JP2020040736A - Supplying of sheet - Google Patents

Abstract

To stably deliver a sheet from a tray.SOLUTION: There is provided a sheet supplying device. The sheet supplying device comprises a tray for storing a stack of sheets; a sheet lifting mechanism for lifting the stack of sheets until an uppermost sheet of the stack of sheets reaches a predetermined height position, that is provided at a bottom portion of the tray; a paper feeding roller for delivering the uppermost sheet from the tray via rotation with a motor, that is arranged above the tray so as to come into contact with the uppermost sheet that has reached the predetermined height position; and a controller for adjusting a height position of the stack of papers in such a manner that frictional force generated between a second sheet and the paper feeding roller is substantially equal to frictional force generated between a first sheet and the paper feeding roller during delivery of the first sheet, for controlling the sheet lifting mechanism based on driving-torque of the motor when delivering the second sheet with the paper feeding roller, after delivering the first sheet from the tray by the paper feeding roller.SELECTED DRAWING: Figure 1

Description

  The sheet supply device supplies sheets of a print medium one by one to the image forming apparatus. Each time a sheet is fed by the feed roller, the height of the stack decreases slightly, so that the contact pressure and frictional force generated between the feed roller and the next sheet during the next paper feed are slightly reduced. descend.

  In order to keep the contact pressure and frictional force as constant as possible, depending on the image forming apparatus, each time the upper end position of the stack deviates from the lower limit of the feedable height (for example, every several to several tens of sheets), Some lift a stack of sheets. In order to perform stable paper feeding, if the first sheet is successfully fed out of the tray, it would be beneficial if the subsequent sheets could be fed out with the same contact pressure (and therefore the same frictional force).

1 is a schematic diagram illustrating an image forming apparatus including a sheet supply device according to an example of the present disclosure. 1 is a diagram illustrating a configuration of an electric circuit of a sheet feeding device according to an example of the present disclosure. FIG. 9 is a timing chart of various signals indicating an operation of the sheet feeding apparatus according to an example of the present disclosure when a current value of a sheet feeding motor decreases. FIG. 11 is a timing chart of various signals indicating an operation of the sheet feeding apparatus according to an example of the present disclosure when a current value of a sheet feeding motor increases. FIG. 11 is a flowchart illustrating an example of an operation of the sheet feeding apparatus according to an example of the present disclosure. FIG. 4 is a flowchart illustrating a method of feeding out a sheet from a tray according to an example of the present disclosure.

  The present disclosure, in one aspect, includes a tray that stores a stack of sheets, and a stack provided on the bottom of the tray, wherein the top sheet of the stack of sheets reaches a predetermined height position. A sheet elevating mechanism to be lifted, disposed above the tray so as to contact the top sheet reaching the predetermined height position, rotated by a motor, and pays out the top sheet from the tray. A sheet feeding roller and a sheet elevating mechanism based on a driving torque of the motor when a second sheet is fed by the sheet feeding roller after a first sheet is fed from the tray by the sheet feeding roller. And the frictional force generated between the second sheet and the sheet feeding roller causes the first sheet and the sheet feeding roller to move during feeding of the first sheet. To provide a sheet feeding apparatus including a controller for adjusting the height position of the frictional force substantially equal as the stack of sheets that occurred between La.

  The sheet feeding device further includes a current detection circuit that measures a current value of the motor that indicates a driving torque of the motor, and the controller is configured to control the motor by the current detection circuit during feeding of the first sheet. 1 and the controller measures a second current value of the motor by the current detection circuit during the feeding of the second sheet, and (a) the second current value is the second current value. When the reference current value determined based on the current value of 1 is smaller than a predetermined threshold value by more than a predetermined threshold value, the sheet elevating mechanism is controlled to raise the stack of sheets; (b) the second current value and When the absolute value of the difference from the reference current value is equal to or smaller than the predetermined threshold, the movement of the stack of sheets may be stopped by controlling the sheet lifting / lowering mechanism.

  The controller may further control the sheet elevating mechanism to lower the stack of sheets when the second current value is larger than the reference current value by more than the predetermined threshold value.

  The sheet supply device may further include a leading edge sensor for detecting that the sheet has been successfully fed out of the tray, and the controller may have a configuration in which the first sheet is successfully fed out of the tray. May be carried out only when the leading edge sensor detects the second sheet.

  The controller may measure the first current value of the motor by the current detection circuit after a predetermined standby time has elapsed from the start of the feeding of the first sheet. The second current value of the motor may be measured by the current detection circuit after the predetermined standby time has elapsed from the start of feeding of the second sheet.

  The controller may measure the first current value of the motor a plurality of times by the current detection circuit after the predetermined standby time has elapsed from the start of the feeding of the first sheet. In some cases, the reference current value is determined based on the plurality of first current values.

