JP7166879B2 - sheet feeder - Google Patents

Description

The present invention relates to a sheet feeding device, and more particularly to a sheet feeding device provided in an image forming apparatus such as a printer, a facsimile machine, a copying machine, etc., for feeding sheets such as recording sheets and originals.

2. Description of the Related Art Some conventional image forming apparatuses include a sheet feeding device for automatically feeding sheets toward an image forming section that forms an image on the sheets. The sheet feeding device includes a sheet stacking section provided to be able to move up and down in the sheet stacking section, and a sheet feeding section for feeding the uppermost sheet among the sheets stacked on the sheet stacking section. After the sheet stacking unit is lifted to position the uppermost sheet at the sheet feeding position, the sheet feeding unit feeds the uppermost sheet to the image forming unit.

An example of the sheet feeding device will be described with reference to FIGS. A feeding cassette 1006 as a sheet stacking unit can be pulled out into the apparatus main body 1100. In the pulled out state, a sheet S is placed on an intermediate plate 1007 as a sheet stacking unit provided in the feeding cassette 1006. loaded. A sheet feeding unit 1000 for sequentially feeding the sheets S stacked on the intermediate plate 1007 is arranged in the apparatus main body 1100 . The sheet feeding unit 1000 includes a pickup roller 1001 that contacts the upper surface of the sheet S on the intermediate plate 1007 and feeds out the uppermost sheet S1, and a pickup roller 1001 that separates the sheets S fed from the pickup roller 1001 one by one. A separation unit 1002 is provided. This separating section 1002 includes a feed roller 1003 and a retard roller 1004 . The feed roller 1003 is rotationally driven in the sheet S feeding direction. The retard roller 1004 is capable of swinging around a swing center 1004c, and is biased in the direction of arrow Y1 by a spring (not shown) to press against the feed roller 1003, via a torque limiter (not shown), It is rotationally driven in the direction in which the sheet S is returned.

Some conventional image forming apparatuses feed sheets at regular time intervals in order to keep the throughput constant when continuously feeding sheets. Also, in order to keep the interval between sheets constant during feeding, a sensor provided in the conveying path detects that the trailing edge of the preceding sheet has passed. There is one that feeds the next sheet (see, for example, Japanese Unexamined Patent Application Publication No. 2002-100002). Throughput is the number of images formed per unit time. The sheet interval is the distance from the trailing edge of the preceding sheet to the leading edge of the next sheet.

Japanese Patent Application Laid-Open No. 2003-206038

In recent years, in an image forming apparatus, particularly in an image forming apparatus configured to start writing an image to be transferred onto a sheet after feeding, for reasons such as productivity improvement, sheets are spaced apart during feeding. There is a great need to shorten it as much as possible. However, if the sheet interval during feeding is too narrow, the following feeding failures are likely to occur. When the trailing edge of the preceding sheet to be fed passes through the separating portion 1002, the retard roller 1004 is separated from the feed roller 1003 by the momentum of the passing sheet, and swings and vibrates about the swing center 1004c. While the retard roller 1004 vibrates and is separated from the feed roller 1003, there is no resistance to the rotational driving of the retard roller 1004 in the direction opposite to the feeding direction. However, while in contact with the feed roller 1003, the retard roller 1004 rotates unstable because it receives a reaction force against the reverse rotation. Therefore, when the next sheet is fed while the retard roller 1004 is vibrating and the leading edge of the next sheet enters the separating portion 1002, the following occurs. That is, when the leading edge of the next sheet abuts against the retard roller 1004 that is not rotating or rotating in the opposite direction to the feeding direction, the leading edge of the next sheet may be folded. Further, if the sheet bundle is conveyed to the separation unit 1002 while the retard roller 1004 is separated from the feed roller 1003, the sheet bundle cannot be separated into individual sheets, and thus feeding such as multi-feeding is not possible. Poor delivery is more likely to occur. The time that the retard roller 1004 vibrates varies depending on the following factors. For example, the pressure of the retard roller 1004 against the feed roller 1003, the coefficient of sheet friction, the rigidity of the sheet, the coefficient of friction of the feed roller 1003 and the retard roller 1004, the torque of a torque limiter (not shown) provided on the shaft of the retard roller, etc. be. For this reason, conventionally, with respect to sheets that are fed at regular time intervals, the feeding interval is set so that the feeding failure does not occur even when the vibration time is the longest. In addition, in the case where a sensor provided in the conveying path detects that the trailing edge of the preceding sheet has passed, and based on the detection result, the next sheet is fed immediately after that or after a predetermined time. like That is, the distance in the feeding direction from the separation unit 1002 to the sensor and the time from when the sensor detects the trailing edge of the previous sheet to when the next sheet starts to be fed are set. However, if the interval between sheets during feeding is set as in the conventional method, depending on the conditions of the sheet feeding device used, the interval between sheets becomes unnecessarily long, and the throughput is not optimized.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to improve productivity without deteriorating feeding performance.

In order to solve the above problems, the present invention has the following configurations.
(1) A sheet stacking unit on which sheets are stacked, a feeding rotator that feeds the sheet from the sheet stacking unit, a conveying rotator that conveys the sheet fed by the feeding rotator, and the conveying unit. A separating rotator that forms a nip portion with a rotator and separates a sheet into one sheet at the nip portion, wherein the separating rotator is urged against the conveying rotator by an urging member, and the separating rotator. In a sheet feeding apparatus having output means for outputting a signal corresponding to the rotation state of a body and driving means for driving the feeding rotator, the driving means is controlled to cause the feeding rotator to move the first sheet. After the trailing edge of the first sheet has passed through the nip portion, the first sheet is followed by the feeding rotary member based on the signal output from the output means. A sheet feeding apparatus, comprising control means for changing the timing of feeding the second sheet.
(2) a sheet stacking unit on which sheets are stacked; a feeding rotator that feeds the sheet from the sheet stacking unit; a conveying rotator that conveys the sheet fed by the feeding rotator; A separating rotator that forms a nip portion with a rotator and separates a sheet into one sheet at the nip portion, wherein the separating rotator is urged against the conveying rotator by an urging member, and the separating rotator. In a sheet feeding apparatus having a holder for holding a sheet, detection means for detecting acceleration of the holder, and driving means for driving the feeding rotator, the driving means is controlled to control the feeding rotator. to feed the first sheet, and after the trailing edge of the first sheet has passed through the nip portion, the first sheet is fed by the feeding rotator based on the acceleration detected by the detecting means. A sheet feeding apparatus comprising control means for changing the timing of feeding a second sheet following a sheet.

According to the present invention, it is possible to improve productivity without deteriorating the feeding performance.

