JP2009256037A - Paper feeder and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an error stop when it is turned out that paper is emptied after start of feeding of the next paper, and to improve productivity of a print job. <P>SOLUTION: This paper feeder is provided with a paper empty detecting means 25 detecting that the paper in a paper feeding section 2a is emptied, and a paper near empty detecting means 23 detecting that the residual amount of the paper in the paper feeding section 2a is reduced below a prescribed amount. When the reduction in the residual amount of the paper is detected by the paper near empty detecting means 21, feeding of the next paper is started after a timing capable of confirming that the paper in the paper feeding section 2a is not emptied based on an output from the paper empty detecting means 23 after the start of feeding of the last paper. When the reduction in the residual amount of the paper is not detected by the paper near empty detecting means 21, feeding of the next paper is started at a timing earlier than that in the case where the reduction in the residual amount of the paper is detected by the paper near empty detecting means 21. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a paper feeding device that feeds paper contained in a paper feeding unit one by one and an image forming apparatus including the paper feeding device.

  An image forming apparatus such as a printer apparatus or an MFP (Multi Function Peripheral) includes a sheet feeding apparatus that feeds sheets one by one to an image forming unit. The sheet feeding device supplies the sheet to the image forming unit at a timing that matches the toner image formed in the image forming unit. In order to improve the productivity of print jobs in the image forming apparatus, such a paper feeding device is required to perform continuous paper feeding at as short a paper interval as possible (for example, Patent Document 1 or 2).

  Conventionally, various proposals have been made on techniques for detecting the presence or absence of a sheet stored in a sheet feeding unit of a sheet feeding device (for example, Patent Document 3). In Patent Document 3, a sheet near empty sensor that detects that the number of sheets stored in a sheet feeding unit is less than a predetermined amount and a sheet empty sensor that detects that a sheet is empty are integrated. It is configured.

JP 2001-206583 A JP 2003-104589 A JP-A-5-97278

  By the way, when a paper empty sensor that detects that the paper has been emptied is disposed in the paper feeding unit, it is preferable to install it as downstream as possible in the paper transport direction. This is because if a paper empty sensor is installed upstream of the pickup roller that feeds paper from the paper supply unit and the user accidentally sets the paper upstream of the pickup roller, the paper empty sensor This is because the pickup roller that detects “paper is present” cannot feed the paper, resulting in a paper feeding error.

  However, if the paper empty sensor is installed on the downstream side in the paper transport direction, it is not possible to detect that the paper in the paper feed unit is empty after the last paper has passed through the installation position. The timing detected by the sensor is delayed. For this reason, for example, during continuous paper feeding, after the pickup roller feeds the last paper and then starts the paper feeding operation for the next paper, a paper empty sensor may detect the empty paper. . In this case, the feeding operation of the next sheet is started in the sheet feeding device, but the next sheet is not conveyed downstream from the sheet feeding unit, so the image forming apparatus erroneously detects a jam. There is a problem that the error stops.

  On the other hand, in order to prevent an error stop of the image forming apparatus, even when the paper feeding device is continuously feeding, the paper is not empty by the paper empty sensor after the pickup roller feeds the previous paper. It is necessary to start the feeding operation of the next sheet after the above is confirmed. Therefore, in this case, there is a problem that the interval between the feeding of the previous sheet and the feeding of the next sheet becomes large, and the productivity of the print job in the image forming apparatus cannot be improved. .

  Accordingly, the present invention has been made for the purpose of solving the above-described conventional problems, and prevents an error stop when it is detected that a sheet is empty after starting the next sheet feeding operation. In addition, the present invention provides a paper feeding device and an image forming apparatus that can improve productivity.

  In order to achieve the above object, according to a first aspect of the present invention, in a paper feeding device, a paper feeding mechanism feeds and feeds the paper stored in the paper feeding unit one by one; Control means for controlling the paper feeding operation, paper empty detecting means for detecting that the paper in the paper feeding section is empty, and detecting that the remaining amount of paper in the paper feeding section has decreased below a predetermined amount Paper near empty detection means, and when the paper near empty detection means detects a decrease in the remaining amount of paper, the control means starts feeding the previous paper and then the paper After the timing at which it can be confirmed that the paper in the paper feeding unit is not empty based on the output from the empty detection means, the paper supply of the next paper is started, and the paper near empty detection means If the decrease is not detected, the paper near empty detection means is characterized in that to start the next sheet of paper feed at a timing earlier than when detecting the decrease of the residual paper.

  According to such a configuration, when the paper near empty detecting means detects a decrease in the remaining amount of paper, it is checked whether or not the paper in the paper feeding unit is empty before starting the paper feeding of the next paper. Therefore, it is possible to prevent an error stop when the paper becomes empty. Further, when the paper near empty detection means does not detect a decrease in the remaining amount of paper, the paper interval between the previous paper and the next paper can be reduced, so that continuous paper feeding can be performed, thereby improving productivity. Can do.

  According to a second aspect of the present invention, in the paper feeding device according to the first aspect, when the paper near empty detecting means does not detect a decrease in the remaining amount of paper, the control means supplies the previous paper. The feeding of the next sheet is started before the timing at which it can be confirmed that the sheet in the sheet feeding unit is not empty based on the output from the sheet empty detecting means after the sheet is started.

  According to such a configuration, it is possible to sufficiently reduce the sheet interval when the sheet near empty detecting unit does not detect a decrease in the remaining amount of the sheet, and the productivity can be further improved.

According to a third aspect of the present invention, in the paper feeding device according to the first or second aspect, the rear end of the paper is the paper empty after the transport mechanism starts feeding the paper in the paper feeding unit. The time until the detection unit passes the detection position is defined as Te, and the control unit outputs the paper in the paper feeding unit based on the output from the paper empty detection unit after the trailing edge of the paper passes the detection position. When Tr is the time required to confirm that the paper is empty, the control unit starts feeding the previous paper when the paper near empty detection unit detects a decrease in the remaining amount of paper. Feed interval Tpne from the start of feeding the next sheet to
Te + Tr <Tpne <(Te + Tr) × 2
Set within the range.

According to a fourth aspect of the present invention, in the paper feeding device according to the third aspect, the control means feeds the previous paper when the paper near empty detecting means does not detect a decrease in the remaining amount of paper. The paper feed interval Tp from the start to the start of feeding the next paper is
Tp <Te + Tr
Set within the range.

  According to a fifth aspect of the present invention, in the paper feeding device according to the fourth aspect of the present invention, the paper feeding device further comprises storage means for storing the paper feeding intervals Tpne and Tp. Is detected, the paper feed interval Tpne is read from the storage means to set the paper feed interval, and the paper near empty detection means has not detected a decrease in the remaining amount of paper. Reads the paper feed interval Tp from the storage means and sets the paper feed interval.

  According to such a configuration, the control unit reads the paper feed interval from the storage unit according to the detection result of the remaining amount of paper by the paper near empty detection unit, thereby setting the paper feed interval for continuous paper feeding. Can do.

