JPH0789625A - Sheet feeding device - Google Patents

Abstract

PURPOSE:To provide accurate and stable feeding of one sheet at appropriate floating position without affected by sheet material, etc., by providing air jetting quantity control means for controlling a quantity of spraying air according to a detected position of a sheet floated by air by means of a position detecting means CONSTITUTION:A distance from a sensor 20 to a floated top part sheet document 1 is found out by a CPU 40 by means of a distance measuring sensor 20 after time passes by the time when the top part sheet document 1 might be floated from the time when the air is sprayed by a supply opening 5. If this measured distance is within its proper state, the blown-out air quantity by the flowing out opening is considered as the optimum state and the blown-out flow rate is fixed, that is, a number of revolution of the motor 45 of a fan motor device 15 is locked. Then the driving motor 48 of the fan device 13 of a feeding belt 4 is driven. Thereby, the floated sheet document 1 is sucked on the feeding belt 4 and a belt 17 moves according to the driving of a driving motor 44 and the sheet document 1 is sent to a designated position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for feeding a sheet cut to a predetermined size to a predetermined position, for example, feeding a sheet original or the like to a reading position, or feeding a sheet of paper to an image forming position. The sheet feeding device that is fed with
In particular, the present invention relates to a sheet feeding device for separating one sheet by using air and feeding one sheet.

[0002]

2. Description of the Related Art Conventionally, according to an image recording apparatus, a sheet-shaped recording sheet is conveyed to a recording position, a recording image is formed on the sheet, and then the sheet is ejected to the outside of the apparatus. For example, a copying apparatus in which an image of an original is directly formed on a recording medium, the image on the recording medium is transferred to a sheet-shaped conveyed sheet, and the sheet after the transfer is discharged to the outside of the apparatus through a fixing step. Etc.

In the copying apparatus, a document is placed at a predetermined position, that is, an exposure position which is a document reading position, and the document at the exposure position is projected on a recording medium. In this case, in order to save the trouble of manually placing the sheet original at the exposure position, the sheet original is placed on the original placing tray, and the sheet original on the original placing tray is moved to the exposure position. There is a copying machine equipped with an automatic document feeder that automatically conveys.

Among the automatic document feeders described above, when the image exposure of the sheet document at the exposure position is completed, the document is fed from the exposure position and re-conveyed to the exposure position again to form an image. Some are put back on the document tray. As described above, there is a recirculating document handler (hereinafter referred to as RDH) that returns the sheet document from the document placing tray to the exposure position and from the exposure position to the document placing tray.

Further, in addition to feeding the sheet original, according to the image forming apparatus, in order to transfer an image formed on a photoconductor, which is a recording medium, particularly a toner image, to a sheet paper,
A sheet feeding device for feeding the sheet of paper to the transfer position is provided. As this sheet feeding device,
Besides using a friction roller, for example, Japanese Patent Laid-Open No. 60-825.
As described in Japanese Laid-Open Patent Publication No. 37-37 (Japanese Patent Publication No. 62-56056), there is also one that feeds a sheet of paper placed on a loading tray by air means, that is, air blowing and air suction. According to this apparatus, for example, in order to perform sheet feeding, the pressure for sucking the uppermost sheet is controlled to ensure single sheet feeding.

As described above, the image forming apparatus is equipped with a device for feeding sheet originals and a feeding device for feeding sheet papers, and automatically feeds them as needed.

[0007]

In particular, the sheets placed on the placing tray are separated by the force of air, and the uppermost sheet is sucked by air, for example, sucked by a suction belt to be fed. There is. Therefore, in order to attract the uppermost sheet to the suction belt, it is necessary to separate it from the sheets below the uppermost sheet, and for that reason, the air is blown to the leading edge of the stacked sheets to move the uppermost sheet to the suction belt side. Levitate and separate from the second and subsequent sheets.

Conventionally, since the sheets on the loading tray are always fed by a constant amount of air, feeding failure is inevitable. In other words, if the topmost sheet is always floated at a fixed position when the separated sheets are sucked by the suction belt, the suction belt will ensure
It is possible to enable sheet feeding. However, it is not possible to know what the state of the top sheet is.

Therefore, in the prior art, Japanese Patent Laid-Open No. 60-8253
As disclosed in Japanese Patent Laid-Open Publication No. 7, the suction force is controlled in accordance with the flow rate of air, especially the time until the sheet is sucked by the suction belt, so that one sheet is fed.

However, by simply controlling the suction force of air, even if the suction force of air is controlled by the weight of the sheet itself, especially the material, it is not possible to reliably feed one sheet. In other words, even if there is no problem if there is only one stacked sheet that is separated by blowing air, if not only the topmost sheet but a few sheets float at the same time,
If the suction force is strong, a few sheets will be sucked at the same time,
It may be double-fed. Further, if the suction force is weak, the uppermost sheet may not be sucked, which may result in defective feeding.

In view of the above-mentioned problems, the present invention detects the floating state of the uppermost sheet on the loading tray and separates the sheets without controlling the air suction force by the suction belt. By controlling
The object is to solve the above problems.

[0012]

According to a first aspect of the present invention, there is provided a sheet feeding device for placing a sheet cut into a predetermined length, and a sheet on the placing tray having a predetermined length. Feeding means including air suction means for feeding to a position,
And a sheet feeding device provided with an air ejecting unit for blowing air to the tip of the sheet on the placing tray to separate a stack of placed sheets, wherein the air ejecting unit is applied to the sheet placed on the placing tray. Position detection means for detecting the position of the sheet floated by the air blown at, and air discharge amount control means for controlling the air discharge amount of the air blown based on the position detection by the position detection means. It is characterized by having.

According to a second aspect of the present invention, in the sheet feeding device according to the first aspect, the air ejection amount control means has a position detection value in a floating state by the position detection means,
Determine whether it is within the specified range of the predetermined floating position, if it is outside the specified range, increase or decrease the air discharge amount,
It is characterized in that the air discharge amount is controlled so that the floating position of the sheet is positioned within the specified range.

According to a third aspect of the present invention, in the sheet feeding device according to the second aspect, the air discharge amount control means preliminarily raises the sheet within a prescribed range by blowing air before the sheet feeding is started. Is recognized, the air ejection amount for the blowing is stored, and the air ejection amount is controlled based on the stored contents when the sheet feeding is started.

According to a fourth aspect of the present invention, in the sheet feeding apparatus according to the third aspect, the air amount control means is responsive to a signal for detecting a state in which the sheet is set on the loading tray. Perform levitation recognition.

According to a fifth aspect of the present invention, in the sheet feeding device according to the first aspect, the position detecting means measures the distance to the uppermost sheet floated at the position of the feeding means. It is characterized by being constituted by a measurement sensor.