  The sheet feeding device may further include an upper limit sensor for detecting that the top sheet of the stack of sheets has reached the predetermined height position.

  The controller may further include: (d) stopping the motor when the second current value is smaller than a predetermined idle feed detection value or larger than a predetermined double feed detection value.

  According to another aspect of the present disclosure, there is provided a method of feeding out a sheet from a tray, wherein the sheet elevating mechanism moves the stack of sheets onto the tray until a top sheet of the stack of sheets reaches a predetermined height position. Lifting the tray from above, so that a feed roller disposed above the tray comes into contact with the top sheet; rotating the feed roller by a motor; and feeding the top sheet by the feed roller. After the first sheet is fed out from the tray by the paper feed roller, and when the second sheet is fed out by the paper feed roller, the sheet elevating and lowering is performed based on the driving torque of the motor. A mechanism for controlling a mechanism that causes a frictional force generated between the second sheet and the sheet feeding roller to cause the first sheet to move during feeding of the first sheet The method comprising adjusting the height position of the frictional force substantially equal as the stack of sheets without between the paper feed roller.

  Controlling the seat elevating mechanism based on the driving torque of the motor includes measuring a first current value of the motor indicating a driving torque of the motor during feeding of the first sheet; A second current value of the motor indicating a driving torque of the motor is measured during feeding of a sheet, and (a) the second current value is determined based on a reference current value determined based on the first current value. Is smaller than a predetermined threshold value, the sheet elevating mechanism is controlled to raise the stack of sheets; (b) a difference between the second current value and the reference current value is equal to or less than the predetermined threshold value. In some cases, controlling the sheet lifting mechanism to stop the movement of the stack of sheets may be included.

  The controlling the seat lifting mechanism based on the driving torque of the motor includes: (c) controlling the seat lifting mechanism when the second current value is larger than the reference current value by more than the predetermined threshold. And lowering the stack of sheets.

  The feeding of the second sheet may be performed only when the first sheet is successfully fed from the tray.

  Measuring the first current value of the motor indicating the driving torque of the motor during the feeding of the first sheet is performed after a predetermined standby time has elapsed from the start of feeding of the first sheet. Measuring the first current value of the motor may include measuring the second current value of the motor indicating a driving torque of the motor during feeding of the second sheet. It may include measuring the second current value of the motor after the predetermined standby time has elapsed from the start of the feeding of the second sheet.

  Measuring the first current value of the motor after the elapse of the predetermined standby time from the start of the feeding of the first sheet is performed by measuring the predetermined standby time from the start of the feeding of the first sheet. Measuring the first current value of the motor a plurality of times after elapse of, and determining the reference current value based on the measured first current value may include measuring And determining the reference current value based on the plurality of first current values.

  The method may further include: (d) stopping the motor when the second current value is smaller than a predetermined empty feed detection value or larger than a predetermined double feed detection value. is there.

  Hereinafter, the present disclosure will be described in more detail with reference to the drawings.

  FIG. 1 illustrates an image forming unit 10 for forming an image on a sheet P of a print medium passing through a conveyance path L, and a sheet supply apparatus according to an example of the present disclosure for supplying the sheet P of the print medium to the conveyance path L. 20 illustrates an example of the image forming apparatus 1 including the image forming apparatus 20. FIG. 2 shows an example of an electronic circuit of the sheet feeding device 20.

  Referring to FIGS. 1 and 2, the sheet supply device 20 includes a tray 21 that stores a stack of sheets P of print media, and is provided at the bottom of the tray 21. And a sheet lifting mechanism 22 that lifts the stack of sheets P until the sheet reaches a height position H (not shown), and a top of the tray 21 so as to contact the uppermost sheet P that has reached a predetermined height position H. A sheet feeding roller R1 that is arranged and rotated by the sheet feeding motor M1 and feeds out the top sheet P of the stack of sheets P from the tray 21.

  At the predetermined height position H, the sheet feeding roller R1 disposed above the tray 21 is pressed against the uppermost sheet P reaching the predetermined height position H with an appropriate contact pressure, and There may be a height position where the top sheet P can be fed out by rotation. In order to detect that the top sheet P of the stack of sheets P has reached the predetermined height position H, the sheet feeding device 20 may further include an upper limit sensor S1. The upper limit sensor S1 may be any sensor as long as it can detect the height position of the top sheet P of the stack of sheets P. In one example, the upper limit sensor S1 may be a transmissive or reflective optical sensor. In order to generate the contact pressure, the feed roller R1 is connected to the upper feed roller R2 by an elastic support member such as a spring extending from the rotation axis of the upper feed roller R2 to the feed roller R1. There is a case where it is supported so as to be able to swing vertically as a center.

