JP2002370840A - Sheet feeding device, image forming device and image evaluating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable sheet feeding device, an image forming device and an image evaluating device with favorable sheet separating performance capable of continuously carrying out sheet suction to conveyance. SOLUTION: The existence of overlapped feeding is detected by moving an overlapped feeding detecting sensor 24 near an end part 1 side of a sheet 8 conveyed by a suction finger 2. When overlapped feeding is detected, the overlapped sheet is separated by suitably repeating aligning actions. It corresponds to sheets with a wide variety of basis weights, a program is included automatically correcting a reference value in overlapped feeding detection, and highly reliable detection ability is provided. In regard to a hardly separable sheet with high adhering power, separating performance is enhanced by including the aligning actions or the like. Strain is removed and sheet suction with no gap is carried out even to a sheet with a curl by sequentially sucking from small sections of a sheet tip and not by simultaneously sucking throughout the whole sheet size area by a sheet suction table.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding apparatus for separating and feeding sheets from a sheet bundle stacked on a sheet stacking table, and an image for forming an image on a sheet separated and fed by such a sheet feeding apparatus. The present invention relates to a forming apparatus and an image evaluation apparatus for evaluating an image on a sheet separated and fed by such a sheet feeding apparatus.

[0002]

2. Description of the Related Art Conventionally, as a sheet feeding apparatus of this type, for example, air is blown on a sheet bundle stacked on a predetermined sheet mounting table to float several sheets and adsorb them to an adsorbing mechanism. An air blow type in which air is further blown to perform separation is known.

A sheet feeding device having an air blow type sheet separating mechanism has a sheet feeding tray and a sensor for detecting the upper surface height of a sheet bundle stored in the sheet feeding tray. And an air nozzle for floating the upper sheet, an air nozzle for separating the sheet sucked by the suction mechanism, and a transport device for moving the separated sheet.

In the above configuration, when air is blown from a pair of left and right air nozzles toward the vicinity of the center of the sheet width at the upper end of the sheet, several sheets are separated and levitated by the converged air. The levitated sheet is pressed against the suction mechanism located above, is fixed by air suction, and is sensed by the negative pressure sensor. In addition, a gap is created in the overlapping part of several sheets that has been blown and adsorbed by air on the sheet end face with a slit-shaped air nozzle, and the air layer is penetrated,
One sheet is separated and fed.

The sheets fed one by one in this manner can be subjected to image forming processing on the surface thereof by, for example, a predetermined image forming means (laser printer or the like).

On the other hand, when sheets on which image forming processing has been performed in advance are stacked on a sheet mounting table, an image on the sheet separated and fed by the above-described sheet feeding apparatus is recognized by a sensor or the like. There is known an image evaluation apparatus that evaluates images one by one based on the recognition. In such an image evaluation apparatus, in addition to the above-described sheet feeding apparatus, a sheet suction table (mechanism) for sucking and fixing the sheets separated and fed by the sheet feeding apparatus, and a sheet suction table (mechanism) fixed by the sheet suction table mechanism. And a sensor for recognizing an image on the sheet.

[0007]

However, the above-mentioned conventional sheet feeding apparatus has the following problems.

That is, the sheets adsorbed by the suction means are separated by separation means provided individually in the vicinity of the suction means to create gaps between the sheets and are pushed and spread by air. There was a case where a sheet was fed.

In the double feed detection mechanism, if a suction failure occurs near the detection sensor, the first sheet that has been suctioned first is sucked, and the other sheet that is sucked along with the first sheet causes a suction failure. May be in a state. As described above, there have been cases where a double feed cannot be detected despite the double feed.

If the sheet sucked by the suction conveyance means is separated at the leading end in the sheet advancing direction, the leading end of the sheet interferes with the transfer of the sheet to the sheet suction table.
Peeling or bending could occur.

In the double feed detecting mechanism, when automatically detecting the thickness of one sheet, an erroneous reference may be set if double feed occurs in the first separation as a reference.

When the sheet is fed by the suction conveyance means, if the sheet dropped on the sheet feed tray in the immediately preceding separation is not aligned properly and leans against the sheet feed tray or the side wall of the sheet positioning, sufficient separation is performed. In some cases, the sheet positioning is not performed, and the sheet positioning accuracy in the next process varies.

When a double feed occurs, the sheet has a strong adhesion, so that the double feed may occur again.

On the other hand, the conventional image evaluation apparatus (sheet suction table mechanism) has the following problems.

That is, since the sheets sucked by the sheet suction table mechanism are simultaneously subjected to the suction order, the sheets are sucked while the sheet is distorted due to curling, and wrinkles and undulations may remain on the sheet surface. In addition, by not dividing the section to be adsorbed into small pieces, small-sized sheets are adsorbed in a wider range than the sheet size, and the capability of the negative pressure air generator is reduced, and sheet floating may occur.