Further, according to the sheet feeding apparatus of the sixth aspect of the present invention, a loading tray on which a sheet cut into a predetermined length is placed, and the sheet on the loading tray is fed to a predetermined position. In the sheet feeding apparatus, the sheet feeding device includes an air sucking unit and an air ejecting unit that blows air to the front end of the sheet on the placing tray to separate a stack of the placed sheets. Distance measuring means for measuring the distance between the sheet placed on the sheet and the sheet floated by the air blown by the air ejecting means, and the distance measured by the distance measuring means and the appropriateness of the sheet blown by air. The discriminating means for discriminating the floating position, the storing means for storing the air discharge amount at that time when the discriminating means discriminates that the discriminating means is within the proper range, and the discriminating means for confirming that the discriminating means is outside the proper range. The air amount control means is configured to repeatedly increase and decrease the air amount by a certain amount and repeatedly perform the blowing of the sheet with the increased / decreased air discharge amount, and the air amount control means, When the discharge amount of exceeds the maximum value or falls below the minimum value, it is treated as a failure state of the distance measuring stage, and the air discharge amount by the discharge means is set to the standard state, It is characterized in that the feeding control is executed based on the stored discharge amount or the set discharge amount in the standard state.

According to the seventh aspect of the present invention, in the sheet feeding apparatus according to the sixth aspect, the jam detection means at the time of air feeding and the number of times of jam detection by the jam detection means by the failure diagnosis are counted. A jam counter is provided, and the sheet feeding by the sheet feeding device is stopped when the counter reaches a predetermined value.

According to the eighth aspect of the invention, in the sheet feeding apparatus of the first or sixth aspect, the confirmation of the floating state of the sheet deactivates the air suction of the air suction means. It is characterized by setting and performing.

[0020]

According to the sheet feeding device of the first aspect of the present invention, in order to feed the cut sheet placed on the placing tray, air is blown from the tip of the sheet by the air ejecting means. The placed sheet bundle is separated and separated. In accordance with this, the uppermost sheet separated by the feeding means is sucked by the air suction means, so that feeding of the sheet by the feeding means is started. The air suction force at this time is fixed to a predetermined value, and the uppermost sheet on the loading tray is attracted to the feeding means side.

The sheet is floated by blowing air by the air ejecting means, and the position of the uppermost sheet is detected by the position detecting means. The position detecting means is claim 5.
Measure the distance to the levitated top sheet as described in. The amount of air discharged by the air discharging means is controlled based on the detected distance.

In the invention according to claim 2, the air discharge amount is such that the measured distance is within a reference value (specified value),
That is, if the amount of air that can be sucked by the air sucking unit is within a range suitable for sucking one sheet, the amount of air hit by the air discharging unit is maintained as it is. Further, when the uppermost sheet is less than the above range (long distance) with respect to the feeding means, the air blowing amount is increased to correct this. As a result, the uppermost sheet is further lifted and lifted to the side of the feeding means and positioned within the specified range.
On the other hand, if the measurement distance is very close to the feeding means and exceeds the above-specified range, that is, if it is a short distance, there is a high possibility that the next sheet will be floated together with the uppermost sheet. Therefore, the air ejection amount control means controls so as to reduce the amount of air blown by the air ejection means. As a result, the rising of the sheet is suppressed, the sheet is lowered, and the uppermost sheet can be corrected within the specified levitation range.

According to a third aspect of the present invention, the timing of controlling the flow rate of the air is executed in advance before the start of sheet feeding, and the discharge amount thereof is detected in advance, that is, the control value is adjusted. , The discharge amount is stored. Based on the stored discharge amount, the feeding is started, and the feeding can be performed in the normal levitating state of the sheet. As an example of this timing, it can be performed on the basis of a signal that detects the state in which the sheet is set on the loading tray as described in claim 4. Therefore, the start of feeding is not delayed. This set means a detection signal when a new sheet is placed on the loading tray, a detection signal when the loading tray is extended, or a new sheet is added or a new sheet is set and the loading tray is mounted,
Alternatively, if the loading tray is a replaceable cassette type, it can be performed by a signal or the like based on the replacement operation of the cassette.

Further, according to the apparatus of claim 6 of the present invention, as in the apparatus of claim 1 described above, while controlling the discharge amount of air for maintaining the floating state of the sheet within a predetermined range, When the distance measuring sensor detects that the sheet is not floated within the proper range even if the discharge amount of the air is above a predetermined minimum or maximum range, for example, below the minimum discharge amount or exceeds the minimum discharge amount. , Self-diagnose the distance measuring sensor as abnormal. As a result, defective feeding due to malfunction of the distance measuring sensor is prevented. Moreover, when the distance measuring sensor is in a failure state, a standard value is set as the air discharge amount, that is, the air discharge amount within the proper range of the floating state of the sheet in the standard state is set for each device, and the standard value is set. Fixed to a value to control feeding.

In this case, according to the device of claim 7,
The feeding jam detection when fixed to the standard value is counted each time, and when the count value reaches a predetermined value or more,
The feeding operation is stopped for the first time. This makes it possible to self-diagnose the sheet feeding device itself as having an abnormality, and prevent an operation due to further feeding failure.

Here, in the above-described sheet feeding apparatus, when the floating state is recognized, the air suction means is set to the non-operating state, so that the floating state is accurately recognized without being affected by the suction force. You can do it.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of a sheet feeding apparatus for cutting sheets of a predetermined size according to the present invention will be described below with reference to the drawings. Further, in the following embodiments, a copying apparatus will be described as an example of the recording apparatus, but the present invention is not limited to such an apparatus. That is, it can be applied to all devices for feeding cut sheets to a predetermined position. In particular, the present invention can be applied to a feeding device that feeds a sheet of paper on a loading tray to a transfer position in an image forming apparatus to process a sheet, a document feeding device that feeds a sheet document to a reading position, and the like.
Further, not only the image forming apparatus but also a facsimile or the like can be applied not only to an apparatus for feeding one sheet of a transmission document to a reading position, but also to a sheet paper feeding apparatus by a printer. .

FIG. 1 is a sectional view showing a specific example of the sheet feeding apparatus of the present invention applied to a copying apparatus, and FIG. 2 is a sectional view showing an example in which the sheet feeding apparatus is applied to a document circulating and conveying apparatus (RDH). Is.

In FIG. 1, the copying machine is equipped with a document circulating device (RDH) 30 having an original placing tray for placing sheet originals on the upper part of the copying apparatus main body.

The sheet-shaped original 1 is placed on the original placing tray 2. An operation piece of a micro switch 3 for detecting the presence or absence of a sheet original placed on the placing tray is located on the placing tray 2, and the micro switch 3 is located on the original placing tray 2. The operation piece is pushed down by the placed document to operate, and the presence of the document is detected. The loading tray 2 is provided in a fixed state, but a height detection switch 19 is provided to always position the uppermost sheet at a constant height, and the loading tray 2 is controlled to be raised. There is also. Further, in order to feed one sheet of paper to the image forming position in the copying apparatus, the placing tray 2 is provided so as to be able to be pulled out from the main body of the apparatus and has the same configuration as the feeding apparatus of FIG. Some are configured to simplify the placing or setting of the seat. further,
There is also a cassette system in which the loading tray itself is replaceable, that is, a loading tray is provided in the replaceable cassette body.