  The sheet supply device 20 conveys the sheet P fed by the sheet feeding roller R1 along the conveying path L toward the conveying roller R3, and conveys the sheet P sent from the sheet feeding roller R2. There may be a case where a pair or a plurality of pairs of transport rollers R3 that transport the image to the image forming unit 10 along the path L are further included. The sheet feeding device 20 further includes a sheet feeding controller 23 that controls the operation of various components of the sheet feeding device 20 including the sheet lifting / lowering mechanism 22, the sheet feeding rollers R1, R2, and the conveyance roller R3.

  The sheet elevating mechanism 22 may be any mechanism as long as it can move the stack of sheets P up and down under the control of the sheet feeding controller 23. In one example, the sheet elevating mechanism 22 may include a rack and pinion mechanism that is driven by the elevating motor M2 and that can move the stack of sheets P up and down. The paper feed controller 23 can control the operation of the sheet elevating mechanism 22 by controlling the drive circuit of the elevating motor M2.

  At the start of the sheet feeding operation, the sheet feeding controller 23 first controls the sheet lifting / lowering mechanism 22 until the top sheet P of the stack of sheets P reaches a predetermined height position H (not shown). Lift P's stack. When the upper limit sensor S1 detects that the uppermost sheet P of the stack of sheets P has reached the predetermined height position H, the sheet feed controller 23 controls the sheet elevating mechanism 22 to stack the sheets P. Is stopped, the paper feed motor M1 is turned on, and the rotation of the paper feed rollers R1 and R2 is started. The paper feed controller 23 can control the rotation of the paper feed motor M1 by controlling the drive circuit of the paper feed motor M1.

  The uppermost sheet P fed out of the tray 21 by the paper feed roller R1 is further sent out to the transport roller R3 by a pair of paper feed rollers R2. However, in order to prevent the double feeding of the sheet P, the lower sheet feeding roller R2 of the pair of sheet feeding rollers R2 has the same direction as the rotation direction (counterclockwise direction) of the upper sheet feeding roller R2. (Ie, the direction in which the sheet P is pushed back to the tray) in some cases.

  After the first sheet P (that is, the first sheet P fed after the stack of the sheets P is lifted by the sheet lifting / lowering mechanism 22) is fed by the sheet feeding roller R1, the second sheet P (that is, the subsequent sheet P) The frictional force generated between the second sheet P and the sheet feeding roller R1 when any one of the sheets P is fed out by the sheet feeding roller is reduced due to a decrease in the stack height of the sheet P or the like. May be. Further, after the first sheet P is fed out by the sheet feeding roller R1, the vibration at the time of sheet feeding affects the sheet lifting / lowering mechanism 22 so that the sheet P slightly moves in the ascending direction, or the first sheet P contains water. Depending on the state, the frictional force generated between the second sheet P and the paper feed roller R1 may increase due to the difference in the frictional force between the second sheet P and the sheet.

  In order to correct such a variation in the frictional force, the sheet feeding controller 23 determines whether the second sheet P is fed out by the sheet feeding roller R1 after the first sheet P is fed out from the tray 21 by the sheet feeding roller R1. In addition, the sheet elevating mechanism 22 is controlled based on the driving torque of the sheet feeding motor M1 so that the frictional force generated between the second sheet P and the sheet feeding roller R1 causes the first sheet P to be pulled out during feeding of the first sheet P. In some cases, the height position of the stack of sheets P is adjusted so as to be substantially equal to the frictional force generated between the sheet P and the sheet feeding roller R1. The driving torque of the sheet feeding motor M1 increases as the frictional force between the second sheet P and the sheet feeding roller R1 increases, and the frictional force between the second sheet P and the sheet feeding roller R1 decreases. Decreases as Therefore, the sheet feeding device 20 may further include a current detection circuit 24 that measures a current value of the sheet feeding motor M1 indicating a driving torque of the sheet feeding motor M1. In one example, the sheet feeding device 20 may perform such frictional force control for each of the subsequent sheets P. In this specification, “substantially equal” may mean that a difference between two compared values is equal to or smaller than a predetermined threshold.

  Specifically, the sheet feeding device 20 may further include a storage device 25, and the sheet feeding controller 23 controls the current detection circuit 24 to feed the first current of the sheet feeding motor M1 during feeding of the first sheet P. The value may be measured one or more times, and the measured first current value may be stored in the storage device 25. Thereafter, the sheet feeding controller 23 measures the second current value of the sheet feeding motor M1 by the current detection circuit 24 during the feeding of the second sheet P, and the measured second current value of the sheet feeding motor M1 is The height of the stack of the sheets P is adjusted by controlling the sheet lifting / lowering mechanism 22 so as to be substantially equal to the reference current value determined based on the first current value stored in the storage device 25. There are cases. In one example, the sheet feeding device 20 may perform such a height position adjustment for each of the subsequent sheets P. The paper feed controller 23 may determine an average value of the plurality of first current values stored in the storage device 25 as a reference current value. Alternatively, the paper feed controller 23 may determine the single first current value stored in the storage device 25 as the reference current value.

