Sheet feeding device, control method of sheet feeding device, and program

Abstract

To solve the problem in which, when a paper feeding roller is stopped in a state where a sheet detection sensor is detecting a sheet, a sheet travels back to a position which is not detected by the sheet detection sensor, following the reverse rotation of the paper feeding roller, and a sheet interval becomes unstable and productivity of sheet feeding deteriorates.SOLUTION: When a tip of a sheet fed by a feeding roller 6 is detected by a pre-registration sensor 32 (S104), a control unit 45 measures (S107) a sheet interval which is an interval between the tip of the sheet and a rear end of the sheet which is being precedently conveyed, and in the case where the sheet interval is less than a threshold value (NO in S108), it feeds the sheet to be fed to the downstream side by a predetermined distance L, and then stops the feeding by the feeding roller (S109-S111).SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a sheet feeding device that feeds sheets by means of rollers. [Background technology]

[0002] When conveying sheets in a scanner or the like, it is necessary to convey a large number of sheets per unit time. To achieve this, methods such as increasing the rotation speed of the rollers and shortening the gap between sheets are widely known.

[0003] If the spacing between sheets being fed and transported is too short, the leading edge of the following sheet may reach the top of the output tray before the preceding sheet falls onto the stacking surface of the output tray. This could cause the trailing edge of the preceding sheet to collide with the leading edge of the following sheet above the output tray. If the sheets collide in this way, the alignment of the sheets on the stacking surface of the output tray will be poor. For this reason, the spacing between sheets cannot be shortened too much; a certain spacing must be maintained.

[0004] Patent Document 1 proposes a technology for maintaining an appropriate interval between sheets (hereinafter referred to as "sheet interval"). Patent Document 1 proposes a method for maintaining an appropriate sheet interval by providing sheet detection sensors at three points on the sheet transport path: upstream, downstream, and somewhere in between, and controlling the timing of sheet feeding and transport based on the timing of each sheet detection. One of the rollers whose rotation timing is controlled here is a pair of separation rollers for separating sheets.

[0005] The pair of separating rollers is composed of a paper feed roller and a double-feed prevention roller. The double-feed prevention roller is driven via a torque limiter. The torque limiter is a mechanism that transmits torque when a torque smaller than the limit torque is applied, but when a torque exceeding the limit torque is applied, the inner ring slips and does not transmit torque above the limit torque. When multiple sheets enter the separation roller pair, the frictional force between the sheets is smaller than the limit torque of the torque limiter. Therefore, the double-feed prevention roller does not move in response to the paper feed roller, and can separate the sheets.

[0006] When torque is applied to the torque limiter, the expansion and contraction of the coil spring that makes up the torque limiter creates a rotational difference between the inner and outer rings of the torque limiter. Because the double-feed prevention roller and the paper feed roller form a nip, torque is applied to the torque limiter incorporated in the double-feed prevention roller when the paper feed roller rotates. When the paper feed roller stops, the torque limiter is released from the torque, and the repulsive force of the coil spring causes the outer ring to return in the opposite direction to the torque direction by an amount equal to the rotational difference between the inner and outer rings. This return action also affects the paper feed roller, which forms a nip with the double-feed prevention roller, causing the paper feed roller to rotate in the opposite direction by an amount equal to the backlash of the gear that transmits the driving force of the paper feed roller. In other words, the paper feed roller may rotate in the opposite direction when stopped. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-206038 Summary of the Invention [Problem to be solved by the invention]

[0008] In the control of Patent Document 1, the paper feed roller is stopped when a sheet is detected by an upstream or intermediate sheet detection sensor. When the paper feed roller is stopped, the torque limiter acts to reverse the paper feed roller, causing the sheet to travel backwards. In this case, there is a possibility that the sheet may travel backwards to a position where it is not detected by the sheet detection sensor. Conventionally, no consideration has been given to such a situation. As a result, the occurrence of such a situation could cause the sheet spacing during sheet feeding to become unstable, resulting in a decrease in sheet feeding productivity.