Overall perspective view of printer 1 of Examples 1 to 4 Cross-sectional view of the printer 1 of Examples 1 to 4 Schematic diagram of a drive train of the sheet feeding unit 100 of the first embodiment Sectional view of sheet feeding unit 100 of embodiment 1 Sectional view of sheet feeding unit 100 of embodiment 1 Embodiment 1 Explanatory diagram of a series of operations of the sheet feeding unit 100 FIG. 4 is a diagram showing output signals of the encoder 109 of the first embodiment; Schematic diagram of a drive train of the sheet feeding unit 100 of the second embodiment FIG. 10 is an explanatory diagram of a series of operations of the sheet feeding unit 100 according to the second embodiment; A perspective view of the sheet feeding unit 100 according to the third embodiment. Explanatory diagram of a series of operations of the sheet feeding unit 100 of the third embodiment. Sectional view of sheet feeding unit 100 of embodiment 4 10A and 10B are an overall perspective view showing a conventional image forming apparatus and a cross-sectional view of a sheet feeding portion 1000;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[Image forming apparatus]
A sheet feeding device provided in a laser beam printer (hereinafter referred to as a printer) as an image forming apparatus according to the first embodiment will be described as an example. First, the outline of the configuration of the printer will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is an overall image of the printer, and FIG. 2 is a cross-sectional view showing the overall configuration of the printer provided with a feed cassette 106 as a sheet stacking unit. The printer 1, which is an image forming apparatus, includes a feeding cassette 106 for stacking sheets S and a display unit 121 for displaying information to the user. The feeding cassette 106 is provided with an intermediate plate 107 for stacking the sheets S, and is movable in the feeding direction (also the conveying direction) of the sheets S and in the direction opposite to the feeding direction (reverse direction). The feeding cassette 106 has a sheet trailing edge regulating portion 120 that regulates the position of the trailing edge of the sheet S stacked on the intermediate plate 107 in the feeding direction. A sheet feeding section 100 is provided above the feeding cassette 106 . The sheet feeding section 100 has a pickup roller 101 as a feeding rotating body, a feed roller 103 as a first conveying rotating body, and a retard roller 104 as a separating rotating body. The retard roller 104 can swing around a swing center 104c. The retard roller 104 is pressed against the feed roller 103 by being urged toward the feed roller 103 by a spring (not shown) by an urging member. The pickup roller 101 comes into contact with the uppermost sheet S1 of the sheets S stacked in the feed cassette 106 and feeds it. The feed roller 103 and the retard roller 104 are in contact with each other to form a separation nip portion 102, in which the sheets S delivered by the pickup roller 101 are separated one by one and conveyed.

The process cartridge 7 is a process cartridge containing a known electrophotographic process means for image formation, and is detachably attached to the printer 1 . A photosensitive drum 7a serving as an image carrier is incorporated in the process cartridge 7, and a laser beam is irradiated to the photosensitive drum 7a by a laser exposure device 8 according to image information to perform writing. A charger 7b, a developer 7c, a cleaner 7d, and the like are arranged around the photosensitive drum 7a to develop and clean the toner image. The sheet S sent out from the sheet feeding portion 100 passes through a conveying roller 105, which is a second conveying rotating member, and a registration roller (hereinafter referred to as a registration roller) 6 provided in the sheet conveying path indicated by the dashed line. . When the leading edge of the sheet S that has passed through the registration rollers 6 is detected by the top sensor 13 arranged downstream of the registration rollers 6 in the conveying direction, the transfer nip portion is moved so that the positions of the sheet S and the toner image are aligned. transported to. Here, the transfer nip portion is a nip portion formed by the photosensitive drum 7a and the transfer roller 9, which is the transfer means, in contact with the photosensitive drum 7a. Thereafter, the toner image developed on the surface of the photosensitive drum 7a is transferred onto the sheet S passing between the photosensitive drum 7a and the transfer roller 9. FIG. The fixing device 10 fixes the toner image by applying heat and pressure to the sheet S onto which the unfixed toner image has been transferred. After the toner image is fixed, the sheet S is discharged by the discharge roller pair 11 onto a discharge tray 12 formed on the upper surface of the printer 1 with the image surface facing downward. The configuration of the image forming section of the printer 1 is not limited to the configuration shown in FIG. 2, and may be a color printer having a plurality of process cartridges corresponding to a plurality of colors, for example.

The printer 1 includes a control section 150 as control means. The control unit 150 controls the overall operation of the printer 1 while using an internal RAM (not shown) as a work area according to a program pre-stored in an internal ROM or the like (not shown). The control unit 150 also controls the feeding operation of the sheet S by the sheet feeding unit 100 as a sheet feeding device. That is, the control unit 150 controls the later-described feed motor 110 and the connection or disconnection of the electromagnetic clutch 112 (see FIG. 3, etc.) (ON/OFF of the electromagnetic clutch 112 by the feed signal). Further, the control unit 150 controls contact/separation of the pickup roller 101 to/from the sheet S, which will be described later. In addition, the control unit 150 executes various judgments based on the detection results of detection means (described later) (see FIG. 6, etc.). Further, the control unit 150 has an internal timer (not shown), and measures the passage of time (t1, t2, t3), which will be described later, by the timer. The same applies to the second and subsequent embodiments.

[Sheet feeding section]
A detailed configuration of the sheet feeding unit 100 according to the first embodiment will now be described with reference to FIGS. 3 and 4. FIG. 3 is a schematic diagram of the drive train of the sheet feeding section 100, and FIG. 4 is a sectional view of the sheet feeding section 100. As shown in FIG. FIG. 3(a) is a block portion for explaining transmission of driving force, and (b) and (c) are side views for explaining transmission of driving force from a driving source to each roller. A feed motor 110 serving as a drive source rotates the feed roller 103 and the pickup roller 101 in the feed direction via a feed roller driving gear train 113 having an electromagnetic clutch 112 . Further, the feed roller drive gear train 113 has a one-way clutch gear 114 with a built-in one-way clutch. The one-way clutch gear 114 is set to idle when a rotational load is applied to the pickup roller 101 and the feed shaft 118 holding the feed roller 103 is rotated in the opposite direction to the feeding direction.

On the other hand, the retard roller 104 is driven by a feeding motor 110 as a drive source and is driven in the direction opposite to the feeding direction via a retard roller driving gear train 111 having a torque limiter 108 . The drive transmission force of the torque limiter 108 is always set larger than the frictional force generated between the sheets due to the friction coefficient of the sheet S used. Further, the drive transmission force of the torque limiter 108 is set smaller than the frictional force due to the friction coefficient between the sheet S and the feed roller 103 . Therefore, when the number of sheets S entering the separation nip portion 102 is one, or when there is no sheet S, the retard roller 104 rotates together with the sheet S or the feed roller 103 . Further, when two or more sheets S enter the separation nip portion 102, the retard roller 104 rotates in the direction opposite to the feeding direction to separate the sheets S one by one.