  For example, during the feeding of the second sheet P, the sheet feeding controller 23 sets (a) the second measurement value of the sheet feeding motor M1 measured by the current detection circuit 24 to a predetermined threshold value Th that is larger than the reference current value. If it is smaller than this, the stack of sheets P may be raised by controlling the sheet lifting / lowering mechanism 22. In addition, during the feeding of the second sheet P, the sheet feeding controller 23 determines that (b) the second measurement value measured by the current detection circuit 24 is larger than the reference current value by more than the predetermined threshold value Th. There are cases where the stack of sheets P is lowered by controlling the sheet lifting mechanism 22. Further, during the feeding of the second sheet P, the sheet feed controller 23 sets the absolute value of the difference between the second measured value measured by the current detecting circuit 24 and the reference current value to be equal to or less than a predetermined threshold Th. In some cases, the sheet raising / lowering mechanism 22 may be controlled to stop the operation of raising or lowering the stack of sheets P. The sheet feeding controller 23 controls the sheet feeding during the feeding of the second sheet P until the absolute value of the difference between the second measurement value measured by the current detection circuit 24 and the reference current value becomes equal to or less than a predetermined threshold Th. In some cases, the second current value of the motor M1 is repeatedly measured, and the above operation (a) or (b) is continuously performed. In order to shorten the time required for adjusting the frictional force, the predetermined threshold Th may be preferably 5 mA or more, more preferably 10 mA or more. In order to realize stable paper feeding, the desired threshold value Th may be preferably 5 mA or less, more preferably 1 mA or less.

  Further, (d) when the second measurement value measured by the current detection circuit 24 is smaller than a predetermined empty-feed detection value or larger than a predetermined double-feed detection value, It may be determined that there is a possibility of feeding or double feeding, and the operation of the sheet feeding motor M1 may be stopped. In order to reliably detect the idle feeding in the feed roller R1, the predetermined idle detection value may be preferably 90% or less of the reference current value, and more preferably 80% of the reference current value. May be: In order to reliably detect the double feed in the paper feed roller R1, the predetermined double feed detection value may be preferably 110% or more of the reference current value, and more preferably 120% of the reference current value. It may be more than that.

  The sheet feeding device 20 may further include a leading edge sensor S2 in order to detect that the sheet P has been safely fed from the tray 21. The leading edge sensor S2 is disposed in the vicinity of the transport path L at a position between the paper feeding roller R2 and the transporting roller R3, and may detect the leading edge of the sheet P sent from the paper feeding roller R2. The leading edge sensor S2 may be any sensor as long as it can detect the leading edge of the sheet P sent from the paper feed roller R2. In one example, the tip sensor S2 may be a reflective optical sensor. In order to ensure that the reference current value is an appropriate value, the paper feed controller 23 controls the second sheet only when the leading edge sensor S2 detects that the first sheet P has been safely fed out of the tray 21. May be carried out.

FIG. 3 shows the operation of the sheet feeding device 20 when the current value of the sheet feeding motor M1 decreases when the second sheet P is fed out, based on the current value of the sheet feeding motor M (first stage) and the sheet feeding motor M1. Signal (ON / OFF) (second stage), drive signal UP / DOWN / OFF (third stage) of the lifting / lowering motor M2, and output signal ON / OFF (fourth stage) from the tip sensor S2. ing. During the feeding of the first sheet P, at time T _0, when the sheet feeding controller 23 turns ON the paper feeding motor M1, the current value of the feed motor M1 (shown in solid lines in the first stage) is , And rises sharply from zero due to the inrush current. The mechanical elements such as a gear for transmitting the rotation of the feed motor M1 to the paper feed roller R1 engages, at time T _1, the current value of the feed motor M1 is stable, not almost vary. The current value of the sheet feeding motor M1 after reaching the stable state is proportional to the driving torque of the sheet feeding motor M1, and therefore, the frictional force between the sheet feeding roller R1 and the sheet P fed by the sheet feeding roller R1 and It has been found to be proportional to the contact pressure. Therefore, the paper feed controller 23 at the time after the time T _1, which may be measured by the current sensing circuit 24 to a first current value of the feed motor M1.