[0009] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a mechanism that stabilizes the sheet interval during sheet feeding and contributes to improving productivity of sheet feeding. [Means for solving the problem]

[0010] The present invention is characterized by comprising a feed roller that feeds a sheet to a conveying path, a separation means that forms a nip between the feed roller and the feed roller and separates the sheet fed by the feed roller from other sheets, a conveying means that conveys the sheet fed by the feed roller along the conveying path, a detection means that is arranged on the conveying path downstream of the feed roller and upstream of the conveying means and that detects the sheet, and a control means that, when the leading edge of a sheet fed by the feed roller is detected by the detection means, if the sheet spacing, which is the distance between the leading edge of the sheet and the rear end of the preceding sheet being conveyed by the conveying means, is below a threshold value, stops feeding by the feed roller after feeding the fed sheet a predetermined distance downstream from the detection means, and controls the feed roller to resume feeding when a predetermined time has elapsed since the stop. [Effects of the Invention]

[0011] According to the present invention, it is possible to stabilize the sheet intervals during sheet feeding, thereby contributing to an improvement in productivity of sheet feeding. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a partial cross-sectional view of an image reading apparatus including a sheet feeding device according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram illustrating a configuration of a main part of an image reading apparatus according to an embodiment of the present invention; [Figure 3] FIG. 2 is an enlarged view of a sheet feeding unit in the image reading apparatus according to the embodiment. [Figure 4] 10 is a flowchart illustrating a sheet feeding operation according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described. [First embodiment] Fig. 1 is a partial cross-sectional view showing an example of the configuration of an image reading device equipped with a sheet feeding device according to one embodiment of the present invention. Fig. 2 is a schematic diagram showing the configuration of the main parts of the image reading device according to this embodiment. Here, as an example, a case where the sheet feeding device of the present invention is applied to an image reading device will be described, but the present invention can be applied to various types of sheet feeding devices, such as a printing device (such as a printer) that prints on sheets, or a device with a sheet transport system such as a multifunction peripheral that combines an image reading device (such as a scanner) and a printing device.

[0014] 1 and 2, an image reading apparatus 200 includes a sheet take-in device 101 as a sheet feeding device of this embodiment.

[0015] The sheet feeding device 101 has a sheet stacking tray (document placing tray) 1. A plurality of sheets are stacked on the sheet stacking tray 1, and the sheet stacking tray 1 is configured to be able to move up and down freely. A sheet stacking tray drive motor 2 raises and lowers the sheet stacking tray 1. A sheet detection sensor 3 detects that the sheets stacked on the sheet stacking tray 1 are at the sheet feeding position. A sheet stacking detection sensor 12 detects that a sheet is stacked on the sheet stacking surface 1a of the sheet stacking tray 1.

[0016] Furthermore, movable regulating members 51 are provided on both ends of the width direction of the sheet stacking tray 1 in the conveying direction to regulate the width direction of the sheet. By moving the regulating members 51 in the width direction to match the width of the document to be conveyed, it is possible to prevent the sheet from skewing during conveyance.

[0017] Furthermore, the sheet bounce-up detection sensor 35 includes a plurality of sensors arranged in a direction perpendicular to the sheet stacking surface 1a, and detects any bounce-up of sheets stacked on the sheet stacking tray 1. For example, the sheet bounce-up detection sensor 35 can detect any bounce-up of sheets that occurs when stapled sheets or the like are stacked on the sheet stacking tray 1 and fed. This makes it possible to perform control such as stopping the feeding of stapled sheets or the like.

[0018] A pickup roller 4 (take-in unit), which is an example of a sheet feeding unit, feeds a sheet from the sheet stacking table 1. A pickup roller drive motor 5 rotates the pickup roller 4. In FIG. 2, the upper surface of the sheet is at the sheet take-in position, and the sheet take-in begins when the pickup roller 4 is rotated. The pickup roller 4 can be moved by a drive unit (not shown) between the sheet take-in position and a retracted position above the sheet take-in position. The pickup roller 4 is moved to the take-in position when taking in a sheet, and is moved to the retracted position after the take-in is completed. In the example of FIG. 1, the pickup roller 4 rotates around a rotation center 64 of the pickup roller, which is located downstream of the pickup roller 4 in the conveying direction. In this way, the pickup roller 4 is configured to easily push the sheet in the conveying direction when it comes into contact with the sheet.

[0019] The control unit 45 issues instructions to rotate the pickup roller 4 and to move between the sheet take-in position and the retracted position. The control unit 45 has a CPU, ROM, RAM, etc. (not shown), and the CPU executes programs stored in the ROM to realize various controls. The pickup roller 4 also plays an auxiliary role in ensuring that separation and feeding by a pair of separation rollers 42, which will be described later, is performed reliably. If the pickup roller 4 sends the sheet on the sheet stacking tray 1 into the nip portion of the pair of separation rollers 42, separation and feeding by the pair of separation rollers 42 can be performed reliably.