In the retard roller drive gear train 111 , a code wheel 115 is provided on a retard shaft 116 that holds the retard roller 104 . The encoder 109 is output means for outputting a signal corresponding to the rotation state of the code wheel 115 to the control section 150 . Based on the output signal of the encoder 109, the control unit 150 can determine whether the retard roller 104 is rotating forward or backward, the angular velocity of the rotation of the retard roller 104, and the like. As a result, the controller 150 detects that the rotation of the retard roller 104 is unstable when the retard roller 104 oscillates in the arrow Y2 direction about the retard roller oscillation center 104c. be able to. Further, the pickup roller 101 swings in the arrow Y3 direction about the pickup roller swing center 101c, thereby coming into contact with the uppermost sheet S1 of the sheets S stacked in the feed cassette 106. It is possible to separate them from each other.

<Series of Operations of Sheet Feeding Unit 100 in Case of Print Job Designating One Sheet>
5A and 5B show a state in which the pickup roller 101 is separated from the sheet S. FIG. 5A is a cross-sectional view from the left side. (b) is a cross-sectional view from the right side. 5(c) and 5(d) show a state in which the pickup roller 101 is in contact with the sheet S. FIG. 5(c) is a cross-sectional view from the left side. (d) is a cross-sectional view from the right side. In each figure, the conveying direction (feeding direction) of the sheet S is indicated by an arrow.

As shown in FIGS. 5A and 5B, the pick roller pressing spring 125 always presses the pick holder 126 holding the pickup roller 101 in the direction in which the pickup roller 101 comes into contact with the sheet S. . Before the start of the feeding operation, the pickup roller 101 is separated from the sheet S by setting the pick roller contact/separation cam 124 to the phase of contacting the pick holder 126 . When a feeding signal for starting the feeding operation is sent, the feeding motor 110 is rotationally driven, and the retard roller 104 rotates in the opposite direction to the feeding direction via the torque limiter 108 . At this time, since the electromagnetic clutch 112 is not energized and not drivingly connected, the feed roller 103 in contact with the retard roller 104 rotating in the reverse direction rotates together with the retard roller 104 in the feeding direction. reverse rotation.

5(c) and 5(d), the pick roller abutment/separation cam 124 is set to a phase to separate from the pick holder 126 as the feeding motor 110 starts to rotate. The pickup roller 101 separated from the sheet S swings in the arrow Y3 direction about the pickup roller swing center 101c, and comes into contact with the sheet S by the pressing force of the pick roller pressing spring 125. . After contacting the sheet S, the pickup roller 101 does not rotate because the one-way clutch gear 114 idles. After that, by energizing the electromagnetic clutch 112 , the electromagnetic clutch 112 connects the drive, rotates the feed roller 103 and the pickup roller 101 in the feeding direction, and feeds the sheet S from the feeding cassette 106 . After the leading edge of the sheet S being conveyed passes through the separation nip portion 102, the pickup roller 101 is separated from the sheet S by setting the phase in which the pick roller contact/separation cam 124 is brought into contact with the pick holder 126. . After the leading edge of the sheet S has passed the conveying roller 105, the electromagnetic clutch 112 is deenergized to release the drive connection. The feed roller 103 and the retard roller 104 rotate together with the sheet S conveyed by the conveying roller 105 . The feeding motor 110 rotates after the trailing edge of the sheet S passes through the nip portion of the registration roller 6, which is the most downstream roller in the feeding direction among the rollers driven by the feeding motor 110. to stop.

<Series of Operations of Sheet Feeding Unit 100 During Continuous Feeding>
The operation of continuously feeding a plurality of sheets by the pickup roller 101 (hereinafter referred to as continuous feeding) will be described by dividing the time into sections with reference to FIG. In FIG. 6A, the horizontal axis represents time, and the vertical axis represents the behavior of the retard roller 104, the behavior of the feed roller 103, the behavior of the pickup roller 101, the detection result based on the output signal of the encoder 109, the ON/OFF state of the electromagnetic clutch 112, and the section. is shown. The behavior of each roller is represented by "forward rotation", "unstable", "reverse rotation", and the like. For each roller, rotation in the feeding direction is forward rotation, and rotation in the direction opposite to the feeding direction is reverse rotation. The ON/OFF state of the electromagnetic clutch 112 corresponds to the power supply signal. When the power supply signal is at a high level, the electromagnetic clutch 112 is "ON" to indicate that the drive is connected, and the power supply signal is at a low level. , the electromagnetic clutch 112 is "OFF", indicating that it is not driven. Further, the section is from section 1 to section 6. FIG. 6B to 6G are sectional views of the sheet feeding portion 100 in sections 1 to 6, respectively. Further, in the arrows indicating the rotation direction of each roller, the solid line indicates that the roller is rotated by the drive source, and the dashed line indicates that the roller is driven to rotate.

During continuous feeding, the feeding motor 110 is always driven to rotate, and the retard roller 104 rotates in the direction opposite to the feeding direction (reverse rotation direction) via the torque limiter 108, as described with reference to FIG. ) is being driven. The control unit 150 measures the absolute value of the angular velocity and angular acceleration of the number of revolutions of the retard roller 104 based on the waveform of the output signal of the encoder 109 . When the absolute value of the angular acceleration of the retard roller 104 is smaller than a predetermined absolute value of the angular acceleration continuously for a predetermined time based on the detection result based on the output signal of the encoder 109, the control unit 150 determines that the rotation is in a steady state. Judged as stable (stable region). On the other hand, if the absolute value of the angular acceleration of the retard roller 104 is greater than or equal to the predetermined absolute value of the angular acceleration from the detection result based on the output signal of the encoder 109, the control unit 150 determines that the retard roller 104 is accelerating or decelerating. (unstable region). This state is shown in FIG. FIG. 7 shows the output signal of the encoder 109 and the absolute value (interval average) of the angular acceleration of the rotation speed of the retard roller 104 based on the output signal. A pulse signal with a uniform width is output in a stable region where the absolute value of the angular acceleration is small. On the other hand, the width of the pulse signal changes in the unstable region where the absolute value of the angular acceleration is large. A sheet that is fed precedingly is called a preceding sheet (first sheet), and a subsequent sheet that is fed after the preceding sheet is called a next sheet (second sheet). Further, a succeeding sheet that is fed following the next sheet is called a next sheet (third sheet). For one sheet, the period from when the pick-up roller 101 starts feeding (from section 4) to when the trailing edge of the fed sheet passes through the separation nip portion 102 (up to the next section 4) is Feed operation. Therefore, in FIG. 6A, the feeding operation of the preceding sheet is from section 1 to section 4, and the feeding operation of the next sheet is from the same section 4 to the next section 4. FIG.