  According to a sixth aspect of the present invention, in the paper feeding device according to any one of the first to fourth aspects, the control unit starts feeding the paper in the paper feeding unit. It takes until the trailing edge of the paper passes the detection position by the paper empty detection means, and the control means confirms that the paper in the paper feed unit is empty based on the output from the paper empty detection means. The paper feeding interval from the start of feeding the previous paper to the start of feeding the next paper when the time is measured and the paper near empty detection means detects a decrease in the remaining amount of paper Is set to a time longer than the measurement time by the measurement.

  According to such a configuration, the paper feed interval when the paper near empty detecting means detects a decrease in the remaining amount of paper can be set based on the measured result. A suitable paper feed interval can be set.

  According to a seventh aspect of the present invention, in the paper feeding device according to the sixth aspect of the present invention, the paper feeding device further includes a storage unit that stores a paper feeding interval set to a time longer than the measurement time, and the control unit includes the paper near When the empty detection means detects a decrease in the remaining amount of paper, the paper feed interval is read from the storage means and the paper feed interval is set.

  According to this configuration, by reading the paper feed interval stored in the storage unit, the paper feed interval when the paper near empty detecting unit detects a decrease in the remaining amount of paper is set based on the measured result. can do.

  According to an eighth aspect of the present invention, in the paper feeding device according to the seventh aspect, the storage unit is configured to measure and set a paper feeding interval for each type or size of paper stored in the paper feeding unit. When the paper near empty detecting means detects a decrease in the remaining amount of paper, the control means feeds paper corresponding to the type or size of the paper contained in the paper feed. The interval is read from the storage means to set the sheet feeding interval.

  According to such a configuration, it is possible to set the paper feed interval when the paper near empty detecting means detects a decrease in the remaining amount of paper based on the result of measurement for each paper type or each size. For example, it is possible to set an optimum sheet feeding interval for the sheet actually used by the user.

  According to a ninth aspect of the present invention, in the paper feeding device according to the first or second aspect, when the paper near empty detecting means detects a decrease in the remaining amount of paper, the control means detects the previous paper. Then, after confirming that the paper in the paper feeding unit is not empty based on the output from the paper empty detecting means, the paper feeding of the next paper is started.

  According to such a configuration, when the paper near empty detecting means detects a decrease in the remaining amount of paper, after actually confirming that the paper in the paper feeding unit is not empty after starting feeding the previous paper Since the feeding of the next sheet is started, the sheet feeding operation is not performed when the sheet is empty, and an error stop when the sheet becomes empty can be prevented. Also, in this case, the paper feed interval Tpne from the start of feeding the previous paper to the start of feeding the next paper when the paper near empty detecting means detects a decrease in the remaining amount of paper. There is no need to set in advance.

  According to a tenth aspect of the present invention, there is provided an image forming apparatus for forming an image on the paper feeding device according to any one of the first to ninth aspects and a paper fed by the paper feeding device. And an image forming means for performing.

  According to such a configuration, the sheet feeding operation is not performed when the sheet is empty, the error stop in the image forming apparatus can be prevented in advance, and the productivity when performing a print job is improved.

  According to the paper feeding device and the image forming apparatus according to the present invention, when the paper near empty detecting unit detects a decrease in the remaining amount of paper, the paper feeding unit before starting the feeding of the next paper. Since it is possible to check whether or not the sheet is empty, the feeding operation for the next sheet is not started when the sheet is empty. Therefore, it is possible to prevent an error stop due to an erroneous detection of a jam. If the paper near empty detection means does not detect a decrease in the remaining amount of paper, the paper feeding interval between the previous paper and the next paper is reduced, so that continuous paper feeding can be performed at short paper intervals. Productivity can be improved.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected about the member which is mutually common in some embodiment demonstrated below, and the description which repeats about them is abbreviate | omitted.

(First embodiment)
FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 is an apparatus called a so-called multifunction machine or MFP, and includes a plurality of functions such as a copy, a network printer, a scanner, and a FAX. The image forming apparatus 1 includes a paper feeding device 2 at a lower portion thereof, and an image forming unit 3 is provided at an upper portion of the paper feeding device 2. The sheet feeding device 2 and the image forming unit 3 function when a print job is executed in the image forming device 1, that is, when an image is formed on a sheet by a copy function, a printer function, a FAX function, etc. The apparatus 2 supplies sheets one by one to the image forming unit 3, and the image forming unit 3 forms an image by transferring a toner image onto the sheet. The paper on which the image has been formed is sequentially discharged to the discharge unit 5 through the discharge port 4 provided on the upper part of the image forming unit 3. An operation panel 6 that can be operated by the user is provided on the front side of the image forming apparatus 1, and the user inputs various instructions to the image forming apparatus 1 by operating the operation panel 6. can do. As shown in FIG. 1, the paper feeding device 2 has a plurality of paper feeding units 2a, 2b, 2c, and 2d that are assembled vertically. The plurality of paper feeding units 2a, 2b, 2c, and 2d can be pulled out to the front side of the image forming apparatus 1 to set different types of paper and different sizes of paper. Although not shown, the paper feeding device 2 may be configured to include a manual paper feeding unit that feeds sheets set manually from the side surface of the image forming apparatus 1 to the image forming unit 3 one by one.

  FIG. 2 is a diagram illustrating an overall schematic configuration of the sheet feeding device 2. As shown in FIG. 2, each of the plurality of sheet feeding units 2 a, 2 b, 2 c, and 2 d includes a sheet storage unit 20 that stores and holds a plurality of stacked sheets 9, and the remaining amount of sheets in the sheet storage unit 20. Is a sheet near empty detection sensor 21 that detects that the amount of ink has decreased below a predetermined amount (that is, sheet near empty), and a pickup roller 22 that is provided in contact with the uppermost sheet 9 accommodated in the sheet accommodating unit 20. The paper empty detection sensor 23 for detecting that the paper in the paper storage unit 20 is empty (that is, paper empty) and the paper 9 fed by the pickup roller 22 are further downstream along the paper transport path 8. And a paper feed sensor 25 for detecting the paper 9 fed by the paper feed roller 24.

  The paper near empty detection sensor 21 is configured by, for example, a photoelectric sensor, and is provided at a predetermined position on the side surface of the paper storage unit 20. The paper near empty detection sensor 21 outputs a signal indicating that the remaining amount of paper is greater than a predetermined amount when the stack height of the paper 9 in the paper storage unit 20 is higher than the predetermined height. Is lower, a signal indicating that the remaining amount of paper has decreased below a predetermined amount is output. The paper near empty detection sensor 21 only needs to be able to output these signals in accordance with the remaining amount of paper, and the configuration is not limited to that described above.

  The pickup roller 22 operates in response to an instruction to start feeding, and feeds the paper 9 in the paper storage unit 20 toward the paper feeding roller 24. When the pickup roller 22 operates, the uppermost sheet 9 accommodated in the sheet accommodating unit 20 moves toward the downstream side in the transport direction F. At this time, the uppermost sheet 9 and the sheet below it may move downstream in the transport direction. Therefore, even when two or more sheets arrive by the sheet feeding operation of the pickup roller 22, the sheet feeding roller 24 has a function of feeding only one sheet 9 on the uppermost surface thereof to the downstream side. is doing.