Sheets adsorbed by the sheet adsorbing table mechanism are simultaneously adsorbed in order. In the case of a sheet having a large curl such as a document sheet, the sheet cannot be adsorbed in a section having a small adsorbing force, and may float off the table. there were.

Since the sheet adsorbed by the sheet adsorbing table mechanism performs the order of adsorption at the same time, in the case of a document sheet to be fixed by a heat roller, a large amount of heat is given to the rear end of the sheet compared to the front end, and the curl increases. There was a tendency, and depending on the type of sheet, there was a case where a lift appeared at the rear end.

Since the sheets sucked by the sheet suction table mechanism are simultaneously subjected to the suction order, distortion tends to remain. Also, in the case of a sheet having a large curl such as a document sheet, the sheet is sometimes lifted because suction is not preferentially performed in a section having a weak suction force.

Further, since the sheet sucked by the suction table mechanism is subjected to the suction order at the same time, distortion tends to remain. In the case of a document sheet that is fixed by a heat roller, the rear end of the sheet is given a larger amount of heat than the front end,
The curl tends to be large, and depending on the type of sheet, a lift may appear at the rear end.

In addition, since the sheets sucked by the sheet suction table mechanism are simultaneously subjected to the suction order, there is a problem that distortion tends to remain in the case of a curled sheet.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a sheet having a good sheet separation performance and a reliability capable of continuously performing from sheet suction to conveyance. An object of the present invention is to provide a sheet feeding device, an image forming device, and an image evaluation device with high operability.

[0022]

According to a first aspect of the present invention, there is provided a sheet feeding apparatus for separating and feeding sheets from a sheet bundle stacked on a sheet stacking table. A suction conveyance unit that suctions and conveys the sheet from the sheet bundle, a separation claw that abuts on one corner of the sheet being conveyed by the suction conveyance unit and curves the sheet, and a one that is directly suctioned by the suction conveyance unit. A separating unit that blows positive pressure air into a minute gap between the sheet and another sheet that is sucked at the same time as the sheet; and a double feed detecting mechanism that detects the fact that the number of separated sheets is not one. I do.

Further, it is preferable that a rubbing rib for rubbing the end portion of the sheet bundle sucked by the suction conveyance means is further provided.

Further, it is preferable that the suction conveyance means has a plurality of suction fingers which are sucked on the upper surface of the stacked sheet bundle.

Further, when the sheet is separated by suction only at the suction finger closest to the separation claw among the suction and conveyance means, it is preferable to provide a suction separation detecting mechanism for detecting this.

Also, of the suction and conveyance means, only the suction finger disposed at a position facing the suction finger closest to the separation claw in the sheet advancing front direction including the suction finger closest to the separation claw, sucks and separates the sheet. It is preferable to provide a second suction / separation detection mechanism that detects the occurrence of the suction.

Further, the double feed detecting mechanism detects the thickness of the separated sheet and, if the detected thickness exceeds a predetermined reference value, determines that the number of separated sheets is not one. It is better to judge.

Further, it is preferable that the double feed detecting mechanism updates the reference value based on a history of the detected sheet thickness.

Further, prior to the sheet feeding operation, it is preferable to perform the sheet alignment operation.

It is preferable that the separation operation is performed after the sheet alignment operation is performed only when the double feed detection mechanism detects that the separated sheets are not one sheet twice in succession.

According to a second aspect of the present invention, there is provided an image forming apparatus having a function of forming an image on a sheet, wherein the image forming means forms an image on a sheet separated and fed by the sheet feeding apparatus having the above-described configuration. It is characterized by having.

According to a third aspect of the present invention, there is provided an image evaluation apparatus having a function of evaluating an image on a sheet, comprising a sensor for recognizing the image on the sheet separated and fed by the sheet feeding apparatus having the above-described configuration. Evaluating an image on the sheet based on the recognition of the sensor.

Further, the sheet feeding apparatus having the above-mentioned configuration is a sheet suction table having a plurality of sections corresponding to the separated sheets and generating an attraction force from each section to the sheets. It is preferable to further include a sheet suction table for sequentially generating an attraction force from each of the divided sheets from the leading end to the trailing end of the separated sheet.

A sheet suction table having a plurality of sections corresponding to the separated sheets and generating an attraction force from each of the sheets, wherein a center of the separated sheet is selected from the plurality of sections. It is preferable to provide a sheet suction table that generates a suction force from the section corresponding to the section and generates the suction force simultaneously or alternately sequentially toward the front end or the rear end.

A sheet suction table having a plurality of sections corresponding to the separated sheets and generating an attraction force for each sheet from the respective sections, wherein the sheet suction table is provided after the separated sheet among the plurality of sections. A sheet suction table that generates a suction force from a section corresponding to the end and sequentially generates a suction force toward the front end may be provided.

