Sheet feeding device, image forming apparatus, image forming system, and sheet processing apparatus

A sheet feeding device includes a sheet stacker configured to stack a sheet bundle; a blower configured to float a sheet on an upper portion of the sheet bundle; a conveyor configured to convey the sheet floated by the blower; a lift configured to lift up and down the sheet stacker; a first reflective optical sensor configured to detect the sheet floated by the blower; a second reflective optical sensor configured to detect the sheet bundle and a side face of the sheet stacker, the side face including a detection region to be detected by the second reflective optical sensor and a non-detection region not to be detected by the second reflective optical sensor; and circuitry configured to control the lift based on a detection result of the first reflective optical sensor and a detection result of the second reflective optical sensor. The circuitry is configured to cause the lift to lift up the sheet stacker in response to a change from a detection state to a non-detection state of the second reflective optical sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2017-254510, filed on Dec. 28, 2017, and No. 2018-145287, filed on Aug. 1, 2018, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.

BACKGROUND

Technical Field

Aspects of the present disclosure relate to a sheet feeding device, an image forming apparatus, an image forming system, and a sheet processing apparatus that performs processing on a sheet.

Related Art

A sheet feeding device is known that is incorporated in or coupled to a processing apparatus, such as an electrophotographic or inkjet image forming apparatus, and floats the uppermost sheet of a bundle of sheets, such as a sheet or a prepreg, to feed (convey) the sheet with a conveyor, such as an attracting conveyance unit.

SUMMARY

In an aspect of the present disclosure, there is provided a sheet feeding device that includes a sheet stacker, a blower, a conveyor, a lift, a second reflective optical sensor, and circuitry. The sheet stacker is configured to stack a sheet bundle. The blower is configured to float a sheet on an upper portion of the sheet bundle. The conveyor is configured to convey the sheet floated by the blower. The lift is configured to lift up and down the sheet stacker; a first reflective optical sensor configured to detect the sheet floated by the blower. The second reflective optical sensor is configured to detect the sheet bundle and a side face of the sheet stacker. The side face includes a detection region to be detected by the second reflective optical sensor and a non-detection region not to be detected by the second reflective optical sensor. The circuitry is configured to control the lift based on a detection result of the first reflective optical sensor and a detection result of the second reflective optical sensor. The circuitry is configured to cause the lift to lift up the sheet stacker in response to a change from a detection state to a non-detection state of the second reflective optical sensor.

In another aspect of the present disclosure, there is provided an image forming apparatus that includes the sheet feeding device configured to separate and feed a sheet from the sheet bundle and an image forming device configured to form an image on the sheet.

In still another aspect of the present disclosure, there is provided an image forming system that includes the sheet feeding device configured to separate and feed a sheet from the sheet bundle and an image forming apparatus configured to form an image on the sheet that has been fed from the sheet feeding device.

In still yet another aspect of the present disclosure, there is provided a sheet processing apparatus that includes the sheet feeding device configured to separate and feed a sheet from a sheet bundle and a sheet processing device configured to perform processing on the sheet that has been separated and fed from the sheet feeding device.

DETAILED DESCRIPTION

Hereinafter, an embodiment of a sheet feeding device to the present invention is applied will be described.

FIG. 1is a schematic configuration view of an image forming system1according to the present embodiment.

As illustrated inFIG. 1, the image forming system1includes an electrophotographic image forming apparatus100serving as an image former that forms an image on a sheet, and a sheet feeding device200that feeds a sheet to the image forming apparatus. The sheet feeding device is provided on a side face of an apparatus body of the image forming apparatus100.

First, the general arrangement and operation of the image forming apparatus such as a printer to which the sheet feeding device of the present embodiment can be applied, and a copier including an equivalent image forming function will be described.

FIG. 2is a schematic configuration view of the image forming apparatus100according to the present embodiment.

The image forming apparatus100is a full-color printer that uses toners of four colors of yellow (Y), cyan (C), magenta (M), and black (K) and includes an equivalent image forming function. As illustrate inFIG. 2, four image forming units101Y,101M,101C, and101K are disposed side by side in an upper portion in the apparatus body. The four image forming units101Y,101M,101C, and101K serve as image forming devices that form an image with the respective color toners.

The arrangement and operation of each of the image forming units101Y,101M,101C, and101K are substantially the same. Therefore, the image forming unit may be described below by omitting the signs (Y, C, and K) indicating the colors. Each image forming unit101has, for example, a charger103(103Y,103M,103C, or103K), a developing device104(104Y,104M,104C, or104K), and a cleaning device105(105Y,105M,105C, or105K) disposed in the periphery of a photoconductor drum102(102Y,102M,102C, or102K) serving as an image bearer. Furthermore, an exposure unit107(107Y,107M,107C, or107K) is disposed above the photoconductor drum102.

