted to the second sheet attracting unit 8 and adheres to the transport belt 14. At this time,
Since only the second sheet suction unit 8 is operating and the part behind the sheet S1 is not restrained, the sheet S1
Only the leading end is reliably attracted to the second sheet attracting portion 8.

Therefore, it becomes easy to separate and convey only the sheet S1. Thereafter, the valve 13A is switched to the position c by switching means such as a solenoid (not shown), and air is sucked through the suction opening 6 and the suction hole 14a. Then, the sheet is bent with the displacement fulcrum 15a as a fulcrum against the stiffness of the sheet, and both the leading end and the center of the sheet are in close contact with the transport belt 14. For details, see FIG.
As shown in (1), the vicinity of the center of the sheet is sucked by the first sheet suction unit 4, and the vicinity of the leading end of the sheet is sucked by the second sheet suction unit 8.

That is, the sheet S1 has a substantially planar bottom surface 5,
In accordance with 9, the shape becomes a downwardly convex "ku" shape with the displacement fulcrum 15a as a fulcrum. At this time, temporarily assume that the second sheet S
2, it is assumed that the sheet S2 is in close contact with the sheet S1. In this case, the vicinity of the center of the sheet S2 is substantially the same as the sheet S1. However, since the surface of the second sheet suction unit 8 is covered with the sheet S1, no suction force works near the leading end of the sheet S2. Therefore, the stiffness of the sheet prevails, and the sheet S2 maintains a flat shape without bending using the displacement fulcrum 15a as a fulcrum, the leading end of the sheet is separated, and a gap e is formed between the sheets (FIG. 13).

Thereafter, the conveying belt 14 is driven by a driving means (not shown), and the sheet S1 is conveyed in the direction of arrow A. At the same time, the valve 22 is switched to the position b, and air is blown from the nozzle 20 into the gap e between the sheet S1 and the sheet S2 to blow up the second and subsequent sheets (FIG. 14).

Thus, as described with reference to FIG. 18A, the sheet S2 is stably separated. Therefore, only the sheet S <b> 1 is conveyed downstream, and is passed to the conveying roller pair 23. Then, after a predetermined time (the sheet is
After that, the valves 13A and 13B are d and g respectively.
And the blowers 12A and 12B also stop. At the same time, the transport belt 14 also stops. After a further predetermined time (after the sheet has passed through the roller pair 23), the blower 21
Is stopped, the valve 22 is also at the position of a, and the sheet feeding operation ends.

As described above, if the transaction of the sheet suction section on the sheet front end side is performed first, even a thick and stiff sheet can be surely adsorbed to the first and second sheet suction sections, and the sheet can be reliably separated. Can be transported. <Embodiment 4 of the Second Invention> FIG. 16 shows a fourth embodiment of the present invention. In the configuration itself, the second sheet suction unit of the third embodiment is configured by the suction roller shown in the second embodiment, and the operation and the like are completely the same, so that the description is omitted. <Example 1 of Third Invention> Hereinafter, the present invention will be described in detail based on examples.

FIG. 21 shows an air feeding device provided with the sheet physical property detecting device of the present invention.

Reference numeral 1 denotes a sheet tray on which a plurality of sheets can be stacked.
It is loaded so that it can be hit against. Reference numeral 3 denotes a sheet conveying unit. Reference numeral 4 denotes a first sheet suction unit, which includes a substantially flat bottom surface 5 facing the sheet bundle stacked on the sheet tray 1, an air suction opening 6 opened in the substantially flat bottom surface 5, and a suction chamber 7. ing. Reference numeral 8 denotes a second sheet suction portion, which is disposed downstream of the first substantially planar bottom surface 5 in the sheet conveying direction and forms a predetermined angle θ above the first substantially planar bottom surface 5. It comprises a displaced second substantially planar bottom surface 9, an air suction opening 10 opened in the second substantially planar bottom surface 9, and a suction chamber 11.

The first sheet suction section 4 and the second sheet suction section 8 are connected to a blower 12 for sucking air. The suction of the blower 12 can be turned on / off by the valve 13. A conveyor belt 14 is stretched over the surfaces of the first sheet suction unit 4 and the second sheet suction unit 8. The transport belt 14 has a plurality of suction holes 14.
a is opened. The transport belt 14 includes rollers 15,
It is supported by a predetermined tension by 16, 17, and 18,
It is intermittently driven in the direction of arrow A by the driving means 58 to convey the sheet. The roller 15 is disposed at a position where the first substantially planar bottom surface 5 and the second substantially planar bottom surface 9 intersect, and is a displacement fulcrum 5 for displacing the sheet so as to be convex downward.
Functions as a.