◆ Section 1
In section 1, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows.
Leading edge position of the preceding sheet: Downstream from the conveying roller 105 Trailing edge position of the preceding sheet: Upstream of the pickup roller 101 beyond X mm (see FIG. 6C) Next sheet: Inside the feeding cassette 106 Each roller, encoder 109, electromagnetic The clutch 112 is as follows.
Retard roller 104 behavior It rotates with the preceding sheet (broken line arrow) and rotates in the forward direction with respect to the feeding direction.
·Feed roller 103 behavior It rotates with the preceding sheet (broken line arrow) and rotates in the forward direction with respect to the feeding direction.
- The behavior of the pickup roller 101 is separated from the preceding sheet.
Rotates forward in the feed direction. Since the electromagnetic clutch 112 is turned off as will be described later, the arrow pointing in the forward rotation direction is indicated by a dashed line.
・Detection result based on the output signal of the encoder 109 It is detected that the retard roller 104 rotates forward and is stable. It should be noted that the control unit 150 cannot determine whether the retard roller 104 is rotating forward or backward only from the output signal of the encoder 109 . However, since the control unit 150 uses a counter to manage the interval in which the retard roller 104 can only rotate forward and the interval in which the retard roller 104 can only rotate in the reverse direction, it can be determined whether the retard roller 104 is rotating in the forward direction or in the reverse direction. .
・Electromagnetic clutch 112 (feeding signal)
After the leading edge of the preceding sheet passes the conveying roller 105, the electromagnetic clutch 112 is turned off to release the driving connection.

◆ Section 2
In section 2, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows.
Leading edge position of the preceding sheet: Downstream of the conveying roller 105 Trailing edge of the preceding sheet: Between the position X mm upstream of the pickup roller 101 and the separation nip portion 102 Next sheet: Inside the feeding cassette 106 Each roller, encoder 109, electromagnetic clutch 112 is as follows.
Retard roller 104 behavior It rotates with the preceding sheet (broken line arrow) and rotates in the forward direction with respect to the feeding direction.
·Feed roller 103 behavior It rotates with the preceding sheet (broken line arrow) and rotates in the forward direction with respect to the feeding direction.
Behavior of the pickup roller 101 After a predetermined time t2 has passed since the feeding signal of the preceding sheet is turned on, the pickup roller 101 comes into contact with the preceding sheet. The predetermined time t2 is determined by the set sheet length. That is, during the predetermined time t2, the trailing edge of the preceding sheet is positioned upstream in the feeding direction by a predetermined distance X mm from the position where the pickup roller 101 contacts the preceding sheet (hereinafter simply referred to as the contact position). It is determined based on the time to pass through the location. In other words, it can be said that it is the time for the pickup roller 101 to pass the position of the predetermined distance X mm downstream in the feeding direction from the trailing edge of the preceding sheet. When the sheet length is short, the time required for the trailing edge of the sheet to pass a predetermined distance X mm on the upstream side of the contact position in the feeding direction after the start of feeding of the sheet is shortened. On the other hand, when the sheet length is long, the time required for the trailing edge of the sheet to pass the predetermined distance X mm on the upstream side in the feeding direction from the contact position after the start of sheet feeding is longer than when the sheet length is short. also longer. Note that the sheet length is the length of the sheet S in the feeding direction.
The peripheral speed of the feed roller 103 is set faster than the peripheral speed of the pickup roller 101 . Therefore, during section 2, the conveying speed of the preceding sheet is faster than the circumferential speed of the pickup roller 101 . Also, since the one-way clutch gear 114 has a built-in one-way clutch, in the section 2, the pickup roller 101 idly rotates along with the preceding sheet (broken line arrow).
・Detection result based on the output signal of the encoder 109 It is detected that the retard roller 104 rotates forward and is stable.
・Electromagnetic clutch 112 (feeding signal)
The electromagnetic clutch is OFF and the drive is not engaged.
The pickup roller 101 contacts the preceding sheet before the next sheet feeding signal is turned ON, thereby minimizing the sheet feeding time after receiving the next sheet feeding signal. . The pickup roller 101 contacts the preceding sheet when feeding the preceding sheet from the feeding cassette 106 . The pickup roller 101 is separated from the preceding sheet when the leading edge of the preceding sheet passes through the separation nip portion 102 . The pickup roller 101 contacts the preceding sheet at the timing when the trailing edge of the preceding sheet passes through a position a predetermined distance (X mm) in the direction opposite to the feeding direction from the position where the pickup roller 101 contacts the preceding sheet. Contact again (again contact with the first sheet).

◆ Section 3
In section 3, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows.
Leading edge position of preceding sheet: Downstream from conveying roller 105 Trailing edge position of preceding sheet: Immediately after passing separation nip portion 102 Next sheet: Inside feed cassette 106 Each roller, encoder 109, and electromagnetic clutch 112 are configured as follows.
Behavior of the retard roller 104 Due to the impact of the trailing edge of the preceding sheet passing through the separation nip portion 102, the retard roller 104 vibrates in the arrow Y2 direction with respect to the feed roller 103 with the retard roller swing center 104c as the swing center. , and the rotation becomes unstable (circles indicated by solid and dashed lines in the figure).
Behavior of feed roller 103 Since the feed roller 103 is not driven and the rotation of the retard roller 104 is unstable, the rotation of the feed roller 103 is also unstable.
・The pickup roller 101 is in contact with the next sheet. not rotating.
・Detection result based on the output signal of the encoder 109 Unstable forward rotation (dotted line) or unstable reverse rotation (solid line) of the retard roller 104 is detected.
・Electromagnetic clutch 112 (feeding signal)
The electromagnetic clutch 112 is OFF and the drive is not engaged.

◆ Section 4
In section 4, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows.
Leading edge position of the preceding sheet: downstream of the conveying roller 105 Trailing edge of the preceding sheet: downstream of the separation nip portion 102 Next sheet: inside the feeding cassette 106 Each roller, encoder 109, and electromagnetic clutch 112 are arranged as follows.
Behavior of the retard roller 104 Vibration of the retard roller 104 converges and stabilizes at the reverse rotation (solid line arrow) of a predetermined number of rotations or more.
・Feed roller 103 behavior The retard roller 104 rotates (broken line arrow) and rotates in the opposite direction.
・The pickup roller 101 is in contact with the next sheet. not rotating.
The detection result based on the output signal of the encoder 109 The retard roller 104 rotates in the reverse direction and is stable.
・Electromagnetic clutch 112 (feeding signal)
The electromagnetic clutch is OFF and the drive is not engaged.