An intermediate transfer belt108wound around a plurality of support rollers is disposed below the four image forming units101Y,101M,1010, and101K. One of the support rollers is rotationally driven by a driver, so that the intermediate transfer belt108is driven to travel in the direction of arrow A. A transfer roller106serving as a primary transferor is disposed facing the photoconductor drum102of the image forming unit101via the intermediate transfer belt108.

In the image forming unit101, the photoconductor drum102is rotationally driven counterclockwise in the view, and the surface of the photoconductor drum102is uniformly charged to a predetermined polarity by the charger103. Subsequently, the charged surface is irradiated with a light-modulated laser beam emitted from the exposure unit107, so that an electrostatic latent image is formed on the photoconductor drum102. The formed electrostatic latent image is developed with the toner given by the developing device104to be visualized as a toner image. The toner images of yellow cyan, magenta, and black formed by each of the image forming units101are transferred so as to be sequentially superimposed on the intermediate transfer belt108.

On the other hand, a sheet feeder114is provided at a lower portion of the apparatus body, the sheet feeder114including a feeding tray114aand a feeding tray114b. A sheet such as a sheet or a prepreg is fed from either the sheet feeder114or the sheet feeding device200coupled to the image forming apparatus100, to be described in detail later. The fed sheet is conveyed in the direction of arrow B to a registration roller111.

The sheet abutted against the registration roller111and temporarily stopped is delivered from the registration roller111in timing with the toner image on the intermediate transfer belt108. Then the sheet is sent into a secondary transfer portion where a secondary transfer roller109and the intermediate transfer belt108come into contact with each other. A voltage having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roller109. Thus, the superimposed toner image (full color image) on the intermediate transfer belt108is transferred onto the sheet. The sheet after the transfer of the toner image is conveyed to a fixing device113by a conveying belt112. Thus, the toner is fixed on the sheet by heat and pressure at the fixing device113. The sheet after the toner image has been fixed is ejected outside the apparatus as indicated by arrow C to be stacked on an ejection tray.

Here, in the case of back-side sheet ejection (face-down sheet ejection) by single-sided printing, the sheet is ejected outside the apparatus as indicated by the arrow C via a sheet reversing portion115. Thus, the front and back sides of the sheet are reversed. In the case of duplex printing, the sheet after fixing is conveyed again from a refeeding path117to the registration roller111via a reversing portion116, and the toner image is transferred from the intermediate transfer belt108to the back side of the sheet. The sheet after the transfer of the toner image is fixed at the fixing device113. As in the case of single-sided printing, the sheet is ejected outside the apparatus from the fixing device113as indicated by the arrow C, or via the sheet reversing portion115as indicated by the arrow C, to be stacked on the ejection tray. Switching claws118and119that switch the sheet conveying direction are appropriately disposed on the sheet conveyance path.

In the case of monochrome printing, for the image forming apparatus100of the present embodiment, the toner image is formed using only the image forming unit101K of black (K), and then the toner image is transferred onto the sheet via the intermediate transfer belt108. The handling of the sheet after the fixing of the toner image is the same as in the case of full-color printing.

The upper face of the apparatus body has a toner bottle set housing120in which toner bottles121for the colors containing toner are set so as to be supplied to the developing devices104of the image forming units101. The upper face of the apparatus body has also an operation unit124, the operation unit124including a display122and an operation panel123.

The side face on the right side in the view of the image forming apparatus100illustrated inFIG. 2has a sheet carrier D leading from a sheet feeding device200(seeFIG. 3) to be described later. The sheet carrier D has an opening125that receives a sheet and a conveyor126that conveys the sheet.

FIG. 3is a schematic explanatory view of the sheet feeding device200according to the present embodiment coupled to the side face of the apparatus body of the image forming apparatus100.

The sheet feeding device200includes two feeding trays10tandem up and down. The feeding trays10each include a sheet stacker11on which a bundle of sheets S is stacked. In the present embodiment, the feeding trays10each are capable of storing a maximum of about 2500 sheets. An attracting conveyance unit20is disposed above each feeding tray10, the attracting conveyance unit20serving as a conveyor that attracts a sheet S stacked on the feeding tray10to convey the sheet S. The attracting conveyance unit20includes an attracting belt21that is a conveyance member and a suction device23. That is, the sheet feeding device200is a so-called air-pickup sheet feeding device.

Furthermore, the feeding tray10each adopt sheet-face detection control. The control causes a sheet detection sensor31including two reflective optical sensors to detect a plurality of sheet side faces of an upper portion of the sheet bundle stacked on the sheet stacker11. Then the control lifts up and down the sheet stacker11in accordance with the output value.

