JP3618898B2 - Sheet conveying apparatus, automatic document conveying apparatus, and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention separates and feeds one sheet at a time from the uppermost sheet on a sheet stacking tray in a sheet conveying apparatus represented by an image forming apparatus such as a copying machine, a laser beam printer, a facsimile, and an automatic document conveying apparatus. This is related to the upper separation sheet feeding.
[0002]
[Prior art]
Conventionally, in a sheet feeding operation of a sheet feeding device that feeds a sheet document toward a document reading device, the pickup roller is waiting at a standby position away from the paper surface, and the pickup roller is moved up and down by a sheet feeding start signal. By actuating the driving means to operate, the pickup roller descends and rides on the uppermost surface of the sheet original, and is driven to rotate so that the first (uppermost) sheet original is fed into the apparatus. Be transported. When the leading edge of the first sheet document reaches the sheet detection sensor on the downstream side in the sheet document conveyance direction, the driving unit is driven again, and the pickup roller rises to return to the standby position, and the next sheet Prepare for document feeding.
[0003]
Then, in feeding the second sheet document, the previous first sheet document is transported by other transport means, and it is detected again that the trailing edge has passed through the sheet detection sensor. When the driving means is actuated, the pickup roller descends and rides on the uppermost surface of the sheet original, and is driven to rotate, whereby the sheet original is fed and conveyed into the apparatus. The same operation is repeated, and the third and subsequent sheet originals are also fed into the apparatus.
[0004]
A similar operation is also performed in a sheet feeding apparatus that feeds a recording sheet to an image forming unit in the image forming apparatus.
[0005]
[Problems to be solved by the invention]
However, in the conventional example of the sheet feeding device for the document reading device or the image forming apparatus , after detecting that the trailing edge of the sheet has passed through the sheet detection sensor unit provided on the downstream side of the separation unit, The lowering operation of the pickup roller was started. On the other hand, in order to improve the actual processing speed of a sheet document without increasing the sheet document conveying speed in response to the recent increase in the speed of the apparatus, the interval between the sheet document and the sheet document (between sheets) is reduced. It is necessary to process many sheet originals in a short time. However, in the above configuration, the sheet detection sensor unit detects the passage of the trailing end of the sheet and then the pickup roller descends to feed the sheet. Therefore, the gap between the sheets becomes considerably large, and the sheet feeding amount per unit time This is a hindrance to speeding up the device.
[0006]
The object of the present invention is to solve the problem that the sheet conveyance amount per unit time, which is restricted by the large distance between the preceding sheet and the succeeding sheet as described above, is relatively small, and increases the sheet conveyance amount. An object of the present invention is to provide a sheet conveying apparatus.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a sheet conveying apparatus according to a first aspect of the present invention is moved from a sheet stacking unit that stacks sheets to a sheet feeding position that contacts a sheet from a standby position that is separated from the sheet, In the sheet conveying apparatus, comprising: a sheet feeding unit that feeds an outermost sheet among the sheets stacked on the sheet stacking unit; and a conveying unit that conveys the sheet fed by the sheet feeding unit. A sheet rear end passage detecting means for detecting the rear end of the sheet fed by the paper means is provided at a position corresponding to the sheet stacking portion, and based on a sheet rear end passage detection signal by the sheet rear end passage detecting means. And a control means for controlling the moving operation timing of the paper feeding means .
[0009]
According to a second aspect of the present application, the sheet rear end passage detecting means in the first aspect is a photosensor having a light emitting means and a light receiving means for receiving light from the light emitting means, and rotates according to the movement of the sheet. And a light shielding means for blocking light traveling from the light emitting means to the light receiving means at a predetermined cycle.
[0010]
According to a third invention of the present application, the sheet stacking means in the first invention has a tray capable of stacking a plurality of sheets, and the sheet trailing edge passage detecting means in the first invention is provided on the tray. It is characterized by providing.
[0011]
A fourth invention according to the present application is characterized in that the sheet trailing edge passage detecting means in the first invention is provided upstream of the sheet feeding means in the sheet conveying direction.
[0012]
A fifth invention according to the present application is characterized in that the sheet trailing edge passage detecting means in the first invention is provided at substantially the center in the sheet width direction with respect to the sheet conveying direction.