◆ Section 5
In section 5, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows.
Leading edge position of the preceding sheet: Downstream from the conveying roller 105 Trailing edge position of the leading sheet: Downstream from the separation nip portion 102 Leading edge position of the next sheet: Upstream from the separation nip portion 102 Further, each roller, encoder 109, and electromagnetic clutch 112 are arranged as follows. ing.
Behavior of the retard roller 104 When the feed roller 103 rotates forward (solid line arrow), the retard roller 104 rotates (broken line arrow) with the feed roller 103 and accelerates in forward rotation. In addition, in FIG. 6A, it is described in the column of instability even during acceleration.
・Feed roller 103 behavior Forward rotation (solid line arrow).
・The pickup roller 101 is in contact with the next sheet. Forward rotation is driven (solid line arrow) to feed the next sheet.
・Detection result based on the output signal of the encoder 109 It is detected that the retard roller 104 is accelerating in forward rotation.
・Electromagnetic clutch 112 (feeding signal)
When the detection result based on the output signal of the encoder 109 indicates that the reverse rotation is stable, the feed signal is turned ON. Alternatively, based on the waveform of the output signal of the encoder 109, the timing at which the reverse rotation becomes stable is estimated, and the time from when the feeding signal is started to when the sheet S is actually fed is taken into account. may be forwarded from the timing at which the reverse rotation becomes stable, and the feeding signal may be transmitted.

◆ Section 6
In section 6, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows.
Leading edge position of the preceding sheet: Downstream from the conveying roller 105 Trailing edge position of the preceding sheet: Downstream from the separation nip portion 102 Leading edge position of the next sheet: Between the position downstream from the separating nip portion 102 and the position of the conveying roller 105 Each roller and encoder 109 and the electromagnetic clutch 112 are as follows.
Behavior of the retard roller 104 When the next sheet is not multi-fed, it rotates with the next sheet (broken line arrow) and rotates in the forward direction with respect to the feeding direction. When the next sheet is multi-fed, it rotates in the opposite direction to the feeding direction (solid line arrow) (“behavior during multi-feed” indicated by the broken line in FIG. 6A).
・Feed roller 103 behavior Forward rotation (solid line arrow).
Behavior of the pickup roller 101 After a predetermined time t1 has passed since the feeding signal for the next sheet was turned ON (t1<t2), and after the leading edge of the next sheet being fed has passed the separation nip portion 102, the next sheet away from it.
If the result of detection based on the output signal of the encoder 109 is that the next sheet is not multi-fed, it is detected that the retard roller 104 rotates forward and is stable (solid line). When the next sheet is multi-fed, the retard roller 104 detects reverse rotation ("behavior during multi-feed" indicated by the dashed line). It should be noted that there is a case where the double feed is eliminated during sections 5 and 6 and the retard roller 104 rotates from the reverse rotation to the normal rotation, so a dashed line is also shown in FIG.
・Electromagnetic clutch 112 (feeding signal)
The electromagnetic clutch is ON and the drive is connected.

(other design requirements)
The behavior of the retard roller 104 when feeding is started and the sheets S are multi-fed is reverse rotation when the sheet bundle is separated, as indicated by the dashed line from section 5 to section 1 in FIG. , when the separation is completed, the feed roller 103 rotates in the normal direction. For this reason, the feeding of sheets one after another is not started during the reverse rotation operation of the retard roller 104 at the time of separating the sheet bundle. That is, from the start of section 5, in which the feeding signal for the next sheet is turned ON, to the start of section 2, in which the pickup roller 101 comes into contact with the trailing edge of the next sheet, feeding of sheets one after another is prohibited. It is a prohibited section (period). FIG. 6A also shows (part of) the feeding prohibited section of the next sheet during the feeding operation of the preceding sheet.

If the preset length of the sheet S in the feeding direction (sheet length) is longer than the actual sheet length, the detection result based on the output signal of the encoder 109 is reverse rotation across the interval 1 and interval 2. Stabilization may be detected. If feeding is started based on this detection result, the interval between sheets becomes unnecessarily long and the throughput is not optimal. Therefore, the control unit 150 measures the time during which reverse rotation is stabilized, for example, using a timer (not shown), and the time during which reverse rotation is stabilized is longer than the time during which reverse rotation is stabilized, which is assumed based on the sheet length. If it becomes longer, it stops printing without starting feeding. Then, the control unit 150 displays the discrepancy between the set sheet length and the actual sheet length on the display unit 121 to notify the user. When the printer 1 is configured to automatically detect the sheet length at the position of the sheet trailing edge regulation section 120, the control section 150 prompts the display section 121 to correct the position of the sheet trailing edge regulation section 120. The information is displayed and notified to the user.

After the reverse rotation of the retard roller 104 is stabilized and the vibration is converged in this manner (after the timing at which the vibration converges), feeding of the next sheet is started. As a result, an optimum sheet interval can be obtained depending on the conditions of the sheet feeding device to be used. As a result, it is possible to feed the sheets with the shortest distance between the sheets without deteriorating the feeding performance due to the sheet interval being too narrow during feeding, thereby improving the productivity. In the first embodiment, the feeding motor 110 is controlled to cause the pickup roller 101 to feed the first sheet. After the trailing edge of the first sheet passes through the separation nip portion 102, the timing of feeding the second sheet following the first sheet by the pickup roller 101 is changed based on the signal output from the encoder 109. do. As described above, according to the first embodiment, it is possible to improve the productivity without causing a decrease in the feeding performance.

Next, Example 2 will be described with reference to FIG. FIG. 8(a) is a block portion for explaining the transmission of the driving force, and (b) and (c) are side views for explaining the transmission of the driving force from the drive source to each roller. The second embodiment has a bearing 119 and a one-way clutch 117 in addition to the first embodiment. The bearing 119 is non-rotatably supported by the device body, and the one-way clutch 117 is non-rotatably supported by the bearing 119 . The one-way clutch 117 pivotally supports a feed shaft 118 having the feed roller 103, and is set to prevent the feed roller 103 from rotating in the direction opposite to the feeding direction. As a result, even if the retard roller 104 is driven to rotate in the reverse direction, the feed roller 103 does not rotate in the reverse direction. Further, when the friction coefficient between the surfaces of the retard roller 104 and the feed roller 103 in contact with each other is a certain value or more, the reaction force of the feed roller 103 against the rotational force of the retard roller 104 becomes larger than the drive transmission force of the torque limiter 108 . . Therefore, the retard roller 104 does not rotate. Since other configurations are the same as those of the first embodiment, the same configurations are denoted by the same reference numerals, and detailed description thereof is omitted.

