JP6632675B2 - Feeding device - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine and a printer, and to a feeding control of a recording material in a feeding device used in those apparatuses.

  2. Description of the Related Art Conventionally, an image forming apparatus such as a copying machine or a printer includes a feeding device that feeds a sheet loaded on a loading unit such as a cassette to a downstream transport roller. In the feeding device described in Patent Literature 1, a sheet stacked on a stacking unit is fed by a pickup roller. Here, when a plurality of sheets are fed out while overlapping due to the influence of friction, the plurality of sheets are separated into a preceding sheet and a succeeding sheet by a feed roller and a separation roller. In this feeding device, when the preceding sheet reaches a transport roller downstream of the feed roller, the driving of the pickup roller and the feed roller is stopped, and the preceding sheet is pulled out by the transport roller. This prevents the succeeding sheet from being fed downstream of the separation nip formed by the feed roller and the separation roller.

JP-A-10-167494

  FIG. 14A is an enlarged view of the separation nip 111 a formed by the feed roller 110 and the separation roller 111. Here, when the succeeding sheet S2 is taken out by the preceding sheet S1 and two sheets are fed out to the separation nip 111a, the subsequent sheet S2 is fed downstream from the separation nip 111a by the above control. It will not be done. However, as shown in FIG. 14B, the succeeding sheet S2 may enter near the separation nip 111a. When the trailing edge of the preceding sheet S1 passes through the separation nip 111a in this state, the trailing edge of the preceding sheet S1 jumps in the direction of arrow F due to a step due to the thickness E of the succeeding sheet S2, and a sudden sound is generated.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus and a feeding apparatus that reduce a sudden sound when a trailing end of a recording material passes through a separation nip.

A feeding device of the present invention for achieving the above object has a feeding member that feeds a recording material placed on a mounting portion, and a feeding member that feeds the recording material fed by the feeding member. One transport member,
A separation member that forms a nip portion with the first conveyance member, and separates a plurality of recording materials in the nip portion; and a second conveyance member that conveys the recording material conveyed by the first conveyance member. Wherein the first recording material placed on the placement portion is fed by the feeding member, and before the rear end of the first recording material passes through the nip portion, In a state where the second recording material fed next to the first recording material partially overlaps with the first recording material, the leading end of the second recording material passes through the nip portion. And feeding the second recording material placed on the placing portion, wherein the leading end of the second recording material passes through the nip portion and the leading end of the second recording material is the second recording material. Before reaching the conveyance member, the feeding is performed so that the rear end of the first recording material is separated from the front end of the second recording material. The feeding operation of the by the the member first conveying member second recording material is stopped, a control means for conveying the first recording material by said second conveying member, wherein, After the leading end of the first recording material has reached the second transport member and before the trailing end of the first recording material passes through the feeding member, The driving is stopped, and after the trailing end of the first recording material conveyed by the second conveying member has passed through the feeding member, the driving of the feeding member is started again, and the second recording is started. The material is fed .

  According to the present invention, it is possible to provide an image forming apparatus and a feeding apparatus which reduce a sudden sound when a rear end of a recording material passes through a separation nip.

FIG. 4 is a cross-sectional view of the printer according to the first embodiment. 1 is a control block diagram of a printer according to a first embodiment. Timing chart of control during sheet feeding in the first embodiment Flow chart of control at the time of sheet feeding in the first embodiment FIG. 6 is a view for explaining the movement of a sheet according to the first embodiment. FIG. 6 is a view for explaining distribution of the leading edge position of a sheet according to the first embodiment. Timing chart of control during sheet feeding in the second embodiment Flow chart of control at the time of sheet feeding in the second embodiment Timing chart of control at the time of sheet feeding in the third embodiment FIG. 14 is a view for explaining distribution of the leading end position of a sheet according to the third embodiment. Timing chart of control at the time of sheet feeding in the fourth embodiment The figure which shows the ultrasonic sensor in other Examples. Sectional view of a paper feed option device in another embodiment. Diagram explaining problems in conventional technology

[Example 1]
<Structure>
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Elements common to the drawings are assigned the same reference numerals.

  FIG. 1 is a sectional view schematically showing a laser beam printer 90 (hereinafter, referred to as a printer 90) which is an example of an image forming apparatus provided with a feeding device according to a first embodiment of the present invention.

  In FIG. 1, a printer 90 includes a photosensitive drum 1 as an image carrier in a cartridge 7. The charging roller 8 charges the surface of the photosensitive drum 1. The scanner unit 2 irradiates a laser onto the photosensitive drum 1 based on image information, and forms an electrostatic latent image on the photosensitive drum 1. The developing roller 9 visualizes the electrostatic latent image formed on the photosensitive drum 1 with toner. The toner image thus formed on the photosensitive drum 1 is transferred by the transfer roller 5 to a sheet S as a recording material. These process members function as an image forming unit for forming an image on the sheet S.