[0020] The separation roller pair 42 is composed of a feeding roller 6 and a separation roller 7 . In the separation roller pair 42, the feeding roller 6 is driven by the feeding motor 8 to rotate in a direction (feeding direction) in which the sheet is fed downstream in the conveying direction. The separation roller 7 forms a nip with the feed roller 6 and constantly receives rotational force from the separation motor 9 via a torque limiter (slip clutch) not shown, which rotates in a direction that pushes the sheet back upstream in the conveying direction.

[0021] When there is only one sheet between the feed roller 6 and the separation roller 7, the rotational force in the direction of feeding the sheet downstream exceeds the upper limit of the rotational force of the separation roller 7 in the direction of pushing the sheet back upstream. Therefore, the separation roller 7 rotates following the feed roller 6 (co-rotates). The rotational force in the direction of pushing the sheet back upstream is transmitted by a torque limiter.

[0022] On the other hand, when there are multiple sheets between the feeding roller 6 and the separation roller 7, the separation roller 7 receives rotation from the roller shaft in a direction to push the sheets back upstream, so that sheets other than the topmost one are not conveyed downstream.

[0023] In this way, in the separation roller pair 42, the feed roller 6 acts to feed the sheet downstream, and the separation roller 7 acts to prevent the sheet from being fed downstream. When overlapping sheets are fed into the nip portion between the feed roller 6 and the separation roller 7, these two actions cause only the topmost sheet to be fed downstream, and the other sheets are not conveyed downstream, so that the overlapping sheets are separated and fed. In this way, the feed roller 6 and the separation roller 7 constitute a pair of separation rollers 42 (sheet separation portion).

[0024] Although the separation roller pair 42 is used in this embodiment, a separation belt roller pair in which either the separation roller or the feeding roller is a belt may be used instead of the separation roller pair 42.

[0025] The sheet feeding section, which is configured as described above and is composed of the pickup roller 4, feeding roller 6, separation roller 7, etc., separates the sheets stacked on the sheet stacking tray 1 one by one and takes them into the image reading device 200.

[0026] Furthermore, by providing a double feed detection sensor 30 at a position where the separated sheets pass, it is possible to detect whether the sheets have been separated one by one by the sheet separating unit. In this embodiment, a detection device using an ultrasonic transmitter / receiver is used as the double feed detection sensor 30, and double feed can be detected by the amount of ultrasonic attenuation between the transmitter / receivers across the conveyance path.

[0027] The conveying motor 10 drives other rollers (sheet conveying section) to convey the separated sheet to an image reading position where the image on the sheet is read by image reading sensors 14 and 15, and further to a discharge position. The conveying motor 10 also drives each roller so that the sheet conveying speed can be changed according to settings such as the optimum speed for reading the sheet and the sheet resolution.

[0028] The nip gap adjustment motor 11 adjusts the gap between the feed roller 6 and the separation roller 7, or the pressure force with which the feed roller 6 presses against the separation roller 7 via the sheet. This adjusts the gap or pressure force to suit the thickness of the sheet, allowing the sheet to be separated.

[0029] The resist clutch 19 transmits or blocks the rotational driving force of the conveying motor 10 to the resist rollers 18 (sheet conveying section). By stopping the rotation of the first resist roller pair consisting of the resist rollers 17 and 18, the leading edge of the fed sheet may be abutted against the nip portion of the first resist roller pair, thereby correcting skew of the sheet.

[0030] A second registration roller pair consisting of registration rollers 20 and 21, a transport roller pair consisting of transport rollers 22 and 23, a transport roller pair consisting of transport rollers 24 and 25, and a discharge roller pair consisting of discharge rollers 26 and 27 transport the sheet to a discharge stacking section 44. A discharge sensor 16 detects the passage of the transported sheet. After the discharge sensor 16 detects the trailing edge of the sheet, a discharge brake is applied to slow the rotation speed of the discharge roller pair (26, 27), preventing the discharged sheet from flying out and improving discharge alignment.

[0031] The conveying speed during sheet conveyance from the first pair of registration rollers arranged along the sheet conveying direction to the pair of discharge rollers (except when the discharge brake is applied) is approximately the same, and is faster than the conveying speed of the feed roller 6. Therefore, while the sheet is being conveyed by the first pair of conveying rollers, friction with the sheet causes the feed roller 6 to rotate at the conveying speed of the first pair of conveying rollers. The feed roller 6 has a one-way clutch in the drive transmission path from the feed motor 8 to prevent reverse rotation. Therefore, when the feed roller 6 rotates with the sheet while being conveyed by the first pair of conveying rollers, the one-way clutch is disengaged, making it less likely to generate resistance to the sheet, while the outer periphery of the feed roller 6 rotates by the amount of backlash that occurs in each gear in the drive transmission path.

