Patent Grant
10676300
The present invention relates to a sheet feeding apparatus and an image forming apparatus, and particularly relates to a sheet feeding apparatus that is provided in an image forming apparatus, such as a printer, a facsimile machine, and a copying machine, and supplies sheets, such as recording sheets and documents.
Some conventional image forming apparatuses include a sheet feeding apparatus for automatically feeding sheets toward an image forming portion that forms images on the sheets. The sheet feeding apparatus includes a sheet stacking portion provided so as to be able to move upward and downward, and a sheet feeding unit sending out the top sheet of the sheets stacked on the sheet stacking portion. Then, after the sheet stacking portion is moved upward, and the top sheet is located at a sheet feedable position, the top sheet is sent out to the image forming portion by the sheet feeding unit.
An example of the sheet feeding apparatus is described by using
In conventional image forming apparatuses, when continuously feeding sheets, in order to maintain a constant throughput, some image forming apparatuses perform feeding at a constant time interval. Additionally, for example, Japanese Patent Application Laid-Open No. 2003-206038 discloses a feeding apparatus detecting that the trailing edge of a preceding sheet has passed by a sensor provided in a conveying path, and on the basis of the detection result, performing the feeding of the next sheet immediately after the detection or a predetermined time after the detection, so as to keep a constant distance between the sheets at the time of feeding. The throughput refers to the number of sheets on which images are formed per unit time. The distance between the sheets refers to the distance from the trailing edge of a preceding sheet to the leading edge of the next sheet.
Recently, in image forming apparatuses, especially in image forming apparatuses configured to start writing of an image to be transferred on a sheet after the sheet is fed, there has been a great need to shorten the distance between the sheets at the time of feeding as much as possible for the reasons of productivity improvement and the like. However, when the distance between the sheets at the time of feeding is narrowed too much, the following feeding failures tend to occur. When the trailing edge of the preceding sheet that is fed passes the separation portion 1002, under the influence of the passed sheet, the retard roller 1004 is separated from the feed roller 1003, and is oscillated and vibrated about the oscillation center 1004c. While the retard roller 1004 is vibrated and separated from the feed roller 1003, there is no resistance to the driving to rotate in the reverse direction to the feeding direction of the retard roller 1004. However, while contacting the feed roller 1003, since the reaction force is received with respect to reverse rotation, the rotation of the retard roller 1004 becomes unstable. Therefore, when the next sheet is fed, and the leading edge of the next sheet enters the separation portion 1002 while the retard roller 1004 is vibrating, the following will occur. That is, the leading edge of the next sheet may be folded, since the leading edge of the next sheet contacts the retard roller 1004 that is not being rotated or is rotated in the reverse direction to the feeding direction. Additionally, when a sheet bundle is conveyed to the separation portion 1002 while the retard roller 1004 is separated from the feed roller 1003, the sheet bundle cannot be separated into discrete sheets. Thus, feeding failures, such as double feeding, tend to occur. The time during which the retard roller 1004 is vibrated varies due to the following factors. For example, there are the pressure under which the retard roller 1004 is pressed against the feed roller 1003, the sheet friction coefficient, the rigidity of the sheet, the friction coefficients of the feed roller 1003 and the retard roller 1004, the torque of the torque limiter (not shown) provided on a retard roller axis, and the like. Therefore, conventionally, in image forming apparatuses in which the feeding is performed at a constant time interval, the feeding interval is set so that the distance between the sheets is achieved with which the feeding failures do not occur, even when the vibration time is the longest. Additionally, in image forming apparatuses detecting that the trailing edge of the preceding sheet has passed by a sensor provided in a conveying path, and on the basis of the detection result, performing the feeding of the next sheet immediately after the detection or a predetermined time after the detection, the following configuration is adopted. That is, the distance from the separation portion 1002 to the sensor in the feeding direction, or the time after the sensor detects the trailing edge of a preceding sheet until the feeding of the next sheet is started is set. However, when the distance between the sheets at the time of feeding was set as in a conventional manner, depending on the conditions of the sheet feeding apparatus used, the distance between the sheets became unnecessarily long, and the throughput was not optimized.