A sheet suction table having a plurality of sections corresponding to the separated sheets and generating an attraction force for each sheet from each section, wherein the attraction force is generated from a section corresponding to the sheet front end. After that, the suction force is generated from the section corresponding to the central portion of the sheet, and the suction force generated from the section corresponding to the front end of the sheet is released, and then the suction force is simultaneously or alternately sequentially toward the front end or the rear end. A sheet suction table for generating the sheet may be provided.

A sheet suction table having a plurality of sections corresponding to the separated sheets and generating an attraction force for each sheet from each section, wherein the attraction force is generated from a section corresponding to the sheet front end. After that, a sheet suction table that generates suction force from the section corresponding to the sheet rear end, cancels the suction force generated from the section corresponding to the sheet front end, and then sequentially generates the suction force toward the front end may be provided. Good.

Further, the apparatus has a plurality of sections corresponding to the separated sheets, a sheet suction table for generating an attraction force for each of the sheets, and a sheet suction table corresponding to the sheet rear end of the sheet suction table. After the suction force is generated from the section to be sucked, the sheet suction table is slightly moved toward the rear end of the sheet while the suction is being performed only on the front end side of the sheet by the suction conveyance unit, so that the sheet is tensioned. Above, the suction force may be sequentially generated from the section corresponding to the sheet rear end of each section of the sheet suction table toward the front end side.

According to a fourth aspect of the present invention, there is provided an image evaluation apparatus for evaluating an image on a sheet, which recognizes an image on a sheet which has been separated and fed by the sheet feeding apparatus having the above-described configuration and which has been sucked on a sheet suction table. And evaluating the image on the sheet based on the recognition of the sensor.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the drawings. However,
The dimensions, materials, shapes, relative arrangements, and the like of the components described in the embodiments are not intended to limit the scope of the present invention only to them unless otherwise specified.

(First Embodiment) With reference to FIGS. 1 to 5, a sheet separating mechanism, a sheet feeding device, an image forming device and an image evaluation device according to a first embodiment will be described.

FIG. 1 is a schematic sectional view of an image forming apparatus according to an embodiment of the present invention.

The photosensitive drum 41 rotates in the direction of the arrow in the figure, and is uniformly charged by a charging roller 42 to which a bias is applied. The exposure device 45 irradiates the photosensitive drum 41 with a laser beam that is ON / OFF controlled according to an image signal input to the image forming device 40, and forms an electrostatic latent image on the photosensitive drum 41. This electrostatic latent image is developed with a toner as a developer by a developing device 48 disposed close to the photosensitive drum 41, and is visualized as a toner image.

On the other hand, the sheet feeding device 50 starts the feeding operation of the sheet 8 according to the image signal input to the image forming device 40. The suction finger 2 moves up and down, and suction-separates the sheet 8 from the sheet bundle stacked on the sheet feed tray 1, and conveys the sheet 8 to the feed roller 15.

The sheet 8 is conveyed in a direction indicated by an arrow in the drawing by conveying means such as a feeding roller 15, and a toner image on the photosensitive drum 41 visualized by a transfer roller 46 is transferred. The sheet 8 to which the toner image has been transferred is subjected to a fixing process by a fixing device 47, and is discharged outside the device.

The untransferred toner remaining on the photosensitive drum 41 without being transferred to the sheet 8 is scraped off by the cleaning blade 43 and stored in a waste toner container 44.
The cleaned photosensitive drum 41 repeats the above operation, and continuously forms an image.

FIG. 2 is a schematic configuration diagram of the image evaluation apparatus according to the first embodiment of the present invention.

The image evaluation device 60 starts the sheet feeding operation in response to the input measurement start signal.

The suction finger 2 descends, and after the sheet 8 is suction-separated from the sheet bundle stacked on the sheet feeding tray 1, the sheet 8 rises.
Pause. The double feed detection sensor 24 enters so as to sandwich the sheet, detects the presence or absence of double feed, and proceeds to the next operation. After the retracted sheet suction table 18 moves below the suction finger 2, the suction finger descends and transfers the sheet 8.

After the sheet 8 is suction-fixed, the sheet suction table 18 moves below the image evaluation sensor 19, and performs measurement in conjunction with the sensor.

When the measurement is completed, the sheet suction table moves below the sheet discharge suction finger 16, the finger sucks the sheet, and the sheet suction table retracts.

The finger 16 descends toward the discharge tray 14 and discharges the sheet 8.

The separating mechanism and the sheet feeding device according to the present embodiment will be described in more detail with reference to FIGS.

FIG. 3 is a view taken in the direction of arrow A in FIG. FIG.
FIG. 5 is a sectional view taken along the line E-E of the sheet separating mechanism according to the first embodiment of the present invention, and FIG. 5 is a schematic perspective view of FIG.

2 and 3, reference numeral 1 denotes a paper feed tray for arranging and stacking the sheets 8, and reference numerals 6 and 7 are removably attached to the paper feed tray 1 and used for positioning the sheet to define the sheet size. is there. In addition, sheet positioning 6,7
Are arranged on the paper feed tray 1 so as to form 90 ° with each other.