According to a sixth aspect of the present invention, there is provided an automatic document feeder having a sheet conveying device according to any one of the first to fifth aspects, and a document reading means for reading a sheet document conveyed by the sheet conveying device. Features.
[0013]
An image forming apparatus according to a seventh aspect of the present application includes the sheet conveying apparatus according to any one of the first to fifth aspects, and an image forming unit that forms an image on a recording sheet conveyed by the sheet conveying apparatus. It is characterized by that.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a front sectional view of an image reading apparatus to which the present invention can be applied. In FIG. 1, 1 is an image reading apparatus, 2 is a document reading unit that reads a running sheet document S by a flow reading method, and 3 is This is an automatic document feeder as a sheet conveying device for feeding a sheet document to a document reading unit. The automatic document feeder 3 includes a stacking tray 5 on which a plurality of sheet documents can be stacked, a pickup roller 6 that takes out the sheet documents one by one, a separation unit 7 that separates the multi-fed sheet documents, and a sheet document to the document reading unit. Conveying roller pairs 8, 9, 10, 11, and conveying roller pairs 13, 14, 15 that convey the sheet document that has been read by the reading unit 2 to the discharge tray 12. In the illustrated example, the pickup roller 6 is opposed to the uppermost part of the sheet document and is fed upward, but may be opposed to the lowermost sheet and moved downward.
[0015]
Here, the automatic document feeder 3 includes a lower limit sensor 31 for detecting the standby position of the stacking tray 5 and a paper surface height sensor 32 for constantly maintaining the height of the uppermost sheet of the sheet document at the time of feeding. Is provided.
[0016]
Further, a sheet trailing edge passage detection sensor 60 that detects that the trailing edge of the sheet has passed is provided at a predetermined distance upstream from a sheet leading edge detection unit (not shown) that is provided downstream of the pickup roller 6 in the sheet conveyance direction. In the example shown, it is provided on the upstream side of the pickup roller 6 and above the tray. Details of this will be described later.
[0017]
The image reading apparatus 1 includes a first mirror table 16 as a scanning optical unit, second and third mirror tables 17, a lens 18, and a CCD sensor 19 as a reading element. The first mirror table 16 is provided with an exposure lamp 20 that irradiates the document surface, a reflection shade 21, and a first mirror 22 that changes the direction of the reflected light of the irradiated document. The second and third mirror mounts 17 have second and third mirrors 23 and 24 that further change the angle of the reflected light whose angle has been changed by the first mirror 22 and guide the reflected light to the CCD sensor 19 through the lens 18. Is provided.
[0018]
The first mirror table 16 is fixed substantially below the contact glass 26 and constitutes the document reading unit 2.
[0019]
Next, the operation of the image reading apparatus of the present invention will be described. It is assumed that the user of the image reading apparatus stacks the sheet document S on the stacking tray 5 and instructs the start of image reading by an operation unit (not shown). Then, the exposure lamp 20 is turned on first, and then the paper feeding operation is started. The stacking tray 5 starts to rise from the standby position by driving means described in detail below, and continues to rise until the uppermost sheet of the stacked sheet originals S is detected by the paper surface height sensor 32. Then, the pickup roller 6 falls from the standby position onto the uppermost sheet of the sheet document S and rotates to feed the sheet document, and the separation unit 7 separates unnecessary sheets. The pickup roller 6 again waits. Ascend to position. Then, the sheet document is conveyed to the image reading unit 2 by the conveyance rollers 8, 9, 10, and 11. The sheet original is illuminated by the exposure lamp 20 while being conveyed. The reflected light is guided to the lens 18 by the mirrors 22, 23 and 24 and forms an image on the CCD sensor 19. Thereafter, the sheet document is conveyed further downstream by the conveyance rollers 13, 14, and 15 and is discharged to the discharge tray 12. This series of operations is repeated until all the sheet originals are removed from the stacking tray. When all the sheets are removed, the stacking tray is lowered to the standby position, and the exposure lamp 20 is turned off.