Reference numeral 19 denotes a nozzle for ejecting air to float a sheet, and reference numeral 20 denotes a nozzle for ejecting air to separate only one sheet. The nozzles 19 and 20 are connected to a blower 21 for ejecting air. Nozzle 19, 2
The ejection of air from 0 can be selectively switched by the valve 22. Reference numeral 23 denotes a conveying roller pair for conveying the conveyed sheet further downstream, which is driven by the driving means 59.

Reference numeral 50 denotes first detecting means, which is arranged near the first sheet suction section 4. A detection arm 51 is rotatable about a fulcrum 52. In a state where the sheet is not sucked, the detection arm 51 is at a position f protruding from the first suction unit. The detection arm 51 is
When the sheet is sucked, the sheet is pushed by the sheet and pivots around the fulcrum 52 to the position g.
3 detects that the sheet is sucked.

Reference numeral 60 denotes a second detecting means, which is arranged near the second sheet suction section 8. Reference numeral 61 denotes a detection arm, which is rotatable about a fulcrum 62. The detection arm 61 is at a position h protruding from the second suction unit when the sheet is not suctioned. The detection arm 61
When the sheet is sucked, the sheet is pushed by the sheet and pivots around the fulcrum 62 to the position i.
3 detects that the sheet is sucked.

Next, the operation of the above embodiment will be described with reference to the timing charts of FIGS. 21, 22, 23 and 24 and the block chart of FIG.

First, a detection start button on an operation unit (not shown) is pressed. Then, the blower 21 is operated, the valve 22 is switched to the position a by switching means such as a solenoid (not shown), and air is ejected from the nozzle 19 toward the front end of the sheet. Then, several sheets are blown up and float. Then, the blower 12 is operated, and the valve 13 is switched to the position c by switching means such as a solenoid (not shown).
Air is sucked through a.

As a result, since the first sheet suction unit is closer to the sheet than the second sheet suction unit 8, the uppermost sheet S1 is sucked by the first sheet suction unit 4 first.
It adheres closely to the conveyor belt 14. More specifically, as shown in FIG. 22, the vicinity of the center of the sheet is sucked by the first sheet suction unit 4. Then, as described above, the detection arm 51 is pushed by the sheet to the position of g, and is detected by the photo sensor 53, and the first detection means 50 detects that the sheet is sucked.

Next, with a slight delay, the vicinity of the leading end of the sheet is sucked by the second sheet suction section 8 (FIG. 23). At this time, since the suction force of the first and second sheet suction portions is set to be sufficiently strong, the sheet bends around the displacement fulcrum portion 15a against the stiffness of the sheet, and the leading end of the sheet is bent. Second
Closely adheres to the sheet suction part. That is, the sheet S1 follows the substantially planar bottom surfaces 5 and 9, and has a downwardly convex “ku” shape with the displacement fulcrum 15a as a fulcrum. Then, as described above, the detection arm 61 is pushed by the sheet to the position i, and is detected by the photo sensor 63, and the second detection means 6
0 detects that the sheet is sucked.

As described above, a time lag occurs between the time when the sheet is sucked by the first sheet suction unit 4 and the time when the sheet is sucked by the second sheet suction unit 8. This time lag differs depending on the type (physical property) of the sheet. For example, a sheet with a weak (thin) stiffness has a weak stiffness, so that the displacement fulcrum 15a
And the sheet is immediately sucked by the second sheet suction unit 8, so that the time lag is small.

Conversely, a strong (thick) stiff sheet is hard to bend at the displacement fulcrum 5a due to the strong stiffness, and is gradually attracted to the second sheet attracting portion 8, resulting in a large time lag. By measuring this time by a measuring means (not shown), the type (physical properties) of the sheet, particularly the strength of the sheet (thickness of the sheet) can be determined. The strength of the stiffness is displayed on a display device (not shown). By the display,
Optimal conditions for the seat by the user and serviceman,
For example, a transfer current, a suction force of air feeding, a fixing temperature, and the like can be set.