  The paper empty detection sensor 23 is provided at a position near the pickup roller 22 or at a predetermined position downstream of the pickup roller 22 in the paper transport direction. In the illustrated example, the paper empty detection sensor 23 is installed on the downstream side of the pickup roller 22. By providing the paper empty detection sensor 23 in the vicinity of the pickup roller 22 or on the downstream side of the pickup roller 22, when the user sets the paper in each of the paper feeding units 2a, 2b, 2c, 2d, the pickup roller 22 is erroneously set. Even if the paper is set upstream of the paper, the paper empty detection sensor 23 does not detect “paper is present”, so that the feeding operation of the pickup roller 22 can be prevented from being started in this state. .

  FIGS. 3A and 3B are diagrams illustrating a configuration example of the paper empty detection sensor 23. FIG. 3A illustrates a case of “paper present”, and FIG. 3B illustrates a case of “no paper”. FIG. 3 is a view of the sheet feeding unit as viewed from the downstream side in the sheet conveyance direction. The paper empty detection sensor 23 is provided at a shaft portion 31 provided on the upper portion of the paper storage portion 20, a support member 32 pivotally supported by the shaft portion 31, and a tip of the support member 32. The shielding member 33 includes a light projecting unit 35 and a light receiving unit 36 that are arranged with a movement path of the shielding member 33 associated with the rotation of the support member 32 interposed therebetween. In addition, the support member 32 and the shielding member 33 are comprised with the lightweight member. In addition, an opening 20 b is formed in the bottom 20 a of the paper storage unit 20 so as to open a portion corresponding to the rotational position of the support member 32 of the paper empty detection sensor 23. Therefore, when the sheet 9 remains in the sheet storage unit 20, the tip of the support member 32 is in contact with the uppermost sheet 9, and the shielding member 33 projects light as shown in FIG. Since it is located between the part 35 and the light receiving part 36, the light from the light projecting part 35 is shielded by the shielding plate 33 and does not reach the light receiving part 36. On the other hand, when the paper in the paper storage unit 20 becomes empty, the tip of the support member 32 falls into the opening 20b provided in the bottom 20a of the paper storage unit 20, and the shielding member 33 is moved as shown in FIG. Since the light exits from between the light projecting unit 35 and the light receiving unit 36, the light from the light projecting unit 35 reaches the light receiving unit 36, and the sensor is turned on. Thus, the paper empty detection sensor 23 is configured to output a signal indicating “no paper” when the paper in the paper storage unit 20 becomes empty. The paper empty detection sensor 23 is not limited to the one shown in FIG. 3 as long as it can output a signal indicating “no paper” when the paper in the paper storage unit 20 becomes empty.

  Returning to FIG. 2, a conveyance roller 26 is provided on the downstream side of the plurality of paper feeding units 2 a, 2 b, 2 c, 2 d, and a sheet conveyed by the conveyance roller 26 at a predetermined position downstream of the conveyance roller 26. A transport sensor 27 for detecting 9 is provided. In the present embodiment, the sheet 9 is fed from the sheet feeding device 2 by the pickup roller 22 and the sheet feeding roller 24 provided in each sheet feeding unit 2 a, 2 b, 2 c, 2 d and the conveyance roller 26 provided in the conveyance path 8. A conveyance mechanism unit that conveys one sheet at a time and supplies the image formation unit 3 is configured. Further, the paper feeding device 2 is provided with a controller 10 for controlling the transport operation by the transport mechanism. The controller 10 selects one sheet feeding unit from among the plurality of sheet feeding units 2a, 2b, 2c, and 2d according to the type and size of the sheet specified by the user, and images from the selected sheet feeding unit. Control is performed to convey sheets one by one toward the forming unit 3.

  FIG. 4 is a block diagram illustrating a control mechanism of the sheet feeding device 2. In FIG. 4, for convenience of explanation, a control mechanism based on the relationship between one paper feeding unit 2 a and the controller 10 is shown, but a control mechanism based on the relationship between the other paper feeding units 2 b, 2 c, 2 d and the controller 10. The configuration is the same for. In FIG. 4, the conveyance path 8 is schematically shown in a straight line. As shown in FIG. 4, the sheet feeding device 2 includes a sheet feeding motor 15 that drives the pickup roller 22 and the sheet feeding roller 24, and a conveyance motor 16 that drives the conveyance roller 26. The controller 10 controls the paper feeding operation in the paper feeding device 2 by controlling the paper feeding motor 15 and the transport motor 16. The controller 10 includes a CPU 11 and a memory 12. The CPU 11 is a control unit that controls each unit by executing a predetermined program, and the memory 12 is a storage unit that stores a program executed by the CPU 11 and various data. A paper near empty detection sensor 21, a paper empty detection sensor 23, a paper feed sensor 25, and a transport sensor 27 are connected to the controller 10, and the outputs of these sensors are input to the controller 10. When executing a print job in the image forming apparatus 1, the controller 10 is configured to receive a paper feed instruction from a control unit that controls the overall operation of the image forming apparatus 1, for example.

  When the controller 10 receives a paper feed instruction, it drives the paper feed motor 15 to rotate the pickup roller 22 and the paper feed roller 24. As a result, the pickup roller 22 sends out the uppermost sheet 9 of the sheets stored in the sheet feeding unit 2 a in the transport direction F. At this time, even if two or more sheets are fed toward the sheet feed roller 24, the sheet lower than the uppermost sheet is rolled by the sheet feed roller 24, so that only the uppermost sheet 9 is transferred to the sheet feed roller 24. 24 is transported downstream. The leading end of the sheet 9 fed from the sheet feeding roller 24 is detected by a sheet feeding sensor 25 at a predetermined position downstream of the sheet feeding roller 24.

  When the timing at which the paper feed sensor 25 detects the leading edge of the paper is earlier than the predetermined timing, the controller 10 reduces the conveyance speed of the paper 9 by reducing the rotational speed of the paper feed roller 24, and the paper 9 is adjusted so that the timing at which the tip of 9 reaches the conveyance sensor 27 becomes a predetermined timing. That is, in the case of continuous paper feeding, the paper feeding device 2 performs a paper feeding operation so as to continuously feed paper at as short a paper interval as possible, but the next paper collides with the preceding paper. If the timing at which the leading edge of the next sheet is detected by the paper feed sensor 25 is early, the trailing edge of the preceding sheet and the leading edge of the next sheet are reduced by reducing the sheet conveyance speed. Control for ensuring the sheet interval is performed.

  The controller 10 rotates the transport motor 16 at a predetermined rotational speed until the leading edge of the paper 9 reaches the transport roller 26. When the leading edge of the paper 9 reaches the transport roller 26, the transport roller 26 9 is sent further downstream. The leading edge of the sheet 9 fed from the transport roller 26 is detected by a transport sensor 27 at a predetermined position downstream of the transport roller 26.

  When the transport sensor 27 detects the leading edge of the paper, the controller 10 temporarily stops the paper feed motor 15. Thereafter, the sheet 9 is transported by the transport roller 26. Note that a one-way clutch (not shown) is mounted on the rotational drive mechanism of the pickup roller 22 and the paper feed roller 24, and the pickup roller 22 and the paper feed roller 24 are driven as the paper 9 is moved by the transport roller 26. When the trailing edge of the sheet 9 passes through the respective positions of the pickup roller 22 and the sheet feeding roller 24, the follow-up stops. Then, at the timing of feeding the next sheet, the controller 10 drives the sheet feeding motor 15 again and rotates the pickup roller 22 and the sheet feeding roller 24 to perform continuous sheet feeding from the sheet feeding unit 2a.