[0020]
Next, the configuration of the horizontal raising / lowering operation of the stacking tray 5 will be described in detail with reference to FIGS. 2, 3, and 4. FIG. 2 is a configuration diagram of the lifting and lowering operation of the stacking tray, and is a side view seen from the direction of the separation unit 7. FIG. 3 is a bottom view of the stacking tray. FIG. 4 is an operation conceptual diagram of the paper surface height sensor 32.
[0021]
FIG. 2A shows a state in which the stacking tray 5 is waiting at the standby position. A user of the image reading apparatus 1 stacks the sheet document S on the stacking tray 5, and a pair of left and right side guides 33 are perpendicular to the transport direction of the sheet document S in order to prevent skewing when the sheet document S is transported. Fit to the width of the direction. When a copy start is instructed by an operation unit (not shown), the start signal is input to the CPU 50 as the control means, and the control signal is input from the CPU 50 to the drive motor 34 as the drive means of the drive gear 35. The drive motor 34 rotates the drive gear 35 counterclockwise. Then, the fan gear 36 and the pair of arms 38 integrally attached to the fan gear 36 are rotated in the direction of the arrow by the drive gear 35 and the idler gear 37 around the shaft 36a. As a result, the stacking tray 5 is raised through the support roller 39 that is rotatably attached to the arm 38. Here, 31 is a lower limit sensor for detecting the standby position of the stacking tray 5 and is fixedly supported by the frame 40. Here, the description has been made using the configuration in which the driving force from the driving motor is transmitted by the gear, but the same applies if the driving force is transmitted by known power transmission means such as a belt.
[0022]
Next, stop control of the ascending operation will be described.
[0023]
4A shows a state of the paper surface height sensor 32 when the stacking tray is waiting at the standby position, and FIG. 4B shows a state when the sheet document S is at the paper feed position. 32a is a light transmission type photosensor, and 32b is a flag for turning the photosensor on / off, and is supported so as to be movable up and down with respect to the photosensor. When the stacking tray is waiting at the standby position, as shown in (a), the flag 32b is lowered, and the photo sensor 32a transmits light and recognizes the off state. When the stacking tray 5 is raised, the flag 32b is pushed up by the uppermost sheet of the sheet document S. When the sheet document S reaches the paper feed position, the flag 32b enters between the photosensors 32a as shown in FIG. When the light is blocked, the On state is entered, and the rotation of the drive motor 34 is stopped by a control circuit (not shown), resulting in the state shown in FIG.
[0024]
Further, when the sheet document S is sequentially fed from the top sheet, the height of the top sheet is gradually lowered, and the flag 32b is also lowered accordingly. Then, since the photosensor 32a transmits light and enters the off state, a series of operations in which the drive motor 34 is driven again until the photosensor 32a is in the on state are repeated until the sheet original is exhausted.
[0025]
Next, stop control for the descent operation will be described. The lower limit sensor 31 includes a main body 31a, an arm 31b, and a switch 31c. When the stacking tray 5 is in a paper feeding state, as shown in FIG. 2B, the arm 31b includes the main body 31a and a switch. Apart from the part 31c, the lower limit sensor is in the Off state. Then, when the drive motor 34 rotates in the reverse direction and the stacking tray 5 is lowered as shown in FIG. 2A, the tray 5 pushes the arm portion 31b, and the switch portion 31c is pushed, the lower limit sensor is turned on. Thus, the rotation of the drive motor 34 stops.
[0026]
Further, the guide configuration during the raising / lowering operation of the stacking tray 5 will be described with reference to FIG.
[0027]
The stacking tray 5 has four butting rollers 41 rotatably supported by the stacking tray. Two of the butting rollers 41 are butted against the frame 40 by a compression spring 42. Therefore, the stacking tray 5 is positioned between the frames 40 without backlash in the direction perpendicular to the sheet document conveyance direction (arrow direction). On the other hand, the frame 40 has a guide portion 40a provided with an operating range length in the up-and-down direction of the stacking tray, and the butting roller 41 is guided to the guide portion 40a without backlash. The position with respect to the document transport direction (arrow direction) is determined. As a result, the stacking tray 5 can be lifted and lowered without play in the horizontal direction with respect to the frame 40 with respect to the sheet document stacking surface.