Thereafter, the blower 12 stops, and the valve 13
Is at the position d, the blower 21 is stopped, the valve 22 is at the position b, and the sheet returns to the sheet tray 1. <Second Embodiment of the Third Invention> In the above-described embodiment, the sheet physical property detecting device has been described, but it can be combined with the sheet feeding device of the image forming apparatus.

The combined apparatus is shown in FIG.
This will be described with reference to FIGS. 22 and 23, a timing chart FIG. 25, and a block chart FIG. The configuration is as described above.

The operation of the present apparatus will be described.

[0111] The sheets are first and second sheet suction devices 4,
The process up to the step of absorbing the sheet, detecting and displaying the physical properties of the sheet, and setting the optimum conditions has already been described above, and thus the description thereof will be omitted.

Thereafter, a copy start button of the operation unit (not shown) is pressed. Then, in exactly the same manner as described above, the sheet S1 is adsorbed by the first and second sheet adsorption components 4, 8. At this time, the second sheet S2 is the sheet S1
Suppose you were in close contact with

In this case, the vicinity of the center of the second sheet S2 is substantially similar to the sheet S1. However, since the surface of the second sheet suction unit 8 is covered with the sheet S1, no suction force works near the leading end of the sheet S2.
Therefore, the stiffness of the sheet prevails, and the sheet S2 maintains a flat shape without bending using the displacement fulcrum 15a as a fulcrum, the leading end of the sheet is separated, and a gap e is formed between the sheets.

After that, the driving belt 58 drives the transport belt 1.
4 is driven, and the sheet S1 is conveyed in the direction of arrow A.
At the same time, the valve 22 is switched to the position b, air is blown from the nozzle 20 into the gap e between the sheet S1 and the sheet S2, and the entire area of the sheet S2 is stably separated from the sheet S1.

Accordingly, only the sheet S1 is conveyed downstream, and is passed to the conveying roller pair 23. Then, after a predetermined time (after the sheet is nipped by the conveying roller pair 23), the blower 12 is stopped, and the valve 13 is at the position d. After a further predetermined time (after the sheet has passed through the conveying roller pair 23), the blower 21 stops, the conveying belt 14 also stops, and the sheet conveyance is completed. <Example 1 of Fourth Invention> Hereinafter, the present invention will be described in detail based on examples.

FIG. 27 shows an air feeding device of an electrophotographic copying machine embodying the present invention.

Reference numeral 1 denotes a sheet tray on which a plurality of sheets can be stacked;
It is loaded so that it can be hit against. Reference numeral 3 denotes a sheet conveying unit. Reference numeral 4 denotes a first sheet suction unit, which includes a substantially flat bottom surface 5 facing the sheet bundle stacked on the sheet tray 1, an air suction opening 6 opened in the substantially flat bottom surface 5, and a suction chamber 7. ing. Reference numeral 8 denotes a second sheet suction portion, which is disposed downstream of the first substantially planar bottom surface 5 in the sheet conveying direction and forms a predetermined angle θ above the first substantially planar bottom surface 5. It comprises a displaced second substantially planar bottom surface 9, an air suction opening 10 opened in the second substantially planar bottom surface 9, and a suction chamber 11.

The first sheet suction unit 4 and the second sheet suction unit 8 are connected to an air suction blower 12. 7
9b is a flexible duct that can expand and contract in response to the movement of the second sheet suction unit. The suction of the blower 12 can be turned on / off by the valve 13. A transport belt 14 is stretched around the first sheet suction unit 4 and the second sheet suction unit 8 so as to cover the surfaces thereof. The conveyor belt 14 has a plurality of suction holes 14a. The transport belt 14 is supported by rollers 15, 16, 17, and 18 with a predetermined tension, and is driven intermittently in a direction indicated by an arrow A by a drive unit (not shown) to transport the sheet.
The roller 15 is disposed at a position where the first substantially planar bottom surface 5 and the second substantially planar bottom surface 9 intersect, and functions as a displacement fulcrum 15a for displacing the sheet so as to be convex downward.

The roller 17 is moved by the spring 74 to the transport belt 1.
4 also functions as a tensioner. Reference numeral 19 denotes a nozzle for ejecting air to float the sheet, and reference numeral 20 denotes a nozzle for ejecting air to separate only one sheet. The nozzles 19 and 20 are connected to a blower 21 for ejecting air. The ejection of air from the nozzles 19 and 20 can be selectively switched by a valve 22. Reference numeral 23 denotes a pair of conveying rollers for conveying the conveyed sheet further downstream.