At time T _4, after that the first sheet P is successfully fed from the tray 21 is detected by the edge sensor S2, at time T ₅ of a predetermined time TD has elapsed, the sheet feeding controller 23, the feed motor Turn off M1. When the feed motor M1 is turned off, the current value of the feed motor M1 returns to zero. The predetermined time TD is a time required from when the leading edge of the sheet P is detected by the leading edge sensor S2 to when the leading edge of the sheet P reaches the transport roller R3, and can be determined in advance by an experiment or the like.

On the other hand, the second sheet P (i.e., either the succeeding sheet P) during feeding of the, at time T _0, when the sheet feeding controller 23 turns ON the paper feeding motor M1, the current value of the feed motor M1 (Shown by a broken line in the first stage) rises sharply from zero due to the inrush current. When mechanical elements for transmitting the rotation of the feed motor M1 to the paper feed roller M1 are engaged, at time T _1, the current value of the feed motor M1 is stable, not almost vary. The current value of the sheet feeding motor M1 after reaching the stable state is proportional to the driving torque of the sheet feeding motor M1, and therefore, the frictional force between the sheet feeding roller R1 and the sheet P fed by the sheet feeding roller R1 and It has been found to be proportional to the contact pressure. Therefore, the paper feed controller 23 at a later time than the time T _1, which may be measured by the current detecting circuit 24 and the second current value of the feed motor M1.

In the example of FIG. 3, the sheet feeding controller 23 starts the measurement of the second current value of the feed motor M1 (dashed line) at time T _2, the second current value measured was measured previously Since the current is smaller than the first current value (solid line) and therefore smaller than the reference current value, the elevator motor M2 is controlled to raise the stack of sheets P. At time T _3, the second current value is a reference voltage value substantially equal to, the sheet feeding controller 23 stops the rise of the stack of sheets P by controlling the elevator motor M2. At time T _4, after that the second sheet P is successfully fed from the tray 21 is detected by the edge sensor S2, at time T ₅ of a predetermined time TD has elapsed, the sheet feeding controller 23, the feed motor Turn off M1. When the feed motor M1 is turned off, the current value of the feed motor M1 returns to zero.

FIG. 4 shows the operation of the sheet feeding device 20 when the current value of the sheet feeding motor M1 increases when the second sheet P is fed out, based on the current value of the sheet feeding motor M (first stage) and the sheet feeding motor M1. Signal (ON / OFF) (second stage), drive signal UP / DOWN / OFF (third stage) of the lifting / lowering motor M2, and output signal ON / OFF (fourth stage) from the tip sensor S2. ing. In the example of FIG. 4, the second current value (broken line), the current value of the first sheet P in the feeding time of the feed motor M1, which is the previously measured of the feed motor M1 measured at time T ₂ ( greater than the solid line), thus the greater than the reference current value, the sheet feeding controller 23, at time T _2, lowering the stack of sheets P by controlling the elevator motor M2. Thereafter, at time T _3, the second current value becomes the reference current value substantially equal to, the sheet feeding controller 23 stops the downward movement of the stack of sheets P by controlling the elevator motor M2. Other points are the same as those in FIG.

As described above, the current value of the sheet feeding motor M1 after reaching the stable state is proportional to the driving torque of the sheet feeding motor M1, and therefore, the current value between the sheet feeding roller R1 and the sheet P fed by the sheet feeding roller R1. It has been found to be proportional to the frictional force and contact pressure between them. Therefore, the sheet feeding apparatus 20 may time further comprising a measuring means 26, the paper feed controller 23, the time T ₀ in the first sheet P waiting time TW feeding since been started the predetermined has elapsed Is detected by the time measuring means 26, the first current value of the sheet feeding motor M1 by the current detection circuit 24 may be measured once or a plurality of times. Further, the sheet feeding controller 23 detects that a predetermined standby time TW has elapsed since the feeding of the second sheet P was started at time T ₀ by the time measuring unit 26, and then the sheet feeding controller 23 controls the feeding by the current detecting circuit 24. The second current value of the paper motor M1 may be measured. Predetermined standby time TW is the time required for the feed motor M1 is the current value of the feed motor M1 from being turned ON is stabilized, time from time T ₀ in FIG. 3 and FIG. 4 to time T ₁ Is equivalent to The predetermined standby time TW can be obtained in advance by an experiment or the like.

  In order to accurately adjust the frictional force, the predetermined standby time TW may be preferably 50 ms or more, more preferably 80 ms or more. In order to secure a sufficient adjustment time of the frictional force, the predetermined standby time TW may be preferably 200 ms or less, more preferably 120 ms or less.