The sheet detection sensor31includes a first lateral upper-surface sensor31aand a second lateral upper-surface sensor31bto be described later.

A sheet stacked on the lower feeding tray10passes through a lower conveyance path82to be conveyed to the apparatus body of the image forming apparatus100by a pair of exit rollers80. On the other hand, a sheet stacked on the upper feeding tray10passes through an upper conveyance path81to be conveyed to the apparatus body of the image forming apparatus100by the pair of exit rollers80.

FIG. 4is a schematic perspective view of the vicinity of a feeding tray) of the sheet feeding device200.

The attracting belt21of the attracting conveyance unit20has been tensed over two tension rollers22aand22b. A suction hole is provided in the entire region in the circumferential direction, the suction hole penetrating from the front side to the back face side of the attracting belt21. The suction device23is provided inside the attracting belt21. The suction device23is coupled to a suction fan, the suction fan sucking air through an air duct that is an air flow path. The suction device23generates a negative pressure downward to work so as to cause the sheet S to be attracted on the lower face of the attracting belt21.

In addition, the feeding tray10includes a blowing device17, the blowing device17serving as a blower that blows air onto sheets S on an upper portion of a sheet bundle Sb. The blowing device17includes a front blower12and a pair of side blowers13.

The front blower12blows air to the front end (end on the downstream side in the feeding direction) of the upper portion of the sheet bundle Sb. The front blower12includes a floating nozzle, a separating nozzle, and a blowing fan15. The floating nozzle guides air in a direction in which sheets on the upper portion of the sheet bundle Sb are to be floated. The separating nozzle guides air in a direction in which the uppermost floated sheet and the other sheets are to be separated. The blowing fan15sends air into the floating nozzle and the separation nozzle. Of the nozzles, air blown from the floating nozzle in the direction indicated by arrow a1in the view is called floating air, and air blown from the separating nozzle in the direction indicated by arrow a2is called separating air. The floating air and the separating air each are discharged from a location opposed to the front end (end on the downstream side in the feeding direction) of the upper portion of the sheet bundle Sb. Then the floating air and the separating air are blown to the front end (end on the downstream side in the feeding direction) of the upper portion of the sheet bundle Sb.

A blowing fan14is provided on a side fence of each side blower13. The blowing fan14blows air to a side face of the upper portion of the sheet bundle Sb in the direction indicated by arrow b in the view. The side blower13includes a side floating nozzle that guides air in a direction in which the sheet bundle Sb is to be separated and floated. The air blown in the direction indicated by the arrow b from the nozzle is called side air. The side air is discharged from a discharge port provided at a location of each side blower13opposed to the upper portion of the sheet bundle Sb. Then the side air is blown to a side face of the upper portion of the sheet bundle Sb. The air blown from the front blower12and the discharge ports of the pair of side blowers causes the sheets of the upper portion of the sheet bundle Sb to float.

The feeding tray10has an end fence25that aligns the back end of the sheet bundle Sb stacked on the sheet stacker11.

FIG. 5is a schematic cross-sectional view of the vicinity of the feeding tray10of the sheet feeding device200.

A pair of conveying rollers8that is a downstream-side conveyance member is disposed on the downstream side in the conveying direction with respect to the attracting belt21. The conveying rollers8convey, further toward the downstream side, the sheet S that has been separated from the sheet bundle Sb, conveyed by the attracting belt21, and reached between two rollers.

Furthermore, the sheet detection sensor31described above is provided along the sheet stacking direction as illustrated inFIG. 5.

In the present embodiment, as described above, the sheet detection sensor31includes the first lateral upper-surface sensor31aand the second lateral upper-surface sensor31b. The sheet detection sensor31is a reflective optical sensor, and includes a light emitting element and a light receiving element.

Furthermore, the front blower12has the blowing fan15, the floating nozzle, the separating nozzle, and a blowing duct16. The blowing duct16guides air into the floating nozzle and the separating nozzle.

Next, the sheet detection sensor31and lifting control of the sheet stacker11will be described with reference to the drawings.

FIG. 6is an explanatory view of the first lateral upper-surface sensor31aand the second lateral upper-surface sensor31b.

The first lateral upper-surface sensor31aand the second lateral upper-surface sensor31billustrated inFIG. 6are selectively used depending on whether the sheet is being fed. The first lateral upper-surface sensor31ais used during floating in which the floating air is blown onto the sheets, that is, during feeding. On the other hand, the second lateral upper-surface sensor31bdetects the side face of the sheet bundle Sb during non-floating.

In addition, the first lateral upper-surface sensor31ais set so as to detect a position 12 mm lower from the suction surface of the attracting belt21. The second lateral upper-surface sensor31bis set so as to detect a position 18 mm lower from the suction surface of the attracting belt21.