  The feeding device includes a cassette 100 and a roller unit 19. The cassette 100 is provided with a sheet stacking plate 22 which is a stacking unit on which a plurality of sheets S are stacked. In the standby state, the sheet S is lifted to the feeding position by the sheet stacking plate 22, and the uppermost sheet S1 is in contact with the pickup roller 15 (hereinafter, pick roller 15). When a print signal is input, the pick roller 15 feeds the sheet S1 from the sheets S stacked on the sheet stacking plate 22. The feed roller 16 feeds the sheet S1 fed by the pick roller 15 further downstream. The separation roller 17 is fixed to a chassis or the like of the printer 90 via a torque limiter 18. The operation of the separation roller 17 will be described later in detail.

  The sheet S1 fed by the feed roller 16 is conveyed by a pair of pull-out rollers 20, 21 and a pair of registration rollers 3, 4 (conveying unit). The transport sensor 23 and the registration sensor 24 (detection unit) detect the transported sheet S1. The toner image is transferred to the sheet S1 conveyed by the registration roller pairs 3 and 4 by the transfer roller 5 described above. Thereafter, the fixing unit 10 fixes the toner image transferred on the sheet S1 to the sheet S1 by heat and pressure. The sheet S1 on which the toner image is fixed is discharged to a discharge tray 13 by a pair of discharge rollers 11 and 12.

  FIG. 2 is a control block diagram of the printer 90 in the present embodiment. The engine control unit 200 that controls the operation of the printer 90 has a CPU, a ROM, a RAM, and the like therein, and executes processing based on a program stored in the ROM in advance. A motor 201 as a drive unit is connected to the engine control unit 200. The motor 201 drives and rotates the pick roller 15 and the feed roller 16 via the electromagnetic clutch 202. The pick roller 15 and the feed roller 16 have a built-in one-way clutch (not shown). When the electromagnetic clutch 202 is turned off, the pick-up roller 15 and the feed roller 16 can be rotated only in the sheet feeding direction. Further, the motor 201 drives and rotates the pull-out roller pair 20, 21. The engine control unit 200 is configured to be notified of the detection result of the transport sensor 23.

<Operation>
The feeding operation of the present embodiment will be described in detail with reference to FIG. FIG. 3 is a timing chart of control at the time of feeding, and a diagram schematically showing a positional relationship between the rear end position of the sheet S1 being fed and each roller. Here, the rear end of the sheet S1 indicates an end on the upstream side in the feeding direction of the sheet S1.

  When the print signal is input, the engine control unit 200 causes the motor 201 to rotate the pull-out roller pairs 20 and 21. At substantially the same time, the engine control unit 200 turns on the electromagnetic clutch 202 and rotates the pick roller 15 and the feed roller 16 (the timing at which the rear end of the sheet S1 is at the position d in FIG. 3).

  The sheet S1 fed by the pick roller 15 passes through a separation nip portion 17a formed by the feed roller 16 and the separation roller 17, and reaches the pair of extraction rollers 20, 21. When the leading end of the sheet S1 reaches the pair of pull-out rollers 20, 21, the engine control unit 200 turns off the electromagnetic clutch 202. At this time, the rear end of the sheet S1 has not passed through the pick roller 15 (the timing at which the rear end of the sheet S1 is at the position e in FIG. 3).

  The pull-out roller pairs 20, 21 transport the sheet S1 downstream so as to pull out the sheet S1 from the separation nip 17a. At this time, since the electromagnetic clutch 202 is OFF, the driving force from the motor 201 is not transmitted to the pick roller 15 and the feed roller 16. However, the two rollers follow the conveyance of the sheet S1 by the one-way clutch. Then, at a timing when a predetermined time has passed after the rear end of the sheet S1 has passed the pick roller 15, the engine control unit 200 turns on the electromagnetic clutch 202 again (in FIG. 3, the rear end of the sheet S1 is at the position f). Some timing).

  The electromagnetic clutch 202 is turned on again, and the pick roller 15 and the feed roller 16 rotate. At this time, since the sheet S1 has already passed through the pick roller 15, the sheet S2 fed next to the sheet S1 comes into contact with the pick roller 15 and is fed. Then, at the timing when the sheet S2 is conveyed by the predetermined distance B by the pick roller 15, the engine control unit 200 turns off the electromagnetic clutch 202 again. At this time, the sheet S1 is also being conveyed by a predetermined distance C (= B) by the feed roller 16 and the pair of extraction rollers 20 and 21 (timing when the rear end of the sheet S1 in FIG. 3 is at the position g). Although the drive is transmitted to the feed roller 16 at the time of preceding feeding of the sheet S2 and the sheet S1 is conveyed by the distance C due to the drive train, the drive is not transmitted to the feed roller 16 even if the drive is transmitted to the feed roller 16. no problem.

  After the preceding sheet feeding operation of the sheet S2 is completed, the feed roller 16 is rotated by the sheet S1 until the rear end of the sheet S1 passes through the separation nip portion 17a, and then stops (the rear end of the sheet S1 in FIG. h). On the other hand, since the sheet S2 in contact with the pick roller 15 has been conveyed only by the predetermined distance B, the sheet S2 has not reached the pair of extraction rollers 20 and 21. Therefore, the sheet S2 is stopped when the electromagnetic clutch 202 is off. That is, the pick roller 15 is stopped without being rotated by the sheet S2.

  At the timing when the rear end of the sheet S1 passes through the separation nip portion 17a and further passes through the pair of pull-out rollers 20, 21, the engine control unit 200 stops the motor 201 (the rear end of the sheet S1 in FIG. Some timing). Thus, the feeding operation of the sheet S1 ends.