  FIG. 5 is a flowchart 500 illustrating an example of the operation of the sheet feeding apparatus 20 according to an example of the present disclosure. The operation starts from 502 and proceeds to 504, where the paper feed controller 23 turns on the paper feed motor M1. Next, the operation proceeds to 506, where the paper feed controller 23 determines whether or not a predetermined standby time TW has elapsed. If it is not determined that the predetermined standby time TW has elapsed, the operation returns to 506, and this determination is repeated. If it is determined in 506 that the predetermined standby time TW has elapsed, the operation proceeds to 508, where the sheet feeding controller 23 determines that the sheet P fed by the sheet feeding roller R1 is the first sheet P ( That is, it is determined whether or not the sheet P is the first sheet fed after the stack of sheets P is lifted by the sheet lifting mechanism 22. At 508, if it is determined that the sheet P fed by the sheet feeding roller R1 is the first sheet P, the operation proceeds to 510, where the sheet feeding controller 23 causes the current detection circuit 24 to operate the sheet feeding motor M1. The first current value is measured, and then, at 512, the measured first current value is stored in the storage device 25.

  Thereafter, the operation proceeds to 514, in which the paper feed controller 23 determines whether the leading edge sensor S2 has detected that the first sheet P has been safely fed from the tray 21. If it is determined in 514 that the leading edge sensor S2 has detected that the first sheet P has been safely fed from the tray 21, the operation ends in 540.

  On the other hand, if it is determined at 514 that the first sheet P has been safely fed from the tray 21 has not been detected by the leading edge sensor S2, the operation proceeds to 516, where the sheet feeding controller 23 determines It is determined whether a predetermined time limit TL has elapsed since the paper motor M1 was turned on. If it is determined at 516 that the predetermined time limit TL has not elapsed, the operation returns to 510, where the paper feed controller 23 again measures the first current value of the paper feed motor M1 by the current detection circuit 24. I do. Subsequent operations are the same as above. On the other hand, if it is determined in 516 that the predetermined time limit TL has elapsed, the paper feed controller 23 determines that there is some abnormality in the feeding of the first sheet P, and the operation ends in 516.

  The predetermined time limit TL may be determined according to the position of the leading edge sensor S2, the sheet feeding speed, or the like. For example, in order to accurately detect a paper feed error, the predetermined time limit TL may be preferably 800 ms or more, more preferably 1000 ms or more. In order to shorten the paper feeding time, the predetermined time limit TL may be preferably 700 ms or less, more preferably 500 ms or less.

  If it is determined in 508 that the sheet P fed by the sheet feeding roller R1 is not the first sheet P, the operation proceeds to 520, where the sheet feeding controller 23 stores the first sheet P stored in the storage device 25. A reference current value is determined based on the current value. For example, the paper feed controller 23 may determine an average value of a plurality of first current values stored in the storage device 25 as a reference current value. Alternatively, the paper feed controller 23 may determine the single first current value stored in the storage device 25 as the reference current value.

  After the reference current value is determined at 520, operation proceeds to 522, where the feed controller 23 measures the second current value of the feed motor M1 by the current sensing circuit 24, and then at 524, the second current value. Calculate the difference between the current value and the reference current value. Thereafter, the operation proceeds to 526, where the sheet feeding controller 23 determines whether or not the absolute value of the difference between the second current value and the reference current value is equal to or smaller than the predetermined threshold Th.

  If it is determined in 526 that the absolute value of the difference between the second current value and the reference current value is not less than or equal to the predetermined threshold Th (that is, the absolute value of the difference exceeds the predetermined threshold Th), the operation is performed. Proceeds to 528, where the paper feed controller 23 determines whether the difference between the second current value and the reference current value is negative (that is, whether the second current value is smaller than the reference current value). Judge. If it is determined at 528 that the difference between the second current value and the reference current value is negative (i.e., the second current value is less than the reference current value), operation proceeds to 530 where the paper is fed. The controller 23 controls the sheet lifting / lowering mechanism 22 to raise the stack of the sheets P. On the other hand, if it is determined at 528 that the difference between the second current value and the reference current value is not negative (ie, the second current value is greater than the reference current value), operation proceeds to 532, where The paper feed controller 23 controls the sheet elevating mechanism 22 to lower the stack of sheets P. If it is determined in 526 that the absolute value of the difference between the second current value and the reference current value is equal to or smaller than the predetermined threshold Th, the operation proceeds to 534, where the sheet feeding controller 23 sets the sheet elevating mechanism 22 is controlled to stop the operation of raising or lowering the stack of sheets P.

  After the control of the sheet lifting / lowering mechanism 22 at 530, 532 or 534, the operation proceeds to 536, where the sheet feeding controller 23 detects that the second sheet P has been safely fed from the tray 21 by the leading edge sensor S2. Is determined. If it is determined in 536 that the leading edge sensor S2 has detected that the second sheet P has been safely fed from the tray 21, the operation ends in 540.