FIG. 7is a block diagram illustrating an example of the arrangement of a control system of the sheet feeding device200.

As illustrated inFIG. 7, the lateral upper-surface sensors31aand31bof the feeding tray10are coupled to a sheet controller18serving as circuitry of the sheet feeding device200. The blowing fan15, the blowing fan14, and a suction fan24of the suction device23are also coupled to the sheet controller18. The blowing fan15blows air into the floating nozzle and the separating nozzle of the front blower12. The blowing fan14blows air into the side floating nozzle of the side blower13. A lift motor19included in a lift190that lifts up and down the sheet stacker11is also coupled to the sheet controller18.

The sheet controller18is included in the sheet feeding device200as described above. As a result, even in the case of coupling to the image forming apparatus100where the lift motor19that lifts up and down the sheet stacker11cannot be directly controlled, the sheet feeding device200capable of feeding a sheet at an appropriate timing can be provided.

FIG. 8is a schematic explanatory view of the lift of the sheet feeding device.

As illustrated inFIG. 8, the sheet stacker11is coupled to a wire292. A pulley291rotates to wind up the wire292, so that the sheet stacker11is horizontally lifted up. The pulley291is coupled to a drive shaft of the lift motor19via a gear train. The drive shaft of the lift motor19rotates to wind up the wire292.

FIG. 9is an explanatory view of an example of the lifting control of the sheet stacker11in accordance with the detection result of the sheet detection sensor31.

As in illustrated inFIG. 9, based on the output value of the first lateral upper-surface sensor31a, the sheet controller18detects sheet density (whether the sheets exist densely or sparsely) in a certain region in front of the sensor. When the number of sheets decreases due to the feeding operation and the density of the floated sheets in a monitor region D1is more sparse (that is, in non-detection state) than a preset threshold, the sheet controller18causes the lift190to lift up the sheet stacker11.

Next, the reason why insufficient floating of a sheet occurs at the time of almost running out of the sheet bundle on the sheet stacker11, which causes non-feeding of the sheet, will be described with reference to the drawings.

FIG. 10is an explanatory view of an attractable area E1for the attracting conveyance unit20.

The position of the sheet stacker11is controlled in accordance with the detection result of the first lateral upper-surface sensor31a, to position the uppermost sheet of the floating sheet bundle in the attractable area E1illustrated inFIG. 10. Here, the attractable area E1is an area where the attracting belt21of the attracting conveyance unit20can attract a sheet.

Meanwhile, when the uppermost sheet is separated from the attractable area E1, the attracting conveyance unit20cannot attract the uppermost sheet. Thus, non-feeding of the sheet, so-called non sheet feeding occurs. The area where the non sheet feeding occurs is hereinafter referred to as a non sheet-feeding occurrence area E2.

FIGS. 11A and 11Bare explanatory views of the positional relationship between the sheet stacker11and a floating nozzle201at the time of almost running out.FIG. 11Ais an explanatory perspective view in the vicinity of the floating nozzle201, andFIG. 11Bis an explanatory cross-sectional view in the vicinity of the floating nozzle201.

When the number of the sheets of the sheet bundle stacked on the sheet stacker11decreases and the sheet bundle on the sheet stacker11is in almost running out, as illustrated inFIGS. 11A and 11B, a bottom plate207of the sheet stacker11rises to a position at which the air from the front blower12being the blower of air is blocked. Consequently, since the air is difficult to blow to the sheets, the sheets are difficult to float. Thus, there is a disadvantage that even when the floated sheets exist in the monitor region D1of the first lateral upper-surface sensor31a, the uppermost floated sheet is difficult to float up to the attractable area E1.

FIG. 12is an explanatory view of a structure of the sheet stacker11that reduces occurrence of non-feeding of a sheet.

During sheet feeding, as the sheets stacked on the sheet stacker11are fed, a surface to be detected (hereinafter, appropriately referred to as detection surface204) gradually rises while facing the lateral upper-surface sensors31aand31b. The detection surface204is provided on a side face of the sheet stacker11and is to be detected by the lateral upper-surface sensors31aand31b. The detection surface204includes a sheet metal that can be detected by the lateral upper-surface sensors31aand31b.

The detection surface204is provided with a non-detection region205that does not reflect light from a light emitter of each of the lateral upper-surface sensors31aand31b.