<Series of Operations of Sheet Feeding Unit 100 During Continuous Feeding>
Time is divided into intervals and explained using FIG. 9(a) and (b) are similar to FIGS. 6(a) and (b), and the description of how to read the figures is omitted. Note that the behavior of the retard roller 104 is not "reverse rotation" (FIG. 6A) but "stop" (FIG. 9A). Further, since the feed roller 103 cannot rotate in the reverse rotation direction, the behavior of the feed roller 103 is not "reverse rotation" (FIG. 6A) but "stop" (FIG. 9A). ing. Furthermore, regarding the detection result based on the output signal of the encoder 109, "reverse rotation unstable" (Fig. 9(a)) is not "reverse rotation unstable or accelerating" and "reverse rotation stable" (Fig. 6(a)). ).

◆ Section 1 to Section 2
Since it is the same as the first embodiment, the description is omitted.

◆ Section 3
In section 3, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows.
Leading edge position of preceding sheet: Downstream from conveying roller 105 Trailing edge position of preceding sheet: Immediately after passing separation nip portion 102 Next sheet: Inside feed cassette 106 Each roller, encoder 109, and electromagnetic clutch 112 are arranged as follows. there is
Behavior of the retard roller 104 Due to the impact of the trailing edge of the preceding sheet passing through the separation nip portion 102, the retard roller 104 vibrates in the arrow Y2 direction with respect to the feed roller 103 with the retard roller swing center 104c as the swing center. and the rotation becomes unstable.
Behavior of feed roller 103 Since the feed roller 103 is not driven and the one-way clutch 117 prevents the feed roller 103 from rotating in the reverse direction, the feed roller 103 is stopped.
・The pickup roller 101 is in contact with the next sheet. not rotating.
Detection result based on the output signal of the encoder 109 Unstable forward rotation of the retard roller 104 indicated by the dashed line or unstable reverse rotation indicated by the solid line is detected.
・Electromagnetic clutch 112 (feeding signal)
The electromagnetic clutch is OFF and the drive is not engaged.

◆ Section 4
In section 4, the leading edge position and trailing edge position of the preceding sheet and the next sheet are as follows.
Leading edge position of the preceding sheet: downstream of the conveying roller 105 Trailing edge of the preceding sheet: downstream of the separation nip portion 102 Next sheet: inside the feeding cassette 106 Each roller, encoder 109, and electromagnetic clutch 112 are arranged as follows.
Behavior of the retard roller 104 The vibration of the retard roller 104 is converged, and the rotation is stopped by the configuration of the second embodiment.
- The behavior of the feed roller 103 is stopped.
・The pickup roller 101 is in contact with the next sheet. not rotating.
・Detection result based on the output signal of the encoder 109 Stopping of the retard roller 104 is detected.
・Electromagnetic clutch 112 (feeding signal)
The electromagnetic clutch is OFF and the drive is not engaged.

◆ Section 5
In section 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.
Leading edge position of the preceding sheet: Downstream from the conveying roller 105 Trailing edge position of the leading sheet: Downstream from the separation nip portion 102 Leading edge position of the next sheet: Upstream from the separation nip portion 102 Further, each roller, encoder 109, and electromagnetic clutch 112 are arranged as follows. ing.
Behavior of the retard roller 104 When the feed roller 103 rotates forward, the retard roller 104 rotates together with the feed roller 103, and is accelerating from the stopped state in section 4 to forward rotation. Therefore, "unstable" is used in FIG. 9(a).
・Feed roller 103 behavior Forward rotation.
・The pickup roller 101 is in contact with the next sheet. It rotates forward and feeds the next sheet.
・Detection result based on the output signal of the encoder 109 It is detected that the retard roller 104 is accelerating in forward rotation.
・Electromagnetic clutch 112 (feeding signal)
When the detection result based on the output signal of the encoder 109 indicates stop, the feed signal is turned ON. Alternatively, the timing to stop is estimated from the waveform of the output signal of the encoder 109, and in view of the time from when the feeding signal is turned ON until the sheet S is actually fed, the time is moved forward from the timing to stop. to turn on the feed signal.

◆ Section 6
In section 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.
Leading edge position of the preceding sheet: Downstream from the conveying roller 105 Trailing edge position of the preceding sheet: Downstream from the separation nip portion 102 Leading edge position of the next sheet: Between the position downstream from the separating nip portion 102 and the position of the conveying roller 105 Each roller and encoder 109 and the electromagnetic clutch 112 are as follows.
Behavior of the retard roller 104 When the next sheet is not multi-fed, it rotates with the next sheet and rotates in the forward direction with respect to the feeding direction. When the next sheet is multi-fed, it rotates in the opposite direction to the feeding direction. In addition, since FIG. 9A does not show "reverse rotation", the case of multi-feeding is not shown.
・Feed roller 103 behavior Forward rotation.
Behavior of the pickup roller 101 After a predetermined time t1 (t1<t2) after the feeding signal of the next sheet is turned ON, and after the leading edge of the preceding sheet being conveyed passes through the separation nip portion 102, the pickup roller 101 separates from the next sheet.
If the result of detection based on the output signal of the encoder 109 is that the next sheet is not multi-fed, it is detected that the retard roller 104 rotates forward and is stable. When the next sheet is multi-fed, the retard roller 104 detects reverse rotation. Note that FIG. 9(a) does not show "reverse rotation stable", so the case of double feed is not shown.
・Electromagnetic clutch 112 (feeding signal)
The electromagnetic clutch is ON and the drive is connected.

(other design requirements)
The coefficient of friction between the roller surfaces of the feed roller 103 and the retard roller 104 decreases due to abrasion of the roller surface due to advanced use and adhesion of paper dust to the roller surface. When the coefficient of friction falls below a certain value, the retard roller 104 may rotate in the reverse direction without stopping in section 4 . In that case, the encoder 109 cannot detect the stoppage of the retard roller 104, and the feeding is never started. Therefore, as a countermeasure, the control unit 150 forcibly feeds the sheet after a predetermined time t3, which is the third time based on the start of feeding of the preceding sheet, has passed, even if the feeding signal is not turned ON. start sending. When this forced feeding occurs continuously for a predetermined number of times, the control unit 150 may display information prompting replacement of the feed roller 103 and the retard roller 104 on the display unit 121 .

In the second embodiment, the feeding of the next sheet is started after the vibration is converged substantially at the same time when the rotation of the retard roller 104 is stopped. Therefore, effects similar to those of the first embodiment can be obtained. As described above, according to the second embodiment, it is possible to improve the productivity without deteriorating the feeding performance.