Next, a mechanism for making the angle θ variable according to the stiffness of the sheet will be described. 75 is a roller 15,
An angle adjusting shaft support plate through which 16 shafts pass is rotatable around the shaft center of the roller 15 as a fulcrum. Reference numeral 76 denotes an angle adjustment arm rotatably attached to the angle adjustment support plate 75. Reference numeral 77 denotes a rack to which the angle adjustment arm 76 is rotatably attached. It can be moved in any direction.
79 is a motor for rotating the pinion gear 79a.

These are angles θ depending on the sheet to be fed.
Is set to an angle satisfying the following two conditions. The first is that only the uppermost sheet S1 is completely attracted to the second sheet attracting section 8, and the second is that the second sheet S2 is in the position of the first sheet S1. This means that the force for keeping the second sheet S2 flat due to the stiffness of the paper is greater than the force for simultaneously attracting and becoming downwardly convex with the displacement fulcrum 15a as a fulcrum.

Next, means for detecting the stiffness of a sheet, which is the center of the present invention, will be described. Reference numeral 30 denotes a detection projection which is movable in the direction of arrow C in the figure. Reference numeral 31 denotes a photo sensor that detects the position of the detection protrusion.

The operation of the above-described air sheet feeding device when the sheet is stiff will be described with reference to FIG. The valve 22 is switched to the position a by switching means such as a solenoid (not shown), the blower 21 is operated, and air is ejected from the nozzle 19 toward the front end of the seat. Then, several sheets are blown up and float. Then, the valve 13 is switched to the position c by switching means such as a solenoid (not shown), the blower 12 is operated, and air is sucked through the suction openings 6, 10 and the suction hole 14a.

As a result, the top sheet S1 is the first sheet S1,
The sheet is sucked by the second sheet suction units 4 and 8,
Adhere to More specifically, as shown in FIG. 27, the vicinity of the center of the sheet is suctioned by the first sheet suction unit 4, and the vicinity of the leading end of the sheet is suctioned by the second sheet suction unit 8. A downward force is applied to the detection protrusion 30 by its own weight,
Because the paper is strong, the rear end of the paper does not drop much with respect to the substantially planar bottom surface 5, and the detection protrusion 30 is pushed upward by the paper to turn on the photo sensor 31.

When the separation angle θ is large, the first sheet S1
Is not stably adsorbed by the second sheet adsorbing section 8,
The following operation is performed to reduce the separation angle. The control means 37 having received the ON signal of the photo sensor controls the motor 7
9, the rack 77 is lowered via the pinion gear 79a, and the angle θ is set to the above-mentioned angle.

As a result, the sheet is bent with the displacement fulcrum 15a as a fulcrum against the stiffness of the sheet, and both the leading end and the center of the sheet come into close contact with the conveyor belt 14. That is, the sheet S1 follows the substantially planar bottom surfaces 5 and 9, and has a downwardly convex “ku” shape with the displacement fulcrum 15a as a fulcrum. At this time, it is assumed that the second sheet S2 is in close contact with the sheet S1. In this case, since the angle θ is set in advance to the above angle, the second sheet S2 is
A flat shape is maintained without bending with a as a fulcrum, the leading end of the sheet is separated, and a gap e is formed between the sheets.

Thereafter, the transport belt 14 is driven by a driving means (not shown), and the sheet S1 is transported in the direction of arrow A. At the same time, the valve 22 is switched to the position b, air is blown from the nozzle 20 into the gap e between the sheet S1 and the sheet S2, and the sheet S2 is separated stably. Therefore, only the sheet S <b> 1 is conveyed downstream, and is passed to the conveying roller pair 23. Thereafter, an image is formed by a known image forming apparatus.

FIG. 28 shows a setting in the case where the stiffness of the sheet is weak. Since a downward force due to its own weight is applied to the detection protrusion 30, the rear end of the paper is lowered with respect to the substantially planar bottom surface 5 when the paper is sucked. That is, the detection protrusion 30 is in a lowered state, and the photo sensor 31 is off. When the stiffness of the sheet is weak and the separation angle θ is small, when the first sheet S1 is sucked, the second sheet S2 is also easily sucked at the same time. Moves in the direction in which the rack 77 goes up.