  Next, a paper feed timing when continuous paper feeding is performed in the paper feeding device 2 of the present embodiment will be described. As described above, the paper feeder 2 detects that the paper near empty detection sensor 21 that detects that the remaining amount of paper in the paper feeder 2a has decreased below a predetermined amount, and that the paper in the paper container 20 has become empty. A paper empty detection sensor 23 is provided. The paper empty detection sensor 23 detects “no paper” when the paper near empty detection sensor 21 detects a decrease in the remaining amount of paper. In other words, when the paper near empty detection sensor 21 detects that more paper than the predetermined amount remains, the paper empty detection sensor 23 does not detect “no paper”.

  When the paper near empty detection sensor 21 detects a decrease in the remaining amount of paper, the paper empty detection sensor 23 detects “no paper” when the pickup paper 22 feeds the last paper 9. This is the timing when the trailing edge of the sheet 9 has passed the position of the sheet empty detection sensor 23 after being started. Also, after the paper empty detection sensor 23 detects “no paper”, it takes a certain processing time until the controller 10 inputs the signal and recognizes that the paper in the paper feed unit has become empty. That is, a certain time is required until the controller 10 recognizes “no paper” after the paper feeding device 2 starts feeding paper from the paper feeding unit 2a.

  Thus, in the present embodiment, when the paper near empty detection sensor 21 detects a decrease in the remaining amount of paper in the continuous paper feeding of the paper feeding device 2, the controller 10 starts feeding the previous paper, The feeding of the next sheet is started after the timing at which it can be confirmed that the sheet in the sheet feeding unit is not empty based on the output from the sheet empty detection sensor 23.

  FIG. 5 is an operation diagram showing a paper transport locus when continuous paper feeding is performed in a state in which the remaining amount of paper is less than a predetermined amount, with the horizontal axis along time and the vertical axis along the transport path 8. It is assumed that the position. Note that the operation lines PA1, PA2, PB1, and PB2 indicated by solid lines in the drawing indicate the locus of the leading edge of the paper. Among these, the operation lines PA1 and PA2 indicate the leading edge of the previous sheet, and the operation lines PB1 and PB2 indicate the next sheet. Shows the tip. In addition, an operation line PA3 indicated by a broken line in the drawing indicates the locus of the trailing edge of the previous sheet.

  The leading end position of the paper 9 that is started to be fed by the pickup roller 22 varies within the range of the distance D shown in FIG. For this reason, when the pickup roller 22 starts feeding the previous sheet at time T1, the leading edge of the sheet that reaches the sheet feeding sensor 25 first follows the operation line PA1 in FIG. Further, the leading edge of the paper when it reaches the paper feed sensor 25 latest follows the operation line PA2 in FIG. Therefore, when the previous sheet is fed, the leading edge of the sheet becomes an operation line passing through any position between the operation lines PA1 and PA2. The same applies to the relationship between the operation lines PB1 and PB2 at the leading edge of the next sheet. Further, the conveyance control is performed so that the operation lines PA1 and PA2 and the operations PB1 and PB2 become one operation line further downstream of the conveyance path 8, respectively.

  As shown in FIG. 5, when feeding of the previous sheet is started at time T1, it takes time Te until the trailing edge of the sheet passes the position of the sheet empty detection sensor 23. Note that when the trailing edge of the sheet passes the position of the sheet empty detection sensor 23, the variation in the initial position of the sheet has already been eliminated by the above-described transport control. The time Te passing through the position of the sensor 23 is substantially constant. Also, it takes time until the controller 10 recognizes that the paper in the paper feed unit 2a is empty based on the output from the paper empty detection sensor 23 after the trailing edge of the paper passes the position of the paper empty detection sensor 23. If Tr is required, the timing at which the controller 10 can confirm whether or not the paper in the paper feed unit 2a is empty is time TC shown in FIG.

  For this reason, when it is detected by the paper near empty detection sensor 21 that the remaining amount of paper has decreased below a predetermined amount, the controller 10 detects the paper in the paper feed section at time T2 when the next paper starts to be fed. Is set after the time TC at which it can be confirmed whether or not is empty. Thus, the controller 10 can start feeding the next sheet after confirming whether or not the next sheet remains in the sheet feeding unit 2a after feeding the previous sheet. Then, the controller 10 starts feeding the next sheet at time T2 if the next sheet remains in the sheet feeding unit, and if the next sheet does not remain in the sheet feeding unit, the controller 10 The paper feeding operation is stopped without starting the paper feeding operation. Therefore, when the sheet remains in the sheet feeding unit 2a, the next sheet can be reliably conveyed to the downstream side of the sheet feeding unit 2a, and when the sheet does not remain in the sheet feeding unit 2a, the sheet can be fed. Since the paper operation is not started, the image forming apparatus 1 does not erroneously detect a jam, and the error stop of the image forming apparatus 1 can be prevented.

  Here, as shown in FIG. 5, assuming that the paper feed interval when the remaining amount of paper is less than the predetermined amount is Tpne, the paper feed interval Tpne is set within the range of Te + Tr <Tpne <(Te + Tr) × 2. It is preferable to do. In this case, the lower limit value of the paper feed interval Tpne is the time Te from the start of feeding the previous paper until the rear edge of the paper passes the position of the paper empty detection sensor 23, and the rear edge of the paper. Can be determined by the time Tr required for the controller 10 to confirm that the paper in the paper feeding unit is empty based on the output from the paper empty detection sensor 23 after the position of the paper empty detection sensor 23 passes. . On the other hand, if the paper feed interval Tpne is larger than necessary, the paper interval between the previous paper and the next paper will be excessively widened. Since the life of each part may be adversely affected, the upper limit value of the paper feed interval Tpne is set to (Te + Tr) × 2 in order to prevent this.

  On the other hand, as described above, when the sheet near empty detection sensor 21 detects that more sheets than the predetermined amount remain, the sheet empty detection sensor 23 does not detect “no sheet”. . Therefore, in this case, if the sheet feeding operation is performed, the next sheet can always be transported to the downstream side of the sheet feeding unit 2a, so there is no possibility that the image forming apparatus 1 erroneously detects a jam.

  Therefore, in this embodiment, when the paper near empty detection sensor 21 does not detect a decrease in the remaining amount of paper in the continuous feeding of the sheet feeding device 2, the controller 10 determines that the paper near empty detection sensor 21 decreases the remaining amount of paper. The feeding of the next sheet is started at an earlier timing than when the image is detected.

  FIG. 6 is an operation diagram illustrating a paper transport locus when continuous paper feeding is performed in a state where the remaining amount of paper is not decreasing. In FIG. 6, the same components as those in FIG. In the present embodiment, as shown in FIG. 6, when it is not detected by the paper near empty detection sensor 21 that the remaining amount of paper is less than a predetermined amount, the time T <b> 2 for starting feeding the next sheet is The time is set before the time TC when the controller 10 can confirm whether or not the paper in the paper feeding unit is empty. Therefore, after feeding the previous paper, the controller 10 starts feeding the next paper before it can be confirmed whether or not the next paper remains in the paper feed unit. Therefore, in this case, the paper feed interval from feeding the previous paper to feeding the next paper is shortened. Since the interval between the previous sheet and the next sheet is also shortened, the productivity of the print job in the image forming apparatus 1 can be improved.