<Structure of Separation Unit>
Next, Example 3 will be described. The same reference numerals are assigned to the same configurations as those of the first embodiment, and detailed description thereof will be omitted. FIG. 10 is a diagram showing the configuration of the separation nip portion 102 of the third embodiment. As shown in FIG. 10, in the third embodiment, the code wheel 115 and the encoder 109, which are detection means for the retard roller 104, are replaced with the first and second embodiments as follows. That is, in the third embodiment, the retard roller swing center 104c is set as the swing center, and the retard holder 122 that holds the retard roller 104, the retard shaft 116, and the torque limiter 108 is provided with an acceleration sensor 123 as a detection means for detecting acceleration. are provided. In Example 3, the acceleration sensor 123 detects unstable vibration of the retard roller 104 in the section 3 . Based on the detection result of the acceleration sensor 123, the control unit 150 determines that the unstable vibration of the retard roller 104 has converged and stabilized.

<Series of Operations of Sheet Feeding Unit 100 During Continuous Feeding>
Using FIG. 11, a series of operations will be described by dividing time into sections. 11 is similar to FIG. 9(a), but the "detection result based on the output signal of the encoder 109" in FIG. 9(a) is replaced with the "detection result of the acceleration sensor 123". The detection result of the acceleration sensor 123 includes "acceleration/deceleration" and "steady state" states. Behaviors of rollers and the like other than the detection result of the acceleration sensor 123 are the same as those in FIG. In Embodiments 1 and 2, the control unit 150 turns ON the feeding signal based on the detection result based on the output signal output by the encoder 109 according to the rotation state of the retard roller 104 . On the other hand, in the third embodiment, based on the detection result of the acceleration sensor 123 in section 4, the control unit 150 determines that the absolute value of the detected acceleration is equal to or less than a predetermined value, that is, the steady state for a predetermined time. The feed signal is turned ON based on the occurrence of the above.

In Embodiments 1 and 2, the period from the start of section 5 after sending a feeding signal for feeding the next sheet to the start of section 2 where the pickup roller 101 contacts the trailing edge of the next sheet is set as a sheet feeding prohibition section one after another (see FIG. 6A). In the first and second embodiments, the state of the retard roller 104 (for example, forward/reverse rotation, angular velocity, etc.) is detected based on the detection result based on the output signal of the encoder 109 . However, in the third embodiment, the acceleration sensor 123 is provided on the retard holder 122 and detects whether "acceleration/deceleration is present" or "steady state". Therefore, in the third embodiment, the acceleration sensor 123 may be in a steady state between the section 5 and the section 2 of the next sheet. In some cases, the sheets start to be fed one after another. For this reason, in the third embodiment, the interval between the section 5 of the next sheet and the section after the start of the section 3 in which the trailing edge of the next sheet reliably passes through the separation nip portion 102 is set as the sheet feeding prohibition section. The feeding prohibition section (close time) of the next sheet after another is determined based on the set sheet length of the sheet S in the feeding direction.

Further, in the first and second embodiments, the retard roller 104 is driven to rotate in the opposite direction to the feeding direction. The retard roller 104 does not have to be reversely rotated.

Since the feeding is started after the vibration of the retard roller 104 converges based on the detection result of the acceleration sensor 123, the same effect as in the first embodiment can be obtained. As described above, according to the third embodiment, it is possible to improve the productivity without deteriorating the feeding performance.

Next, Example 4 will be described. In Examples 1 to 3, 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 the preceding sheet to the start of feeding the next sheet is not constant. On the other hand, in the fourth embodiment, the interval from the start of feeding the preceding sheet to the start of feeding the next sheet is a constant time.

12A and 12B are diagrams showing a state (a) in which the sheet feeding unit 100 is not used much and a state (b) in which the use is advanced. The same symbols are attached to the same configurations as in the first embodiment. Further, the retard roller 104s shows a state in which the retard roller 104 has swung and is at the farthest position from the feed roller 103 (hereinafter referred to as a swing stop position). A retard roller 104 t shows the position where the retard roller 104 is in contact with the feed roller 103 . As shown in FIG. 12, as the use of the sheet feeding unit 100 progresses, the roller diameters of the feed roller 103 and the retard roller 104 become smaller. In addition, progress of use is hereinafter referred to as durability. Therefore, the swing angles of the retard roller 104s at the swing stop position and the retard roller 104t in contact with the feed roller 103 are as follows.
A1 before endurance < A2 after endurance
Here, the pre-endurance A1 is the swing angle of the retard roller 104s and the retard roller 104t in a state of not being used much. After endurance A2 is the swing angle of the retard roller 104s and the retard roller 104t in a state of advanced use.

As a result, the vibration of the retard roller 104 converges as the use progresses, and the time until the rotation stabilizes increases. Therefore, if the interval from the start of feeding the preceding sheet to the start of feeding the next sheet is set to a fixed time, the vibration of the retard roller 104 has not yet subsided within the fixed time, and the rotation becomes unstable. When the next sheet starts to be fed, a feeding failure may easily occur. As a countermeasure, in the fourth embodiment, the control unit 150 starts feeding the next sheet when the vibration of the retard roller 104 has subsided and the rotation is not stable at the start of feeding after a certain period of time has elapsed. Instead, it is set to start feeding after the vibration has settled and the rotation has stabilized. In this manner, the start of feeding the next sheet is changed according to the usage time of the retard roller 104 . In other words, when the vibration of the retard roller 104 is converged within a certain period of time, the next sheet is fed at the timing when the certain period of time has elapsed. Then, if the vibration of the retard roller 104 does not settle within a certain period of time, the next sheet is fed at the timing after the certain period of time after the vibration of the retard roller 104 has settled.

At that time, the control unit 150 notifies the user by displaying on the display unit 121 that the feed roller 103 and the retard roller 104 need to be replaced. As a result, it is possible to delay the exchange timing of the feed roller 103 and the retard roller 104 while reducing feeding failure caused by starting the feeding of the next sheet while the retard roller 104 is vibrating, and the throughput is lowered. As a result, it is possible to eliminate downtime until the user purchases and replaces replacement parts for the feed roller 103 and the retard roller 104 . As described above, according to the fourth embodiment, it is possible to improve productivity without incurring a decrease in feeding performance.