  The timing for starting the preceding sheet feeding operation of the sheet S2 (FIG. 3, f) and the timing for ending the preceding sheet feeding operation (FIG. 3, g) are based on the engine control based on the timing when the sheet S1 reaches the conveyance sensor 23. The unit 200 calculates. The engine control unit 200 calculates these timings in consideration of the length of the sheet S1 and the transport speed of the sheet S1. Further, a delay due to backlash of the drive train (not shown) occurs after the electromagnetic clutch 202 is turned on until the pick roller 15 rotates, and the engine control unit 200 calculates the timing taking this into consideration.

  Note that the timing of starting or ending the preceding sheet feeding operation may be calculated based on the timing at which the sheet S1 reaches the registration sensor 24 instead of the conveyance sensor 23. Alternatively, it may be calculated based on the timing at which the sheet S1 loaded on the cassette 100 is started to be fed by the pick roller 15 and the feed roller 16.

  When a plurality of sheets S are continuously fed, the motor 201 may be continuously rotated, and the electromagnetic clutch 202 may be repeatedly turned on and off.

  FIG. 4 is a flowchart summarizing the above feeding operation. The control based on the flowchart in FIG. 4 is executed by the engine control unit 200 based on a program stored in a ROM or the like.

  First, in response to the print instruction, the engine control unit 200 determines whether it is time to feed the sheet S from the cassette 100 (S400). If it is determined that it is time to feed the sheet S, the engine control unit 200 starts the sheet S1 feeding operation (S401). Specifically, as described above, the motor 201 is driven and the electromagnetic clutch 202 is turned on. Thereby, the pick roller 15, the feed roller 16, and the pull-out roller pair 20, 21 are rotated.

  Next, the engine control unit 200 determines whether or not the sheet S1 is detected by the conveyance sensor 23 (S402). When determining that the sheet S1 is detected by the conveyance sensor 23, the engine control unit 200 turns off the electromagnetic clutch 202 (S403). As a result, the sheet S1 is conveyed by the pair of pull-out rollers 20 and 21, and the pick roller 15 and the feed roller 16 follow the conveyance of the sheet S1.

  Next, the engine control unit 200 determines whether at least the timing when the rear end of the sheet S1 has passed the pick roller 15, that is, the timing when a predetermined time T1 has elapsed since the conveyance sensor 23 detected the sheet S1. (S404). When it is determined that the timing has passed the predetermined time T1, the engine control unit 200 turns on the electromagnetic clutch 202 to start the preceding sheet feeding operation of the sheet S2 (S405).

  Next, the engine control unit 200 determines whether the timing at which the sheet S2 has been conveyed by the predetermined distance B, that is, the timing at which the predetermined time T2 has elapsed since the conveyance sensor 23 detected the sheet S1 has come (S406). ). If it is determined that the timing has passed the predetermined time T2, the engine control unit 200 turns off the electromagnetic clutch 202 to end the preceding sheet feeding operation of the sheet S2 (S407). After the conveyance of the sheet S1 is completed, the engine control unit 200 stops the motor 201 (S408).

  On the other hand, if it is determined in S402 that the sheet S1 has not been detected by the conveyance sensor 23, the engine control unit 200 determines whether or not the timing has passed the threshold time Tth from the start of the sheet feeding operation of the sheet S1. A determination is made (S409). Here, the threshold time Tth is a time longer than at least the predetermined time T1. If it is determined that the timing has passed the threshold time Tth, the engine control unit 200 displays a message indicating that a jam has occurred on an operation panel (not shown) provided in the printer 90 (S410). This is the end of the control of this flowchart.

  Next, the movement of the sheet S by the above-described feeding control will be described with reference to FIG. FIG. 5A shows a state in which the sheet S1 being fed has passed through the pick roller 15, and the subsequent sheet S2 has not advanced from the sheet setting position j. That is, this indicates a state in which no take-out has occurred. In this case, the succeeding sheet S2 is conveyed by a predetermined distance B as shown in FIG. Then, as shown in FIG. 5C, the sheet S1 being fed passes through the separation nip 17a. At this time, since the leading end (the downstream end in the feeding direction) of the succeeding sheet S2 is located upstream of the separation nip 17a, a large sudden burst occurs when the sheet S1 being fed passes through the separation nip 17a. No sound is produced.

  FIG. 5D shows a state in which the succeeding sheet S2 has advanced to the separation nip portion 17a at the timing when the sheet S1 being fed has passed through the pick roller 15. That is, a state is shown in which the sheet S2 has been taken out due to the effect of friction with the sheet S1 even though the sheet S2 and the pick roller 15 are not in contact. In this case, due to the preceding sheet feeding operation of the sheet S2, the succeeding sheet S2 is conveyed by a predetermined distance as shown in FIG. Then, as shown in FIG. 5F, the sheet S1 being fed passes through the separation nip 17a. At this time, since the leading end of the succeeding sheet S2 is located downstream of the separation nip 17a, no large sudden sound is generated when the sheet S1 being fed passes through the separation nip 17a.