  Here, as shown in FIG. 6, when the paper feed interval when the remaining amount of paper has not decreased below the predetermined amount is Tp, the paper feed interval Tp is preferably set in a range of Tp <Te + Tr. As a result, feeding of the next sheet can be started at an earlier timing than when the sheet near empty detection sensor 21 detects a decrease in the remaining amount of the sheet, and the productivity of the print job can be improved. . If the paper feed interval Tp is set to a value smaller than necessary, the occurrence frequency of jam increases due to the overlap between the previous paper and the next paper, so that the previous paper does not overlap with the next paper. It is preferable to set an appropriate value.

  In this embodiment, the memory 12 previously stores the paper feed interval Tpne when the remaining amount of paper is less than the predetermined amount and Tp when the paper remaining amount is not less than the predetermined amount. I remember it. Then, the controller 10 reads the paper feed interval Tp or Tpne from the memory 12 according to the amount of remaining paper detected by the paper near empty detection sensor 21, sets the read paper feed interval, and performs continuous paper feed. To control.

  FIG. 7 is a flowchart illustrating an example of a processing procedure performed by the controller 10. This process starts when the controller 10 receives a paper feed instruction when a print job is executed in the image forming apparatus 1. First, the controller 10 monitors the output of the paper empty detection sensor 23 and determines whether or not the paper in the designated paper feeding unit (for example, the paper feeding unit 2a) is empty (that is, whether or not the paper is empty). Is determined (step S10). If the designated paper feed unit 2a is empty, the result of step S10 is YES, and the paper feed operation is stopped without starting paper feed (step S19). On the other hand, if the designated paper feed unit 2a is not empty (NO in step S10), the controller 10 next monitors the output of the paper near empty detection sensor 21 and the remaining paper amount of the designated paper feed unit 2a. Is determined to be less than a predetermined amount (that is, whether or not the paper is near empty) (step S11).

  If the remaining amount of paper has not decreased below the predetermined amount (NO in step S11), the controller 10 reads the paper feed interval Tp from the memory 12, and starts feeding from the paper feed unit 2a at the paper feed interval Tp. (Step S12). As a result, the sheet feeding device 2 starts continuous sheet feeding at the sheet feeding interval Tp, and repeats the operation to start feeding the next sheet when the sheet feeding interval Tp elapses from the timing at which the previous sheet is started. When paper feeding is started in step S12, the controller 10 feeds the next paper after feeding the previous paper and before checking whether the next paper remains in the paper feeding unit. Therefore, continuous paper feeding is performed in a state where the paper interval between the previous paper and the next paper is sufficiently small. Therefore, in this case, the productivity of the print job in the image forming apparatus 1 can be improved.

  The controller 10 appropriately monitors the output of the paper near empty detection sensor 21 even when continuous paper feeding is performed at the paper feeding interval Tp, and whether or not the remaining amount of paper in the paper feeding unit 2a has decreased below a predetermined amount. (That is, whether or not paper near empty has been reached) (step S13). As long as the paper near empty detection sensor 21 does not detect a decrease in the remaining amount of paper, NO is determined in step S13, and the paper feeding operation at the paper feeding interval Tp is repeated until the continuous paper feeding is completed (NO in step S14). When the continuous sheet feeding ends, the process ends (YES in step S14).

  On the other hand, if the remaining amount of paper is less than the predetermined amount in step S11, it is determined as YES and the process proceeds to step S15. The controller 10 reads the paper feed interval Tpne from the memory 12, and starts paper feed at the paper feed interval Tpne (step S15).

  If it is detected in step S13 that the remaining amount of paper has decreased below the predetermined amount, it is determined YES and the process proceeds to step S16. The controller 10 reads the paper feed interval Tpne from the memory 12, and changes the setting of the paper feed interval during continuous paper feed from the previous interval Tp to Tpne (step S16). Therefore, thereafter, the paper feed interval in the paper feeder 2 is changed to Tpne.

  Through steps S15 and S16, the sheet feeding device 2 starts continuous sheet feeding at the sheet feeding interval Tpne, and when the sheet feeding interval Tpne elapses from the timing at which feeding of the previous sheet starts, feeding the next sheet. Repeat the operation to start. In this case, after feeding the previous paper, the controller 10 checks whether or not the next paper remains in the paper feed unit after the paper feed time Tpne has elapsed, and then starts feeding the next paper. Therefore, continuous paper feeding is performed in a state where the paper interval between the previous paper and the next paper is slightly large.

  The controller 10 feeds paper based on the output from the paper empty detection sensor 23 when the paper feed interval Tpne elapses after feeding the previous paper when continuous feeding is performed at the paper feed interval Tpne. It is determined whether or not the sheet of the section 2a has become empty (that is, whether or not the sheet has become empty) (step S17). As long as the paper empty detection sensor 23 does not detect “no paper”, NO is determined in step S17, and the paper feeding operation at the paper feeding interval Tpne is repeated until the continuous paper feeding is completed (NO in step S18). When the continuous paper feeding is finished, the process is finished (YES in step S18).

  If the paper empty detection sensor 23 detects “no paper”, the determination in step S17 is YES, and the controller 10 stops the paper feeding operation without starting the paper feeding operation for the next paper (step S19). If NO is determined in step S17, if other types of papers of the same type and size as the paper feed unit 2a are stored in the other paper feed units 2b, 2c, and 2d, the paper feed unit that feeds paper is fed. The continuous feeding can be continued by switching from the unit 2a to another sheet feeding unit.

  In the above description, the case where continuous paper feeding is mainly performed from the paper feeding unit 2a is illustrated, but the same applies to the case where continuous paper feeding is performed from the other paper feeding units 2b, 2c, and 2d.

  As described above, in the paper feeding device 2 according to the present embodiment, when the paper near empty detection sensor 21 detects a decrease in the remaining amount of paper, the paper empty detection is performed after feeding of the previous paper is started. When the next sheet is fed after the timing (time TC) at which it can be confirmed that the sheet in the sheet feeding unit is not empty based on the output from the sensor 23. In addition, it is possible to prevent the error of the image forming apparatus 1 from being stopped.

  When the paper near empty detection sensor 21 does not detect a decrease in the remaining amount of paper, the next paper is fed at an earlier timing than when the paper near empty detection sensor 21 detects a decrease in the remaining amount of paper. Since the paper is started, the paper interval from feeding the previous paper to feeding the next paper can be shortened, and the productivity of the print job in the image forming apparatus 1 can be improved. In this case, in particular, the feeding of the next sheet is started before the timing (time TC) at which it can be confirmed that the sheet in the sheet feeding unit is not empty after the feeding of the preceding sheet is started. By doing so, the sheet interval can be made sufficiently small, so that the productivity can be further improved.