On the original placed on the placing tray 2, a feeding belt 4 as a feeding means for sequentially feeding the uppermost sheet original 1 is arranged. The feeding belt 4 is internally provided with a part of suction means for sucking air. The uppermost sheet original 1 is sucked (adsorbed) to the belt by air suction, and the sheet original is fed by moving the belt. To send. The feeding belt 4 which is this feeding means
At the same time, an air outlet 5 is provided, which constitutes an air ejecting means for separating the stacked originals placed on the original placing tray 2 into each one and reliably feeding one original.
The air outlet 5 blows air from the front surface (front surface in the feeding direction) of the placed original document to separate and separate the stack of the placed original documents 1. The uppermost one of the sheet originals 1 separated by the air blowing from the air outlet 5 is sucked onto the feeding belt 4 by the suction means, and the belt 4 is rotated in the arrow direction, so that the original 1 Will be fed.

As shown in FIG. 2, the fed sheet original 1 is fed along a feeding path 6 formed by a guide plate, and is fed by various feeding rollers 7 arranged in the middle of the feeding path. They are transported one after another. An exposure unit 8 for projecting an image of the sheet original 1 on the surface of a photosensitive drum, which is a recording medium provided in the main body of the copying apparatus and is rotationally driven, is disposed in the middle of the conveying path. The exposure unit 8 has a transparent plate 9 such as glass, and an exposure light source for irradiating light from below the transparent plate 9 is arranged. The copy image surface (lower surface) of the original document 1 conveyed to the position of the exposure unit 8 is pressed by the pressing roller 10 or the like from the opposite surface and is conveyed at a constant speed.

The original 1 that has passed through the exposure section 8 is further conveyed through the conveying rollers 7c, and the original placing tray 1
It will be returned to the lower part of the and will be circulated again. When the original document shown in FIG. 1 is circulated and conveyed, the upper and lower surfaces of the original document 1 are inverted and returned to the original document tray 1. Therefore, when the original document 1 is a double-sided original document, the original document is read at the first circulation (odd circulation). One side (front side) of the second side (the even number side) is presented to the exposure section 8 on the opposite side (back side), and images on both sides are read and can be projected onto, for example, a photosensitive drum.

In the case of a single-sided original, the original 1 can be returned to the original tray 1 by reversing it before returning it to the original tray. Therefore, FIG.
In addition, a reverse conveyance path is further provided in the original conveyance path of, and the reverse conveyance path is selected when reading an image of a single-sided original,
For a double-sided original, the path shown in FIG. 2 may be selected and circulated.

The above is the R equipped with the sheet feeding device of the present invention.
1 is a schematic configuration of DH30. A copying apparatus main body (not shown) is located below the RDH 30. That is,
The main body of the copying apparatus is provided with an optical system for irradiating the transparent plate 9 constituting the exposure section 8 with light and projecting it onto the surface of the photosensitive drum. This optical system includes a copy lamp such as a halogen lamp, a plurality of mirrors, a zoom lens, and the like, and projects the image of the original document 1 conveyed to the transparent plate onto the photosensitive drum.

A photosensitive drum formed in a drum shape is rotatably arranged below the optical system. Various devices for forming an image are arranged around the photosensitive drum. For example, a charging unit, a developing unit, a transfer unit, a cleaning unit, a static eliminator and the like are arranged, and the exposure by the optical system is performed between the charging unit and the developing unit. Therefore, on the photosensitive drum, an electrostatic latent image corresponding to the original image by exposure is formed, the image is developed with toner, and the sheet paper appropriately fed by the transfer device is transferred, and then the sheet paper is transferred. Is separated from the photosensitive drum surface and conveyed to the fixing unit,
After that, it is ejected to the outside of the copying machine. At this time, when a further image is formed on the sheet of paper on which the image is formed, for example, when an image is formed again on the opposite side of the sheet of paper on which the image is formed, the sheet of paper is temporarily discharged to the intermediate tray without being discharged. The sheet is conveyed, and the sheet is again fed from the intermediate tray to the transfer position.

In order to expose an image on the photosensitive drum as described above, it is necessary to feed the sheet original 1 placed on the original placing tray 2 by the feeding belt 4 and feed it to the exposure section 8. There is. Therefore, FIG. 1 shows the details of the structure of the air discharging means including the air outlet 5 for separating the feeding belt 4 and the original document and surely feeding one sheet.

The feeding belt 4 is provided with an opening 11 of an air intake duct 12 suspended from above at an intermediate portion thereof.
The intake duct 12 is connected to a fan device 13 and forms an air flow in the direction of the arrow. That is, air suction is performed.

Further, the air outlet 5 has a plurality of air blowing nozzles (not shown) for blowing the end portion of the front surface of the sheet original in order to separate the stack of placed sheet originals. The air outlet 5 is connected to the fan device 15 via the exhaust duct 14 and forms an air flow in the direction of the arrow. These devices constitute the air ejection means.

As shown in the perspective view of FIG. 3, the feeding belt 4 is constructed by winding a plurality of endless belts 17 around a driving roller 16a and a driven roller 16b at a predetermined interval. The endless belt 17 is formed with a number of vent holes 18 which are inserted in the thickness direction in a dispersed manner, and the sheet original 1 is sucked through the intake duct 12 from the opening 12 through the vent holes 18 and the like. Adsorb.

In the sheet feeding apparatus of the original configured as described above, the flow rate of the air from the feeding belt 4 and the outlet 5 as the feeding means is controlled, and the sheet is placed on the original placing tray 2. Make sure to feed the sheet original 1. for that reason,
According to the present invention, the floating state of the uppermost sheet document due to the blowing of air from the blowout port 5, that is, the raised state, is detected by facing the sheet document 1 placed on the document placing tray 2. Means are provided. As shown in FIG. 1, this position detecting means is composed of a distance measuring sensor 20 placed and opposed to the front end of the sheet original 1. The position detecting means illuminates the surface of the sheet original to be levitated and reflects the reflected light. Light is received by the light receiving means, and the distance from the sensor 20 to the raised document surface is measured under this light receiving condition. By measuring this distance, the positional relationship between the sheet original and the transport belt 17 of the feeding belt 4 can be determined. Therefore, it is possible to determine whether or not the rising state (position) of the sheet original document is in an appropriate state, and the sheet original document 1 attracted to the feeding belt 4 is reliably fed.

Therefore, the operation of the feeding belt 4 is controlled on the basis of the distance measured by the distance measuring sensor 20, and the air is ejected to secure the lifted state of the sheet original 1 within an appropriate (specified) range. It also controls the amount (blowing amount). In other words, by controlling the air flow rate from the air outlet 5, the position of the uppermost sheet document is within a specified range, particularly the feeding belt 4 eliminates double feeding, and only the uppermost sheet is accurately adsorbed. It can be positioned at a position where it can be fed.

The distance measuring sensor 20 is essentially the uppermost floating sheet original 1 which is separated from the sensor at the outlet 5.
Since the state can be grasped from the distance to the air flow rate, the air flow rate from the air outlet 5 is controlled according to the distance. Details of the distance measuring sensor 20 will be described later, but the distance measuring sensor 20 includes an infrared light emitting element 21,
And a light receiving element 22 for receiving the reflected light from the original,
The output to the light receiving element 22 is obtained by calculating the distance through a signal processing circuit.