[0028]
Next, the configuration and operation control of the pickup roller when feeding will be described in detail with reference to FIGS. 5, 6, and 7.
[0029]
First, FIG. 5 is a detailed configuration diagram of the rear end passage detection sensor 60. In FIG. 5, reference numeral 61 denotes a rotating roller of a light shielding means, a rigid core member 61a such as metal or plastic, and a rubber fitted to the outer periphery thereof. , A friction member 61b made of an elastic body such as plastic, and 61c is a light shielding member or photointerrupter provided coaxially with the roller 61 and rotating integrally therewith, and provided with light transmission holes 61d at equal angular intervals. A disk member 61e is provided. The rotating roller 61 can contact the uppermost portion of the stacked sheets, that is, the outermost sheet as described later. Reference numeral 62 denotes a rotating shaft that rotatably supports the rotating roller 61 and is fixedly supported by the holder 63. However, the rotating roller 61 may be fixed to the rotating shaft 62 and supported by the holder 63 so as to be rotatable. . Reference numeral 64 denotes a light transmission type photosensor having a light emitting means and a light receiving means, which is fixed to the holder 63, and regularly blocks light emitted from the light emitting means toward the light receiving means by a light shielding member 61e. The rotation of the light shielding member is detected. The rear end passage detection sensor 60 is rotatably supported by the apparatus main body (not shown) by a support member that is inserted into the elongated hole 63a of the holder, and has its own weight according to the height of the top sheet of the sheet document. It is on the page. As the roller 61 rotates in response to the sheet document conveying operation, the disk 61c rotates in the same manner. Accordingly, the sensor 64 alternates Hi / Low signals according to the light passing through the holes 61d. To the CPU 50.
[0030]
FIG. 6 is an upper perspective view showing a driving configuration of the vertical movement of the pickup roller 6. The pickup roller 6 is rotatably attached to the arm 72, and the arm 72 is rotatably attached to the shaft 73. Yes. The pickup roller 6 can be rotated by the driving force of the driving motor 76 via the driving belts 74 and 75. The pivot support lever 77 is pivotable about a shaft 78, and the pivot support lever 77 pivots, and the arm 72 pivots by pushing up the E portion of the lever. The rotation support lever 77 can be rotated by a stepping motor 80 via a drive belt 79. With the configuration described above, the pickup roller 6 is driven by the rotation of the stepping motor 80 so that the rotation support lever 77 pushes the arm 72 upward, the standby position away from the sheet S, and the rotation support lever is lowered. Can be switched to a paper feed position in contact with the sheet. Further, by driving the drive motor 76 at the paper feed position of the pickup roller 6, the pickup roller 6 rotates and feeds the sheet from the uppermost paper. As described above, the rear end passage detection sensor 60 is preferably provided at a position facing the sheet stacking portion or a position in contact with the stacked sheets, and is provided upstream of the pickup roller 6 in the sheet document conveyance direction. In addition, the detection sensor is provided at a substantially central position in a direction perpendicular to the conveyance direction, that is, provided at a substantially central portion in the width direction of a sheet having a high frequency of use in the conveyance direction.
[0031]
FIG. 7 is a graph showing the control of the vertical movement of the pickup roller 6. The upper part of the graph shows Hi / Low of the output signal of the rear end detection sensor output according to the light shielding by the light shielding means, and the lower part. Indicates the position of the pickup roller.
[0032]
Here, the output signal of the rear end passage detection sensor 60 repeats Hi / Low at equal intervals since the sheet document is conveyed and passed through the sensor portion up to F. Since the signal output is constant after F when the signal changes to Low and half a cycle, it is possible to detect that the trailing edge of the sheet document has passed through the trailing edge passage detection sensor unit. As a result, a rotation command is issued from the CPU 50 to the stepping motor 80 immediately after F or after a certain period of time G, and the pickup roller 6 in the standby position starts to descend toward the paper feeding position due to the rotation of the motor. , H to contact or land on the next sheet document. Here, the sheet document whose rear end has passed through the rear end passage detection sensor unit 60 is conveyed by a predetermined distance downstream from the pickup roller unit 6 until time H, and the previous sheet document being conveyed is The pickup roller does not come into contact with the sheet document. Further, at I after a certain time, a rotation command is issued from the CPU 50 to the drive motor 76, the pickup roller 6 rotates, the next sheet document is conveyed, and the output signal of the sensor again becomes Hi / Low, etc. Repeat at intervals. Then, when the leading edge of the sheet original reaches a paper detection sensor (not shown) downstream of the separation unit 7, a rotation command is issued from the CPU 50 to the stepping motor 80. The pickup roller 6 starts to rise toward the standby position, returns to the standby position at K, and prepares for the next paper feeding operation. Here, the rotational drive of the drive motor 76 stops at K when the pickup roller returns to the standby position.