(Second Embodiment)
Next, a second embodiment will be described. When the remaining amount of paper is less than the predetermined amount, the feed interval Tpne may be a fixed value and the control described in the first embodiment may be performed. More than the required time Ts (Ts = Te + Tr) from the start timing (time T1 in FIG. 5) to the timing (time TC in FIG. 5) at which the controller 10 can confirm that the paper in the paper feed unit is empty. If the value is set too large, the productivity of the print job will decrease. Therefore, it is preferable to set the paper feed interval Tpne to a value that is slightly larger than the time Ts. However, since the required time Ts from the start of paper feeding to the time when it can be confirmed that the paper in the paper feeding unit is empty varies depending on the paper actually used by the user, When the paper feed interval Tpne is set to a fixed value, it is necessary to set a paper feed interval having a certain margin in advance in consideration of variations in the required time Ts, and the productivity of the print job is reduced to some extent. Inevitable.

  Therefore, in the present embodiment, in order to minimize the decrease in productivity when the remaining amount of paper is less than the predetermined amount, the paper feeding is started after starting the paper feeding separately from the mode in which the print job is executed. A measurement mode for measuring the time Ts until it can be confirmed that the paper in the paper section is empty is prepared, and the measurement mode is executed in the image forming apparatus 1 so that the actually measured required time Ts is obtained. Based on this, the optimum paper feed interval Tpne is set. In this embodiment, the configurations of the image forming apparatus 1 and the paper feeding apparatus 2 are the same as those described in the first embodiment.

  FIG. 8 is a view of the operation panel 6 of the image forming apparatus 1 as viewed from the front side. As shown in FIG. 8, the operation panel 6 includes a display unit 6a configured by, for example, a touch panel type liquid crystal display device, and a plurality of operation buttons are provided around the display unit 6a. The plurality of operation buttons include a measurement button B1 for instructing the image forming apparatus 1 to execute the measurement mode, and a start key B2 for instructing the image forming apparatus 1 to start job execution. When the user operates the measurement button B1, the measurement mode is started in the image forming apparatus 1, and a procedure for measuring the required time Ts is displayed on the display unit 6a of the operation panel 6 as shown in FIG.

  In the measurement mode, the paper empty detection sensor 23 detects “no paper” after the paper feeding unit (for example, the paper feeding unit 2a) starts feeding the last paper, and the controller 10 further detects the paper in the paper feeding unit 2a. Since the time Ts required for recognizing that the printer has become empty is measured, it is necessary to set only one sheet in advance in the paper feed unit 2a before actually starting the measurement. . Therefore, after the user operates the measurement button B1, according to the procedure displayed on the display unit 6a, the user sets only one sheet in the sheet feeding unit 2a and operates the start key B2 when the setting is completed. Instruct the start of measurement. Before operating the start key B2, it is preferable to select a paper feed unit for measurement and to specify the size and type of paper to be measured. When the user operates the start key B2 to instruct the start of measurement in the measurement mode, the controller 10 of the sheet feeding device 2 starts the sheet feeding operation and starts measuring the time Ts.

  FIG. 9 is a flowchart illustrating an example of a processing procedure of the controller 10 in the measurement mode. When the measurement mode is entered, the controller 10 does not perform the paper feeding operation until the user operates the start key B2, and waits until the start key B2 is operated (step S20). When it is detected that the start key B2 has been operated (YES in step S20), the pickup roller 22 of the paper feed unit 2a is driven to feed the last sheet of paper set in the paper feed unit 2a. Start (step S21), and start time measurement with it (step S22). The controller 10 monitors the output of the paper empty detection sensor 23 and waits until it is confirmed that the paper in the paper supply unit 2a is empty (that is, paper empty) (step S23). The paper empty detection sensor 23 is turned on when the trailing edge of the last paper fed by the pickup roller 22 passes, and outputs a signal indicating “no paper” to the controller 10. Then, the controller 10 recognizes that the paper in the paper feeding unit 2a has become empty after a predetermined processing time has elapsed since the signal indicating "no paper" is input from the paper empty detection sensor 23. When the controller 10 detects that the sheet is empty (YES in step S23), the controller 10 ends the time measurement started in step S22 (step S24). Thereby, the measurement time Ts is determined.

  Based on the measurement time Ts, the controller 10 calculates an optimum paper feed interval Tpne when the remaining amount of paper is less than a predetermined amount (step S25). Specifically, the paper feed interval Tpne is calculated by calculating the paper feed interval Tpne = measurement time Ts + ΔT (where ΔT> 0). Here, by setting ΔT to a minimum value, the value of the paper feed interval Tpne can be determined to an optimum value that matches the paper actually used by the user.

  Then, the controller 10 registers the paper feed interval Tpne calculated in step S25 in the paper feed interval storage table and stores it in the memory 12 (step S26). Thus, the process in the measurement mode ends. After that, when the print job is executed in the image forming apparatus 1, if the remaining amount of paper is less than the predetermined amount, the controller 10 calculates the paper feed interval Tpne calculated based on the measurement time Ts from the paper feed interval storage table of the memory 12. Is read and set, continuous feeding can be performed at an optimum feeding interval according to the sheet used by the user, and a decrease in productivity can be minimized.

  Next, a processing procedure different from that in FIG. 9 will be described. In the processing procedure shown in FIG. 9, the number of times Ts from the start of paper feeding to the time when it can be confirmed that the paper in the paper feeding unit is empty is one. You may make it perform measurement of times. FIG. 10 is a flowchart illustrating an example of a processing procedure of the controller 10 when measuring a plurality of times in the measurement mode. The user sets only one sheet in the sheet feeding unit 2a, and operates the start key B2 when the setting is completed. The controller 10 does not perform the paper feeding operation until the user operates the start key B2, and waits until the start key B2 is operated (step S30). When it is detected that the start key B2 has been operated (YES in step S30), the pickup roller 22 of the paper feed unit 2a is driven to feed the last sheet of paper set in the paper feed unit 2a. Start (step S31), and start time measurement with it (step S32). The controller 10 monitors the output of the paper empty detection sensor 23 and waits until it is confirmed that the paper in the paper supply unit 2a is empty (that is, paper empty) (step S33). (YES in step S33), the time measurement started in step S32 is terminated (step S34). Thereby, the measurement time Ts is determined. The controller 10 temporarily stores the determined measurement time Ts in the memory 12 (step S35).

  Then, the controller 10 determines whether or not the user has instructed the measurement to be continued (step S36). If the measurement is instructed to continue, the controller 10 returns to step S30. Then, the user sets only one sheet again on the sheet portion 2a, and operates the start key B2 when the setting is completed. Thereafter, the processes in steps S30 to S36 are repeatedly performed, and the time Ts from the start of paper feeding until the paper in the paper feeding unit can be confirmed to be empty is measured a plurality of times. The measurement time Ts is stored in the memory 12.

  When the user instructs the end of measurement in step S36, the process proceeds to step S37, where the controller 10 reads all the measurement times Ts from the memory 12, and calculates the average value of a plurality of measurement times Ts (step S38). Moreover, the process of step S38 is good also as a process which selects the maximum value of the measurement time Ts of multiple times. Then, the controller 10 calculates an optimum paper feed interval Tpne when the remaining amount of paper is less than a predetermined amount based on the average value or the maximum value of the measurement time Ts (step S39). Specifically, the paper feed interval Tpne is calculated by calculating the paper feed interval Tpne = measurement time Ts (average value or maximum value) + ΔT (where ΔT> 0). Here, by setting ΔT to a minimum value, the value of the paper feed interval Tpne can be determined to an optimum value that matches the paper actually used by the user.