Reference numeral 2 denotes a suction finger as suction conveyance means for suction-conveying the sheet by the negative pressure air generated by the negative pressure air generator 10. The suction finger 2 is
The sheet 8 moves up and down in the direction of B in the figure together with a sheet height detection sensor 9 that detects the height of the upper surface of the sheets 8 stacked on the sheet feed tray 1.

Reference numerals 3 and 4 denote separation claws, two of which are provided so as to sandwich an air blow above the corner of the sheet. The separation claws come into contact with one corner of the sheet when the suction finger 2 rises and descends. Form a curve (loop).

Reference numeral 5 denotes an air blow as a separating means for blowing out the positive pressure air generated by the positive pressure air generator 11.

Reference numerals 20 and 21 denote rubbing ribs formed on the sheet positioning members 6 and 7, and reference numerals 22 and 23 denote rubbing ribs formed on the sheet feeding tray 1. The rubbing ribs 22 and 23 have a gradient in which the contact amount increases as the sheet rises, and the rubbing ribs 20 and 21 have a gradient in which the contact amount decreases.

In the above configuration, when an instruction to start the feeding operation is issued from the main body of the image forming apparatus 40 and the main body of the image evaluating apparatus 60, the suction finger 2 is lowered and aligned with the paper feed tray 1.
The sheet 8 comes into contact with the upper surface of the stacked sheets 8, descends while applying a built-in spring pressure until the paper height detection sensor 9 detects the sheet 8, and sucks air to thereby obtain the sheet 8.
To adsorb.

When the suction is completed, the suction finger 2 starts to rise. At this time, as shown in FIG. 4, the suction finger 2 sucks several sheets.

Next, referring to FIG. 5, which is a view taken in the direction of the arrow in FIG.
The sheet separating operation will be described.

The sheet 8 sucked by the suction finger 2 and starting to rise is blocked at one corner by the separation claws 3 and 4 to form a small gap between the loop and the sheet. The gap is widened by blowing air. The suction finger 2 repeatedly passes and abuts the separation claws 3 and 4 several times, and performs separation by blowing air.

The sheet 8 after the specified separation step is lifted by the suction finger 2, and the waiting double feed detection sensor 24 measures the thickness, approaches the corner of the sheet, and retreats.

According to the measurement result of the double feed detection sensor 24,
If the separation is insufficient, the separation process is performed again. When it is determined that the number of sheets is one, the sheet is transferred to the sheet suction table 18 in the next process.

The double feed detection sensor 24 optically measures the transmission amount of the sheet. The relationship between various sheets used in the apparatus and the amount of transmitted light corresponding to the number of sheets is determined in advance, and the detection means is set.

The present detection sensor has two sheets, one sheet and one sheet.
Although the accuracy of discrimination is required, the basis weight is 60 g / m ² to 200 g / m ^2.
Compatible with a wide range of sheets of g / m ² .

(Second Embodiment) FIG. 6 is a schematic perspective view of a sheet separating mechanism according to a second embodiment.
Note that the basic configuration of the image evaluation device to which each mechanism according to each embodiment described later is mounted, including the second embodiment, is the same as the image evaluation device according to the first embodiment ( (See FIG. 2), and thus redundant description in each embodiment will be omitted.

In the second embodiment, the separation claws 3, 4
Sheet suction table 1
The first suction separation sensor 25 detects that the sheet has separated from the suction finger in a direction slightly inclined with respect to the sheet conveyance direction in which the sheet 8 moves.

When the leading end of the sheet in the sheet advancing direction is attracted and separated, the leading end of the sheet may interfere with the transfer of the sheet to the sheet attracting table, and may peel off or bend. Although it is sufficient to raise the position at which the suction finger is raised, this leads to an increase in the size of the apparatus or an increase in the sheet conveyance time.

Further, in the double feed detection according to the first embodiment, if a suction failure occurs near the detection sensor, the first sheet that has been suctioned first is sucked, and the first sheet that is sucked along with the first sheet is sucked. In some cases, the sheet may cause poor suction, and may be sucked by other fingers to be hung.
In such a case, the double feed detection determines that two sheets are one.

As described above, the first suction / separation detecting sensor 25 can detect these phenomena and prevent them before they occur.

(Third Embodiment) FIG. 7 shows a third embodiment. In the present embodiment, it is detected that the sheet has separated from the suction finger in a direction perpendicular to the sheet surface with respect to the sheet conveying direction in which the sheet suction table 18 moves through the suction finger in the vicinity of the separation claws 3 and 4. The sensor 2 (26) is provided.

If the leading end of the sheet in the sheet advancing direction is attracted and separated, the leading end of the sheet may interfere with the transfer of the sheet to the sheet attracting table, and may peel off or bend. Although it is sufficient to raise the position at which the suction finger is raised, this leads to an increase in the size of the apparatus or an increase in the sheet conveyance time.