[0033]
In the above embodiment, the sheet trailing edge detection sensor is provided at the top of the tray. However, when the pickup roller is provided at the bottom of the tray as described above, the trailing edge detection sensor is also provided at the bottom of the tray. The rotating roller 61 itself may also be used as the light shielding member without providing the disk member of the rear end passage detection sensor separately from the rotating roller.
[0034]
(Second Embodiment)
In the first embodiment, an example in which the sheet feeding device 3 is used for the image reading device 1 has been described. However, it is also possible to configure an image forming device using this. For example, as shown in FIG. 8, it is also possible to read the original fed by the above-described sheet feeding device 3 with the image reading device 1 and form an image with image forming means based on the read information. It is.
[0035]
When the image forming apparatus 100 according to this embodiment receives an image forming signal, the recording sheet S2 is fed from the cassette 101 serving as a sheet stacking unit toward the registration roller pair 103B by the pickup roller 102 and the conveying roller pair 103A serving as a sheet feeding unit. Transport. An image is formed on the sheet S2 based on the information read by the image reading device 1 by the image forming means. In this embodiment, the image forming unit uses an electrophotographic recording method, and the surface of the electrophotographic photosensitive drum 104 is charged by the primary charger 105 and a laser beam image corresponding to the read information is received from the optical unit 106. A latent image is formed by irradiating the photosensitive drum 104, and the toner image formed by developing the latent image with the developing device 107 is transferred to the recording sheet S 2 by the transfer charger 108. Then, the recording sheet S2 to which the toner image is transferred is conveyed to the fixing device 109 to be fixed with toner, and the sheet S2 is discharged to the discharge tray 110.
[0036]
In the case of this image forming apparatus, not only the recording sheet S2 is supplied from the cassette 101 but also the recording sheet S2 set on the sheet placing member 111 can be supplied. Further, the pick-up roller as the paper feeding means is not necessarily accompanied by the vertical movement of its rotating shaft as in the above-described embodiment, and may be a partially cut-off half-moon shape as is known in the art. Good. For separating and conveying the sheet, a known separation means such as a retard roller system that also serves as a roller conveyance or a separation claw method that separates the conveyance roller and the separation means is used.
[0037]
In this embodiment as well, the sheet rear end passage detection sensor 60 is provided opposite to the stacked sheets, and determines the start timing of the movement of the pickup roller to the sheet feeding position earlier, and the pickup roller and its Image formation processing can be speeded up by reducing the space between the recording sheets before and after being fed by the downstream conveying roller.
[0038]
In the above embodiment, the trailing edge detection sensor as the sheet trailing edge detection means is provided at a position facing the stacked sheet, and the pickup roller is moved from the standby position to the sheet feeding position by detecting the sheet trailing edge of the sensor. Compared with the conventional method in which a sheet detection sensor is provided at a certain distance downstream from the pickup roller in the sheet conveyance direction and the pickup roller is moved to the sheet feeding position by the detection sensor, the sheet feeding start timing of the sheet by the pickup roller is set. Early, the interval between the succeeding sheet and the preceding sheet, that is, the gap between the sheets can be shortened, the number of sheets conveyed per unit time, that is, the substantial sheet conveying speed can be increased, and high-productivity conveyance can be performed. Further, when the rear end passage detection sensor is placed in a substantially middle portion in the direction perpendicular to the sheet conveyance direction (that is, the sheet width direction with respect to the sheet conveyance direction), the sensor does not apply a skewing force to the sheet.