An aspect of the present invention has been conceived under such circumstances, and is a feeding apparatus that can achieve the improvement of productivity, without causing a deterioration in the feeding performance.
Another aspect of the present invention is a sheet feeding apparatus including a sheet stacking unit on which sheets are stacked, a feeding rotary member configured to feed the sheets from the sheet stacking unit, a conveyance rotary member configured to convey the sheets fed by the feeding rotary member, a separation rotary member forming a nip portion with the conveyance rotary member, and separating the sheets into discrete sheets in the nip portion, the separation rotary member urged to the conveyance rotary member by an urging member, an output unit configured to output a signal according to a rotation state of the separation rotary member, a driving unit configured to drive the feeding rotary member, and a control unit configured to control the driving unit to make the feeding rotary member feed a first sheet, and change a timing at which the feeding rotary member feeds a second sheet following the first sheet based on the signal output from the output unit after a trailing edge of the first sheet passes the nip portion.
A further aspect of the present invention is a sheet feeding apparatus including a sheet stacking portion on which sheets are stacked, a feeding rotary member configured to feed the sheets from the sheet stacking portion, a conveyance rotary member configured to convey the sheets that are fed by the feeding rotary member, a separation rotary member forming a nip portion with the conveyance rotary member, and separating the sheets into discrete sheets in the nip portion, the separation rotary member being urged to the conveyance rotary member by an urging member, a holder configured to hold the separation rotary member, a detection unit configured to detect an acceleration of the holder, a driving unit configured to drive the feeding rotary member, and a control unit configured to control the driving unit, make the feeding rotary member feed a first sheet, and change a timing at which the feeding rotary member is made to feed a second sheet following the first sheet, based on the acceleration detected by the detection unit after a trailing edge of the first sheet passes the nip portion.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings.
Hereinafter, embodiments of the present invention are described in detail with reference to the drawings by using Examples.
[Image Forming Apparatus]
A sheet feeding apparatus provided in a laser beam printer (hereinafter referred to as the printer) as an image forming apparatus of Example 1 is described as an example. First, the outline of the configuration of the printer is described by using
A process cartridge 7 is a process cartridge housing a process means of a known electrophotography system for image forming, and is removably provided in the printer 1. A photosensitive drum 7a as an image carrier is housed in the process cartridge 7, and writing is performed by irradiating laser light to the photosensitive drum 7a by a laser exposure apparatus 8 according to image information. Additionally, a charging device 7b, a developing device 7c, a cleaning device 7d, etc., are arranged around the photosensitive drum 7a, and the development of a toner image and cleaning are performed. The sheets S sent out from the sheet feeding unit 100 pass through conveyance rollers 105 that are second conveyance rotary members and registration rollers (hereinafter referred to as the resist rollers) 6, which are provided in a sheet conveying path illustrated by a broken line. When the leading edge of the sheet S that passed the resist roller 6 is detected by a top sensor 13 arranged more downstream in the conveyance direction than the resist roller 6, the sheet S is conveyed to a transfer nip portion so that the position of the sheet S and the position of a toner image are aligned. Here, the transfer nip portion is a nip portion formed by the photosensitive drum 7a and a transfer roller 9, which is a transfer means contacting the photosensitive drum 7a. Thereafter, the toner image developed on the surface of the photosensitive drum 7a is transferred to the sheet S that passes through between the photosensitive drum 7a and the transfer roller 9. A fixing apparatus 10 fixes the toner image by applying heat and pressure to the sheet S on which an unfixed toner image was transferred. Then, the sheet S on which the toner image is fixed is discharged by a pair of discharge rollers 11 to a discharging tray 12 with the image surface facing down. The discharging tray 12 is formed on an upper surface of the printer 1. Further, the configuration of the image forming portion of the printer 1 may be other configurations, and is not limited to the configuration of