As described above, the second suction separation detecting sensor 2
6 can detect these phenomena and prevent them before they occur.

(Fourth Embodiment) FIG. 8 shows a fourth embodiment. In the present embodiment, the thickness of one sheet serving as a reference for double feed detection is reviewed and updated.

Normally, when a paper feeding operation is performed, the paper type, the basis weight, and the like are not known even though the paper size is known. Even if it is found, there is variation among lots. Since it is conceivable that the sheets separated at the first time are multi-fed, the separating operation is performed twice and is taken as a reference value (S4).

After the second time, the reference value is compared with the reference value up to the previous time.
If the number of separated sheets is determined to be one, the data is updated.

In comparison with the reference value, in the case of this apparatus, it is determined whether there is a difference of ± 20% or more from the previous reference value (S6).
9). If it is smaller, the previous sheet is regarded as double feed and grouped. Also, the previous reference value is multiplied by the number of sheets up to the previous time, the current value is added, and the average value divided by the number of sheets up to this time is updated as a new reference value (S10).

In this apparatus, it has been confirmed by experiments that the amount of transmitted light tends to decrease by about 40 to 50% each time one sheet is added. Including variations during measurement,
20% was set as the value of the comparison judgment.

By incorporating the update of the multi-feed reference value into the program as described above, the initial reference value can be reviewed, and a sheet group without multi-feed can be specified by using the sheet counter.

(Fifth Embodiment) FIG. 9 shows a fifth embodiment. In the present embodiment, the sheet alignment operation is performed at the beginning of the sheet feeding operation.

After the start of sheet feeding, the suction finger 2 comes into contact with and suctions the sheet 8 and rises. At this time, the suction finger 2 is suctioning several sheets. At a position elevated by about 10 mm from the upper surface of the remaining sheet in the sheet feeding cassette 1, the sheet is sucked off and freely dropped on the upper surface of the remaining sheet.

In FIG. 9, one finger or two fingers are used for the alignment according to the sheet size in the part C in FIG. 9, and one or two fingers in the part D are used when the sheet arrangement is perpendicular to the figure.

By performing this operation, the sheet 8 is brought into contact with and aligned with the sheet cassette 1 and the sheet positioning 6, 7, and
The accuracy of positioning the sheet with respect to the sheet suction table 18 in the subsequent process is maintained. Further, since several sheets 8 are dropped and aligned while being guided by the side walls, the adhesive force between the sheets is weakened and the separating performance can be improved.

(Sixth Embodiment) In this embodiment,
When the sheet is fed twice consecutively, the separating operation is performed after the sheet is aligned.

By performing this operation, the sheet 8 comes into contact with and aligns with the sheet cassette 1 and the sheet positioning 6 and 7.
The accuracy of positioning the sheet on the sheet suction table 18 as a subsequent step is improved. Further, since several sheets 8 are dropped and aligned while being guided by the side walls, the adhesive force between the sheets is weakened and the separating performance can be improved.

(Seventh Embodiment) FIG. 10 is a top view (A 'arrow) of a sheet suction table mechanism according to a seventh embodiment of the present invention, and FIG. E-
It is E sectional drawing. FIG. 12 is a schematic perspective view of the sheet suction mechanism.

10 and 11, reference numeral 18 denotes the sheet 8
This is a sheet suction table for sucking and fixing
Cl to C corresponding to sheet size and sheet length and width
It is divided into 22 sections. 21 is an air cell, C
An isolation chamber is formed to ensure that the sections from 1 to C22 work. Reference numerals 22 and 23 denote an air joint and an air tube.
A decompression path is formed between the pressure-reducing path and zero.

In FIG. 11, every other one is drawn to avoid complication, but one set of piping is provided in each section.

Reference numeral 2 denotes a suction finger as suction conveyance means for suction-conveying the sheet by the negative pressure air generated by the negative pressure air generator 10. The suction finger 2 is
The sheet 8 moves up and down in the direction of B in the figure together with a sheet height detection sensor 9 that detects the height of the upper surface of the sheets 8 stacked on the sheet feed tray 1.

Reference numerals 3 and 4 denote separation claws, two of which are provided so as to sandwich the air blow above the corner of the sheet. The separation claws come into contact with one corner of the sheet when the suction finger 2 moves up and down. Form a curve (loop).

Reference numeral 5 denotes an air blow as a separating means for blowing out the positive pressure air generated by the positive pressure air generator 11.

Reference numeral 20 denotes a rubbing rib formed on the sheet positioning 6 and a rubbing rib formed on the sheet feeding tray 1 (not shown) has a gradient such that the contact amount increases as the sheet rises.
The rubbing rib has a gradient that reduces the contact amount.