In this embodiment, the measurement of the amount of movement of the detection projection 30 is described in only two steps. However, the present invention is not limited to this, and the measurement can be performed in more steps using a slide volume or the like. It is easily conceivable that stable feeding can be performed on various types of paper if the measurement is carried out or measured continuously. Further, in the present embodiment, the detection projection 30 attempts to fall downward by its own weight. However, the present invention is not limited to this. It is easy to imagine.

In this embodiment, the case where the stiffness is detected at the rear end of the sheet is shown. However, the present invention is not limited to this. Needless to say, a great effect can be obtained.

[0131]

According to the present invention, there is provided a sheet feeding device including a sheet tray on which a plurality of sheets are stacked and a sheet conveying unit having a sheet suction unit. The sheet stiffness is detected by means for detecting sheet stiffness provided in the vicinity of the sheet suction unit, and a control device having received the signal detects the sheet thickness (weight) and the sheet stiffness and thickness (weight). Judgment is made from the correlation described above, and the distance between the sheet tray and the first and second sheet suction units is automatically changed to the most suitable distance, so that a stable sheet feeding with the same suction force can be performed for various types of sheets. It can be performed. <Effects of the Second Invention> As described above, according to the present invention, in the air feeding apparatus using the suction force of air, the leading end of the sheet is first attracted to the transport belt to cause the leading end of the sheet to stick. Since the separation is ensured, there is no paper feeding failure such as double feeding, and stable paper feeding with no change in paper feeding performance with time is possible. <Effect of Third Invention> As described above, according to the present invention, the first detecting means detects that the sheet has been attracted to the first sheet attracting portion, and the second detecting means delays the sheet. It is possible to detect the physical properties of the sheet by detecting that the sheet is adsorbed by the second detecting means and measuring the time between both adsorptions by the measuring means. Various conditions can be set to an optimal state. <Effects of the Fourth Invention> According to the present invention, the sheet transporting section includes a first sheet suction section,
In a sheet feeding apparatus having a second sheet suction unit formed at an angle with respect to the first sheet suction unit, at least the sheet suction unit is provided near the substantially planar sheet suction unit of the first sheet suction unit. The protrusion that can be moved in the vertical direction of the sheet reliably detects the amount of movement by the force received from the sheet when the sheet suction unit starts to feed the sheet and the sheet suction unit sucks the sheet. By detecting the stiffness (thickness) and receiving the signal, the control device automatically changes the angle formed by the first and second sheet suction portions to an angle most suitable for the stiffness of the sheet, so that various types of sheets can be obtained. However, stable paper feeding can be performed with the same suction force.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view of a sheet feeding apparatus according to an embodiment of the first invention.

FIG. 2 is a longitudinal side view of the sheet feeding apparatus when a sheet having a low stiffness is fed.

FIG. 3 is a longitudinal sectional side view of the sheet feeding device showing a sheet position at a home position.

FIG. 4 is a vertical sectional side view of the sheet feeding apparatus showing a weakly stiff sheet position.

FIG. 5 is a vertical sectional side view of the sheet feeding apparatus when the number of sheet suction units is one;

FIG. 6 is a longitudinal sectional side view of a sheet feeding apparatus according to a conventional technique 1;

FIG. 7 is a vertical sectional side view of the sheet feeding device according to the first embodiment of the second invention.

FIG. 8 is an operation diagram of the sheet feeding device.

FIG. 9 is a timing chart according to the operation of the present invention.

FIG. 10 is a block diagram related to control of the sheet feeding apparatus.

FIG. 11 is a longitudinal sectional side view of a sheet feeding apparatus according to a second embodiment of the second invention.

FIG. 12 is a longitudinal side view of the longitudinal side view according to the third embodiment of the second invention.

FIG. 13 is an operation diagram of the third embodiment of the second invention.

FIG. 14 is an operation view of the third embodiment of the second invention.

FIG. 15 is a timing chart according to the second embodiment of the present invention.

FIG. 16 is a longitudinal sectional side view of a sheet feeding apparatus according to a fourth embodiment of the second invention.

FIG. 17 is a longitudinal sectional side view of a sheet feeding apparatus according to the related art 2.