In the first to fourth embodiments described above, the retard roller 104 to which the driving force is transmitted in the direction opposite to the feeding direction of the sheet S was described as an example. The present invention can also be applied to

101 pickup roller 102 separation nip portion 103 feed roller 104 retard roller 105 transport roller 106 feed cassette 109 encoder 150 control unit

Claims (18)

a sheet stacking unit on which sheets are stacked;
a feeding rotator that feeds the sheet from the sheet stacking unit;
a conveying rotator for conveying the sheet fed by the feeding rotator;
a separation rotator that forms a nip portion with the conveying rotator and separates the sheet into one sheet at the nip portion, the separating rotator being urged against the conveying rotator by a biasing member;
output means for outputting a signal corresponding to the rotation state of the separation rotor;
a driving means for driving the feeding rotator,
After the trailing edge of the first sheet has passed through the nip portion, the drive means is controlled to feed the first sheet by means of the feeding rotary body, based on the signal output from the output means. and a control means for changing the timing of feeding the second sheet succeeding the first sheet by the feeding rotary member. Based on the signal output from the output means, the control means determines the timing at which the vibration of the separation rotor due to the passage of the first sheet through the nip portion converges, and the feeding rotation is performed. 2. The sheet feeding apparatus according to claim 1, wherein the timing of feeding the second sheet by the body is changed after the timing when the vibration of the separation rotating body converges. the separation rotator has a torque limiter and receives a driving force so as to rotate in a direction opposite to the conveying direction of the sheet;
Based on the signal output from the output means, the control means controls the feeding rotor to cause the first rotation at the timing when it is determined that the absolute value of the angular acceleration of the separation rotor is smaller than a predetermined value. 3. The sheet feeding apparatus according to claim 1, wherein feeding of two sheets is started. The control means is
setting the timing to start feeding the second sheet in advance to the timing after the first time has elapsed since the feeding of the first sheet is started;
If it is determined that the absolute value of the angular acceleration of the separation rotating body is smaller than a predetermined value before the first time elapses, the second sheet is moved at the timing when the first time elapses. When the absolute value of the angular acceleration of the separation rotor cannot be determined to be smaller than the predetermined value even after the first time has elapsed after the start of feeding, the first time has elapsed. 3. After that, feeding of the second sheet is started based on the timing when it is determined that the absolute value of the angular acceleration of the separating rotor is smaller than the predetermined absolute value of the angular acceleration. The sheet feeding device described in . The separation rotor has a torque limiter,
The conveying rotor has a one-way clutch,
The control means feeds the second sheet by the feeding rotary body based on the timing at which it is determined that the separation rotary body has stopped rotating based on the signal output from the output means. 3. The sheet feeding apparatus according to claim 1 or 2, characterized in that it starts the The control means is
setting the timing to start feeding the second sheet in advance to the timing after the first time has elapsed since the feeding of the first sheet is started;
if it is determined that the rotation of the separation rotating body has stopped before the first time elapses, the feeding of the second sheet is started at the timing when the first time elapses; If it cannot be determined that the separation rotor has stopped rotating even after the first time has passed, the separation rotor has stopped rotating after the first time has passed. 6. The sheet feeding apparatus according to claim 5, wherein feeding of the second sheet is started based on the timing determined as. a second conveying rotator provided downstream of the nip portion in the sheet conveying direction;
3. The control means causes the feeding rotor to start feeding the second sheet after the leading edge of the first sheet passes through the second conveying rotor. 7. The sheet feeding device according to any one of 6. The driving means includes a driving source that generates a driving force, and a clutch that connects or disconnects the driving source and the feeding rotor,
the control means controls the clutch based on the signal output from the output means after the trailing edge of the first sheet fed by the feeding rotary body passes through the nip portion; 8. The sheet feeding apparatus according to claim 1, wherein feeding of the second sheet is started by connecting the driving source and the feeding rotor. After the leading edge of the first sheet has passed through the nip portion, the control means separates the feeding rotary member in contact with the first sheet from the first sheet, and the clutch causes the feeding rotary member to move away from the first sheet. 9. The method according to claim 8, wherein the feeding rotator is brought into contact with the first sheet again at a timing after a second period of time has passed since the connection between the driving source and the feeding rotator. sheet feeder. 10. The sheet feeding apparatus according to claim 9, wherein the second time is determined based on the length of the first sheet in the conveying direction. a sheet stacking unit on which sheets are stacked;
a feeding rotator that feeds the sheet from the sheet stacking unit;
a conveying rotator for conveying the sheet fed by the feeding rotator;
a separation rotator that forms a nip portion with the conveying rotator and separates a sheet into one sheet at the nip portion, the separating rotator being urged against the conveying rotator by an urging member;
a holder that holds the separation rotating body;
detection means for detecting acceleration of the holder;
a driving means for driving the feeding rotator,
After the trailing edge of the first sheet has passed through the nip portion, the driving means is controlled to feed the first sheet by the feeding rotating body, based on the acceleration detected by the detecting means. and a control means for changing the timing of feeding the second sheet succeeding the first sheet by the feeding rotary member. Based on the acceleration detected by the detection means, the control means determines the timing at which the vibration of the separation rotating body due to the passage of the first sheet through the nip portion converges, and the feeding rotation is performed. 12. The sheet feeding apparatus according to claim 11, wherein the timing of feeding the second sheet by the body is changed after the timing when the vibration of the separation rotating body converges. The control means causes the feeding rotor to start feeding the second sheet based on the timing when the absolute value of the acceleration detected by the detection means becomes equal to or less than a predetermined value. 13. The sheet feeding device according to claim 11 or 12. The control means is
setting the timing to start feeding the second sheet in advance to the timing after the first time has elapsed since the feeding of the first sheet is started;
When it is determined that the absolute value of the acceleration detected by the detection means is smaller than the predetermined value before the first time elapses, the second acceleration is detected at the timing when the first time elapses. If it cannot be determined that the absolute value of the acceleration detected by the detection means is smaller than the predetermined value even after the sheet feeding is started and the first time elapses, the first time is reached. after the elapse of, the feeding of the second sheet is started based on the timing at which it is determined that the absolute value of the acceleration detected by the detecting means is smaller than the predetermined value. 14. The sheet feeding device according to 13. a second conveying rotator provided downstream of the nip portion in the sheet conveying direction;
11. The control means causes the feeding rotator to start feeding the second sheet after the leading edge of the first sheet passes through the second conveying rotator. 15. The sheet feeding device according to any one of 14. The driving means includes a driving source that generates a driving force, and a clutch that connects or disconnects the driving source and the feeding rotor,
The control means controls the clutch based on the acceleration detected by the detection means after the trailing edge of the first sheet fed by the feeding rotary member passes through the nip portion. 16. The sheet feeding apparatus according to claim 11, wherein the feeding of the second sheet is started by connecting the driving source and the feeding rotary member. After the leading edge of the first sheet has passed through the nip portion, the control means separates the feeding rotary member in contact with the first sheet from the first sheet, and the clutch 17. The method according to claim 16, wherein the feeding rotator is brought into contact with the first sheet again at a timing after a second period of time has passed since the connection between the driving source and the feeding rotator. A sheet feeder as described. 18. The sheet feeding apparatus according to claim 17, wherein the second time is determined based on the length of the first sheet in the conveying direction.

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