[0032] The two guide plates, the upper guide plate 40 and the lower guide plate 41, guide the sheets conveyed by the separation roller pair, the registration roller pair, each conveying roller pair, and the paper discharge roller pair.

[0033] The pre-registration sensor 32 is disposed upstream of the first pair of registration rollers (17, 18) and detects the conveyed sheet. The post-registration sensor 34 is disposed downstream of the second pair of registration rollers (20, 21) and detects the conveyed sheet. Furthermore, the mid-registration sensor 33 is disposed downstream of the first pair of registration rollers (17, 18) and upstream of the second pair of registration rollers (20, 21) and detects the conveyed sheet.

[0034] When the post-registration sensor 34 detects the sheet, the control unit 45 issues an instruction to the image reading sensors 14 and 15 to read the image, and the image on the conveyed sheet is read. Reference numerals 14a and 15a denote platen rollers. The sheet image read by the image reading sensors 14 and 15 is transmitted to an external device such as an information processing device via an interface unit (not shown).

[0035] <Separation feeding section> 3 is an enlarged view showing a sheet feeding unit having a feeding roller 6, a separation roller 7, and a pre-registration sensor 32. Note that the illustration omits components other than the main components. In this embodiment, the direction in which the sheet is fed is referred to as forward rotation, and rotation in the opposite direction is referred to as reverse rotation.

[0036] The separating and feeding section will be described below with reference to FIG. As described above, the separation roller 7 is attached to the roller shaft 7a via a torque limiter. This torque limiter is made up of three components: an inner ring that receives driving force from the roller shaft 7a of the separation roller 7, a coil spring that has a certain binding force against the inner ring and binds it so that it slips when a torque above a certain level is applied, and an outer ring that is connected to the coil spring and configured to cover the periphery of the torque limiter.

[0037] When the difference in torque between the roller shaft 7a of the separation roller 7 and the surface of the separation roller exceeds a certain level, the inner ring of the torque limiter and the coil spring slip, limiting the driving force on the surface of the separation roller. When torque is applied from a stationary state, a certain amount of rotational difference occurs between the inner ring and the outer ring due to the expansion and contraction of the coil spring before the coil spring and inner ring slip. Then, when the torque is released, the repulsive force of the coil spring generates a return action that causes the outer ring to return in the opposite direction to the torque direction by an amount equal to this rotational difference.

[0038] The torque caused by this return action is received by the feed roller 6, which is in contact with the separation roller 7, and the feed roller 6 rotates in the reverse direction by the amount of backlash of the gear that transmits the driving force of the feed roller 6. The distance that the feed roller 6 moves the sheet backward due to this reverse rotation is designated as a predetermined distance L in FIG. 3. Note that the predetermined distance L is shorter than the distance from the pre-registration sensor 32 to the first pair of registration rollers (17, 18).

[0039] In this embodiment, the control for widening the sheet interval includes, for example, control for stopping the feed roller 6 when the sheet interval with the preceding sheet is below a threshold value when the leading edge of the sheet is detected by the pre-registration sensor 32. Here, the sheet interval is defined as the distance between the leading edge of the sheet detected by the pre-registration sensor 32 and the trailing edge of the sheet immediately preceding this sheet that is being conveyed by the conveyance roller pair (22, 23) ahead of this sheet.

[0040] As mentioned above, when the feed roller 6 is stopped to widen the sheet spacing, if a sheet is in contact with the feed roller 6 and friction is applied to the sheet, the reverse rotation of the feed roller 6 may cause the sheet to run backward from the position where it is detected by the pre-registration sensor 32 to a position where it is not detected by the pre-registration sensor 32.

[0041] 4, which will be described later, is executed, and when the feed roller 6 is stopped when the pre-registration sensor 32 detects the leading edge of the sheet, the sheet is fed ahead of the pre-registration sensor 32 by the amount of reverse rotation of the feed roller 6 (predetermined distance L) downstream in the conveying direction. With this configuration, even in a situation where the sheet is returned by the amount of backlash described above, the sheet will not travel backward to a position where the pre-registration sensor 32 does not detect the sheet.

[0042] Hereinafter, an example of the control operation of the sheet feeding device in the sheet feeding operation instructed by the control unit 45 in the first embodiment will be described with reference to the flowchart of FIG. When the sheet feeding operation is started, the upper surface of the sheets loaded on the sheet stacking tray 1 is at the sheet intake position as shown in Figures 1 and 2, and the sheet intake will begin when the pickup roller 4 is rotated.