FIGS. 18A and 18B are sheet feeding devices according to the principle of the air feeding device, wherein FIG. 18A is a longitudinal sectional side view, and FIG.

FIG. 19 is a vertical sectional side view of a sheet feeding apparatus according to the conventional technology 2;

FIG. 20 is an operation diagram of a sheet feeding apparatus according to the conventional technique 2;

FIG. 21 is a longitudinal sectional side view of a sheet feeding device to which the sheet physical property detecting device according to the first embodiment of the third invention is applied;

FIG. 22 is an operation diagram of the sheet feeding device and the sheet physical property detecting device.

FIG. 23 is an operation diagram of the sheet feeding device and the sheet physical property detecting device.

FIG. 24 is a timing chart of the sheet physical property detecting device.

FIG. 25 is a timing chart of the sheet physical property detecting device.

FIG. 26 is a block diagram of a sheet physical property detection device

FIG. 27 is a longitudinal sectional side view of a sheet feeding apparatus according to a fourth invention.

FIG. 28 is an operation diagram of the sheet feeding device.

FIG. 29 is a longitudinal sectional side view of a sheet feeding apparatus according to a conventional technology 4;

FIG. 30 is an operation diagram of FIG. 29;

FIG. 31 is an operation view of FIG. 29;

[Explanation of symbols]

 S sheet S1 first sheet S2 second sheet 1 sheet tray 4 first sheet suction unit 5 substantially flat bottom surface 6 air suction opening 8 second sheet suction unit 9 substantially flat bottom surface 10 for air suction Opening 12 Blower (air suction means) 12A, 12B Blower (air suction means) 14 Conveyor belt (feeding means) 15a Displacement fulcrum 19 Nozzle (air blowing means) 29 Motor (variation means) 30 Detection protrusion 31 Photosensor 30, 31 Means for detecting sheet stiffness 37 Control means 40 Detecting projection 41 Photosensor 40, 41 Means for detecting sheet stiffness 40A Second sheet suction unit (suction roller) 41A Suction roller 41a Suction hole 47 Control means 50 First Detecting means 51, 61 detecting arms 53, 63 photosensor 57 control unit 57a measuring unit (measuring ) 60 second detecting means 75 angular adjustment support plate 76 angle adjusting arm 77 the rack 79 the motor 79a pinion 79b flexible duct 75,76,77,79 angle variation means

Continuation of the front page (56) References JP-A-4-313546 (JP, A) JP-A-5-92829 (JP, A) JP-A-60-52429 (JP, A) JP-A-60-52428 (JP) JP-A-61-254438 (JP, A) JP-A-62-16944 (JP, A) JP-A-62-249835 (JP, A) JP-A-54-29483 (JP, A) 3-172244 (JP, A) JP-A 50-38073 (JP, U) JP-A 49-92120 (JP, U) JP-B 49-16070 (JP, B1) JP-B 46-32101 (JP, U) B1) JP 49-18203 (JP, B1) JP 46-18590 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B65H 3/12 310 B65H 1/14 322

Claims (23)