In the above configuration, when an instruction to start a feeding operation is issued from the main body of the image evaluation apparatus 60, the suction finger 2 descends and comes into contact with the upper surface of the sheets 8 aligned and stacked on the sheet feeding tray 1 to increase the sheet height. The sheet 8 is lowered while applying a built-in spring pressure until the detection of the sensor 8 is obtained, and the sheet 8 is sucked by sucking air.

When the suction is completed, the suction finger 2 starts to rise, but at this time, the suction finger 2 is suctioning several sheets.

The sheet 8 sucked by the suction finger 2 and starting to rise is blocked at one corner by the separation claws 3 and 4 to form a small gap between the loop and the sheet. The gap is widened by blowing air. The suction finger 2 repeatedly passes and abuts the separation claws 3 and 4 several times, and performs separation by blowing air.

The sheet 8 having undergone the specified separation step is lifted by the suction finger 2, and the waiting double feed detection sensor 24 measures the thickness, approaches a corner of the sheet, and retreats. The double feed detection sensor 24 optically measures the amount of transmission of the sheet, and the apparatus main body determines the presence or absence of the double feed based on this.

According to the measurement result of the double feed detection sensor 24,
If the separation is insufficient, separation and kneading are performed again, and when it is determined that the number of sheets is one, the sheet is transferred to the sheet suction table 18 in the next step.

The sheet suction table 18 is divided into sections from Cl to C22 as shown in FIG.
Many suction holes of m or less are drilled. When adsorbing the A4 vertically placed sheet, the apparatus body issues an instruction to reduce the pressure of C5 from Cl. C for LETTER portrait seat
An instruction to reduce the pressure of C4, C9, and Cl0 from 1 is issued.

In FIG. 10, the sheet has sections arranged at mirror symmetric positions with respect to a line connecting Cl and C17.
The reference of the sheet is always located on Cl. In the present embodiment, the sheet delivered from the suction finger is
And C2,3,4,5 for vertical installation and C for horizontal installation
1, 2, 9, 11, and 15 are successively adsorbed. When the first suction of the sheet suction table is completed, the suction finger cancels the suction and retreats upward.

As described above, by sequentially performing the operations without adsorbing all the sections at the same time, the distortion of the sheet is removed,
A sheet suction table without sheet lifting can be provided.

(Eighth Embodiment) FIG. 13 shows an eighth embodiment. In the present embodiment, the first suction of the sheet suction table is performed at C3 or C9, and the sheet is sequentially spread toward the leading end and the trailing end.

C3 and C9 are areas where the area of the section where the sheet size changes is minimized, and the suction force is low. The sheet has air permeability, and the permeability varies depending on the type of the sheet. However, when a wide area is first adsorbed, air flows through the sheet, and the performance of the negative pressure air generator is reduced. As a result, the adsorbing power of C3 and C9 is further reduced, so that sufficient adsorbing may not be performed due to the size of the curl of the sheet.

As described above, the suction order is performed from the central section having a weak suction force, thereby preventing defective suction. Also,
The sheet can be distorted by sequentially expanding the adsorption section at the front end and the rear end of the sheet.

(Ninth Embodiment) FIG. 14 shows a ninth embodiment. In the present embodiment, the first suction of the sheet suction table is performed from the rear end of the sheet and is sequentially spread toward the front end of the sheet.

When evaluating a document sheet to be fixed by a heat roller, the rear end of the sheet is applied with a larger amount of heat than the front end, so that the curl tends to increase.
If the rear end section is suctioned last, poor suction may occur depending on the sheet, and floating may occur at the end.

As described above, by performing the suction order from the section at the rear end of the sheet, it is possible to prevent the sheet from floating.

(Tenth Embodiment) In the present embodiment, the first suction is performed at the leading end of the sheet, and then the suction at the leading end is released after the central section having a weak suction force is sucked. Thereafter, the suction is sequentially spread toward the front end and the rear end of the sheet.

After adsorbing the leading edge and the central portion of the sheet, the adsorbing of the leading end is released to reduce the distortion of the sheet, and by sequentially expanding the adsorbing section, it is possible to prevent defective adsorption and remove the distortion of the sheet. it can.

(Eleventh Embodiment) In the present embodiment, the first suction is performed at the leading edge of the sheet, and then the trailing edge is released, and then the leading edge is released. Thereafter, the suction is sequentially spread toward the sheet front end.

After suctioning the leading and trailing ends of the sheet, the suction at the leading end is released to reduce the distortion of the sheet, and by sequentially expanding the suction section, it is possible to prevent poor suction and remove the distortion of the sheet. it can.

(Twelfth Embodiment) FIG.
Two embodiments are shown. In the present embodiment, after suctioning the sheet rear end, the sheet suction table is slightly moved in the F direction while suction is being performed only on the sheet front end side of the suction finger, and the sheet suction table is brought into a state where tension is applied to the sheet. Are sequentially adsorbed toward the front end side.