Next, FIG. 4 shows a control system of the sheet feeding apparatus according to the present invention. The control system will be described with reference to FIG.

As shown in FIG. 4, the control system has a microcomputer 40 including a master CPU as a control means.
Is equipped with. The master CPU 40 receives signals from various keys and sensors according to a program previously stored in the ROM 41, and controls the copying operation and the document feeding operation by the RDH 30.

For example, the master CPU 40 controls the supply and stop of the voltage supply to the copy lamp of the optical system via the copy lamp lighting circuit 42, and adjusts the execution voltage level applied to the copy lamp 43. Further, the master CPU 40 controls the voltage supplied to the charging device, the developing device, the transfer device, the cleaning device, the static eliminator and the like through various drive circuits as necessary.

Further, the master CPU 40 receives a signal relating to the measurement from the distance measuring sensor 20 according to the present invention through the signal processing circuit 50, and drives the feeding belt 4 which is a feeding means according to the signal. The motor 44 and
The speed control circuit 46 controls the rotation speed of the drive motor 45 for controlling the discharge amount of the fan unit 15 for forming the air flow from the air outlet 5 for separating the original and feeding one sheet. Give instructions. As a result, the speed control circuit 46
Performs control according to the rotation speed command from the CPU 40 via the driver 47.

The CPU 40 also controls the drive including the suction drive motor 48 for driving the fan unit 13 which constitutes the suction means of the feeding belt 4. Therefore, a speed command signal is sent to the rotation speed control circuit 49, and the rotation speed of the motor 48 is controlled according to the speed command. In this case, in this embodiment, it is fixed so that a constant suction force acts.

The distance measuring sensor 20 has a light emitting element 21 for measuring the distance. Therefore, the master CPU 40 causes the light emitting element 21 to be driven by the driver 5 at a predetermined timing in order to measure the distance of the distance measuring sensor 20.
Drive for driving through 0, receiving a signal output according to the light receiving state of the distance measuring sensor 20 at this time through the signal processing circuit 51, and controlling the flow rate of the air discharged from the outlet 5. The rotation speed of the motor 45 is controlled.

The motors 45 and 48 are rotary encoders 52 via drivers 47 and 52 in speed control circuits 46 and 49 which receive a speed command signal from the CPU 40.
Drive control is performed at a speed according to the measurement command based on the outputs of the output signals 53 and 53. In order to control this rotation speed, the rotation speed of the motor can be easily controlled by controlling the voltage supplied to the motor or by controlling the frequency that determines the rotation speed of the motor. For this, the well-known rotation speed control technique can be directly applied.

The operation of the copying apparatus having the above structure will be described.

The copy original 1 is placed, for example, with the image side facing up, in the original placing tray 2 when copying is performed using the RDH 30, for example. Switch this mounting state to switch 3
To detect. Therefore, copy start switch (copy
Button 40), the CPU 40 receives the operation signal and starts the copying operation. At the start of this copying operation, the CPU 40 rotates the drive motor 45 at a reference speed in order to eject the air from the air outlet 5 to blow the sheet originals 1 to be placed, so that the sheet originals 1 are bundled. Separate and separate.

As the amount of air blown out from the air outlet 5, an appropriate amount for use in a standard state, for example, a standard value, is set for each device when the copying machine is initially operated (for example, when the power is turned on). The standard value (fa) is calculated and stored. This can be determined during the manufacturing process.
This standard value is stored as the number of rotations of the motor 45 corresponding to the air blowing amount in the proper state.

Therefore, the distance measurement by the distance measurement sensor 20 is started after the time when the uppermost sheet original 1 will be levitated from the time when the air is blown from the air outlet 5. Therefore, to measure the above distance,
The distance measuring sensor 20 starts measurement.

In the above distance measurement, the light from the light emitting member 21 of the distance measuring sensor 20 is received by the light receiving member 22 through the document, and the signal processing circuit 51 outputs a signal based on the light receiving condition.
The distance between the sensor 20 and the levitated uppermost sheet original 1 is calculated by inputting by the CPU 40 via
Desired. If the measured distance is within the range of the proper state, it is determined that the amount of air blown out by the air outlet 5 is in the optimum state, and the blowout flow rate is fixed, that is, the rotation speed of the motor 45 is locked. Then, the drive motor 48 that constitutes the suction means of the feeding belt 4 is driven. As a result, the levitated sheet original 1 is attracted to the feeding belt 5, and the belt 17 moves according to the drive of the drive motor 44 and is fed to a predetermined position.

Here, in FIG. 1, a proper range in which the sheet (original) 1 to be levitated is adsorbed to the feeding belt 4 is shown by a symbol "a". For example, even if the same amount of air is blown, the floating state differs depending on the material of the sheet, particularly the thickness of the sheet, plain paper, OHP sheet, or the like. Therefore, a range in which the floated sheet can be adsorbed to the belt 17 surface of the feeding belt 4 is set as an appropriate range (specified range). In this case, although the proper range due to the suction force is slightly different, it is preferable that the standard sheet is not sucked by two or more sheets and is fixed to a suction amount that can be sufficiently sucked even at the lower limit position of the proper range. Therefore, the drive motor 48 is fixed at a rotation speed for obtaining the above-mentioned suction force. Also, if the sheet is thinner than the standard sheet, if the amount of air blown is large, it tends to be levitated to the position of b, and the risk of the next sheet being levitated at the same time and being double-fed is high. Moreover, when the sheet is thick, the amount of floating tends to be small, and the sheet only rises to the position c, which cannot be adsorbed to the feeding belt 4.

Therefore, when the distance measurement by the distance measuring sensor 20 is judged as the distance at the position c apart from the feeding belt 4 in the state shown in FIG. 1, the amount of air blown out is still small and the flow rate is increased. Drive motor 4
Increase the rotation speed of 5. It is conceivable that such a state occurs, for example, when the sheet is thick and does not float so much due to air blowing.

If the measured distance is a distance that levitates beyond the proper range of FIG. 1a, control is performed to lower the rotation speed of the drive motor 44 so that the amount of air blown out is reduced. This happens because when the weight of the sheet itself is light, that is, when the sheet is thin, the sheet tends to rise even with the normal blowing amount, and not only the uppermost sheet but also the next sheet continues. Similarly, the sheet also rises and is attracted to the feeding belt 4. In order to prevent this, the amount of air blown out is controlled to be small. This is controlled based on the distance measured by the distance measurement sensor 20 described above.

To determine whether the sheet original 1 is within the proper position range with respect to the feeding belt 4, information corresponding to the distance is stored in advance in a predetermined area of the RAM 54 or ROM 41 which is a storage means. deep. This value can be obtained in advance during the manufacturing process of the device. Further, the position may be obtained from the relationship with the suction force of the feeding belt 4.

The stored proper value and the distance measuring sensor 2
By comparison with the measured distance detected at 0, if the detected distance exceeds an appropriate value, that is, in the state of c in FIG. 1, the air amount can be increased and the sheet original can be further raised. It is possible to correct up to the state of a. Further, in the case of the state of c that exceeds the specified value, the sheet original 1 is controlled so as to be in the state of a and the flow rate of the air is reduced.