(57) [Claims] 1. A sheet tray on which a plurality of sheets are stacked, a sheet suction unit opposed to the stacked sheet bundle and having a plurality of air suction openings in a substantially planar bottom surface, and an air of the sheet suction unit. At least one air suction unit for sucking the sheet by sucking air through the suction opening, and a detection unit provided near the sheet suction unit for detecting the stiffness of the sheet; A variation unit that varies a distance between a sheet tray and the sheet suction unit in accordance with the stiffness of the sheet; a control unit that controls the variation unit; and a feeding unit that feeds the sheet. Sheet feeding device. 2. The sheet feeding device according to claim 1, further comprising at least one air blowing unit that blows air near a front end of the sheet bundle stored in the sheet tray. 3. The sheet feeding apparatus according to claim 1, wherein the feeding unit is a conveyance belt wound around the sheet suction unit and provided with a plurality of suction holes on a surface. 4. A projection which is movable by being pressed by a sucked sheet;
The sheet feeding device according to claim 1, further comprising at least one measurement unit that measures a movement amount of the protrusion. 5. The apparatus according to claim 4, wherein the protrusion is movable in a direction substantially perpendicular to the sheet suction unit.
3. The sheet feeding device according to 1. 6. A sheet tray on which a plurality of sheets are stacked, a first sheet suction unit opposed to the stacked sheet bundle and having a plurality of air suction openings in a substantially planar bottom surface; A second sheet suction unit disposed downstream of the sheet suction unit in the sheet conveyance direction and having a plurality of air suction openings in a substantially planar bottom surface; and a second sheet downstream of the first sheet suction unit and the second sheet suction unit. A displacement fulcrum disposed upstream of the suction unit and displacing the sheet sucked by the first and second sheet suction units so as to be convex downward; and the first and second sheet suction units At least one air suction unit for sucking the sheet by sucking air through the air suction opening of the air suction unit; a detection unit provided near the air suction unit for detecting the stiffness of the sheet; Tray and said A variation unit that varies the distance between the first and second sheet suction units according to the stiffness of the sheet, a control unit that controls the variation unit, and a feeding unit that feeds the sheet. Characteristic sheet feeding device. 7. The sheet feeding device according to claim 6, wherein the feeding unit is a conveyance belt wound around the sheet suction unit and having a plurality of suction holes on a surface. 8. A projection which is movable by being pushed by the attracted sheet;
7. The sheet feeding device according to claim 6, wherein the sheet feeding device is configured by at least one measuring unit that measures a moving amount of the protrusion. 9. The sheet feeding device according to claim 8, wherein the protrusion is movable in a direction substantially perpendicular to the first sheet suction unit. 10. A sheet tray on which a plurality of sheets are stacked, a first sheet suction unit opposed to the stacked sheet bundle, and having a plurality of air suction openings in a substantially planar bottom surface; A second sheet suction unit disposed on the downstream side in the sheet conveyance direction with respect to the sheet suction unit and having a plurality of air suction openings displaced upward with respect to the substantially planar bottom surface; A displacement fulcrum disposed downstream and near the upstream side of the second sheet suction unit for displacing the sheet sucked by the first and second sheet suction units so as to be convex downward; At least one air blowing means for blowing air near the front end of the sheet bundle stored in the sheet tray; and a plurality of air blowing means wound around at least the first and second sheet suction portions and the displacement fulcrum portion. A conveyor belt having a suction hole, conveying the first and the suction holes of the belt, at least one for attracting the sheet to the conveying belt by sucking air through the air suction opening of the second sheet suction section
A sheet feeding device comprising: a plurality of air suction units; and a control unit for performing suction of air from the first and second sheet suction units independently of each other. A sheet feeding apparatus characterized in that control is performed by control means such that air is first suctioned from the sheet suction section, and then air is suctioned from the first sheet suction section. 11. The second sheet suction section is constituted by a substantially planar bottom surface having a plurality of air suction openings, and the first sheet suction section and the second sheet suction section are connected to the displacement fulcrum. 11. The sheet feeding device according to claim 10, wherein the sheet feeding device has a predetermined angle such that the portion is formed as a vertex and convex downward. 12. The suction device according to claim 12, wherein the second sheet suction unit includes a suction roller having a plurality of air suction openings, and the displacement fulcrum is a part of a surface curvature of the suction roller. A sheet feeding device according to claim 10. 13. A sheet tray on which a plurality of sheets are stacked, a first sheet suction unit opposed to the stacked sheet bundle and having a plurality of air suction openings in a substantially planar bottom surface; A second sheet suction unit disposed on the downstream side in the sheet conveying direction with respect to the sheet suction unit and having a plurality of air suction openings displaced downward with respect to the substantially planar bottom surface; A displacement fulcrum disposed downstream and near the upstream side of the second sheet suction unit, for displacing the sheet sucked by the first and second sheet suction units so as to be convex upward; At least one air blowing means for blowing air near the front end of the sheet bundle stored in the sheet tray; and a plurality of air blowing means wound around at least the first and second sheet suction portions and the displacement fulcrum portion. A conveyor belt having a suction hole, conveying the first and the suction holes of the belt, at least one for attracting the sheet to the conveying belt by sucking air through the air suction opening of the second sheet suction section