By performing this operation, it is possible to remove the distortion of the sheet having a large curl and perform the sheet positioning without lifting at the rear end. Since the suction finger has an equalizing property, it is possible to apply tension within a range in which the positional deviation between the sheet and the sheet suction table does not occur.

[0115]

As described above, according to the present invention,
By detecting the double feed by approaching the double feed detection mechanism (double feed detection sensor) to the sheet after the separation operation, it is possible to prevent the double fed sheet from being conveyed to the next process.

Further, by providing the first and second suction-separation detecting mechanisms (the first and second suction-separation detection sensors 25 and 26), it is possible to suppress an increase in the size of the apparatus, and to prevent sheet suction separation and bending. Will be able to do it.

Further, by providing a function of reviewing and updating the thickness of one sheet serving as a reference for double feed detection, highly reliable double feed detection can be performed.

Further, by performing the sheet aligning operation at the beginning of the sheet feeding operation or when the multi-feed operation is continued, the sheet positioning accuracy and the separating performance can be improved.

Further, the sheet suction table does not simultaneously perform suction over the entire sheet size, but sequentially sucks the sheet from the small section at the sheet front end, thereby removing the distortion even for the curled sheet, and thereby preventing the sheet from being lifted. Will be able to do.

Further, by performing suction by the sheet suction table from a section having a weak sheet suction force, defective suction can be prevented and sheet distortion can be eliminated.

Further, by performing suction by the sheet suction table from the section at the rear end of the sheet, the floating of the sheet can be removed.

Further, the suction by the sheet suction table is performed in the section at the rear end of the sheet, and then the sheet suction table is slightly moved while only the front end side of the sheet of the suction finger is sucked, and tension is applied to the sheet. By sequentially adsorbing the sections toward the front end, it becomes possible to remove the distortion of the sheet having a large curl and to adsorb the sheet while suppressing the lifting at the rear end.

[Brief description of the drawings]

FIG. 1 is a schematic configuration sectional view of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an image evaluation device according to the embodiment of the present invention.

FIG. 3 is a schematic plan view as viewed from an arrow A in FIG. 2;

FIG. 4 is a sectional view taken along line EE of FIG. 3;

FIG. 5 is a schematic perspective view of a sheet separating mechanism according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram illustrating detection of suction and separation of a sheet according to the second embodiment of the present invention.

FIG. 7 is an explanatory diagram illustrating detection of sheet attraction and separation according to a third embodiment of the present invention.

FIG. 8 is a flowchart illustrating an operation of updating a reference value for double feed detection according to a fourth embodiment of the present invention.

FIG. 9 is a schematic explanatory diagram of a sheet alignment operation according to a fifth embodiment of the present invention.

FIG. 10 is a top view of a sheet suction table mechanism according to a seventh embodiment of the present invention.

FIG. 11 is a sectional view taken along line EE of FIG. 10;

FIG. 12 is an explanatory diagram showing a suction procedure of the sheet suction table according to the embodiment;

FIG. 13 is an explanatory diagram showing a suction procedure of a sheet suction table according to an eighth embodiment of the present invention.

FIG. 14 is an explanatory diagram showing a suction procedure of a sheet suction table according to a ninth embodiment of the present invention.

FIG. 15 is an explanatory diagram showing a suction procedure of a sheet suction table according to a twelfth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paper feed tray 2, 16 Suction finger 3, 4 Separation claw 5 Air blow 6, 7 Sheet positioning 8 Sheet 9, 17 Paper height detection sensor 10 Negative pressure air generator 11 Positive pressure air generator 14 Discharge tray 15 Conveyance Roller 18 Sheet suction table 19 Image evaluation sensor 20, 21, 22, 23 Rubbing rib 24 Double feed detection sensor 25 First suction separation detection sensor 26 Second suction separation detection sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B65H 5/22 B65H 5/22 7/12 7/12 7/16 7/16 G03G 15/00 516 G03G 15 / 00 516 (72) Inventor Tsuyoshi Yokota 1248 Shimokagemori, Chichibu-shi, Saitama F-term (reference) in Canon Electronics Co., Ltd. 2H072 AA04 AA14 AA22 AB03 BA02 BA05 CA01 3F048 AA05 AB01 BA12 BA13 BB02 CA02 CB03 DA01 EB13 3F049A CA06 FA05 LA06 LB01 3F343 FA02 FB05 FC01 GA01 GB01 GC01 GD04 HA33 HD14 HE03 JB02 JB19 JB20 JB27 JB28 JC09 JC18 JC20 JD11 JD15 JD27 JD33 JD34 KA06 KA16 KB03 KB04 KB17 KB20

Claims (18)