  Here, the operation of the separation roller 17 will be described. First, when the sheet S does not exist in the separation nip 17a, the force received by the separation roller 17 due to the friction with the rotating feed roller 16 is set to exceed the rotational load of the torque limiter 18. Therefore, the separation roller 17 rotates in the direction of feeding the sheet S. When one sheet S1 is conveyed to the separation nip 17a, the force received by the separation roller 17 due to friction with the one sheet S1 is set to exceed the rotational load of the torque limiter 18. Therefore, the separation roller 17 rotates in a direction for feeding the sheet S1 (FIG. 5A). When one sheet S1 is conveyed to the separation nip portion 17a and the sheet S2 is taken out by the influence of friction with the sheet S1, the rotational load of the torque limiter 18 is separated by friction with the two sheets S1 and S2. The setting is superior to the force received by the roller 17. Therefore, the separation roller 17 stops rotating (FIG. 5D).

  On the other hand, when one sheet S1 is conveyed to the separation nip portion 17a and the sheet S2 is further conveyed by the pick roller 15, the force received by the separation roller 17 due to friction with the two sheets S1 and S2 is a torque limiter 18 It is set to exceed the rotational load of. Therefore, the separation roller 17 rotates in a direction for feeding the sheet S1 (FIG. 5E). When the two sheets S1 and S2 are conveyed to the separation nip portion 17a and the sheet S3 is taken out due to the influence of the friction with the sheet S2, the rotational load of the torque limiter 18 is increased by the friction with the three sheets S1 to S3. Thus, the setting is superior to the force received by the separation roller 17. Therefore, the separation roller 17 stops rotating.

  Paying attention to FIGS. 5D and 5E, even when the same two sheets S1 and S2 are conveyed to the separation nip portion 17a, the sheet S2 is taken along as shown in FIG. 5D. When the sheet is ejected, the separation roller 17 stops and the sheet S2 is not conveyed downstream of the separation nip 17a. Then, when the sheet S2 is fed in advance as shown in FIG. 5E, the separation roller 17 rotates to convey the sheet S2 downstream of the separation nip 17a.

  In the present embodiment, the term “take out” refers to a state in which the succeeding sheet has moved due to the influence of friction with the preceding sheet. In other words, the subsequent sheet has moved despite the fact that the pick roller 15 is not in contact with the subsequent sheet. On the other hand, the preceding sheet feeding means that the succeeding sheet is moved by a predetermined distance in advance by the pick roller 15 during the sheet feeding operation of the preceding sheet. That is, in the preceding sheet feeding, the succeeding sheet is in contact with the pick roller 15.

  FIG. 6 is a diagram showing the distribution of the leading end position of the succeeding sheet S2. FIG. 6A shows the distribution of the leading end position of the sheet S2 when there is no preceding sheet feeding operation. The distribution of the leading end position of the sheet S2 has two peaks at the set position j of the cassette 100 and the position m of the separation nip portion 17a, and the frequency is high. The frequency at which the leading end of the sheet S2 is located in the range k therebetween is low. This is because the type of sheet S that is difficult to take out hardly moves due to the effect of friction with the sheet S1, and the type of sheet S that easily takes out moves due to the effect of friction with the sheet S1. This is for separating from the sheet S1 and stopping.

  As described with reference to FIG. 14B, when the trailing end of the fed sheet S1 passes through the separation nip 17a and the leading end of the succeeding sheet S2 is at the position m of the separation nip 17a, The rear end of the sheet S1 being fed is jumped by a step due to the thickness of the sheet S2, and a sudden sound is generated. When the preceding sheet feeding operation is not performed, the frequency of the leading edge of the succeeding sheet S2 at the position m of the separation nip portion 17a increases, so that the trailing edge of the sheet S1 being fed passes through the separation nip portion 17a. The frequency of sudden sound generation also increases.

  FIG. 6B shows the distribution of the leading end position of the sheet S2 when there is a preceding sheet feeding operation. The distribution of the leading end position of the sheet S2 is shifted to a position which is advanced by a predetermined distance B to the downstream side in the feeding direction as a whole with respect to FIG. In this embodiment, the predetermined distance B to be moved by the preceding sheet feeding operation is set shorter than the distance A from the leading end position j of the sheet S set in the cassette 100 to the position m of the separation nip 17a. Therefore, the peak of the leading end position of the sheet S2 is shifted to a position n upstream of the separation nip 17a and a position p downstream of the separation nip 17a. Since the frequency at which the leading end of the sheet S2 is present at the position m of the separation nip 17a is low (range o), a sudden sound is generated when the trailing end of the fed sheet S1 passes through the separation nip 17a. Occurs less frequently. That is, sudden sounds can be reduced.

  As described above, according to the present embodiment, it is possible to provide an image forming apparatus and a feeding apparatus that reduce a sudden sound when the rear end of the recording material passes through the separation nip.

[Example 2]
Next, a second embodiment of the present invention will be described. In the second embodiment, differences from the first embodiment will be mainly described, and description of the same components as the first embodiment will be omitted. The configuration of the second embodiment is the same as that of the first embodiment.

  The feeding operation of this embodiment will be described in detail with reference to FIG. FIG. 7 is a timing chart of control at the time of feeding, and a diagram schematically showing a positional relationship between the rear end position of the sheet S1 being fed and each roller.