[0043] 4 is a flowchart showing an example of a sheet feeding operation instructed by the control unit 45 in the first embodiment. That is, the process shown in this flowchart is realized by a CPU (not shown) of the control unit 45 executing a program stored in a ROM.

[0044] When the control unit 45 starts the sheet feeding operation (S101), it rotates the pickup roller 4 (S102). Next, the control unit 45 rotates the feeding roller 6 at a rotation speed v1 (S103). Next, in S104, the control unit 45 checks the output of the pre-registration sensor 32 and determines whether the pre-registration sensor 32 has detected the leading edge of the sheet. Here, if it is determined that the pre-registration sensor 32 has not detected the leading edge of the sheet (No in S104), the control unit 45 controls to make the determination of S104 again and waits until the pre-registration sensor 321 detects the leading edge of the sheet.

[0045] On the other hand, if it is determined that the pre-registration sensor 32 has detected the leading edge of the sheet (Yes in S104), the control unit 45 advances the process to S105. In S105, the control unit 45 stops the rotation of the pickup roller 4.

[0046] Next, in S106, the control unit 45 starts counting the time for controlling the rotation timing of the feed roller 6. This count is used in the process (S109 to S111) described later to move the feed roller 6 a predetermined distance L and then stop its rotation. By multiplying the counted time by the rotation speed of the feed roller 6, the distance the sheet has been fed by the rotation of the feed roller 6 can be determined. From the distance calculated in this way, it can be determined in S110 described later whether the feed roller 6 has rotated the predetermined distance L. Details will be explained in S109 to S111 described later.

[0047] Next, in S107, the control unit 45 measures the sheet interval (hereinafter referred to as the "determination sheet interval"). Here, a method for measuring the sheet interval will be described. The control unit 45 starts counting the sheet interval measurement time in S118 (at the timing when the trailing edge of the previous sheet passes the pre-registration sensor 32), which will be described later. The control unit 45 measures the above-mentioned determination sheet interval by multiplying the value of this counter by the sheet feeding speed. Note that when the first sheet is fed, there is no preceding sheet being transported, so the counting in S118 has not yet started. In this case, the sheet interval will not become too short, so when the first sheet is fed, the control unit 45 does not measure the determination sheet interval in S107.

[0048] Next, in S108, the control unit 45 determines whether the determination sheet interval exceeds the threshold value. Note that when the first sheet is being fed (i.e., when the determination sheet interval has not been measured in S107), the determination in S108 is Yes.

[0049] In the above S108, if the determined sheet interval does not exceed the threshold (No in S108), the control unit 45 determines that the sheet interval with the preceding sheet has become shorter, and proceeds to S109. In S109, the control unit 45 sets the rotation speed of the feed roller 6 to v2. Here, v2 is a speed that satisfies v2≦v1. By reducing the rotation speed, the responsiveness at the timing of stopping the feed roller 6, which will be described later, improves, and the sheet position can be controlled more accurately. However, to simplify the control, it is also possible to leave the rotation speed unchanged and set v2=v1.

[0050] Next, in S110, the control unit 45 determines whether the feed roller 6 has rotated a predetermined distance L. As described above, the predetermined distance L is the distance the feed roller 6 rotates in the reverse direction after being stopped. The distance the feed roller 6 has advanced the sheet is calculated by multiplying the rotation speed v2 of the feed roller 6 by the value of the rotation timing control time, which was started to be counted in S106, at the time of S110. Whether the feed roller 6 has rotated a predetermined distance L is determined by the fact that the sheet has advanced a predetermined distance L since passing the pre-registration sensor 32. Therefore, the determination can be made based on the actual time. For example, if the sheet leading edge is detected by the pre-registration sensor 32 in S104 and a predetermined time is required for some processing or a predetermined waiting time is included, the time can be taken into consideration. Therefore, even if the count of the rotation timing control time itself has not reached the predetermined distance L, it can be determined whether the sheet has rotated a predetermined distance L as the total elapsed time.

[0051] If it is determined in S110 above that the feed roller 6 has not yet rotated the predetermined distance L (No in S110), the control unit 45 controls the control unit 45 to make the determination in S110 again, continues rotating the feed roller 6 at the rotation speed v2, and waits for the feed roller 6 to rotate the predetermined distance L. On the other hand, if it is determined that the predetermined distance L has already been rotated (Yes in S110), the control unit 45 advances the process to S111.