  Then, the controller 10 registers the paper feed interval Tpne calculated in step S39 in the paper feed interval storage table and stores it in the memory 12 (step S40). Thus, the process of FIG. 10 ends. After that, when the print job is executed in the image forming apparatus 1, if the remaining amount of paper is less than a predetermined amount, the controller 10 calculates the paper feed calculated based on the measurement results of a plurality of times from the paper feed interval storage table of the memory 12. By reading and setting the interval Tpne, it is possible to perform continuous sheet feeding at an optimum sheet feeding interval according to the sheet used by the user, and to minimize productivity degradation.

  As described above, in the present embodiment, in the measurement mode, after the feeding of the paper in the paper feeding unit 2a is started, the trailing edge of the paper passes the detection position by the paper empty detection sensor 23, and the controller 10 Based on the output from the empty detection sensor 23, the time Ts required to confirm that the paper in the paper feed unit is empty is measured, and when the print job is executed, the paper near empty detection sensor 21 detects the remaining amount of paper. When the decrease is detected, the paper feed interval Tpne from the start of feeding the previous paper to the start of feeding the next paper is set to a time slightly longer than the actually measured time Ts. Therefore, the paper feed interval Tpne when the remaining amount of paper is less than the predetermined amount can be set to an optimum interval according to the user's usage status, etc. It is possible to suppress a decrease.

  The measurement in the measurement mode is preferably performed for each paper feed unit 2a, 2b, 2c, 2d, and for each paper type and size used by the user. In this case, the paper feed interval storage table stored in the memory 12 is, for example, a table as shown in FIG. As shown in FIG. 11, since the optimum paper feed interval Tpne is stored for each paper feed unit and for each paper type and size, the paper feed interval storage table stored in the memory 12 executes a print job. Sometimes, when the paper near empty detection sensor 21 detects a decrease in the remaining amount of paper, the optimum paper feed interval Tpne based on the measurement result is always set. As shown in FIG. 11, the paper feeding device 2 sets the paper conveyance speed to a high speed when the paper to be fed is plain paper, and the paper conveyance speed when the paper is a thick paper or an OHP. May be set to low speed. In such a case, by performing measurement in the measurement mode for each type of paper, it is possible to set an optimum paper feed interval Tpne corresponding to each conveyance speed.

  Although the measurement mode has been mainly described in the present embodiment, the sheet feeding operation of the sheet feeding device 2 when executing a print job in the present embodiment is the same as the processing procedure described in the first embodiment. Procedures can be applied.

(Third embodiment)
Next, a third embodiment will be described. In this embodiment, when the remaining amount of paper has decreased below a predetermined amount, the controller 10 can confirm the fact that the sheet to be fed next remains in the sheet feeding unit when it is actually confirmed. Starts feeding the original paper. For example, the paper empty detection sensor 23 detects “no paper” at the time when the rear edge of the previous paper is detected by the paper feed sensor 25 or the conveyance sensor 27 after the start of feeding the previous paper. If not, the controller 10 can confirm that the sheet to be fed next remains in the sheet feeding unit. In this embodiment, the configurations of the image forming apparatus 1 and the paper feeding apparatus 2 are the same as those described in the first embodiment.

  FIG. 12 is a flowchart illustrating an example of a processing procedure of the controller 10 in the present embodiment. This process starts when the controller 10 receives a paper feed instruction when a print job is executed in the image forming apparatus 1. First, the controller 10 monitors the output of the paper empty detection sensor 23 and determines whether or not the paper in the designated paper feeding unit (for example, the paper feeding unit 2a) is empty (that is, whether or not the paper is empty). Is determined (step S50). If the designated paper feed unit 2a is empty, the result of step S50 is YES, and the paper feed operation is stopped without starting paper feed (step S58). On the other hand, if the designated sheet feeding unit 2a is not empty (NO in step S50), the controller 10 starts feeding from the sheet feeding unit 2a (step S51).

  Next, the controller 10 monitors the output of the paper near empty detection sensor 21 and determines whether or not the remaining amount of paper in the designated paper feed unit 2a has decreased below a predetermined amount (that is, whether or not the paper is near empty). Is determined (step S52). If the remaining amount of paper has not decreased below the predetermined amount (NO in step S52), the controller 10 waits until a predetermined time (paper feeding time Tp) elapses after the previous paper is fed (step S53). ) If a predetermined time has elapsed (YES in step S53), it is determined whether or not the paper feeding is completed (step S54). When continuous paper feeding is performed, feeding of the next paper is started (step S55). ). Then, the process returns to step S52. If the remaining amount of paper has not decreased below the predetermined amount, the processes in steps S52 to S55 are repeated, and continuous paper feeding at the paper feeding interval Tp is performed.

  If it is determined in step S52 that the remaining amount of paper has decreased below the predetermined amount (YES in step S52), the process proceeds to step S56, and the controller 10 determines that the trailing edge of the sheet before paper feeding has already been performed. It is determined whether or not the paper feed sensor 25 has been passed (step S56). For example, the paper feed sensor 25 is turned on if a paper is detected, and is turned off if no paper is detected. Therefore, the controller 10 waits until the paper feed sensor 25 is switched off. When the paper feed sensor 25 is turned off, the controller 10 determines that the trailing edge of the previous paper has passed through the paper feed sensor 25.

  If the controller 10 determines that the trailing edge of the preceding paper has passed through the paper feed sensor 25, the controller 10 monitors the output of the paper empty detection sensor 23 and determines whether or not the paper in the paper feed unit 2a is empty (ie, Whether or not the sheet is empty is determined (step S57). If the sheet is empty, the process advances to step S58 to stop the sheet feeding operation without starting the sheet feeding operation for the next sheet. On the other hand, if the paper in the paper supply unit 2a is not empty (NO in step S57), it is determined whether or not the paper supply is completed (step S54). Is started (step S55). Then, the process returns to step S52.

  Therefore, when the remaining amount of paper is less than the predetermined amount, the processing of steps S52, S56, S57, S54, and S55 is repeated in this order, and the controller 10 causes the next paper to be fed to the paper feeding unit 2a. After confirming that the sheet remains in the printer, continuous feeding is performed by starting feeding of the next sheet. When the continuous sheet feeding is completed, YES is determined in the step S54, and the process is terminated.

  As described above, in the present embodiment, when the paper near empty detection sensor 21 detects a decrease in the remaining amount of paper, the controller 10 starts from the paper empty detection sensor 23 after feeding of the previous paper is started. After actually confirming that the paper in the paper feed unit is not empty based on the output of, the next paper feed is started, so that the next paper can be reliably conveyed downstream from the paper feed unit. it can. In the case of the present embodiment, it is not necessary to preset the paper feed interval Tpne when the remaining amount of paper is less than a predetermined amount as in the first and second embodiments.