The printer 1 includes a control portion 150, which is a control unit. The control portion 150 controls the operation of the entire printer 1 according to a program stored in advance in, for example, a ROM (not shown) provided inside the control portion 150, while using, for example, a RAM (not shown) provided inside the control portion 150 as a workspace. The control portion 150 also controls a feeding operation, etc. of the sheets S by the sheet feeding unit 100 as the sheet feeding apparatus. That is, the control portion 150 controls the control of a feed motor 110, the connection or disconnection of an electromagnetic clutch 112 (see
[Sheet Feeding Unit]
Here, the detailed configuration of the sheet feeding unit 100 of Example 1 is described by using
On the other hand, the driving in the direction opposite to the feeding direction is transmitted to the retard roller 104 via a retard roller driving gear column 111 including a torque limiter 108 with the feed motor 110 as a driving source. The drive transmission force of the torque limiter 108 is always set to be greater than the frictional force generated between the sheets due to the friction coefficient of the sheets S used. Additionally, the drive transmission force of the torque limiter 108 is set to be smaller than the frictional force due to the friction coefficient between the sheet S and the feed roller 103. Therefore, when the number of the sheets S entering the separation nip portion 102 is one, or when the sheet S has not entered the separation nip portion 102, the retard roller 104 corotates with the sheet S or the feed roller 103. Additionally, when two or more sheets S enter the separation nip portion 102, the retard roller 104 is rotated in the direction opposite to the feeding direction, and separates the sheets S into discrete sheets.
Additionally, in the retard roller driving gear column 111, a code wheel 115 is provided to a retard axis 116 holding the retard roller 104. An encoder 109 is an output unit that outputs a signal according to the rotation state of the code wheel 115 to the control portion 150. The control portion 150 can determine that the retard roller 104 is performing normal rotation or reverse rotation, and can determine the angular velocity of the rotation of the retard roller 104, based on the output signal of the encoder 109. Accordingly, the control portion 150 can detect that the rotation of the retard roller 104 is unstable, when the retard roller 104 is vibrating in arrow Y2 directions about the retard roller oscillation center 104c as the oscillation center. Further, the pick-up roller 101 can contact or can be separated from the top sheet S1 of the sheets S stacked on the feeding cassette 106 by oscillating in arrow Y3 directions about a pick-up roller oscillation center 101c as the oscillation center.
<A Series of Operations of Sheet Feeding Unit 100 in the Case of Printing Job Specifying One Sheet>
As illustrated in
Then, with the start of driving and rotation of the feed motor 110, as illustrated in
<A Series of Operations of Sheet Feeding Unit 100 during Continuous Feeding>
Using
During the continuous feeding, the feed motor 110 is always driven to rotate, and the retard roller 104 is driven in the direction opposite to the feeding direction (the direction for performing reverse rotation) via the torque limiter 108, as described with reference to
State Zone 1
In the state zone 1, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows:
the preceding sheet leading edge position is more downstream than the conveyance roller 105;
the preceding sheet trailing edge position is more upstream than the pick-up roller 101 by X mm (see
the next sheet is inside the feeding cassette 106.
Additionally, each roller, the encoder 109, and the electromagnetic clutch 112 are as follows:
the retard roller 104 behaves corotating with the preceding sheet (the broken-line arrow), and performing normal rotation with respect to the feeding direction;
the feed roller 103 behaves corotating with the preceding sheet (the broken-line arrow), and performing normal rotation with respect to the feeding direction; and
the pick-up roller 101 is separated from the preceding sheet, performing normal rotation with respect to the feeding direction. Further, since the electromagnetic clutch 112 is turned OFF as described later, the arrow in the normal rotation direction is illustrated with a broken line.