As described above, the feeding of the sheet document which has been levitated in an appropriate state is started. Therefore, the sheet original 1 is adsorbed to the feeding belt 4 by the suction means from the uppermost portion and sent to the conveying path 6, and the original image is formed on the photosensitive drum by the optical system at the exposing portion 8 in the middle of the conveying path. Is imaged by. The sheet original 1 that has passed through the exposure unit is returned to the original tray 1 via the conveyance roller 7c.

When the sheet originals shown in FIG. 2 are cyclically fed, the original placing amount is constant except for the originals being fed,
The top position does not change. Therefore, after the feeding is started, one sheet can be reliably fed even in the fixed state without performing the above-mentioned air control, that is, the control of the discharge amount.
However, when the stacked sheet originals have different thicknesses, the above-described control may be executed every time the sheet is fed to control the air flow rate from the air outlet 5.

When circulating the original, the position of the uppermost original is maintained at a substantially constant position as described above, but when the sheets such as recording paper are sequentially fed, the feeding is performed. The position of the uppermost sheet lowers with each feeding. Therefore, it is necessary to increase the flow rate of air blown in order to raise the uppermost sheet to a predetermined position. In other words, the uppermost sheet position does not rise to the predetermined position simply by maintaining the blowout flow rate as it is, and by detecting this with the distance measurement sensor 20, the air flow rate can be controlled according to the decrease amount.

Here, in order to set the uppermost position to a predetermined position by reducing the sheet amount, the loading tray 2 is provided so as to be movable up and down, and, for example, in response to detection of the uppermost detection switch 19. The loading tray 2 is controlled to rise.
As a result, the uppermost sheet is always held within the range of the predetermined position.

Next, one specific example of the distance measurement by the distance measuring sensor 20 of the present invention will be described in detail. This distance measuring sensor 20 is disclosed, for example, in "Sensor Technology", Vol. 11 uses the “8-bit precision distance measuring sensor” described on pages 24 to 27. This distance measuring sensor is a PSD (Position Sensitive).
It is called a Deector sensor, which irradiates light from a light emitting element onto an object to be measured, and measures the distance by the incident position of the reflected light from the object to be measured on the sensor.

The distance measuring sensor will be briefly described below. This is a kind of PIN type photodiode, and as shown in FIG. 5, it has ap ⁻ layer on the front surface of the silicon chip, an n ⁺ layer on the back surface thereof, and an intermediate layer therebetween. It is composed of an i layer, and electrodes A, B and C as shown in the figure are provided on the respective layers on the front surface and the back surface. An equivalent circuit of the PSD sensor having the structure shown in FIG. 5 is shown in FIG.

In FIG. 6, by supplying the bias voltage VB to the terminal of the electrode C, the resistances R1 and R2 change at the position of the light incident on the surface (spot position). For example, if light is incident on the midpoint (point d) between the electrodes A and B,
Although R1: R2 = 1: 1, the ratio of R1: R2 changes in proportion to the position of the incident light if the incident light deviates to one of the A and B electrodes. Now, assuming that the incident position of light is shifted to the B electrode side by x with respect to the center point d, and the length of the light receiving surface of the sensor (distance between A and B electrodes) is D, R1 + R2 = R0, R1 = R0 / 2 (1 + 2x / D) and R2 = R0 / 2 (1-2x / D).

Therefore, the current I extracted from the electrodes A and B in FIG. 6 is utilized by utilizing the above resistance change depending on the incident position (spot position) of the light on the light receiving surface of the PSD sensor.
1 and I2, and the current ratio I1 / I at this time
2 is, for example, proportional to the distance from the electrode B (inversely proportional to the distance from the electrode A). At this time, although the absolute values of the currents I1 and I2 change depending on the amount of light incident on the PSD sensor, since the incident position of light is proportional to the current ratio I1 / I2, the amount of light itself has no effect.

Therefore, in the relation of the current ratio I1 / I2, the position of the incident light on the light receiving surface on the PSD sensor can be specified, and thus accurate distance detection can be performed. In particular, when the current ratio becomes large, the incident light comes closer to the electrode A side of the PSD sensor, and conversely, when the current ratio becomes smaller, the electrode B side is irradiated with the incident light.

For example, as shown in FIG. 7, a light emitting element (infrared LED) 21 constituting the distance measuring sensor 20 of the present invention.
Is emitted to the object to be measured (the uppermost sheet original), and the reflected light is transmitted through the light receiving lens to the distance measuring sensor 2
The light receiving portion 22 of the PSD sensor that constitutes 0 is caused to receive light.
The position x1 of the light receiving point (spot) at this time is obtained by x1 = A · f / L1 in the relationship shown in the figure. In the above formula, A is the center distance between the light projecting lens and the light receiving lens, L1 is the distance from the light projecting lens to the object to be measured, and f is the focal length of the light receiving lens. Therefore, the position x1 of the light receiving spot on the light receiving surface of the PSD sensor becomes smaller and the position moves to the position x2 as the distance to the object to be measured increases. On the contrary, when the position x1 of the light receiving spot becomes large, the distance to the object to be measured becomes short.

The point x on the light receiving surface of the PSD sensor is the current ratio I1 / I2 obtained from the electrodes A and B as described above.
Therefore, the distance D from the light emitting element 21 to the object to be measured, that is, the distance to the light receiving portion 22 of the distance measuring sensor 20 can be easily measured according to the above equation.

Therefore, in the present invention, as shown in FIG. 4, currents I1 and I2 obtained from the PSD sensor, which is the distance measuring sensor 20, are applied to the voltage V1 by the signal processing circuit 51.
And V2 and input via the analog port input section of the master CPU 40. Here, the signal processing circuit 51
Is to be converted into a voltage value equivalent to or equal to the obtained currents I1 and I2. Master CPU 4
0 calculates the value corresponding to I1 / I2 on the basis of this voltage value to obtain the spot position (x) of the distance measuring sensor 20. The distance L can be calculated.

Therefore, if necessary, the master CPU 4
0 outputs a signal for driving the driver 50 to cause the light emitting element 22 which is an infrared LED to emit light. Further, based on the output from the distance sensor 20, the rotation speed of the blowing motor 45 is controlled in order to control the drive of the feeding belt 4 or the flow rate of the air blown from the blowout port 5 according to the obtained distance. And outputs a speed command to the rotation control circuit 46. In this case, the air amount of the suction means of the feeding belt 4 can be controlled, but it is fixed in this embodiment.

Some control examples of the feeding means according to the distance measurement of the distance measuring sensor 20 according to the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 8 is a flow chart showing an example in which a sheet original is placed on the original placing tray 2 and feeding control is performed based on the original.

The sheet originals 1 are stacked and placed on the original placing tray 2 with the image side facing up. This placement state is detected by the document detection switch 3 provided at an appropriate position on the document placement tray 2. Then, when the print switch is operated, the control starts. When the copy start command signal is output, the process proceeds from step n0 to n01. When this command signal is output, pre-rotation (pre-processing) in the copying machine operates (n2) prior to the start of copying. This is a preparation for the pre-stage of starting the image forming operation after the photosensitive member is pointed several times in order to stabilize the photosensitive member and prepare the developing device and the like at the start of copying. In order to recognize the separation state (floating state) of the sheet original during this preparation operation,
In order to blow out the air from the outlet 5, the drive motor 45
To drive.