[0052] In S111, the control unit 45 stops the feed roller 6. At this time, the sheet being fed by the feed roller 6 stops before reaching the second pair of registration rollers (20, 21). At this time, the second pair of registration rollers (20, 21) and the conveyance rollers (22, 23, 24, 25) do not stop, so the conveyance of the preceding sheet continues. As a result, the sheet gap between the sheet being conveyed by the feed roller 6 and the preceding sheet widens.

[0053] Next, in S112, the control unit 45 starts counting the predetermined time T. Here, the predetermined time T is the time from when the feed roller 6 is stopped until the sheet interval is secured and the feed roller 6 starts rotating again. The sheet interval to be secured is set based on the difference between the aforementioned sheet interval threshold, which is set in advance within a range in which the sheets do not collide with each other on the sheet discharge tray and the number of fed sheets does not become too small, and the determined sheet interval. Specifically, the predetermined time T is set to the time required for the second registration roller pair to transport the difference distance, or the time obtained by adding a small margin to that.

[0054] Subsequently, in S113, the control unit 45 determines whether a predetermined time T has elapsed. If it is determined that the predetermined time T has not yet elapsed (No in S113), the control unit 45 controls to make the determination in S113 again, and waits until the predetermined time T has elapsed. On the other hand, if it is determined that the predetermined time T has already elapsed (Yes in S113), the control unit 45 advances the process to S114.

[0055] In S114, the control unit 45 restarts the stopped feed roller 6. This restarts the conveyance of the stopped sheets. Since the necessary sheet spacing is already ensured at this point, setting the rotation speed of the feed roller 6 to v1, which is faster than v2, can prevent the sheet spacing from widening further. On the other hand, setting the speed v2 to a slower speed reduces the burden on the sheets, reducing the possibility of sheet damage. Therefore, if the sheets are waste paper or thin paper (e.g., when a predetermined mode for conveying thin paper is being executed), the feed roller 6 may be configured to start rotating at speed v2 in S114. Alternatively, the feed roller 6 may be configured to restart at speed v1 when a mode with a high-speed conveyance speed set as the reading setting (e.g., normal mode) is executed, and to restart at speed v2 when a mode with a low-speed conveyance speed set as the reading setting (e.g., thin paper mode) is executed. Following the process of S114, the control unit 45 proceeds to S115.

[0056] Furthermore, in S108, if it is determined that the determination sheet interval exceeds the threshold value (Yes in S108), the control unit 45 proceeds to S115. Note that, as described above, when the first sheet is being fed, Yes is determined in S108, and the process proceeds to S115.

[0057] In S115, the control unit 45 determines whether the registration sensor 33 has detected the leading edge of the sheet. By confirming that the registration sensor 33 has detected the leading edge of the sheet, it is possible to confirm whether the sheet has reached the first pair of registration rollers (17, 18).

[0058] Here, if the registration sensor 33 has not yet detected the leading edge of the sheet (No in S115), the control unit 45 controls to perform the determination in S115 again and waits until the leading edge of the sheet reaches the registration sensor 33. On the other hand, if the registration sensor 33 has already detected the leading edge of the sheet (Yes in S115), the control unit 45 advances the process to S116.

[0059] In S116, the control unit 45 stops the feed roller 6. This ends the sheet feeding operation by the feed roller 6 in S116. Note that the sheet that has been fed by the feed roller 6 has already reached the registration sensor 33, and the sheet is transported by the first registration roller pair (17, 18).

[0060] Next, in S117, the control unit 45 determines whether the pre-registration sensor 32 has detected the trailing edge of the sheet being conveyed. If it is determined that the pre-registration sensor 32 has not yet detected the trailing edge of the sheet being conveyed (No in S117), the control unit 45 controls to perform the determination of S117 again and waits until the trailing edge of the sheet reaches the pre-registration sensor 32. On the other hand, if it is determined that the pre-registration sensor 32 has already detected the trailing edge of the sheet being conveyed (Yes in S117), the control unit 45 advances the process to S118.

[0061] In S118, the control unit 45 starts counting the sheet interval measurement time. By starting counting the sheet interval measurement time at this timing, it is possible to measure the interval between the trailing edge of the preceding sheet conveyed in S107 described above and the leading edge of the sheet to be fed, i.e., the sheet interval.