In the detection result based on the output signal of the encoder 109, it is detected that the retard roller 104 is performing normal rotation and is stable. Further, the control portion 150 cannot determine whether the retard roller 104 is performing normal rotation or reverse rotation only from the output signal of the encoder 109. However, the control portion 150 manages, with the counter, the state zones in which the retard roller 104 can only perform normal rotation and the state zones in which the retard roller 104 can only perform reverse rotation. Thus, the control portion 150 can determine whether the retard roller 104 is performing normal rotation or reverse rotation.
In the electromagnetic clutch 112 (feeding signal), after the preceding sheet leading edge passes the conveyance roller 105, the electromagnetic clutch 112 is turned OFF, and driving and coupling is canceled.
State Zone 2
In the state zone 2, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows:
preceding sheet leading edge position is more downstream than the conveyance roller 105;
preceding sheet trailing edge position: between the position that is X mm upstream of the pick-up roller 101 and the separation nip portion 102; and
the next sheet is inside the feeding cassette 106.
Additionally, each roller, the encoder 109, and the electromagnetic clutch 112 are as follows:
the retard roller 104 behaves corotating with the preceding sheet (the broken-line arrow), and performing normal rotation with respect to the feeding direction; and
the feed roller 103 behaves corotating with the preceding sheet (the broken-line arrow), and performing normal rotation with respect to the feeding direction.
The pick-up roller 101 behaves contacting the preceding sheet after a predetermined time t2 passes since the feeding signal of the preceding sheet is turned ON. The predetermined time t2 is determined according to the set sheet length. That is, the predetermined time t2 is determined based on the time for the trailing edge of the preceding sheet to pass the position that is more upstream in the feeding direction than the position at which the pick-up roller 101 contacts the preceding sheet (hereinafter referred to as the contacting position) by a predetermined distance X mm. In other words, the predetermined time t2 can be said to be the time required for the position more downstream in the feeding direction than the trailing edge of the preceding sheet by the predetermined distance X mm to pass the pick-up roller 101. When the sheet length is short, the time for the trailing edge of the sheet to pass the predetermined distance X mm that is more upstream in the feeding direction than the contacting position after feeding of the sheet is started becomes short. On the other hand, when the sheet length is long, the time for the trailing edge of the sheet to pass the predetermined distance X mm that is more upstream in the feeding direction than the contacting position after feeding of the sheet is started becomes longer than the case where the sheet length is short. Note that the sheet length is the length of the sheet S in the feeding direction.
The circumferential speed of the feed roller 103 is set to be faster than the circumferential speed of the pick-up roller 101. Therefore, in the state zone 2, the conveyance speed of the preceding sheet is faster than the circumferential speed of the pick-up roller 101. Additionally, the one-way clutch is housed in the one-way clutch gear 114. Thus, in the state zone 2, the pick-up roller 101 corotates with the preceding sheet (the broken-line arrow) and performs idle rotation.
In the detection result based on the output signal of the encoder 109, it is detected that the retard roller 104 is performing normal rotation and is stable.
In the electromagnetic clutch 112 (feeding signal), the electromagnetic clutch is turned OFF, and driving is not coupled.
The pick-up roller 101 contacts the preceding sheet before the feeding signal of the next sheet is turned ON, thereby minimizing the time in which the sheet is fed after the feeding signal of the next sheet is received. The pick-up roller 101 contacts the preceding sheet when the preceding sheet is fed from the feeding cassette 106. The pick-up roller 101 is separated from the preceding sheet when the leading edge of the preceding sheet passes the separation nip portion 102. The pick-up roller 101 contacts the preceding sheet again (contacts the first sheet again) at the timing when the trailing edge of the preceding sheet passes the position that is in the direction opposite to the feeding direction by the predetermined distance (the above-described X mm) from the position at which the pick-up roller 101 contacts the preceding sheet.