  On the other hand, if it is determined in 536 that the second sheet P has been safely unreeled from the tray 21 has not yet been detected by the leading edge sensor S2, the operation proceeds to 538, in which the sheet feeding controller 23 It is determined whether a predetermined time limit TL has elapsed since the paper motor M1 was turned on. If it is determined at 538 that the predetermined time limit TL has not elapsed, the operation returns to 522, where the paper feed controller 23 again measures the second current value of the paper feed motor M1 by the current detection circuit 24. I do. Subsequent operations are the same as above. On the other hand, if it is determined in 538 that the predetermined time limit TL has elapsed, the paper feed controller 23 determines that there is some abnormality in the feeding of the second sheet P, and the operation ends in 542.

  FIG. 6 is a flow diagram illustrating a method 600 for unwinding a sheet from a tray according to an example of the present disclosure. The method 600 begins at block 602 and proceeds to block 604, where a sheet elevating mechanism moves the stack of sheets to the bottom of the tray until the top sheet of the stack of sheets reaches a predetermined height position. , So that the paper feed roller disposed above the tray comes into contact with the uppermost sheet. Next, in block 606, the paper feed roller is rotated by a motor, and the top sheet is fed out of the tray by the paper feed roller. Next, in block 608, after the first sheet is fed from the tray by the feed roller, when the second sheet is fed by the feed roller, the second sheet is fed based on the driving torque of the motor. Controlling a lifting mechanism, wherein a frictional force generated between the second sheet and the sheet feeding roller generates friction between the first sheet and the sheet feeding roller during feeding of the first sheet; Adjust the height position of the stack of sheets to be substantially equal to the force. Finally, proceed to block 610, where the method 600 ends.

  Controlling the seat elevating mechanism based on the driving torque of the motor includes measuring a first current value of the motor indicating a driving torque of the motor during feeding of the first sheet; A second current value of the motor indicating a driving torque of the motor is measured during feeding of a sheet, and (a) the second current value is determined based on a reference current value determined based on the first current value. Is smaller than a predetermined threshold value, the sheet elevating mechanism is controlled to raise the stack of sheets; (b) a difference between the second current value and the reference current value is equal to or less than the predetermined threshold value. In some cases, controlling the sheet lifting mechanism to stop the movement of the stack of sheets may be included.

  The controlling the seat lifting mechanism based on the driving torque of the motor includes: (c) controlling the seat lifting mechanism when the second current value is larger than the reference current value by more than the predetermined threshold. And lowering the stack of sheets.

  The feeding of the second sheet may be performed only when the first sheet is successfully fed from the tray.

  Measuring the first current value of the motor indicating the driving torque of the motor during the feeding of the first sheet is performed after a predetermined standby time has elapsed from the start of feeding of the first sheet. Measuring the first current value of the motor may include measuring the second current value of the motor indicating a driving torque of the motor during feeding of the second sheet. It may include measuring the second current value of the motor after the predetermined standby time has elapsed from the start of the feeding of the second sheet.

  Measuring the first current value of the motor after the elapse of the predetermined standby time from the start of the feeding of the first sheet is performed by measuring the predetermined standby time from the start of the feeding of the first sheet. Measuring the first current value of the motor a plurality of times after elapse of, and determining the reference current value based on the measured first current value may include measuring And determining the reference current value based on the plurality of first current values.

  (D) When the second current value is smaller than a predetermined idle feed detection value or larger than a predetermined double feed detection value, the method may further include stopping the motor.

    Although the sheet supply device 20 is included in the image forming apparatus 1 in the example of FIG. 1, the sheet supply device 20 may be embodied as a separate device from the image forming apparatus 1 as a matter of course. The above examples are intended to illustrate the invention and do not limit the scope of the invention. The scope of the present invention is defined by the appended claims.

1 Image Forming Apparatus 10 Image Forming Unit 20 Sheet Feeding Unit 22 Sheet Elevating Mechanism 23 Feed Controller 24 Current Detecting Circuit 25 Storage L Transport Path M1 Feed Motor M2 Lift Motors R1, R2 Feed Roller R3 Feed Roller S1 Upper Limit Sensor S2 Advanced sensor

Claims (15)