  When the print signal is input, the engine control unit 200 causes the motor 201 to rotate the pull-out roller pairs 20 and 21. At substantially the same time, the engine control unit 200 turns on the electromagnetic clutch 202 and rotates the pick roller 15 and the feed roller 16 (the timing at which the rear end of the sheet S1 is at the position d in FIG. 7).

  The sheet S1 fed by the pick roller 15 passes through a separation nip portion 17a formed by the feed roller 16 and the separation roller 17, and reaches the pair of extraction rollers 20, 21. In this embodiment, even when the leading end of the sheet S1 reaches the pair of pull-out rollers 20, 21, the engine control unit 200 does not switch the electromagnetic clutch 202 off (do not stop it halfway). Then, the pick roller 15 and the feed roller 16 are continuously rotated. When the rear end of the sheet S1 passes through the pick roller 15, and the sheet S2 comes into contact with the pick roller 15, the sheet S2 is pre-fed by the pick roller 15.

  Then, at the timing when the sheet S2 is conveyed by the predetermined distance B by the pick roller 15, the engine control unit 200 turns off the electromagnetic clutch 202. At this time, the sheet S1 is also being conveyed by a predetermined distance C (= B) by the feed roller 16 and the pull-out roller pairs 20 and 21 (timing when the rear end of the sheet S1 in FIG. 7 is at the position g). Although the drive is transmitted to the feed roller 16 at the time of preceding feeding of the sheet S2 and the sheet S1 is conveyed by the distance C due to the drive train, the drive is not transmitted to the feed roller 16 even if the drive is transmitted to the feed roller 16. no problem. The subsequent control is the same as in the first embodiment, and a description thereof will be omitted.

  In this case, the timing at which the rear end of the sheet S1 being fed passes through the pick roller 15 slightly varies due to the influence of the conveying speed of the sheet S1 and the length of the sheet S1. Accordingly, the distance B at which the sheet S2 moves due to the preceding sheet feeding operation also slightly varies, so that the timing for turning off the drive of the pick roller 15 is set so that the sheet S2 is not positioned at the separation nip portion 17a even if it varies. (FIG. 7, g).

  FIG. 8 is a flowchart summarizing the above feeding operation. The control based on the flowchart in FIG. 8 is executed by the engine control unit 200 based on a program stored in a ROM or the like.

  First, in response to the print instruction, the engine control unit 200 determines whether it is time to feed the sheet S from the cassette 100 (S800). If it is determined that it is time to feed the sheet S, the engine control unit 200 starts the sheet feeding operation of the sheet S1 (S801). Specifically, as described above, the motor 201 is driven and the electromagnetic clutch 202 is turned on. Thereby, the pick roller 15, the feed roller 16, and the pull-out roller pair 20, 21 are rotated.

  Next, the engine control unit 200 determines whether or not the sheet S1 is detected by the conveyance sensor 23 (S802). When determining that the sheet S1 has been detected by the transport sensor 23, the engine control unit 200 determines whether or not the timing has passed a predetermined time T3 since the transport sensor 23 detected the sheet S1 (S803). The predetermined time T3 is longer than the predetermined time T1 in the first embodiment. The timing when the predetermined time T3 has elapsed means that the rear end of the sheet S1 passes through the pick roller 15, and the sheet S2 is further moved by a predetermined distance B. This is the timing of the transfer. If it is determined that the timing has passed the predetermined time T3, the engine control unit 200 turns off the electromagnetic clutch 202 to end the preceding sheet feeding operation of the sheet S2 (S804). After the conveyance of the sheet S1 is completed, the engine control unit 200 stops the motor 201 (S805).

  On the other hand, in S802, when it is determined that the sheet S1 has not been detected by the conveyance sensor 23, the engine control unit 200 determines whether or not the timing when the threshold time Tth has elapsed since the start of the sheet feeding operation of the sheet S1. A determination is made (S806). Here, the threshold time Tth is a time longer than at least the predetermined time T3. If it is determined that the timing has passed the threshold time Tth, the engine control unit 200 displays a jam occurrence message on an operation panel (not shown) provided in the printer 90 (S807). This is the end of the control of this flowchart.

  As described above, according to the present embodiment, it is possible to provide an image forming apparatus and a feeding apparatus that reduce a sudden sound when the rear end of the recording material passes through the separation nip.

  Further, in this embodiment, there is an effect that the influence of the back tension caused by turning off the electromagnetic clutch 202 can be suppressed by continuously rotating the pick roller 15. This means that the speed at which the sheet S1 is conveyed by the pair of drawing rollers 20, 21 is stabilized. While the pick roller 15 is in contact with the sheet S1, the electromagnetic clutch 202 is not turned off, so that the pick roller 15 does not shift to the driven state. Therefore, it is possible to prevent the back tension from occurring due to the influence of the pick roller 15 and change in the transport speed of the sheet S1.

[Example 3]
Next, a third embodiment of the present invention will be described. In the third embodiment, a description will be given focusing on differences from the first embodiment, and a description of the same components as the first embodiment will be omitted. The configuration of the third embodiment is the same as that of the first embodiment.