State Zone 3
In the state zone 3, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows:
preceding sheet leading edge position is more downstream than the conveyance roller 105;
preceding sheet trailing edge position is immediately after passing the separation nip portion 102; and
the next sheet is inside the feeding cassette 106. Additionally, each roller, the encoder 109, and the electromagnetic clutch 112 are as follows:
the retard roller 104 behaves, with the impact caused by the trailing edge of the preceding sheet passing the separation nip portion 102, such that the retard roller 104 is vibrated in the arrow Y2 directions about the retard roller oscillation center 104c as the oscillation center with respect to the feed roller 103, and the rotation becomes unstable (the circles illustrated by the continuous line and a broken line in the figure).
The feed roller 103 behaves as not being driven, and since the rotation of the retard roller 104 is unstable, the rotation of the feed roller 103 also becomes unstable.
The pick-up roller 101 behaves contacting the next sheet and not rotating. In the detection result based on the output signal of the encoder 109, the unstable normal rotation (a dotted line) or the unstable reverse rotation (the continuous line) of the retard roller 104 is detected.
The electromagnetic clutch 112 (feeding signal) 112 is turned OFF, and not coupled for driving.
State Zone 4
In the state zone 4, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows:
preceding sheet leading edge position is more downstream than the conveyance roller 105;
preceding sheet trailing edge position is more downstream than the separation nip portion 102; and
the next sheet is inside the feeding cassette 106.
Additionally, each roller, the encoder 109, and the electromagnetic clutch 112 are as follows:
the retard roller 104 behaves such that the vibration of the retard roller 104 is converged, and is stabilized in reverse rotation (the continuous-line arrow) equal to or more than a predetermined rotation frequency.
The feed roller 103 behaves corotating with the retard roller 104 (the broken-line arrow), and performing reverse rotation.
The behavior of the pick-up roller 101 behaves contacting the next sheet but not rotating. In the detection result based on the output signal of the encoder 109, the retard roller 104 is stable in reverse rotation.
The electromagnetic clutch 112 (feeding signal) is turned OFF, and not coupled for driving.
State Zone 5
In the state zone 5, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows:
preceding sheet leading edge position: more downstream than the conveyance roller 105;
preceding sheet trailing edge position: more downstream than the separation nip portion 102; and
the next sheet leading edge position is more upstream than the separation nip portion 102. Additionally, each roller, the encoder 109, and the electromagnetic clutch 112 are as follows:
the retard roller 104 behaves such that, since the feed roller 103 performs normal rotation (the continuous-line arrow), the retard roller 104 corotates with the feed roller 103 (the broken-line arrow), and is under acceleration in normal rotation. Note that, in
The feed roller 103 behaves performing normal rotation (the continuous-line arrow).
The pick-up roller 101 behaves contacting the next sheet, and performing normal rotation driving (the continuous-line arrow), and feeding the next sheet.
In the detection result based on the output signal of the encoder 109, it is detected that the retard roller 104 is under acceleration in normal rotation.
The electromagnetic clutch 112 (feeding signal) is turned ON, on the basis of the fact that the detection result based on the output signal of the encoder 109 becomes “reverse rotation stable.” Alternatively, the feeding signal may be sent by estimating the timing at which reverse rotation stable is achieved from the waveform of the output signal of the encoder 109, considering the time until the sheet S is actually fed after starting the turning ON of the feeding signal, and subtracting the time from the timing at which the reverse rotation stable is achieved.
State Zone 6
In the state zone 6, the leading edge position and trailing edge position of the preceding sheet, and the next sheet are as follows:
preceding sheet leading edge position is more downstream than the conveyance roller 105;
preceding sheet trailing edge position is more downstream than the separation nip portion 102; and
the next sheet leading edge position: between a position more downstream than the separation nip portion 102 and the position of the conveyance roller 105.
