JP2006036439A - Sheet feeding device, image forming device, and image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet feeding device, an image forming device, and an image reader capable of stably separating and feeding a sheet. <P>SOLUTION: The sheet feeding device is provided with a torque transmission means 110 between a separating means 8B which is press-contacted with a carrying means 8A carrying the sheet delivered by the sheet feeding means, and has a transmission rotating torque in the reverse direction to the direction to carry the sheet, and a separation driving means 101 driving the separating means 8B. A predetermined size of the rotating torque is transmitted to the separating means 8B by rotating the torque transmission means 110 with the separation driving means 101, and rotated together with the separating means 8B until the rotating torque in the reverse direction exceeding a predetermined size of the rotating torque is applied to the separating means 8B with the carrying means 8A. When the rotating torque in the reverse direction exceeding a predetermined size is applied to the separating means 8B in the sheet feeding by the separation feed parts 8A, 8B, the number of revolutions of the torque transmission means 110 is reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sheet feeding apparatus, an image forming apparatus, and an image reading apparatus, and more particularly to an apparatus that sequentially separates sheets one by one and feeds them to an image forming unit or an image reading unit.

  2. Description of the Related Art Conventionally, image forming apparatuses and image reading apparatuses such as printers and copiers are provided with a sheet feeding apparatus for conveying a sheet to an image forming unit or an image reading unit. FIG. 8 is a diagram showing the configuration of such a conventional sheet feeding apparatus. The sheet feeding apparatus 201 is configured to feed sheets 202 one by one toward an image forming unit of an image forming apparatus such as a copying machine. Sequentially supplied.

  Here, the sheet feeding apparatus 201 includes a sheet storage apparatus 203 in which a plurality of sheets 202 are stacked and stored on a stacking table (not shown), and the uppermost sheet 202 stored in the sheet storage apparatus 203. Pickup roller 205 that feeds the sheet one by one, and a feed roller that conveys the sheet 202 fed from the sheet storage device 203 by the pickup roller 205 toward the direction of the image forming unit (not shown) (in the direction of arrow b). 206 and a plurality of sheets 202 that are disposed opposite to the feed roller 206 and fed from the sheet storage device 203, rotate in the direction opposite to the rotation direction of the feed roller 206 to be separated into one sheet 202. A retard roller 207 and a conveying roller for conveying the separated sheet 202 to the image forming unit It is and a 209.

  A guide 211 is disposed in the sheet passing area 210 between the pickup roller 205, the feed roller 206, and the retard roller 207, and between the feed roller 206, the retard roller 207, and the conveyance roller pair 209, and the conveyance roller. A guide 212 is disposed between the pair 209 and the image forming unit, and the sheet 202 is guided and conveyed by these guides 211 and 212.

  FIG. 9 is a diagram illustrating a configuration of a drive transmission device 213 that drives the feed roller 206 and the retard roller 207. The drive transmission device 213 includes a feed roller shaft 215 to which the feed roller 206 is fixed and a retard roller 207. A fixed retard roller shaft 216 and a retard roller drive shaft 217 connected to the retard roller shaft 216 are provided substantially in parallel.

  Here, the retard roller shaft 216 is supported by a swingable support member (not shown) so as to be able to contact and separate in parallel with the feed roller shaft 215. A coupling 219 and a torque limiter 220 are disposed between the retard roller shaft 216 and the retard roller drive shaft 217. Further, an electromagnetic clutch 222 is provided at the end of the feed roller shaft 215 for transmitting the driving force transmitted from the main drive means (not shown) via the drive input belt 221 to the feed roller shaft 215.

  Further, a retard driving belt 223 that transmits the rotational driving force transmitted to the feed roller shaft 215 to the retard roller driving shaft 217 is wound between the feed roller shaft 215 and the retard roller shaft 217. The coupling 219 is for transmitting the drive from the retard roller drive shaft 217 to the retard roller shaft 216 even when the retard roller 207 is displaced.

  Next, driving of the feed roller 206 and the retard roller 207 by the drive transmission device 213 will be described.

  A rotational driving force applied from a main driving means (not shown) is first transmitted to a driving input belt 221 and input to a pulley 225 provided in an armature portion of an electromagnetic clutch 222 that is ON / OFF controlled according to a paper feeding timing. Is done. Here, since the feed roller shaft 215 that rotates integrally with the rotor portion of the electromagnetic clutch 222, the retard roller drive shaft 217, and the retard roller shaft 216 are connected by the retard drive belt 223, the feed roller shaft 215 and the retard The roller shaft 216 and the retard roller drive shaft 217 rotate in the same direction, and the feed roller 206 and the retard roller 207 are rotationally driven in synchronization with the paper feed timing ON.

  Next, when the sheets 202 are fed one by one in the feeding direction (in the direction of arrow b shown in FIG. 9) by the pickup roller 205, the retard roller 207 causes the torque limiter by the frictional force between the feed roller 206 and the sheet 202. As the roller 220 idles, the retard roller 207 rotates in the direction opposite to the drive rotation direction of the retard roller drive shaft 217 (feeding direction).