The distance (length) in the height direction (direction along the lifting direction of the sheet stacker11) of the non-detection region205is a distance A from a position where the sheet stacker11comes to the height of a position where the sheet stacker11blocks the air to a position where the floated sheets can float to the attractable area E1(experimental value obtained from evaluation). As illustrated inFIG. 12, a suede material (member)203is attached (provided) on the detection surface204, so that the non-detection region205of the lateral upper-surface sensors31aand31bis formed. The suede material203serves as a reflection reducing material to reduce the reflection of the light from the light emitter of each of the respective lateral upper-surface sensors31aand31b. The non-detection region205is formed with the attachment of the suede material203in this manner. Thus, the accuracy of position detection in the height direction of the sheet stacker (accuracy of lifting operation) can be improved with the simple configuration.

Here, in the detection surface204, a metal sheet portion on which the suede material203is not attached and the light is reflected is a detection region206. As a reflection reducing material to be provided, in addition to the attachment of the suede material203, a sheet or a film that prevents light reflection may be attached, or such a material may coat a desired range of the detection surface204.

Next, using the sheet stacker11provided with the non-detection region205as described above, the flow of control when sheet feeding operation is performed, the position of the bottom plate207of the sheet stacker11in almost running out, and forceful lift-up operation of the sheet stacker11will be described.

FIG. 13is a control flowchart of the lifting operation of the sheet stacker11, andFIG. 14is an explanatory view of the position of the bottom plate207of the sheet stacker11in almost running out.FIGS. 15A and 15Bare explanatory views of forceful lift-up of the sheet stacker11.FIG. 15Ais an explanatory view of the start position of the forceful lift-up, andFIG. 15Bis an explanatory view of the end position of the forceful lift-up.

Normally, during sheet feeding, only a state of the first lateral upper-surface sensor31ais monitored, and control of the lift-up operation of the sheet stacker11is performed.

However, when the remaining sheet quantity calculated by a remaining quantity detector that detects the remaining quantity of the sheets stacked on the sheet stacker11becomes equal to or less than a certain threshold (for example, equal to or less than 5%), the second lateral upper-surface sensor31bis monitored at the same time of monitoring of the first lateral upper-surface sensor31a. Then, in a case where either the lateral upper-surface sensor31aor the lateral upper-surface sensor31bis rendered in non-detection, the sheet controller18performs the control that causes the sheet stacker11to rise (seeFIG. 13).

For example, when the remaining sheet quantity becomes equal to or less than 5%, the sheet stacker11rises to the height of the second lateral upper-surface sensor31b. Thus, the second lateral upper-surface sensor31b, as illustrated inFIG. 14, can substantially monitor the detection surface204on the side face of the sheet stacker11(seeFIGS. 15A and 15B).

Adoption of this arrangement can further enhance the effect of reducing the occurrence of non-feeding of the sheet S due to insufficient floating of the sheet S at the time of almost running out of the sheet bundle Sb on the sheet stacker11.

As an example of a specific control flow, as indicated in the flowchart ofFIG. 13, in control of the sheet feeding operation, first, the lateral upper-surface sensors31aand31beach start monitoring the sheet or the detection surface204(hereinafter referred to as a detection subject) (S101). The lateral upper-surface sensors31aand31beach start monitoring in this manner, and then sheet feeding starts (S102).

Then, it is determined whether the first lateral upper-surface sensor31ahas detected the detection subject (S103). In a case where the detection subject has been detected (Yes in S103), it is determined whether the remaining sheet quantity is equal to or less than 5% (S104). On the other hand, in a case where the detection subject has not been detected (No in S103), the lift-up operation of the sheet stacker11is performed (S106).

In the determination whether the remaining sheet quantity is equal to or less than 5% (S104), in a case where it is determined that the remaining sheet quantity is equal to or less than 5% (Yes in S104), it is determined that whether the second lateral upper-surface sensor31bhas detected the detection subject (S105). On the other hand, in a case where the determination is No, that is, it is determined that the remaining sheet quantity is more than 5% (No in S104), the flow returns to the determination whether the first lateral upper-surface sensor31ahas detected the detection subject (S103).

In the determination whether the second lateral upper-surface sensor31bhas detected the detection subject (S105), in a case where it is determined that the detection subject has been detected (Yes in S105), the flow returns to the determination whether the first lateral upper-surface sensor31ahas detected the detection subject (S103). On the other hand, when the detection subject has not been detected (No in S105), the lift-up operation of the sheet stacker11is performed (S106).

After the performance of the lift-up operation of the sheet stacker11S106), in a case where the sheet stacker11has been lifted by a certain amount X [mm] (S107), it is determined whether the sheet feeding operation has continued (S108).

In the determination (S108), in a case where it is determined that the sheet feeding operation has continued (Yes in S108), the flow returns to the determination whether the first lateral upper-surface sensor31ahas detected the detection subject (S103). On the other hand, in a case where it is determined that the sheet feeding operation has not continued, that is, it is determined the sheet feeding operation has finished (No in S108), the monitoring by the lateral upper-surface sensors31aand31bis completed (S109), and the control of the sheet feeding operation is finished.