A sheet feeding device comprising: a plurality of air suction units; and a control unit for performing suction of air from the first and second sheet suction units independently of each other. A sheet feeding apparatus characterized in that control is performed by control means such that air is first suctioned from the sheet suction section, and then air is suctioned from the first sheet suction section. 14. The second sheet suction portion is constituted by a substantially planar bottom surface having a plurality of air suction openings, and the first sheet suction portion and the second sheet suction portion are connected to the displacement fulcrum. 14. The sheet feeding device according to claim 13, wherein the sheet feeding device has a predetermined angle so as to be convex upward with the portion as a vertex. 15. The apparatus according to claim 15, wherein the second sheet suction unit includes a suction roller having a plurality of air suction openings, and the displacement fulcrum is a part of a surface curvature of the suction roller. 14. The sheet feeding device according to 13. 16. A first sheet suction portion facing a sheet to be measured and having at least one air suction opening at a substantially planar bottom surface, and at least one air at a substantially planar bottom surface facing the sheet. A second sheet suction unit having a suction opening, at least one air suction unit for sucking air through an air suction opening of the first and second sheet suction units, and a first sheet suction unit. A first detection unit that is provided near the first sheet suction unit and detects that the sheet is sucked by the first sheet suction unit; and a first detection unit that is provided near the second sheet suction unit. A second detection unit that detects that the sheet is sucked by the second sheet suction unit; and a sheet that is detected by the second sheet suction unit after the sheet is sucked by the first sheet suction unit. Detect time to Sheet properties detecting apparatus comprising: the measuring means. 17. The sheet according to claim 16, wherein a distance from the sheet to be measured to the first detecting means is different from a distance from the sheet to the second detecting means. Physical property detection device. 18. The apparatus according to claim 16, further comprising display means for displaying a signal measured by said measurement means.
3. The sheet physical property detecting device according to 1. 19. A sheet tray on which a plurality of sheets are stacked, a first sheet suction unit opposed to the stacked sheet bundle and having a plurality of air suction openings in a substantially planar bottom surface; A second sheet suction unit disposed on the downstream side in the sheet conveyance direction with respect to the sheet suction unit and having a plurality of air suction openings displaced upward with respect to the substantially planar bottom surface; A displacement fulcrum disposed downstream and near the upstream side of the second sheet suction unit for displacing the sheet sucked by the first and second sheet suction units so as to be convex downward; At least one air blowing means for blowing air near the front end of the sheet bundle stored in the sheet tray; and a plurality of air blowing means wound around at least the first and second sheet suction portions and the displacement fulcrum portion. A conveyor belt having a suction hole, conveying the first and the suction holes of the belt, at least one for attracting the sheet to the conveying belt by sucking air through the air suction opening of the second sheet suction section
Air suction means, first detection means arranged near the first sheet suction section, and detecting that the sheet is suctioned by the first sheet suction section; and the second sheet A second sensor disposed near the suction unit for detecting that the sheet is suctioned by the second sheet suction unit;
And measuring means for measuring the time from when the sheet is attracted to the first sheet attracting portion to when the sheet is attracted to the second sheet attracting portion. Sheet feeding device. 20. A sheet tray on which a plurality of sheets are stacked, a first sheet suction unit opposed to the stacked sheet bundle and having a plurality of air suction openings in a substantially planar bottom surface; A second sheet suction unit disposed downstream of the sheet suction unit in the sheet conveyance direction and having a plurality of air suction openings in a substantially planar bottom surface; and a second sheet downstream of the first sheet suction unit and the second sheet suction unit. A displacement fulcrum disposed upstream of the suction unit and displacing the sheet sucked by the first and second sheet suction units so as to have a downwardly convex shape; and the first and second sheet suction units. At least one air suction unit for sucking a sheet by sucking air through an air suction opening of the first sheet suction unit, provided near the first sheet suction unit, and pushed by the sucked sheet. Moveable A detecting means for detecting the amount of movement of the protrusion pushed and moved by the sheet when the sheet is sucked by the first sheet sucking portion; and the first sheet sucking. A sheet feeding device, comprising: an angle changing unit that changes an angle formed by the unit and a second sheet suction unit with the displacement fulcrum as a vertex; and a feeding unit that feeds the sheet. 21. The sheet feeding apparatus according to claim 20, further comprising at least one air blowing unit that blows air near a front end of the sheet bundle stacked on the sheet tray. 22. The sheet feeding device is wound around the first and second sheet suction portions and the displacement fulcrum portion,
21. The sheet feeding device according to claim 20, wherein the conveying belt has a plurality of suction holes on a surface. 23. The sheet feeding device according to claim 20, wherein the protrusion is movable at least in a vertical direction of the first sheet suction unit.