A sheet feeding device,
A tray containing a stack of sheets;
A sheet elevating mechanism that is provided at the bottom of the tray and lifts the stack of sheets until the top sheet of the stack of sheets reaches a predetermined height position;
A feed roller that is arranged above the tray so as to contact the top sheet that has reached the predetermined height position, is rotated by a motor, and feeds out the top sheet from the tray;
After the first sheet is fed from the tray by the feed roller, when the second sheet is fed by the feed roller, the sheet lifting mechanism is controlled based on the driving torque of the motor, and A frictional force generated between a second sheet and the paper feed roller is substantially equal to a frictional force generated between the first sheet and the paper feed roller during feeding of the first sheet. And a controller for adjusting the height position of the stack of sheets. A current detection circuit that measures a current value of the motor indicating a driving torque of the motor,
The controller measures a first current value of the motor by the current detection circuit during feeding of the first sheet,
The controller measures a second current value of the motor by the current detection circuit during the feeding of the second sheet,
(A) when the second current value is smaller than a reference current value determined based on the first current value by more than a predetermined threshold value, the sheet elevating mechanism is controlled to raise the stack of sheets; Let;
(B) when the absolute value of the difference between the second current value and the reference current value is equal to or less than the predetermined threshold value, controlling the sheet lifting / lowering mechanism to stop the movement of the sheet stack. 2. The sheet feeding device according to 1. The controller further comprises:
3. The sheet supply according to claim 2, wherein, if the second current value is larger than the reference current value by more than the predetermined threshold value, the sheet raising / lowering mechanism is controlled to lower the stack of sheets. apparatus. A tip sensor for detecting that the sheet has been fed out of the tray safely;
The controller according to any one of claims 1 to 3, wherein the controller executes the feeding of the second sheet only when the leading edge sensor detects that the first sheet has been successfully fed from the tray. A sheet feeding device according to the item. The controller, after a predetermined standby time has elapsed from the start of the feeding of the first sheet, measures the first current value of the motor by the current detection circuit,
The controller according to any one of claims 2 to 4, wherein the second current value of the motor is measured by the current detection circuit after the predetermined standby time has elapsed from the start of feeding of the second sheet. The sheet supply device according to claim 1.   The controller is configured to measure the first current value of the motor a plurality of times by the current detection circuit after the predetermined standby time has elapsed from the start of the feeding of the first sheet, and to determine the plurality of measured values. The sheet feeding device according to claim 5, wherein the reference current value is determined based on a first current value.   The sheet feeding device according to any one of claims 1 to 6, further comprising an upper limit sensor for detecting that the top sheet of the stack of sheets has reached the predetermined height position. The controller further comprises:
(D) stopping the motor when the second current value is smaller than a predetermined idle feed detection value or larger than a predetermined double feed detection value. A sheet feeding device according to the item. A method of feeding out a sheet from a tray,
The sheet lifting mechanism lifts the stack of sheets from the bottom of the tray until the top sheet of the stack of sheets reaches a predetermined height position. Make contact with the top sheet;
Rotating the paper feed roller by a motor, and feeding out the top sheet from the tray by the paper feed roller;
After the first sheet is fed from the tray by the feed roller, when the second sheet is fed by the feed roller, the sheet lifting mechanism is controlled based on the driving torque of the motor, and The frictional force generated between the second sheet and the paper feed roller is substantially equal to the frictional force generated between the first sheet and the paper feed roller during feeding of the first sheet. Adjusting the height position of the stack of sheets as described above. Controlling the seat lifting mechanism based on the driving torque of the motor,
Measuring a first current value of the motor indicating a driving torque of the motor during the feeding of the first sheet;
Measuring a second current value of the motor indicating a driving torque of the motor during the feeding of the second sheet;
(A) when the second current value is smaller than a reference current value determined based on the first current value by more than a predetermined threshold value, the sheet elevating mechanism is controlled to raise the stack of sheets; Let;
(B) when the difference between the second current value and the reference current value is equal to or less than the predetermined threshold value, controlling the sheet lifting / lowering mechanism to stop the movement of the sheet stack. 2. The method according to 1. Controlling the seat lifting mechanism based on the driving torque of the motor,
(C) controlling the sheet lifting mechanism to lower the stack of sheets when the second current value is larger than the reference current value by more than the predetermined threshold value. The described method.   The method according to claim 9, wherein the feeding of the second sheet is performed only when the first sheet is successfully fed from the tray. Measuring the first current value of the motor, which indicates a driving torque of the motor during feeding of the first sheet,
Measuring a first current value of the motor after a predetermined standby time has elapsed from the start of feeding of the first sheet;
Measuring the second current value of the motor indicating the driving torque of the motor during the feeding of the second sheet,
The method according to any one of claims 10 to 12, comprising measuring the second current value of the motor after the predetermined waiting time has elapsed from the start of the feeding of the second sheet. . Measuring the first current value of the motor after the predetermined standby time has elapsed from the start of the feeding of the first sheet,
Measuring the first current value of the motor a plurality of times after the predetermined standby time has elapsed from the start of the feeding of the first sheet,
Determining the reference current value based on the measured first current value,
14. The method of claim 13, comprising determining the reference current value based on a plurality of the measured first current values. (D) stopping the motor when the second current value is smaller than a predetermined idle feed detection value or larger than a predetermined double feed detection value. The method according to claim 1.

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