  In addition, when a plurality of sheets 202 are fed by the pickup roller 205, the frictional force between the plurality of sheets 202 is smaller than the frictional force between the retard roller 207 and the sheet 202. 220 does not idle, and the retard roller 207 rotates in the same direction as the rotational drive direction of the retard roller drive shaft 217 (the direction opposite to the feeding direction). As a result, only the uppermost sheet 202 on the feed roller 206 side, that is, the uppermost sheet 202 in the plurality of sheets 202 fed is separated from the other sheets 202, and the double feeding of the sheets 202 to the image forming unit is prevented. (See Patent Document 1).

JP 2004-59276 A

  By the way, in the image forming apparatus and the image reading apparatus provided with such a conventional sheet feeding device, with the recent increase in speed, there has been a demand for a faster sheet feeding speed and a shorter sheet feeding interval. Yes. Here, when the sheet feeding speed is increased, it is necessary to increase the idling torque of the torque limiter in order to prevent double feeding.

  However, for example, when a magnetic torque limiter is used as the torque limiter, this magnetic torque limiter generates idling torque using hysteresis, so increasing the idling torque increases hysteresis loss. Heat generation due to hysteresis increases. As a result, there is a problem that the torque limiter rises in temperature and the magnetic force decreases, and the idling torque decreases.

  Further, when the sheet feeding interval is shortened, the torque limiter needs to be used in a more continuous rotation state. However, when the torque limiter is used in the continuous rotation state as described above, the time for heat generation becomes longer and the time for heat dissipation becomes shorter. As a result, there is a problem that the torque limiter rises in temperature and the magnetic force decreases, and the idling torque decreases.

  Even when a spring-type torque limiter is used as the torque limiter, it is necessary to increase the frictional force in order to increase the idling torque. However, if the frictional force is increased in this way, there is a problem in durability. there were.

  SUMMARY An advantage of some aspects of the invention is that it provides a sheet feeding apparatus, an image forming apparatus, and an image reading apparatus capable of stably separating and feeding sheets. Is.

  The present invention provides a sheet feeding unit that feeds a sheet stored in a sheet storage unit, a conveying unit that is provided downstream of the sheet feeding unit and that conveys the fed sheet, and is opposite to the direction in which the sheet is conveyed. A sheet feeding unit including a separation unit that transmits a rotational torque in a direction, and a separation feeding unit that separates and feeds the sheet fed by the sheet feeding unit by the conveying unit and the separation unit. In the feeding device, the separation driving means for driving the separation means, and provided between the separation drive means and the separation means, and rotated by the separation drive means to cause the rotation of the separation means to have a predetermined magnitude. Torque transmitting means for transmitting the torque, and when the reverse feeding torque exceeding the predetermined magnitude is applied to the separating means during sheet feeding by the separation feeding section, the torque transmitting means It is characterized in reducing the rotational speed.

  According to the present invention, when a sheet is fed by the separating and feeding unit, if a rotational torque in the reverse direction exceeding a predetermined magnitude is applied to the separating unit, the torque transmitting unit is reduced by reducing the rotational speed of the torque transmitting unit. Heat generation can be mitigated, and stable separation and feeding of sheets can be achieved.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of a color printer that is an example of an image forming apparatus including a sheet feeding device according to a first embodiment of the present invention. This color printer prints a document image with four color toner images of magenta, cyan, yellow, and black.

  In FIG. 1, reference numeral 100 denotes a color printer, and reference numeral 101 denotes a color printer main body (hereinafter referred to as a printer main body). An image forming unit 102 is provided on the upper portion of the printer main body 101.

  Further, two cassette paper feeding units 1 and 2 having cassettes 4 and 5 are provided at the lower part of the printer main body 101, and a manual paper feeding unit 3 having a manual feed tray 6 is provided at one side of the printer main body 101. Is provided. The sheet S stored in each of the sheet feeding units 1 to 3 is selectively configured by a sheet feeding device including a separation roller pair 8 including a pickup roller 7, a feed roller 8A, and a retard roller 8B. The sheet is fed in order from the highest one by the sheet feeding unit 103.

  That is, the sheet S stored in each of the sheet feeding units 1 to 3 is fed out by a pickup roller 7 as a sheet feeding unit, and thereafter, from a feed roller 8A as a conveying unit and a retard roller 8B as a separating unit. Only the uppermost sheet is separated by the separating roller pair 8 constituting the separating sheet feeding unit. After that, the separated sheet S is sent to the registration roller unit 12 that has stopped rotating, and the skew state is corrected by the registration roller unit 12. The sheet S fed from the cassettes 4 and 5 having a long distance to the registration roller unit 12 is relayed by a plurality of conveyance roller pairs 9 to 11 and sent to the registration roller unit 12.

  In FIG. 1, reference numeral 13 denotes a long intermediate transfer belt (endless belt) which is a transfer body provided downstream of the registration roller section 12. The intermediate transfer belt 13 includes a driving roller 13a, a driven roller 13b, and a tension. It is stretched around the roller 13c and rotates clockwise as indicated by an arrow.