Here, the remaining quantity detector for the sheets counts the number of pulses of the lift motor19that is the lift190of the sheet stacker11from a certain start point. Then the remaining quantity detector for the sheets calculates the remaining sheet quantity on the sheet stacker11from the lift-up amount of the sheet stacker11per pulse.

As a result, as illustrated inFIG. 15A, when the sheet stacker11rises to a position where the air flow path is blocked, the detection position of the second lateral upper-surface sensor31bbecomes the non-detection region205of the detection surface204, so that the second lateral upper-surface sensor31bis rendered in non-detection. Thus, the sheet stacker11starts lifting.

Then, as illustrated inFIG. 15B, the sheet stacker11rises to a position where the floated sheets can rise to the attractable area E1(experimental value obtained from evaluation). When such lift-up is made, the detection position of the second lateral upper-surface sensor31bbecomes the detection region206under the suede material203of the detection surface204, so that the second lateral upper-surface sensor31bis rendered in detection. Thus, the lift-up of the sheet stacker11is completed.

A lift-up start position (at which the sheet stacker11blocks the air flow path) and a lift-up end position (at which the floated sheets can float to the attractable area E1) in this control can be controlled with the sheet metal and the suede material203included in the sheet stacker11. With this control, position control with higher accuracy than the position control by the remaining quantity detector can be performed.

In addition, in accordance with a combination of the detection state of the first lateral upper-surface sensor31aand the detection state of the second lateral upper-surface sensor31b, the control of the lift190that lifts up and down the sheet stacker11may be switched.

Normally, the lift-up of the sheet stacker11is performed by repeating lifting at a predetermined specified step rate until a predetermined condition is satisfied. That is, as the specified step rate increases, the amount at which the sheet stacker11can rise at a time increases, whereas the accuracy at the time of stopping deteriorates. By contrast, as the specified step rate decreases, the amount at which the sheet stacker11can rise at a time decreases, whereas the accuracy at the time of stopping improves.

Therefore, in the sheet feeding device200of the present embodiment, the specified step rate in control of the lift190(X1>X3>X2) can also be switched (selectively used), in accordance with a combination of the respective detection states of the lateral upper-surface sensors31aand31b.

With this switching, provided can be the sheet feeding device200capable of feeding the sheet S that has been floated effectively at an appropriate timing.

There are four combinations of the respective detection states of the lateral upper-surface sensors31aand31b, that is, combinations of “detection” and “non-detection” of the lateral upper-surface sensors31aand31b.

Here, Table 1 indicates examples of the combinations.

Table 1 indicates examples of control contents in accordance with a combination of the respective detection states of the lateral upper-surface sensors31aand31band the specified step rates at the time of lift-up operation.

The condition of “combination 1” indicated in Table 1 includes that both of the first lateral upper-surface sensor31aand the second lateral upper-surface sensor31bare in “detection”, the first lateral upper-surface sensor31ahas detected the floated sheets having a sufficient density (not in suspension), and the second lateral upper-surface sensor31bhas detected the sheet bundle. Thus, it is determined that urgent lift-up of the sheet stacker11is not required, and the lift-up operation of the sheet stacker11is not performed.

The condition of “combination 2” indicated in Table 1 includes that the first lateral upper-surface sensor31ais in “non-detection” (=the floated sheets are sparse) and the second lateral upper-surface sensor31bis in “detection”. In this combination, the first lateral upper-surface sensor31ais in non-detection while the floated sheets are sparse, and the second lateral upper-surface sensor31bhas detected the sheet bundle. Thus, a sheet is required to be supplied to the attractable area E1as quickly as possible, and X1 [mm] with the largest step rate is applied.

In both of the conditions of “combination 3” and “combination 4” indicated in Table 1, the second lateral upper-surface sensor31bis in “non-detection” and highly likely to have detected the non-detection region205(suede material203) of the sheet stacker11. Unlike “combination 3” in which the first lateral upper-surface sensor31ais in “detection”, particularly in “combination 4”, the first lateral upper-surface sensor31ais also in “non-detection” (=the floated sheets are sparse). Furthermore, the stop accuracy of the forceful-lift-up end position is required when the forceful lift-up is made, so that X2 or X3 [mm] with a lift-up amount finer than X1 [mm] is used for “combination 3” and “combination 4”. Particularly in “Combination 4”, while the stopping accuracy is required, furthermore, the first lateral upper-surface sensor31ais also in non-detection (=the floated sheets are sparse) Thus, an intermediate step rate that satisfies with the following relationship: X1>X3>X2 and is supportable for both of the stopping accuracy and the lift-up speed, is applied.