The number of revolutions (F) of the motor 45 at this time is a value corresponding to a standard value (fa) which is a discharge amount by which the sheet can be floated in an appropriate range in standard use. This is applied when the power of the copying machine is turned on,
The control value (f) controlled within the range of the proper floating position a is set by controlling the air discharge amount for each copying operation. This is a storage area different from the standard value, such as the ROM 41.
Alternatively, it is stored in the RAM 55.

Therefore, at n1, the rotational speed (F) is set according to the preset air blow amount (fa) in the proper state, and the drive motor 45 is driven at that rotational speed (n2). In this case, the rotation speed corresponding to the discharge amount (fa) is set from the CPU 40 side to the motor speed control circuit 4
Send to 6 side. As a result, the motor 45 is driven by the number of rotations thereof, and air is blown onto the stacked sheets from the outlet 5.

In this blown state of air, the measurement sensor 20 starts measuring the distance to the feeding belt 4 of the uppermost sheet document 1 which is lifted and raised (n).
3). The distance measuring sensor 20 is operated after the time until the uppermost sheet original 1 is levitated by blowing air. This time may be set to a time that allows for a response delay of air blowing and floating.

The distance measuring sensor 20 includes a light emitting element 21.
Is driven, and the distance L from the distance sensor 20 to the uppermost sheet original 1 on which the placed original is floated is measured. This is because, as described above, the master CPU 40 inputs the voltage V1 / V2 corresponding to I1 / I2 from the sensor 20, so that the distance L to the uppermost sheet original 1 which is the object to be measured.
Ask for.

When this distance L is obtained, the CPU 40
Determines, for example, whether the measured distance L is within the range of the specified distance LO or otherwise (n4). This specified distance LO
As described above, corresponds to the appropriate position a where the feeding belt 4 can surely adsorb. The specified value (reference value) LO is stored in the storage means in advance. This storage is stored in a predetermined area such as the ROM 41 or the RAM 55.

When the distance measurement of the levitated sheet original 1 is completed, and the measured distance L is discriminated from the memory distance LO which is a predetermined value stored in advance, the measured distance L falls within the range of the memory distance LO. If there is, the value (f) at that time is stored in the storage unit, assuming that the amount of air blown out from the above-described outlet 5 is appropriate. This discharge amount (f) corresponds to the rotation speed of the motor 45 and is stored for the next feeding operation. This is stored as the control value in step n1 described above (n8).

As described above, when the pre-processing operation in progress is completed in step n01, the copy operation is started (n9) and the set number of copies are executed.
At this time, the driving of the motor 48 for performing the suction operation is started, and the sheet original 1 floated on the feeding belt 4 is attracted to the feeding belt 4 by the air suction by the suction means. Then, the belt 17 is also driven by the drive motor 44, and the feeding of the attracted sheet original 1 is started.

On the other hand, if the distance L measured in step n4 is not within the distance LO within the predetermined range, it is determined in n5 whether the distance L exceeds or is below the specified range. If it is determined to be less than, it is determined that the amount of air blown out is small,
Add Δf so that it will be larger than the previous blowing amount (n6)
To do. The number of revolutions of the motor 45 is set (the number of revolutions is increased) by the air discharge amount added with Δf, and the distance measurement (n3) is performed again. Based on this measurement distance L, it is judged whether or not it is within the proper range LO (n4). This is repeatedly executed until the floating state of the sheet falls within the range LO corresponding to the proper range a. Conversely, the measurement distance L is within the predetermined range LO
If it exceeds the inside, the amount of air blown out is large and the next sheet original 1 is levitated as it is, and there is a risk of double feeding,
A value obtained by subtracting Δf from the previous ejection amount is reset as a control value so that the ejection amount is reduced. The above-described steps n3 and n4 are executed with the subtracted control value, and the air blowing amount is controlled so that the floating state is within the specified range.

By performing the above control, if the air blowing amount f capable of positioning the sheet original at the proper floating position a is determined, this value (f) is stored in the memory, and the next sheet original is fed. Used for sending operation.

Here, every time one sheet original 1 is fed, the above-described operations of steps n3 to n8 may be repeated, but the weight of the sheet original 1 set on the loading tray 2, for example, If the thickness and the like are the same, it can be considered that the floating position of each sheet original is substantially constant even if the flow rate of air blown out is fixed. However, if sheets having different weights are mixed in the bundle to be set, it is sufficient to confirm the levitation state by blowing air again and control the amount of air blown to the appropriate levitation position a.

As described above, when the sheet original is placed on the placing tray 2 and copying is performed, the uppermost sheet original 1 can be adsorbed by the feeding belt 5 regardless of the material and amount of the sheet original 1. Can be levitated to the position a, and can be surely adsorbed by the feeding belt 5 to perform feeding, and one sheet can be reliably fed without causing double feeding or feeding failure. Further, the preprocessing is used as the timing for recognizing the floating state, and the start of the copy start is not delayed.

The timing for confirming the floating state of the sheet original 1 is to detect that the original is placed,
Although the pre-processing stage after the operation of the copy switch is used, the floating state can be confirmed in advance when the power of the copying apparatus is turned on and before the operation of the copy switch. That is, when the sheet paper is fed to the image forming position instead of feeding the sheet original, the sheet paper is preliminarily placed on the placing tray or the like in the sheet feeding unit.

The control therefor will be described with reference to the flowchart of FIG. In this case, as the copying apparatus, not only the apparatus for automatically feeding the sheet original document but also the apparatus for feeding the sheet paper as it is to the image forming position is used as the feeding apparatus shown in FIG. The sheet-shaped paper is placed on the loading tray in advance, and the detection switch 3 detects whether or not the sheet is present on the loading tray when the power is turned on. In this state, the sheet of paper is levitated to an appropriate position, and the amount of air blown to secure the specified position a can be adjusted (controlled) in advance.

Therefore, when the power of the copying machine is turned on at n02, an adjustment mode n10 surrounded by a broken line for controlling the levitating position of the sheet by the loading tray 2 on which the sheet is placed to an appropriate state is executed. To be done. The adjustment mode n10 is the control operation itself of the air discharge amount described in FIG. That is, steps n1 to n8 correspond to s1 to s8, and the same operation is executed.

As described above, in response to the power-on, the floating state of the sheet paper of the feeding device for feeding the sheet paper to the image forming position is confirmed in advance, and the air blowing amount in the proper state is controlled in advance. it can. The controlled blowing amount (f) is stored in the memory and responds to the operation of the copy switch for the copy stat in FIG. 8 to execute the control after n1. In this case, since the levitation state has been confirmed in advance, it is possible to shift to n9 as it is without performing the control from n1 to n8. Alternatively, pretreatment (n01)
If the time is long, the flow in FIG. 8 may be executed to confirm again that the state is proper.