  The feeding operation of this embodiment will be described in detail with reference to FIG. FIG. 9 is a timing chart of control at the time of feeding, and a diagram schematically showing a positional relationship between the rear end position of the sheet S1 being fed and each roller.

  This embodiment is different from the first embodiment in the distance for feeding the sheet S2 in advance. In this embodiment, the predetermined distance B for feeding the sheet S2 in advance is set to be longer than the distance A. Here, the distance A is the distance from the sheet setting position of the cassette 100 to the separation nip 17a as described in the first embodiment.

  FIG. 10 is a diagram showing the distribution of the leading end position of the succeeding sheet S2. In the present embodiment, the distance over which the sheet S2 is conveyed by the preceding sheet feeding operation is longer than in the first embodiment, so that even if the sheet S2 is not taken out due to the influence of friction, the leading end of the sheet S2 is separated by the separation nip. It is located downstream from 17a. Therefore, a large sudden sound does not occur when the fed sheet S1 passes through the separation nip portion 17a.

  Further, when the leading end of the succeeding sheet S2 reaches the pair of pull-out rollers 20 and 21 by the preceding sheet feeding operation, the succeeding sheet S2 is conveyed while overlapping the sheet S1 being fed. In order to prevent this, the predetermined distance B conveyed by the preceding sheet feeding operation is set shorter than the distance D from the separation nip portion 17a to the pair of pull-out rollers 20, 21. That is, it is necessary to satisfy the relationship of distance A <distance B <distance D.

  The flowchart in the present embodiment is basically the same as that in FIG. 4, except for the timing of ending the preceding sheet feeding operation of the sheet S2, that is, only the length of the predetermined time T2 in S406. In the present embodiment, the distance over which the sheet S2 is conveyed by the preceding sheet feeding operation needs to be longer than in the first embodiment, so that the predetermined time T2 also needs to be set longer than in the first embodiment.

  As described above, according to the present embodiment, it is possible to provide an image forming apparatus and a feeding apparatus that reduce a sudden sound when the rear end of the recording material passes through the separation nip.

  Further, in this embodiment, since the leading end of the sheet S2 is always located downstream of the separation nip portion 17a, the sudden sound generated when the rear end of the sheet S1 passes through the separation nip portion 17a is reduced more reliably than in the first embodiment. be able to.

  In the printer 90 illustrated in FIG. 1, the curvature of the transport path downstream of the separation nip 17a is greater than the curvature of the transport path upstream of the separation nip 17a. Therefore, when the rear end of the sheet S1 passes through the separation nip portion 17a, a phenomenon in which the rear end of the sheet S1 jumps due to the stiffness of the sheet S1 may occur. At this time, abnormal noise is generated by the rear end of the sheet S1 colliding with the feed roller 16, the separation roller 17, and the surrounding conveyance guides.

  According to the present embodiment, since the leading end of the sheet S2 is always located downstream of the separation nip 17a, the trailing end of the sheet S1 may be supported by the sheet S2 when the trailing end of the sheet S1 passes through the separation nip 17a. it can. That is, there is an effect that the sound due to the rear end bouncing of the sheet S1 can be reduced.

[Example 4]
Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, a description will be given focusing on differences from the first embodiment, and a description of the same components as the first embodiment will be omitted. The configuration of the fourth embodiment is the same as that of the first embodiment.

  The feeding operation of this embodiment will be described in detail with reference to FIG. FIG. 11 is a timing chart of control at the time of feeding, and a diagram schematically showing a positional relationship between the rear end position of the sheet S1 being fed and each roller.

  In the present embodiment, first, as described in the second embodiment, the pick roller 15 and the feed roller 16 are continuously turned off without turning off the electromagnetic clutch 202 before the rear end of the sheet S1 passes the pick roller 15. Rotate. Then, after the rear end of the sheet S1 has passed the pick roller 15, the preceding sheet feeding operation of the sheet S2 is executed.

  The difference between the present embodiment and the second embodiment is the distance for feeding the sheet S2 in advance. In this embodiment, the predetermined distance B for feeding the sheet S2 in advance is set to be longer than the distance A. Here, the distance A is the distance from the sheet setting position of the cassette 100 to the separation nip 17a as described in the first embodiment.

  That is, this embodiment corresponds to a combination of the second embodiment and the third embodiment. Also in the present embodiment, since the distance over which the sheet S2 is conveyed by the preceding sheet feeding operation is increased as compared with the first embodiment, even if the sheet S2 is not taken out due to the influence of friction, the leading end of the sheet S2 is separated. It is located downstream from the nip 17a. Therefore, a large sudden sound does not occur when the fed sheet S1 passes through the separation nip portion 17a.

  Further, similarly to the third embodiment, when the leading end of the succeeding sheet S2 reaches the pair of pull-out rollers 20 and 21 by the preceding sheet feeding operation, the succeeding sheet S2 is conveyed in an overlapping state with the sheet S1 being fed. I will. In order to prevent this, the predetermined distance B conveyed by the preceding sheet feeding operation is set shorter than the distance D from the separation nip portion 17a to the pair of pull-out rollers 20, 21. That is, it is necessary to satisfy the relationship of distance A <distance B <distance D.