  In the above description, the case where continuous paper feeding is mainly performed from the paper feeding unit 2a is illustrated, but the same applies to the case where continuous paper feeding is performed from the other paper feeding units 2b, 2c, and 2d.

  In the above description, the controller 10 is configured to determine the state of the paper empty detection sensor 23 at the timing when the rear end of the fed paper is detected by the paper feed sensor 25. However, the present invention is not limited to this. Instead, for example, the state of the sheet empty detection sensor 23 may be determined at the timing when the conveyance sensor 27 detects the trailing edge of the sheet. In addition to the paper feed sensor 25 and the transport sensor 27, a dedicated paper trailing edge detection sensor is arranged so that the state of the paper empty detection sensor 23 is determined when the sensor detects the trailing edge of the paper. May be. In this case, it is preferable that the paper trailing edge detection sensor is disposed as downstream as possible from the paper empty detection sensor 23 and at a position close to the paper empty detection sensor 23.

(Modification)
As mentioned above, although several embodiment regarding this invention was described, this invention is not limited to the content mentioned above. In other words, in addition to the above-described contents, various modifications can be applied to the present invention.

  For example, in the above-described embodiment, a multifunction peripheral, an MFP, or the like is illustrated as the image forming apparatus 1, but the image forming apparatus in the present invention is not limited thereto. That is, in the present invention, the image forming apparatus may be a printer dedicated apparatus having only a printer function, or may be a copy dedicated apparatus having only a copy function. Further, a FAX dedicated apparatus having only a FAX function may be used.

  Further, in the above-described embodiment, the case where the paper near empty detection sensor 21 and the paper empty detection sensor 23 are provided separately is exemplified, but these may be configured as an integrated sensor.

1 is a schematic diagram illustrating an example of an image forming apparatus of the present invention. 1 is a diagram illustrating an overall schematic configuration of a sheet feeding device. It is a figure which shows the example of 1 structure of a paper empty detection sensor. FIG. 4 is a block diagram illustrating a control mechanism of a sheet feeding device. FIG. 10 is an operation diagram illustrating a paper transport locus when continuous paper feeding is performed in a state where the remaining amount of paper is less than a predetermined amount. FIG. 10 is an operation diagram illustrating a paper transport locus when continuous paper feeding is performed in a state where the remaining amount of paper is not decreasing. It is a flowchart which shows an example of the process sequence of the controller in 1st Embodiment. FIG. 3 is a diagram of an operation panel of the image forming apparatus as viewed from the front side. It is a flowchart which shows an example of the process sequence of a controller in the case of measuring once in measurement mode. It is a flowchart which shows an example of the process sequence of a controller in the case of measuring in multiple times in measurement mode. It is a figure which shows an example of the paper feed space | interval preservation | save table stored in memory by measurement mode. It is a flowchart which shows an example of the process sequence of the controller in 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper feeding apparatus 3 Image forming part (image forming means)
2a, 2b, 2c, 2d Paper feed unit 10 Controller (control means)
11 CPU
12 Memory (memory means)
21. Paper near empty detection sensor (paper near empty detection means)
22 Pickup roller (conveyance mechanism)
23 Paper empty detection sensor (paper empty detection means)
24 Paper feed roller (conveyance mechanism)

Claims (10)

A transport mechanism that transports and feeds the paper stored in the paper feed unit one by one;
Control means for controlling the sheet feeding operation by the transport mechanism;
Paper empty detection means for detecting that the paper in the paper supply unit is empty;
Paper near empty detection means for detecting that the remaining amount of paper in the paper supply unit has decreased below a predetermined amount;
With
When the paper near empty detecting means detects a decrease in the remaining amount of paper, the control means starts feeding the previous paper and then outputs the paper based on the output from the paper empty detecting means. When the next paper is fed after the timing when it can be confirmed that the paper in the paper feeding unit is not empty, and the paper near empty detecting means has not detected a decrease in the remaining amount of paper. A paper feeding device which starts feeding the next paper at an earlier timing than when the paper near empty detecting means detects a decrease in the remaining amount of paper.   If the paper near empty detecting means has not detected a decrease in the remaining amount of paper, the control means starts feeding the previous paper and then based on the output from the paper empty detecting means The sheet feeding device according to claim 1, wherein feeding of the next sheet is started before the timing at which it can be confirmed that the sheet in the sheet feeding unit is not empty. The time from when the transport mechanism starts feeding the paper in the paper feeding section until the trailing edge of the paper passes the detection position by the paper empty detection means is Te, and the trailing edge of the paper is When the time required for the control means to confirm that the paper in the paper feeding unit is empty based on the output from the paper empty detection means after passing the detection position is Tr,
The control means feeds a paper feed interval Tpne from the start of feeding the previous paper to the start of feeding the next paper when the paper near empty detection means detects a decrease in the remaining amount of paper. The
Te + Tr <Tpne <(Te + Tr) × 2
The sheet feeding device according to claim 1 or 2, wherein the sheet feeding device is set within a range of. The control means feeds a paper feed interval Tp from the start of feeding the previous paper to the start of feeding the next paper when the paper near empty detection means has not detected a decrease in the remaining amount of paper. The
Tp <Te + Tr
The sheet feeding device according to claim 3, wherein the sheet feeding device is set within the range. Storage means for storing the paper feed intervals Tpne and Tp;
When the paper near empty detecting means detects a decrease in the remaining amount of paper, the control means reads the paper feed interval Tpne from the storage means and sets the paper feed interval, and the paper near empty is set. 5. The paper feeding device according to claim 4, wherein when the detecting means does not detect a decrease in the remaining amount of paper, the paper feeding interval Tp is read from the storage means and the paper feeding interval is set. The control means is configured such that after the transport mechanism section starts feeding the paper in the paper feeding section, the trailing edge of the paper passes the detection position by the paper empty detection means, and the control means performs the paper empty. Based on the output from the detection means, measure the time required to confirm that the paper in the paper feed unit is empty,
When the paper near empty detection unit detects a decrease in the remaining amount of paper, the paper feed interval from the start of feeding the previous paper to the start of feeding the next paper is measured by the measurement. The paper feeding device according to claim 1, wherein the paper feeding device is set to a time longer than the time. Storage means for storing a paper feed interval set to a time longer than the measurement time;
7. The sheet feeding apparatus according to claim 6, wherein when the sheet near empty detecting unit detects a decrease in the remaining sheet amount, the control unit reads the sheet feeding interval from the storage unit and sets the sheet feeding interval. Paper device. The storage means stores a paper feed interval set by measurement for each type or size of paper stored in the paper feed unit,
When the paper near empty detection means detects a decrease in the remaining amount of paper, the control means determines a paper feed interval corresponding to the type or size of paper contained in the paper feed from the storage means. 8. The paper feeding device according to claim 7, wherein the paper feeding interval is set by reading.   When the paper near empty detecting means detects a decrease in the remaining amount of paper, the control means starts feeding the previous paper and then outputs the paper based on the output from the paper empty detecting means. The sheet feeding device according to claim 1 or 2, wherein the sheet feeding unit starts feeding the next sheet after confirming that the sheet is not empty. A paper feeding device according to any one of claims 1 to 9,
Image forming means for forming an image on paper fed by the paper feeding device;
An image forming apparatus comprising:

Images