Here, the loading tray 2 may be provided so that it can be pulled out from the apparatus main body when setting sheet paper. That is, this is to facilitate the operation of setting the sheet paper on the loading tray 2. In this case, a drawer detection switch (not shown) for confirming the drawer state is provided. Therefore, this detection switch detects (OFF) the pulled-out state of the loading tray 2, and when the sheet is reattached to the loading tray 2 or the set sheet is changed and then mounted on the apparatus main body, this is detected. The switch detects (ON). By detecting this state, FIG.
The adjustment mode n10 for recognizing the state of being able to levitate in advance to the appropriate state is executed.

(Second Embodiment) In this embodiment, the self-diagnosis of the failure of the distance measuring sensor 20 itself, and the floating control of the placed sheet original or paper in the state where the distance measurement is normally executed. Then, the drive in the standard state for driving the feeding means is executed by the failure diagnosis.

FIG. 10 shows a flowchart of control for that purpose. In this flow, the same parts as those in FIG. 9 are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, what should be particularly noted is the measurement of the floating state before the copy switch is operated in the state where the feeding operation is not performed, that is, the sheet is placed on the placing tray 2. The point is that the mode n10 is executed and the self-diagnosis of the distance measuring sensor 20 is executed in this state.

Therefore, the adjustment mode n10 is executed in the state where the detection switch 3 detects that the sheet paper is placed on the placement tray 2. Therefore, in step s4, if it is within the specified range, the air blowing amount is stored (s8), and in other cases, in s5, it is determined whether the specified range is exceeded or not. Is done.

Therefore, in the case of less than the specified range (state c below the specified range), the rotation speed of the drive motor 45 is increased so as to increase the air blowing amount f, and the air blowing amount is increased by Δf. Do more. The measurement is performed again with this increased blowing amount, and it is determined whether or not it is within the specified range. Repeat this, if within the specified range,
As described above, the value corresponding to the air blowing amount f is stored (s8), and when the feeding operation is executed, that is, FIG.
Is executed in step n1.

However, no matter how much the air blowing amount is gradually increased by Δf and controlled, the sheet paper does not float within the specified range, that is, the rotation speed (Fmax) of the mode 45 corresponding to the maximum air blowing amount. Even if
If the distance measuring sensor 20 detects a state in which the sheet paper does not float up to the specified range, it is determined that the distance measuring sensor 20 has a failure (abnormality). That is, after the increase of the discharge amount in s6, it is determined in s9 whether or not the rotation speed (F) of the motor 45 corresponding to the increase exceeds the maximum rotation speed (Fmax).

On the other hand, in s5, when the distance out of the specified range and the levitation state exceeds the proper state (state of b) is measured, the air blowing amount is reduced by Δf in s7. The rotation speed (F) of the motor 45 is lowered. The levitation state of the sheet paper due to this is confirmed, and if it is not within the specified range, the rotation speed of the motor 45 is lowered so that the blowing amount is controlled again by Δf. Even if the sheet is not lowered to within the proper specified range even if it is driven by the rotation speed (Fmin) of the motor 45 corresponding to the minimum blowing amount, the distance measuring sensor 2
If the measurement by 0 is impossible, it is treated as a failure.
That is, after the discharge amount is reduced by s7, the rotation speed of the motor 45 corresponding to the decreased discharge amount is the minimum rotation speed (Fmi
It is determined in s9 whether it is less than n).

As described above, if the sheet 45 is not levitated to an appropriate position even if the motor 45 is driven at the maximum or minimum rotation speed corresponding to the air blowing amount f at s9, the distance measuring sensor 20 is The fault state of the distance measuring sensor 20 is displayed, assuming that the measured distance is abnormal (s11).
Let At this time, a standard value (fa) that is initially set is set as the air blowing amount, and this is stored.
As described above, as the initial standard value, the apparatus is actually operated and set to a value capable of levitating the sheet paper (or the original document) within the specified range in the standard use state of the apparatus as described above.

Here, if the sheet paper does not float to the position of the specified range a, no matter how much the air blowing amount is controlled, not only is the failure due to the distance measuring sensor 20,
It is possible that air cannot be discharged due to a failure of the outlet 5, that is, a defective rotation or failure of the drive motor 45.
However, when the air cannot be discharged, the determination can be made based on the signal from the encoder that detects the rotation number of the flow rate sensor or the drive motor. Therefore, the self-diagnosis of the distance measurement sensor 20 described above is performed when there is no problem in the air ejection means itself.

Even if the distance measuring sensor 20 fails, if there is no abnormality or failure in the copying apparatus main body and the sheet feeding apparatus itself, the feeding belt 4 can be driven to feed the sheet or the original. Therefore, the drive of the feeding belt 4 is allowed, and as for the control of the air blowing amount, the standard value (fa) is set as described above, the driving control of the air ejection amount is performed, and the feeding control can be executed. .

Therefore, the CPU executes the flow shown in FIG. Therefore, when a copy start command is output by operating the copy switch (n0), step n11 is executed.
At, it is determined whether or not there is a failure due to the distance measuring sensor 20. This determination is as described above, and a failure due to self-diagnosis is detected during the preliminary confirmation of the floating state of the seat. A flag indicating this failure state is set in a predetermined area of the RAM 55 and stored. Keep it. This allows
The distance measuring sensor 20 performs control for executing the feeding operation in the failure state.

In this control, the standard value (fa) of the air from the outlet 5 is stored in step S10 of FIG. 10, and the drive motor 45 is rotated based on this. As a result, the feeding operation is started, and the jammed state when the feeding belt 4 is driven to perform the feeding operation is confirmed every feeding (s12). This jam detection is executed by a conventionally known means. If the jammed state is not confirmed, the operation is continued and the copy control of step n9 in FIG. 8 is executed.

If the distance measuring sensor 20 is not defective, the rotational drive control based on the discharge amount (f) stored in step s8 of FIG. 10 is performed, and the copy control of step n9 of FIG. 8 is started. To be done.

Therefore, at the time of failure diagnosis of the distance measuring sensor 20, if a feeding failure due to the operation of the feeding device, that is, a jam is detected, the counter (C) is incremented every time this jam occurs (n13). Then, it is determined whether or not the count value of the counter C is a predetermined value C0 or more. If the count value is less than the predetermined value C0, the feeding operation is repeated again after the jam processing. Then, if a jam by the feeding device is confirmed after the jam processing, the jam is counted, and when the jam is equal to or more than a predetermined C0 value, a message indicating that the feeding device itself is abnormal is displayed as a message. It is displayed on the section (n15), and at the same time, the feeding operation is stopped (n16), that is, prohibited. This is to stop the copying operation of the copying apparatus.

In the above description, the distance measuring sensor 20
By diagnosing the failure of (1), drive control can be executed with an air blowing amount (fa) that does not hinder the sheet feeding by the copying apparatus without stopping the copying operation itself. Further, by counting the jam detection state in which the feeding operation is performed, the failure state of the feeding device itself can be diagnosed, and the feeding control can be performed more safely.

In each of the above embodiments, the floating state of the placed sheet paper (original) is recognized based on the distance measurement by the distance measuring sensor 20, and the PSD sensor is used as the sensor. However, the present invention can be implemented as long as it can detect as a distance.