Additionally, each roller, the encoder 109, and the electromagnetic clutch 112 are as follows:
the retard roller 104 behaves, when the next sheet is not in double feeding, corotating with the next sheet (the broken-line arrow), and performing normal rotation with respect to the feeding direction, and
The feed roller 103 behaves performing normal rotation (the continuous-line arrow).
The pick-up roller 101 is separated from the next sheet after a predetermined time t1 (t1<t2) passes since the feeding signal of the next sheet is turned ON, and after the leading edge of the next sheet that is being fed passes the separation nip portion 102.
In the detection result based on the output signal of the encoder 109, when the next sheet is not in double feeding, it is detected that the retard roller 104 is performing normal rotation and is stable (the continuous line). When the next sheet is in double feeding, it is detected that the retard roller 104 is performing reverse rotation (“behavior in double feeding” illustrated by the broken line). Note that, since there is a case where double feeding is canceled during the state zones 5 and 6, and the retard roller 104 transitions from reverse rotation to normal rotation, “under acceleration” is also illustrated by the broken line in
The electromagnetic clutch 112 (feeding signal) is turned ON, and coupled for driving.
(Other Design Requirements)
After the reverse rotation of the retard roller 104 is stabilized in this manner, and the vibration is converged (after the timing at which the vibration is converged), feeding of the next sheet is started. Accordingly, the optimum distance between the sheets is achieved according to the conditions of the sheet feeding apparatus used. As a result, deterioration in the feeding performance due to the fact that the distance between the sheets at the time of feeding is too narrow is not caused, and feeding can be performed with the shortest distance between the sheets. Thus, productivity improvement can be achieved. In Example 1, the feed motor 110 is controlled to make the pick-up roller 101 to perform feeding of the first sheet. After the trailing edge of the first sheet passes the separation nip portion 102, based on the signal output from the encoder 109, the timing at which the second sheet following the first sheet is fed by the pick-up roller 101 is changed. As described above, according to Example 1, the improvement of productivity can be achieved, without causing a deterioration in the feeding performance.
Next, Example 2 is described by using
<A Series of Operations of the Sheet Feeding Unit 100 during Continuous Feeding>
Using
State Zone 1 to State Zone 2
Because the state zones 1 and 2 are the same as those in Example 1, a description of those is omitted.
State Zone 3
In the state zone 3, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows:
preceding sheet leading edge position is more downstream than the conveyance roller 105;
preceding sheet trailing edge position is immediately after passing the separation nip portion 102; and
the next sheet is inside the feeding cassette 106.
Additionally, each roller, the encoder 109, and the electromagnetic clutch 112 are as follows:
the retard roller 104 behaves, with the impact caused by the trailing edge of the preceding sheet passing the separation nip portion 102, such that the retard roller 104 is vibrated in the arrow Y2 directions about the retard roller oscillation center 104c as the oscillation center with respect to the feed roller 103, and the rotation becomes unstable.
The feed roller 103 is not driven, and the feed roller 103 does not perform reverse rotation due to the one-way clutch 117. Thus, the feed roller 103 stops.
The pick-up roller 101 behaves contacting the next sheet but not rotating.
In the detection result based on the output signal of the encoder 109, unstable normal rotation illustrated by the broken line of the retard roller 104 or the unstable reverse rotation illustrated by the continuous line is detected.
The electromagnetic clutch 112 (feeding signal) is turned OFF, and not coupled for driving.
State Zone 4
In the state zone 4, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows:
preceding sheet leading edge position is more downstream than the conveyance roller 105;
preceding sheet trailing edge position: more downstream than the separation nip portion 102; and
the next sheet is inside the feeding cassette 106.
Additionally, each roller, the encoder 109, and the electromagnetic clutch 112 are as follows:
the retard roller 104 behaves such that the vibration of the retard roller 104 is converged, and the rotation is stopped by the configuration of Example 2.
The feed roller 103 behaves stopping.
The pick-up roller 101 behaves contacting the next sheet but not rotating.