As a result, in accordance with the density of floated sheets in a floating region and a semi-floating region and the position of the sheet stacker11, the lift-up speed when the sheet stacker11is lifted up and the stopping accuracy when the stopping operation stops can be compatible with each other.

Although the present embodiment has been described with reference to the drawings, the specific configuration is not limited to the configuration including the sheet feeding device200of the present embodiment described above, and a change in design or the like may be made within a range without departing from the gist of the invention.

For example, in the present embodiment, the sheet feeding device200coupled to the electrophotographic image forming apparatus100has been described. However, the sheet feeding device200can be applied to an inkjet image forming apparatus to which a sheet feeding device is to be connected or in which a sheet feeding device to be incorporated.

In addition, an apparatus for the connection or the incorporation is not limited to an image forming apparatus. Thus, an apparatus that performs processing on a sheet such as a sheet folding apparatus that performs folding processing on a sheet or an apparatus that performs inspection processing on a sheet can be also applied to the apparatus.

Furthermore, the image forming system1including the image forming apparatus100and the sheet feeding device200has been described. However, as a system including a sheet feeding device, a sheet folding system including a sheet folding apparatus that performs folding processing on a sheet and a sheet feeding device can be also applied.

The sheet includes, paper, coated paper, label paper, an overhead projector (OHP) sheet, a film, a prepreg and the like.

Here, the prepreg is mainly used as a material of a laminated board or a multilayer printed wiring board. For example, the prepreg is a material manufactured through the following process. A long base material such as glass cloth, paper, nonwoven fabric, and aramid fiber cloth is impregnated with a resin varnish mainly containing a thermosetting resin such as an epoxy resin and a polyimide resin. The long base material is heated and dried, and then cut in to a sheet (sheet material).

The above description is merely an example, and specific effects are exerted for each of the following aspects.

Aspect A

A sheet feeding device, such as the sheet feeding device200, includes: a blower, such as the front blower12, that floats a sheet, such as the sheet S, of an upper portion of a sheet bundle such as the sheet bundle Sb; a conveyor, such as the attracting conveyance unit20, that conveys the floated sheet; a lift, such as the lift190, including, for example, the lift motor19that lifts up the sheet stacker, such as the sheet stacker11, that stacks the sheet bundle; a first reflective optical sensor, such as the first lateral upper-surface sensor31a, that detects the floated sheet; a second reflective optical sensor, such as the second lateral upper-surface sensor31b, that detects the sheet bundle and a side face of, for example, the detection surface204of the sheet stacker; and circuitry, for example, the sheet controller18to control the lift based on a detection result of each reflective optical sensor. The side face of the sheet stacker includes a detection region, such as the detection region206, and a non-detection region, such as the non-detection region205. When the second reflective optical sensor changes from a detection state to a non-detection state, the circuitry causes the lift to lift up the sheet stacker.

Thus, the side surface of the sheet stacker includes the detection region and the non-detection region. Therefore, when the sheet stacker rises to a position where the air is difficult to blow to the floated sheet in the air flow path of the blower, the detection result of the second reflective optical sensor can be changed from detection to non-detection. That is, detection that the sheet stacker positions in the air flow path of the blower and the air is difficult to blow to the floated sheet can be made. Therefore, even in almost running out in which the sheet stacking face positions at a position above the detection range of the second reflective optical sensor, considering a case where the air easily blows to the floated sheet and a case where the air hardly blows to the floated sheet, control suitable for the configuration of the sheet feeding device can be performed.

Here, the following examples can be included as a case in which the lift-up step rate in lifting up the sheet stacker11is changed, based on a combination of the respective detection results of the reflective optical sensors, at the time of almost running out at which the sheet stacking face positions at the position above the detection range of the second reflective optical sensor.

When the second reflective optical sensor has detected the detection region of the sheet stacker, in a case where the first reflective optical sensor is in detection, nothing is done (stop), and in a case where the first reflective optical sensor is in non-detection, the sheet stacker is lifted up at the smallest lift-up step rate.

On the other hand, when the second reflective optical sensor has detected the non-detection region of the sheet stacker and is rendered in “non-detection”, in a case where the first reflective optical sensor is in non-detection, the sheet stacker is lifted up at the intermediate lift-up step rate, and in a case where the first reflective optical sensor is in detection, the sheet stacker is lifted up by the largest lift-up step rate.

This control is adjustable depending on the range of the detection region and the non-detection region included in the sheet stacker. Thus, the control can switch at the position where the floating sheet is difficult to flow because the sheet stacker positions are in the air flow path of the blower and the air difficult to blow to the floating sheet.