Further, the distance measuring sensor 20 is arranged at a position facing the leading end portion of the document placed in the feeding direction in FIG. This is because the front end of the sheet is attracted to the feeding belt 4 to be fed, and air is blown from the front end of the feeding to levitate the front end of the sheet. Moreover, it may be arranged at a position facing the center of the sheet in the width direction of the sheet. This is because the air suction portion of the feeding belt 4 is formed symmetrically with respect to the center in the sheet width direction.

Here, in the case of circulating feeding from the document tray to the exposure section and then to the document tray again, the document on the document tray always has a constant document placement amount except for the document being fed. Therefore, in the case of RDH, it is not necessary to raise the loading tray 2. However, when feeding sheet paper, etc., the loading amount gradually decreases.Therefore, a mechanism for raising according to the decrease is provided so that the uppermost sheet is always at a constant height. It is set.
Therefore, the suction state of the sheet by the feeding belt 4 can be made constant.

Further, in order to recognize the floating state of the sheet, the air suction operation by the air suction means is stopped while the air is being blown from the air outlet 5 which constitutes the air discharge means. This is because the sheet floated by air suction is sucked by the feeding belt and further rises, and accurate recognition cannot be performed. Thereby, the floating state of the seat can be accurately recognized.

In particular, as the distance measurement by the distance measuring sensor 20, the value is used by one measurement, but the measurement may be performed a plurality of times and the average value thereof may be used as the measurement distance L. In this case, as the average value, the average value obtained by dividing the total of each measurement distance by the number of measurements, the average value obtained by the measured maximum and minimum values, the remaining excluding the measured maximum and minimum values You may utilize the average value calculated | required by the measured value. In other words, the distance may be measured more accurately.

[0113]

According to the sheet feeding apparatus of the present invention, the sheet feeding operation can be performed in a floating state of the sheet, that is, in a state where the sheet is levitated at a position where the sheet can be adsorbed by the feeding means. I can hope. In this case, the material is not affected by the material of the sheet, and the sheet can be fed at an appropriate floating position, and one sheet can be reliably fed in a stable manner.

Further, as means for detecting the amount of paper placed,
Since the sensor that can measure the distance can accurately recognize the floating state, it is possible to perform fine feeding control, especially air discharge control,
It is possible to do more and to enable more stable feeding.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a document circulating / conveying device in which a sheet feeding device according to the present invention is applied to a document circulating / conveying device.

FIG. 2 is a schematic configuration diagram in which a recycle type document feeder (RDH) is mounted on a copying apparatus according to an embodiment of the present invention.

FIG. 3 is a perspective view showing an example of a sheet feeding unit that constitutes the sheet feeding apparatus.

FIG. 4 is a block diagram showing a control system of a copying control apparatus including control of a sheet feeding apparatus according to the present invention.

FIG. 5 is a PSD showing an example of the distance measuring sensor of the present invention.
Sectional drawing of a sensor.

6 is an equivalent circuit diagram of the PSD sensor of FIG.

FIG. 7 is a schematic diagram illustrating the principle of distance measurement.

FIG. 8 is a control flowchart showing an example of sheet feeding control according to the present invention.

FIG. 9 is a control flowchart for adjusting an air discharge amount for setting a proper sheet floating position for sheet feeding control according to the present invention.

FIG. 10 is a control flowchart showing an example of an accident diagnosis of the distance measuring sensor according to the sheet feeding control according to the present invention.

FIG. 11 is a flowchart for controlling the feeding operation at the time of failure diagnosis related to the sheet feeding control according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 sheet original (or sheet paper) 2 sheet loading tray 3 sheet presence / absence detection switch 4 feeding belt 5 air outlet of ejection means 13 fan device of suction means 15 fan device of ejection means 20 distance measuring sensor (PSD sensor) 21 Light emitting element 22 Light receiving element 30 Circulation type document feeder (RDH) 40 Master CPU 44 Feed belt drive motor 45 Air ejection drive motor 46 Speed control circuit (motor 46) 48 Air suction drive motor 51 Signal processing device (distance (For measurement)

Claims (8)

[Claims] 1. A placing tray on which a sheet cut into a predetermined length is placed, a feeding unit including an air suction unit for feeding the sheet on the placing tray to a predetermined position, and an upper part. In a sheet feeding device comprising an air ejection means for blowing air to the tip of the sheet on the placing tray to separate a stack of the placed sheets, the above-mentioned air ejecting means is used for the sheet placed on the placing tray. Position detection means for detecting the position of the sheet floated by the blown air, and air discharge amount control means for controlling the air discharge amount of the air blown based on the position detection by the position detection means. A sheet feeding device characterized by the above. 2. The air discharge amount control means determines whether the position detection value of the floating state detected by the position detection means is within a predetermined range of a predetermined floating position. 2. The sheet feeding device according to claim 1, wherein the amount of air discharged is increased or decreased to control the amount of air discharged so that the floating position of the sheet is positioned within the specified range. 3. The air discharge amount control means previously recognizes a sheet floating state within a specified range by blowing air before starting sheet feeding, stores the air discharge amount related to the blowing, and feeds the sheet. 3. The sheet feeding apparatus according to claim 2, wherein the air discharge amount control is performed based on the stored contents when the sheet is started. 4. The sheet feeding apparatus according to claim 3, wherein the air amount control means executes recognition of a sheet floating state in response to a signal for detecting a state in which the sheet is set on the placing tray. 5. The position detecting means comprises a distance measuring sensor arranged at the position of the feeding means for measuring the distance to the uppermost sheet which is levitated. Sheet feeding device. 6. A placing tray on which a sheet cut to a predetermined length is placed, a feeding means including an air suction means for feeding the sheet on the placing tray to a predetermined position, and an upper part. In a sheet feeding device comprising an air ejection means for blowing air to the tip of the sheet on the placing tray to separate a stack of the placed sheets, the above-mentioned air ejecting means is used for the sheet placed on the placing tray. Distance measuring means for measuring a distance to a sheet to be levitated by the air blown, discriminating means for discriminating between a distance measured by the distance measuring means and an appropriate levitating position of the sheet due to air blowing, and the discriminating means. When it is determined that the air amount is within the proper range, a storage unit that stores the air discharge amount at that time, and by determining that the determination unit is outside the proper range, the air amount is increased or decreased by a fixed amount and then increased or decreased again. And an air amount control means for repeatedly spraying a sheet with the air ejection amount, wherein the air amount control means has an air ejection amount exceeding the maximum value or less than the minimum value by the determining means. In this state, the distance measuring means is treated as a failure state, and the air discharge amount by the discharging means is set to the standard state, and the discharge amount stored in the storage means or the standard state set discharge amount. An air feeding device, characterized in that the feeding control is executed based on the above. 7. The sheet feeding device according to claim 6, wherein a jam detecting means at the time of air feeding, a jam counter for counting the number of times of the jam detecting by the jam detecting means by a failure diagnosis of the distance measuring means, and the counter. A sheet feeding device, characterized in that the sheet feeding by the sheet feeding device is stopped in a state where is a predetermined value. 8. The sheet feeding apparatus according to claim 1, wherein the floating state of the sheet is confirmed by setting the air suction of the air suction means to a non-operating state.