In the detection result based on the output signal of the encoder 109, the stop of the retard roller 104 is detected.
The electromagnetic clutch 112 (feeding signal) is turned OFF, and not coupled for driving.
State Zone 5
In the state zone 5, the leading edge position and trailing edge position of the preceding sheet and the leading edge position of the next sheet are as follows:
preceding sheet leading edge position is more downstream than the conveyance roller 105;
preceding sheet trailing edge position is more downstream than the separation nip portion 102; and
the next sheet leading edge position is more upstream than the separation nip portion 102.
Additionally, each roller, the encoder 109, and the electromagnetic clutch 112 are as follows:
the retard roller 104 behaves, when the feed roller 103 performs normal rotation, such that the retard roller 104 corotates with the feed roller 103, and is under acceleration in normal rotation from the stop state in the state zone 4. Therefore, in
the feed roller 103 performs normal rotation;
the pick-up roller 101 behaves contacting the next sheet, driven to perform normal rotation, and feeding the next sheet; and
in the detection result based on the output signal of the encoder 109, it is detected that the retard roller 104 is under acceleration in normal rotation.
The electromagnetic clutch 112 (feeding signal) is turned ON, on the basis of the fact that the detection result based on the output signal of the encoder 109 is stop. Alternatively, the feeding signal may be turned ON by estimating the timing for stop from the waveform of the output signal of the encoder 109, considering the time until the sheet S is actually fed after the feeding signal is turned ON, and subtracting the time from the timing for stop.
State Zone 6
In the state zone 6, the leading edge position and trailing edge position of the preceding sheet, and the leading edge position of the next sheet are as follows:
preceding sheet leading edge position: more downstream than the conveyance roller 105;
preceding sheet trailing edge position: more downstream than the separation nip portion 102; and
the next sheet leading edge position: between a position more downstream than the separation nip portion 102 and the position of the conveyance roller 105.
Additionally, each roller, the encoder 109, and the electromagnetic clutch 112 are as follows:
the retard roller 104 behaves when the next sheet is not in double feeding, corotating with the next sheet, and performing normal rotation with respect to the feeding direction. When the next sheet is in double feeding, performing reverse rotation with respect to the feeding direction. Note that, since “reverse rotation” is not illustrated in
The feed roller 103 performs normal rotation.
The pick-up roller 101 is separated from the next sheet after the predetermined time t1 (t1<t2) from the turning ON of the feeding signal of the next sheet, and after the preceding sheet leading edge that is being conveyed passes the separation nip portion 102.
In the detection result based on the output signal of the encoder 109, when the next sheet is not in double feeding, it is detected that the retard roller 104 is performing normal rotation and is stable. When the next sheet is in double feeding, it is detected that the retard roller 104 is performing reverse rotation. Note that, since the “reverse rotation stable” is not illustrated in
The electromagnetic clutch 112 (feeding signal) is turned ON, and coupled for driving.
(Other Design Requirements)
The friction coefficients of the roller surfaces of the feed roller 103 and the retard roller 104 are decreased due to scratch of the roller surfaces as the rollers are used for a while, and adhesion of paper powders on the roller surfaces. When the friction coefficient is less than a certain value, in the state zone 4, the retard roller 104 may not stop and perform reverse rotation. In that case, the encoder 109 cannot detect the stop of the retard roller 104, and feeding is never started. Therefore, as a countermeasure for that case, even if the feeding signal is not turned ON, the control portion 150 forcibly starts feeding after a predetermined time t3, which is a third time on the basis of the start of feeding of the preceding sheet, has passed. When this forced feeding successively occurs for a predetermined number of times, the control portion 150 may display the information to prompt exchange of the feed roller 103 and the retard roller 104, etc. on the display unit 121.
In Example 2, feeding of the next sheet is started after vibration is converged substantially simultaneously when the rotation of the retard roller 104 is stopped. Therefore, the same effect as in Example 1 can be obtained. As described above, according to Example 2, the improvement of productivity can be achieved, without causing a deterioration in the feeding performance.