[0039]
In addition, since the passage of the trailing edge of the sheet is detected and the sheet feeding timing of the pickup roller is determined, even when sheets having different lengths in the transport direction are mixed and fed, the high productivity between the small sheets is also the same. Sheet conveyance is possible.
[0040]
【The invention's effect】
As described above, according to the present invention, the sheet fed from the outermost sheet among the sheets stacked on the sheet stacking unit is moved from the standby position separated from the sheet to the sheet feeding position in contact with the sheet. A sheet trailing end passage detecting means for detecting a trailing end of the sheet fed by the sheet feeding means, and a sheet conveying apparatus having a conveying means for conveying the sheet fed by the sheet feeding means. And a control unit that controls the movement operation timing of the sheet feeding unit based on a sheet trailing end passage detection signal by the sheet trailing end passage detecting unit. The trailing edge of the preceding sheet fed by the conveying means is detected earlier than the conventional sheet by the sheet trailing edge passage detecting means, and the feeding means moves to the feeding position based on the detection signal. Sheet feeding that can shorten the gap between the preceding sheet and the succeeding sheet by starting the feeding of the starting and succeeding sheets, and enables high-speed processing for reading a sheet document or forming an image on a recording sheet. It can be performed.
[Brief description of the drawings]
FIG. 1 is a front sectional view of an embodiment of a sheet conveying apparatus according to the present invention. FIG. 2 is a schematic configuration diagram of a document stacking tray according to the present invention. FIG. 4 is a conceptual diagram of a paper height sensor for a stacking tray according to the present invention. FIG. 5 is a schematic configuration diagram of a rear end passage detection sensor according to the present invention. 7 is a conceptual graph showing the output signal of the rear end passage detection sensor according to the present invention and the position of the pickup roller. FIG. 8 is a diagram showing another embodiment of the sheet conveying apparatus according to the present invention.
DESCRIPTION OF SYMBOLS 1 ... Original reading apparatus 2 ... Original reading part 3 ... Original feeding apparatus 5 ... Tray 6, 102 ... Pick-up roller 7 ... Separation conveyance part 100 ... Image forming apparatus 101 ... Cassette 103 ... Conveyance roller 104 ... Photosensitive drum 107 ... Developer 108 ... Transfer charger 109 ... Fixer S, S2 ... Sheet

Claims (7)

A sheet stacking unit that stacks sheets, a sheet feeding unit that is moved from a standby position separated from the sheet to a sheet feeding position that contacts the sheet, and that feeds sheets from the outermost sheet among the sheets stacked on the sheet stacking unit; A sheet trailing device for detecting a trailing edge of a sheet fed by the sheet feeding unit, in a sheet conveying apparatus having a conveying unit configured to convey a sheet fed by the sheet feeding unit, A control unit is provided at a position corresponding to the sheet stacking unit, and a control unit is provided for controlling a movement operation timing of the sheet feeding unit based on a sheet trailing end passage detection signal from the sheet trailing end passage detecting unit. Sheet transport device. The sheet rear end passage detecting means includes a photosensor having a light emitting means and a light receiving means for receiving light from the light emitting means, and rotates according to the movement of the sheet, and transmits light from the light emitting means to the light receiving means for a predetermined cycle. The sheet conveying apparatus according to claim 1, further comprising a light shielding unit that interrupts at a point. 2. The sheet conveying apparatus according to claim 1, wherein the sheet stacking unit includes a tray capable of stacking a plurality of sheets, and the sheet rear end passage detection unit is provided on the tray. 2. The sheet conveying apparatus according to claim 1, wherein the sheet rear end passage detecting means is provided upstream of the sheet feeding means in the sheet conveying direction. 2. The sheet conveying apparatus according to claim 1, wherein the sheet rear end passage detecting means is provided at a substantially center in the sheet width direction with respect to the sheet conveying direction. A sheet conveying device according to any one of claims 1 to 5, an automatic document feeder, characterized in that it has a document reading means for reading the sheet original conveyed by the sheet conveying device. A sheet conveying device according to any one of claims 1 to 5, the image forming apparatus characterized by having an image forming means for forming an image on a recording sheet conveyed by the sheet conveying device.

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