Then, when it is detected that the air is difficult to blow to the floated sheet, in accordance with a combination of the respective detection results of the reflective optical sensors, the lift is controlled to cause the sheet stacker to rise. Thus, the floated sheet can be also more appropriately controlled than ever, to the attractable area, such as the attractable area E1.

Therefore, provided can be the sheet feeding device capable of reducing the occurrence of non-feeding of a sheet due to insufficient floating of the sheet at the time of almost running out of the sheet bundle on the sheet stacker.

Aspect B

In the sheet feeding device according to Aspect A, the circuitry, such as the sheet controller18, that controls the lift, based on the detection result of each of the first reflective optical sensor and the second reflective optical sensor, such as detection/non-detection.

Thus, provided can be the sheet feeding device capable of feeding a sheet at an appropriate timing, even in a case where the sheet feeding device is coupled to an apparatus that is difficult to directly control the lift that causes the sheet stacker to lift.

Aspect C

In the sheet feeding device according to Aspect A or Aspect B, the circuitry switches between execution and non-execution of lift-up operation of the lift and changes a lift-up amount, such as the specified step rate X1, X2, or X3, of the sheet stacker, based on a combination, such as combination 1, 2, or 3, of the detection results of the first reflective optical sensor and the second reflective optical sensor, such as the detection/non-detection.

Thus, provided can be the sheet feeding device capable of feeding a sheet that has been effectively floated, at an appropriate timing.

Aspect D

In the sheet feeding device according to any of Aspect A to Aspect C, in a case where the first reflective optical sensor or the second reflective optical sensor is in non detection, the circuitry causes the lift to lift up the sheet stacker when the remaining quantity of the sheet bundle stacked on the sheet stacker becomes equal to or less than a certain threshold that is, for example, 5%.

Such a configuration can further enhance the effect of reducing occurrence of non-feeding of a sheet due to insufficient floating of the sheet at the time of almost running out of the sheet bundle on the sheet stacker.

Aspect E

In the sheet feeding device according to any of Aspect A to Aspect D, a reflection reducing material, such as the suede material203, forming the non-detection region is disposed on the side face of the sheet stacker.

Such a configuration can enhance the accuracy of the position detection in the height direction (accuracy of lifting operation) of the sheet stacker, with the simple configuration.

Aspect F

In the sheet feeding device according to Aspect E, the reflection reducing material is a suede material, such as the suede material203.

Such a configuration can inexpensively enhance the accuracy of the position detection in the height direction (accuracy of lifting operation) of the sheet stacker, with the simple configuration.

Aspect G

In the sheet feeding device according to any of Aspect A to Aspect F, the relationship of X1>X3>X2 is satisfied where X1 represents a specified step rate at which the sheet stacker is lift up when the first reflective optical sensor is in non detection and the second reflective optical sensor is in detection, X2 represents the specified step rate when the first reflective optical sensor is in detection and the second reflective optical sensor is in non detection, and X3 represents the specified step rate when the first reflective optical sensor is in non detection and the second reflective optical sensor is in non detection.

Such a configuration enables the lift-up speed at the time of lifting up the sheet stacker11and the stopping accuracy at the time of the stopping operation stops to be compatible with each other, in accordance with the state of the density of the floated sheet in the floating region and a semi-floating region and the position of the sheet stacker, such as the sheet stacker11.

Aspect H

An image forming apparatus, such as the image forming apparatus100, that forms an image on a sheet, such as the sheet5, that has been separated and fed from the sheet bundle, such as the sheet bundle Sb, includes the sheet feeding device, such as the sheet feeding device200, according to any of Aspect A to Aspect G, to separate and feed a sheet from the sheet bundle.

Thus, provided can be an image forming apparatus capable of exerting an effect similar to the effect of the sheet feeding device according to any of Aspect A to Aspect G.

Aspect I

An image forming system, such as the image forming system1, includes an image forming apparatus, such as the image forming apparatus100, and the sheet feeding device, such as the sheet feeding device200, according to any of Aspect A to Aspect G to feed, to the image forming apparatus, a sheet, such as the sheet5, that has been separated from the sheet bundle, such as the sheet bundle Sb.

Thus, provided can be an image forming system capable of exerting an effect similar to the effect of the sheet feeding device according to any of Aspect A to Aspect G.

Aspect J

A sheet processing apparatus, such as a sheet folding apparatus, that performs processing, such as folding processing, on the sheet, such as the sheet5, that has been separated and fed from the sheet bundle, such as the sheet bundle Sb, includes the sheet feeding device, such as the sheet feeding device200, according to any of Aspect A to Aspect G, to separate and feed a sheet from the sheet bundle.

Thus, provided can be a sheet processing apparatus capable of exerting an effect similar to the effect of the sheet feeding device according to any of Aspect A to Aspect G.