[0062] When the process of S118 above is completed, the control unit 45 ends the sheet feeding started in S101 above and starts the sheet feeding process for the next sheet. The control unit 45 repeats this sheet feeding process until feeding of all sheets stacked on the sheet stacking tray 1 is completed, until a predetermined number of sheets are fed, or until sheet feeding is terminated by a user operation or the like. At this time, the control unit 45 continues counting the sheet interval measurement time started in S118 above until the next sheet interval is measured in S107, until feeding of all sheets stacked on the sheet stacking tray 1 is completed, or until sheet feeding is terminated by a user operation or the like. The above is an example of the control operation of the sheet feeding device during the sheet feeding operation.

[0063] In the above process, the sheet interval (threshold value) to be secured is set in advance, but it may be changed in relation to the operation at the time of sheet ejection. If the sheet is discharged at the same speed as the conveyance speed, the sheet alignment will be poor. Therefore, there is an operation during discharge (discharge deceleration control) to reduce (slow down) the rotational speed (discharge speed) of the pair of discharge rollers (26, 27) when the trailing edge of the sheet is discharged. If the rotational speed of the pair of discharge rollers (26, 27), i.e., the discharge speed, is slower than that of the sheet being conveyed, the sheet interval that must be maintained will be longer. Note that the reduced discharge speed of the pair of discharge rollers (26, 27) is determined by the length of the sheet in the conveyance direction. In other words, the sheet interval threshold may be changed based on the length of the preceding sheet in the conveyance direction. Furthermore, the control unit 45 may change the predetermined time T used in S113 based on the length of the preceding sheet being conveyed, thereby changing the sheet interval that must be maintained.

[0064] Furthermore, both the predetermined time T used in S113 and the threshold value used in S108 may be changed depending on the length in the conveying direction of the sheet that has been conveyed immediately before.

[0065] The length of the preceding sheet is measured, for example, by detecting the sheet with the pre-registration sensor 32 and measuring it by the control unit 45 based on this detection result, but it may also be measured by detecting it with the mid-registration sensor 33 or the post-registration sensor 34, etc.

[0066] 4, when the leading edge of the sheet is detected by the pre-registration sensor 32, if the determination sheet interval does not exceed the threshold value (No in S108), the rotational speed of the feed roller 6 is decelerated to V2 (S109), and after rotating a predetermined distance (S110), the feed roller 6 is stopped for a predetermined time T and then rotated again (S111 to S114). However, if the determination sheet interval does not exceed the threshold value, instead of stopping and re-rotating the feed roller 6 (S109 to S114), the rotational speed of the feed roller 6 may simply be decelerated. In this case, the deceleration speed may be determined from the difference between the determination sheet interval and the threshold value. The predetermined time T may be a preset fixed value. Alternatively, instead of the predetermined time T, the process may transition to S114 based on the detection of the trailing edge of the preceding sheet by a sheet detection sensor provided downstream, such as the registration sensor 33, or the passage of the predetermined time T, whichever is earlier.

[0067] As described above, in this embodiment, when the feed roller 6 is temporarily stopped to ensure the required sheet spacing, the sheet is fed downstream in advance by the amount of reverse rotation of the feed roller 6 (the distance L described above). This prevents the sheet from traveling backward to a position where it is not detected by the pre-registration sensor 32 when the feed roller 6 is stopped, thereby stabilizing the sheet position and the sheet spacing. For example, if the sheet travels backward to a position where it is not detected by the pre-registration sensor 32 and stops there, as described above, operation becomes unstable when sheet feeding is resumed, even if control is performed to prevent a jam error caused by the pre-registration sensor 32 not being detected. This could have conventionally reduced sheet feeding productivity. However, the control of this embodiment stabilizes the sheet position and the sheet spacing, thereby improving sheet feeding productivity.

[0068] There is a sheet feeding device configured to rotate the pickup roller 4 together with the feed roller 6 if the sheet is not detected by the pre-registration sensor 32 when starting to feed a sheet. In such a device, as described above, if the sheet travels backward to a position where it is not detected by the pre-registration sensor 32 and stops, when sheet feeding is resumed, not only the feed roller 6 but also the pickup roller 4 may be rotated, which may result in excessive energy consumption and roller wear. However, the control of this embodiment stabilizes the sheet position and sheet spacing, making it possible to suppress excessive energy consumption and roller wear.

[0069] Note that some sheet feeding devices have the following sheet feeding mode as a mode for feeding weak sheets such as thin paper or recycled paper. In this sheet feeding mode, if the pre-registration sensor 32 does not detect a sheet when feeding a sheet, the pickup roller 4 is moved from the retracted position to the sheet intake position, and the sheet is fed by the pickup roller 4 and the feed roller 6. On the other hand, if the pre-registration sensor 32 detects a sheet, the pickup roller 4 remains in the retracted position and the sheet is fed by the feed roller 6. In a device operating in this sheet feeding mode, by performing the sheet feeding control of the present embodiment described above, the operation of the pickup roller 4 can be omitted, and greater effects can be expected.