<Configuration of Separation Portion>
Next, Example 3 is described. The same reference numerals are assigned to the same configurations as those in Example 1, and a detailed description for such configurations is omitted.
<A Series of Operations of Sheet Feeding Unit 100 during Continuous Feeding>
Using
In Example 1 and Example 2, the feeding prohibition state zone (see
Additionally, in Example 1 and Example 2, the retard roller 104 is driven to perform reverse rotation with respect to the feeding direction. However, in Example 3, the acceleration is detected by the acceleration sensor 123 in the arrow Y2 directions. Thus, it is unnecessary to drive the retard roller 104 to perform reverse rotation.
Since feeding is started after the vibration of the retard roller 104 is converged based on the detection result of the acceleration sensor 123 in this manner, the same effect as in Example 1 can be obtained. As described above, according to Example 3, the improvement of productivity can be achieved, without causing a deterioration in the feeding performance.
Next, Example 4 is described. In Example 1 to Example 3, the rotation or vibration of the retard roller 104 is detected, and feeding of the next sheet is started based on the detection result. That is, the interval from the start of feeding of the preceding sheet to the start of feeding of the next sheet is not a constant time. On the other hand, in Example 4, the interval from the start of feeding of the preceding sheet to the start of feeding of the next sheet is a constant time.
before durability A1<after durability A2.
Here, before durability A1 is the oscillation angle of the retard roller 104s and the retard roller 104t in the state where the rollers are not used much. After durability A2 is the oscillation angle of the retard roller 104s and the retard roller 104t in the state where the rollers are used for a while.
As a result, when used for a while, the vibration of the retard roller 104 is converged, and the time until the rotation is stabilized will be extended. Therefore, when the interval from the start of feeding of the preceding sheet to the start of feeding of the next sheet is set to be a certain time, the vibration of the retard roller 104 has not converged yet within the certain time, feeding of the next sheet is started at the timing at which the rotation is unstable, and feeding failures may tend to occur. As the countermeasure, in Example 4, when the vibration of the retard roller 104 has not converged and the rotation is not stable at the time of the start of feeding after a certain time has passed, the control portion 150 is set not to start feeding of the next sheet, but to start feeding after the vibration is converged and the rotation is stabilized. In this manner, the start of feeding of the next sheet is changed according to the used hours of the retard roller 104. That is, when the vibration of the retard roller 104 is converged within a certain time, the next sheet is fed at the timing when the certain time has passed. Then, when the vibration of the retard roller 104 is not converged within the certain time, the next sheet is fed at the timing after a certain time has passed in which the vibration of the retard roller 104 is converged.
Additionally, in that case, the control portion 150 displays that exchange of the feed roller 103 and the retard roller 104 is necessary on the display unit 121, thereby reporting the necessity to the user. As a result, though the throughput is decreased, the exchange timing of the feed roller 103 and the retard roller 104 can be delayed, while reducing feeding failures caused by starting feeding of the next sheet during the vibration of the retard roller 104. Accordingly, the down time until the user purchases and exchanges the replacement parts such as the feed roller 103 and the retard roller 104 can be eliminated. As described above, according to Example 4, the improvement of productivity can be achieved, without causing a deterioration in the feeding performance.
Further, in the above-described Examples 1 to 4, the retard roller 104 to which driving is transmitted in the direction opposite to the feeding direction of the sheets S was described as an example. However, the present invention can also be applied to a so-called separation roller to which driving is not transmitted from a driving source.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2017-246426, filed Dec. 22, 2017, and Japanese Patent Application No. 2018-209244, filed Nov. 6, 2018, which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-246426 | Dec 2017 | JP | national |
| 2018-209244 | Nov 2018 | JP | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20190193971 A1 | Jun 2019 | US |