[Claims] 1. A sheet feeding apparatus for separating and feeding sheets from a sheet bundle stacked on a sheet stacking table, comprising: a suction conveyance unit for sucking and conveying the sheets from the stacked sheet bundle; A separation claw that abuts one corner of the sheet being conveyed by the means and curves the sheet; If the separating means to spray and the separated sheet is not one,
A sheet feeding device, comprising: a double feed detecting mechanism for detecting the fact. 2. The sheet feeding apparatus according to claim 1, further comprising a rubbing rib rubbing an end portion of the sheet bundle sucked by the suction conveyance means. 3. The sheet feeding apparatus according to claim 1, wherein the suction conveyance unit includes a plurality of suction fingers that suction the upper surface of the stacked sheet bundle. 4. The apparatus according to claim 3, further comprising a suction-separation detecting mechanism for detecting, when the sheet is separated by suction only at the suction finger closest to the separation claw, of the suction conveyance means. The sheet feeding device as described in the above. 5. A sheet suctioning / separating unit which is located at a position facing a suction finger closest to the separation claw in a sheet advancing direction including a suction finger closest to the separation claw among the suction conveyance means. 5. The sheet feeding apparatus according to claim 4, further comprising a second suction / separation detecting mechanism for detecting the occurrence of the sheet separation. 6. The multi-feed detecting mechanism detects a thickness of a separated sheet and, if the detected thickness exceeds a predetermined reference value, determines that the number of separated sheets is not one. The sheet feeding device according to claim 1, wherein the determination is made. 7. The sheet feeding device according to claim 6, wherein the double feed detecting mechanism updates the reference value based on a history of the detected sheet thickness. 8. The sheet feeding apparatus according to claim 1, wherein a sheet aligning operation is performed prior to a sheet feeding operation. 9. The separation operation is performed after the sheet alignment operation is performed only when the double feed detection mechanism detects that the separated sheet is not one sheet twice in succession. The sheet feeding device according to claim 8. 10. An image forming apparatus comprising an image forming means for forming an image on a sheet separated and fed by the sheet feeding apparatus according to any one of claims 1 to 9. . 11. A sensor for recognizing an image on a sheet separated and fed by the sheet feeding apparatus according to any one of claims 1 to 9, and a sensor for recognizing an image on the sheet based on the recognition of the sensor. An image evaluation device for evaluating an image. 12. A sheet suction table having a plurality of sections corresponding to the separated sheets and generating an attraction force for each sheet from the respective sections, wherein a leading end of the separated sheet among the plurality of sections. The sheet feeding device according to any one of claims 1 to 9, further comprising a sheet suction table configured to sequentially generate a suction force from each section toward the rear end. 13. A sheet suction table having a plurality of sections corresponding to the separated sheets and generating an attraction force for each of the sheets, wherein a center of the separated sheets among the plurality of sections is provided. 10. A sheet suction table for generating an attraction force from a section corresponding to a section and simultaneously or alternately sequentially generating an attraction force toward a front end or a rear end.
The sheet feeding device according to any one of the above. 14. A sheet suction table having a plurality of sections corresponding to the separated sheets and generating an attraction force from the respective sections for the sheets, wherein the sheet suction table is provided after the separated sheets among the plurality of sections. The sheet feeding device according to any one of claims 1 to 9, further comprising a sheet suction table that generates a suction force from a section corresponding to an end and sequentially generates a suction force toward a front end. apparatus. 15. A sheet suction table having a plurality of sections corresponding to the separated sheets and generating an attraction force for each sheet from each section, wherein the attraction force is generated from a section corresponding to a sheet front end. After
A suction force is generated from the section corresponding to the center of the sheet,
10. A sheet suction table for generating a suction force simultaneously or alternately sequentially toward a front end or a rear end after releasing a suction force generated from a section corresponding to a sheet front end. The sheet feeding device according to any one of the above. 16. A sheet suction table having a plurality of sections corresponding to the separated sheets and generating an attraction force for each sheet from each section, wherein the attraction force is generated from a section corresponding to a sheet front end. After
A sheet suction table that generates an attraction force from the section corresponding to the sheet rear end, releases the attraction force generated from the section corresponding to the sheet front end, and then sequentially generates the attraction force toward the front end. The sheet feeding device according to any one of claims 1 to 9, wherein: 17. A sheet suction table having a plurality of sections corresponding to the separated sheets, generating a suction force for each sheet from each section, and corresponding to a sheet rear end of the sheet suction table. After the suction force is generated from the section to be sucked, the sheet suction table is slightly moved toward the rear end of the sheet while the suction is being performed only on the front end side of the sheet by the suction conveyance unit, so that the sheet is tensioned. The sheet according to any one of claims 1 to 9, wherein a suction force is sequentially generated from a section corresponding to a sheet rear end of each section of the sheet suction table toward a front end side. Feeding device. 18. A sensor for recognizing an image on a sheet which has been separated and fed by the sheet feeding apparatus according to claim 11 and which has been sucked on a sheet suction table. An image evaluation device for evaluating an image on the sheet based on recognition.