[0070] Although the sheet feeding device of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the spirit and scope of the present invention.

[0071] It goes without saying that the configurations and contents of the various data described above are not limited to those described above, and that the data may be configured in various configurations and contents depending on the application and purpose. Although one embodiment has been described above, the present invention can be embodied as, for example, a system, an apparatus, a method, a program, a storage medium, etc. Specifically, the present invention may be applied to a system made up of multiple devices, or may be applied to an apparatus made up of a single device. Furthermore, the present invention also includes any combination of the above embodiments.

[0072] Other Embodiments The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program.The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. Furthermore, the present invention may be applied to a system made up of multiple devices, or to an apparatus made up of a single device. The present invention is not limited to the above-described embodiments, and various modifications (including organic combinations of the embodiments) are possible based on the spirit of the present invention, and these modifications are not excluded from the scope of the present invention. In other words, all configurations that combine the above-described embodiments and their modifications are included in the present invention. [Explanation of symbols]

[0073] 1 seat loading platform 1a Sheet loading surface 2 Sheet loading tray drive motor 3 Sheet detection sensor 4 Pickup roller 5 Pickup roller drive motor 6 Feeding roller 7 Separation roller 8 Feeding motor 9 Separation motor 10. Transport motor 11 Nip gap adjustment motor 12 Sheet stacking detection sensor 14, 15 Image reading sensor 17, 18, 20, 21 Registration rollers 19 Resist Clutch 22, 23, 24, 25 Conveyor rollers 30 Double feed detection sensor 32 Pre-register sensor 33 Register sensor 34 Post-registration sensor 40 Upper guide plate 41 Lower guide plate 42 Separation roller pair (sheet separation section) 44 Discharge loading section

Claims

1. a feeding roller for feeding the sheet to the conveying path; a separation roller having a torque limiter and forming a nip between the separation roller and the feeding roller to separate the sheet fed by the feeding roller from other sheets; a conveying means for conveying the sheet fed by the feeding roller along the conveying path; a detection unit that is disposed on the conveying path downstream of the feeding roller and upstream of the conveying unit and detects a sheet; a control means for stopping feeding by the feeding roller after feeding the sheet a predetermined distance downstream from the detection means when a sheet interval, which is an interval between the leading edge of the sheet and the trailing edge of the preceding sheet being conveyed by the conveying means, is less than a threshold value when the leading edge of the sheet being conveyed by the feeding roller is detected by the detection means; A sheet feeding device comprising:

2. 2. The sheet feeding device according to claim 1, wherein the control means controls the feeding roller to resume feeding after a predetermined time has elapsed since the feeding roller stopped feeding, and the predetermined time is determined from the difference between the threshold value and the sheet interval.

3. 2. The sheet feeding apparatus according to claim 1, wherein the control means changes the threshold value based on a sheet length, which is a length in a conveying direction of the sheet conveyed by the conveying means.

4. 2. The sheet feeding apparatus according to claim 1, wherein the control means changes the predetermined time based on a sheet length, which is a length in a conveying direction of the sheet conveyed by the conveying means.

5. 5. The sheet feeding apparatus according to claim 3, wherein the control means determines the sheet length based on a result of detection of the sheet by the detection means.

6. 5. The sheet feeding apparatus according to claim 1, wherein the control unit determines the sheet interval based on a result of detection of the sheets by the detection unit.

7. 5. The sheet feeding device according to claim 1, wherein the control unit decelerates the feeding roller while the sheet is being fed a predetermined distance downstream from the detection unit.

8. a feeding roller for feeding the sheet to the conveying path; a separation roller having a torque limiter and forming a nip between the separation roller and the feeding roller to separate the sheet fed by the feeding roller from other sheets; a conveying means for conveying the sheet fed by the feeding roller along the conveying path; a detection unit that detects a sheet and is disposed downstream of the feed roller and upstream of the conveying unit in the conveying path, the detection unit comprising: a stopping step of stopping feeding by the feeding roller after feeding the sheet to be fed a predetermined distance downstream from the detection means when the detection means detects the leading edge of the sheet fed by the feeding roller and a sheet interval between the leading edge of the sheet and the trailing edge of the preceding sheet being conveyed by the conveying means is below a threshold value; 10. A method for controlling a sheet feeding device, comprising:

9. A program for causing a computer to function as the control means according to any one of claims 1 to 4.

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