  The flowchart in the present embodiment is basically the same as that in FIG. 8 except for the timing of ending the preceding sheet feeding operation of the sheet S2, that is, the length of the predetermined time T3 in S803. In the present embodiment, the distance over which the sheet S2 is conveyed by the preceding sheet feeding operation needs to be longer than in the second embodiment, and therefore, the predetermined time T3 also needs to be set longer than in the second embodiment.

  As described above, according to the present embodiment, it is possible to provide an image forming apparatus and a feeding apparatus that reduce a sudden sound when the rear end of the recording material passes through the separation nip.

  Further, in this embodiment, since the leading end of the sheet S2 is always located downstream of the separation nip portion 17a, the sudden sound generated when the rear end of the sheet S1 passes through the separation nip portion 17a is reduced more reliably than in the first embodiment. be able to.

  Further, in the present embodiment, by continuously rotating the pick roller 15 and the feed roller 16, there is an effect that the influence of the back tension caused by turning off the electromagnetic clutch 202 can be suppressed. This means that the speed at which the sheet S1 is conveyed by the pair of drawing rollers 20, 21 is stabilized. While the pick roller 15 and the feed roller 16 are in contact with the sheet S1, the electromagnetic clutch 202 is not turned off, so that the pick roller 15 and the feed roller 16 do not shift to the driven state. Therefore, it is possible to prevent the back tension from occurring due to the influence of the pick roller 15 and the feed roller 16 and to change the transport speed of the sheet S1.

  In the present embodiment, as in the third embodiment, the leading end of the sheet S2 is always located downstream of the separation nip 17a. Therefore, when the trailing end of the sheet S1 passes through the separation nip 17a, the sheet S2 is positioned behind the sheet S1. Can support the edge. That is, there is an effect that the sound due to the rear end bouncing of the sheet S1 can be reduced.

  In the above-described third and fourth embodiments, at least the leading end of the sheet S2 may be located downstream of the separation nip 17a by 2 mm or more in the feeding direction. Here, when the separation nip portion 17a has a predetermined width, it means that the separation nip portion 17a is located at least 2 mm downstream from the downstream end of the width in the feeding direction.

  In the first and second embodiments, the sheet S may be sandwiched in the separation nip 17a by the preceding sheet feeding operation. In the third and fourth embodiments, the sheet S is always sandwiched in the separation nip 17a. If left in this state for a long time, a mark may be formed on the sheet S due to the nip pressure, and the image formed on the sheet S may be affected. Therefore, when feeding the last sheet S of the print job, the preceding sheet feeding operation of the succeeding sheet may not be performed. That is, when feeding the last sheet S, the electromagnetic clutch 202 is controlled to be turned off before the rear end of the last sheet S passes through the pick roller 15.

  In the first to fourth embodiments, the preceding sheet feeding operation is performed regardless of the type of the sheet S to be fed. However, whether or not to perform the preceding sheet feeding operation may be switched according to the thickness or basis weight of the sheet S to be fed. The reason will be described in detail.

  When the sheet S to be fed is thin paper, the sheet S may be bent by the preceding sheet feeding operation. This is because the thin paper S has low rigidity of the sheet itself and loses the resistance of the separation nip portion 17a. Further, since the level difference when the rear end of the fed sheet S1 passes through the separation nip portion 17a is small, the magnitude of the sudden sound is also small. Therefore, when the engine control unit 200 determines that the type of the sheet S to be fed is the thin paper S, the engine control unit 200 controls not to perform the preceding sheet feeding operation, and determines that the type of the sheet S is the thick paper S. Alternatively, control may be performed so as to execute the preceding sheet feeding operation. Here, since the threshold value of the thickness of the sheet S for performing or not performing the preceding sheet feeding operation differs for each apparatus, an optimum value may be derived by an experiment.

  The engine control unit 200 may make the above determination based on information about the thickness of the sheet S input by a user from an operation panel (not shown) provided in the printer 90. Further, the ultrasonic sensor 80 illustrated in FIG. 12 may be arranged in the conveyance path of the printer 90, and the basis weight of the sheet S may be detected by receiving the attenuated ultrasonic wave via the sheet S. The ultrasonic sensor 80 has a transmitting unit 801 that transmits an ultrasonic wave and a receiving unit 802 that receives an ultrasonic wave. In this case, the engine control unit 200 may make the above determination based on information on the thickness of the sheet S indirectly obtained from the basis weight of the sheet S.

  In the first to fourth embodiments, the separation roller 17 is used to separate a plurality of sheets S into one sheet S. However, the present invention is not limited to this. A retard roller that rotates in the direction opposite to the direction in which the sheets S are fed and separates the plurality of sheets S into one sheet S may be used.

  In the first to fourth embodiments, the configuration in which the engine control unit 200 controls the pick roller 15 and the feed roller 16 via one electromagnetic clutch 202 has been described. However, it is not limited to this. The engine control unit 200 may be configured so that the pick roller 15 and the feed roller 16 can be independently controlled. For example, an electromagnetic clutch may be provided between the motor 201 and the pick roller 15, and another electromagnetic clutch may be provided between the motor 201 and the feed roller 16.

  When this configuration is adopted, for example, the electromagnetic clutch between the motor 201 and the pick roller 15 is turned on, and the electromagnetic clutch between the motor 201 and the feed roller 16 is turned on, and the sheet feeding operation of the sheet S1 is started. Then, after the preceding feeding operation of the sheet S2 is completed by the pick roller 15, only the electromagnetic clutch between the motor 201 and the pick roller 15 is turned off. Then, the feed operation of the sheet S1 can be continued by the feed roller 16 while the electromagnetic clutch between the motor 201 and the feed roller 16 is kept ON. That is, in this case, there is no need to pull out the sheet S1 from the separation nip portion 17a by the pair of pullout rollers 20, 21, and the sheet S1 may be fed downstream by the feed roller 16.

  In the first to fourth embodiments, the description has been made using the feeding device fixedly provided to the printer 90. However, it is not limited to this. The present invention may be applied to a paper feed option device 340 that can be attached to and detached from the printer 90 shown in FIG.

  The configuration of the sheet feeding option device 340 is substantially the same as the feeding device described with reference to FIG. The paper feed option device 340 includes the cassette 300 and the roller unit 319. The cassette 300 is provided with a sheet stacking plate 322 which is a stacking unit on which a plurality of sheets S are stacked. In the standby state, the sheet S is lifted to the feeding position by the sheet stacking plate 322, and the uppermost sheet S1 is in contact with the pickup roller 315. When a print signal is input, the pick roller 315 feeds the sheet S1 from among the sheets S stacked on the sheet stacking plate 322. The feed roller 316 feeds the sheet S1 fed by the pick roller 315 further downstream. The separation roller 317 is fixed to a chassis or the like of the sheet feeding option device 340 via a torque limiter 318.

  The sheet S1 fed by the feed roller 316 is conveyed to the printer 90 by a pair of pull-out rollers 320 and 321. The conveyance sensor 323 detects the conveyed sheet S1. Further, a control unit 330 is provided in the paper feed option device 340, and has a configuration similar to the block diagram shown in FIG. Further, the controller may not be mounted on the paper feed option device 340, and the rollers provided in the paper feed option device 340 may be controlled by the engine control unit 200 on the printer side.

Reference Signs List 5 transfer roller 15 pickup roller 16 feed roller 17 separation roller 22 sheet stacking table 90 printer 200 engine control unit 201 motor

Claims (5)

A feeding member that feeds a recording material placed on the placement unit,
A first conveying member for conveying the recording material fed by the feeding member;
A separation member that forms a nip portion with the first transport member, and separates a plurality of recording materials in the nip portion;
A second conveying member for conveying the recording material conveyed by the first conveying member; and
The first recording material placed on the placement section is fed by the feeding member, and before the rear end of the first recording material passes through the nip portion, the first recording material is In a state where the second recording material to be fed next partially overlaps with the first recording material, the second recording material is placed on the placing portion so that the leading end of the second recording material passes through the nip portion. Feeding the second recording material placed,
Before the leading edge of the second recording material passes through the nip and the leading edge of the second recording material reaches the second transport member, the trailing edge of the first recording material and the second The feeding operation of the second recording material by the feeding member and the first conveying member is stopped so that the leading end of the recording material is separated, and the first recording material is moved by the second conveying member. Having control means for transporting ,
The control means, after the leading end of the first recording material reaches the second transport member, and before the trailing end of the first recording material passes through the feeding member, Stopping the driving of the feeding member, and after the rear end of the first recording material conveyed by the second conveying member has passed through the feeding member, starts driving the feeding member again; A feeding device for feeding the second recording material . When feeding the last recording material of a job, the control unit stops driving the feeding member before the rear end of the last recording material passes through the feeding member,
When feeding the first recording material that is not the end of a job, the control unit drives the feeding member after the rear end of the first recording material passes through the feeding member, and The feeding device according to claim 1 , wherein the second recording material is fed. A motor for driving the feeding member, the first conveying member, and the second conveying member; and an electromagnetic motor for transmitting or blocking a driving force from the motor to the feeding member and the first conveying member. Having a clutch,
The control unit may control the electromagnetic clutch to move the motor from the motor before the leading end of the second recording material passes through the nip and the leading end of the second recording material reaches the second transport member. the driving force is cut off to the first conveying member and the feeding member, the feeding according to claim 1 or claim 2, characterized in that to drive the second conveying member by the motor apparatus. Detecting means for detecting a leading end of the recording material conveyed by the second conveying member, wherein the control means detects the leading end of the first recording material by the detecting means based on a timing at which the leading end of the first recording material is detected; The feeding device according to any one of claims 1 to 3 , wherein the timing of stopping or starting the driving of the feeding member is changed. When the first recording material is fed to the nip by the feeding member, the separating member is rotated in a predetermined direction by the first recording material,
When the second recording material is fed to the nip portion by the feeding member in a state where the first recording material is sandwiched between the nip portions, the separation member becomes the second recording material. Is rotated in the predetermined direction by
In a state where the first recording material and the second recording material are sandwiched between the nip portions, and a third recording material lower than the second recording material is fed to the nip portion, the separating member so as to prevent feeding of the third recording material, to any one of claims 1 to 4 and stops or the predetermined direction rotation, characterized in that the rotation in the opposite direction A feeding device as described.

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