  Here, on the upper surface of the horizontal portion of the intermediate transfer belt 13, a plurality of photosensitive drums 14 to 17 that form and carry different color toner images constituting the image forming unit 102 are rotated in the rotational direction of the intermediate transfer belt 13. Are arranged sequentially. In this embodiment, the most upstream photosensitive drum 14 in the intermediate transfer belt rotation direction is a magenta toner image, the next photosensitive drum 15 is a cyan toner image, and the next photosensitive drum 16 is A yellow toner image is carried on the most downstream photosensitive drum 17 and a black toner image is carried thereon. Further, the intermediate transfer belt 13 is in contact with a pair of secondary transfer rollers 40 constituting the secondary transfer portion T2 together with the intermediate transfer belt 13.

  The photosensitive drums 14 to 17 are attached to the primary chargers 27 to 30 for uniformly charging the photosensitive drums 14 to 17 and the photosensitive drums 14 to 17 after the toner image is transferred. Cleaners 31 to 34 for removing the remaining toner are installed.

  In FIG. 1, reference numeral 18 denotes an automatic document feeder. The automatic document feeder 18 sequentially sets a plurality of documents (not shown) on a document table (platen glass) 19 at predetermined positions. Yes.

  Next, an image forming operation of the color printer 100 having such a configuration will be described.

  First, a document is set on the document table 19, and an image (here, a color image) of the set document is read by the reading optical system 20, and then the read color image is read by the CCD element 21 by magenta, cyan, The color components are separated into yellow and black and temporarily stored in an image memory (not shown).

  Next, the image information stored in the image memory in this way is written on the respective photosensitive drums 14 to 17 which are sequentially rotated in the clockwise direction for each color component by the writing optical system 22 including the laser scanner. . That is, first, laser light L (M) based on the magenta component image is projected onto the uppermost photosensitive drum 14 to form an electrostatic latent image on the photosensitive drum 14. Then, the electrostatic latent image is visualized with magenta toner supplied from the developing device 23.

  Next, the laser beam L (C) is projected on the photosensitive drum 15 based on the cyan component image to form an electrostatic latent image on the photosensitive drum 15. The electrostatic latent image is visualized with magenta toner supplied from the developing device 24. Next, after a predetermined time has elapsed from the start of the projection of the laser beam L (M) onto the photosensitive drum 15, the laser beam L (Y) is projected on the photosensitive drum 16 based on the yellow component image, An electrostatic latent image is formed on the photosensitive drum 16. The electrostatic latent image is visualized with yellow toner supplied from the developing device 25.

  Next, after a predetermined time has elapsed since the projection of the laser beam L (Y) on the photosensitive drum 16 is started, the laser beam L (B) is projected on the photosensitive drum 17 based on the black component image, An electrostatic latent image is formed on the photosensitive drum 17. The electrostatic latent image is visualized with black toner supplied from the developing device 26.

  Next, the intermediate transfer belt 13 is sequentially passed between the transfer portions formed by the photosensitive drums 14 to 17 and the transfer chargers 90 to 93, so that magenta, cyan, yellow, and black toner images are intermediated. Overlay on the transfer belt 13.

  On the other hand, the registration roller unit 12 is driven at a timing for aligning the position of the toner image superimposed on the intermediate transfer belt 13 and the leading end of the sheet, whereby the sheet S whose skew state has been corrected thereby is transferred onto the intermediate transfer belt 13. Send to. Then, the magenta, cyan, yellow, and black toner images superimposed on the intermediate transfer belt 13 are collectively transferred to the sheet S thus sent to the intermediate transfer belt 13 at the secondary transfer portion T2.

  Next, the sheet S that has passed through the secondary transfer portion T2 is sent to the fixing device 35 by the intermediate transfer belt 13, heated by the fixing roller 35A in the fixing device 35, and pressurized by the pressure roller 35B to form a transferred toner image. Fix on the sheet surface. Thereafter, the fixed sheet S that has passed through the fixing device 35 is sent to the discharge roller pair 37 by the conveying roller pair 36 and further discharged onto the discharge tray 38 outside the apparatus.

  The color printer 100 is capable of image formation in the duplex mode. When the duplex mode is designated, the fixing processed sheet S that has passed through the fixing device 35 is sent to the reverse path 59 through the vertical path 58. In this case, the flapper 60 opens the vertical path 58, whereby the fixed sheet S is conveyed by the conveyance roller pairs 36, 61, 62 and the reverse rotation roller pair 63.

  When the rear end of the fixed sheet S conveyed in the direction of arrow a by the reverse roller pair 63 passes the point P, the reverse roller pair 63 reverses, whereby the fixed sheet S is moved to the rear end side. Is conveyed in the direction of arrow b. This operation causes the toner image transfer surface of the fixed sheet S to face upward. Further, at the point P, the sheet S can enter from the vertical path 58 to the reverse path 59, and the sheet S can enter from the reverse path 59 to the refeed path 67. A flapper 64 with a flexible sheet that makes it impossible for the sheet S to enter is provided.

  Next, the fixed sheet S conveyed in the direction of the arrow b by the reverse rotation of the reverse rotation roller pair 63 is sent into the refeed path 67, and a plurality of refeed path path transfer roller pairs 68 and the transfer roller pair 11. It is relayed and sent again to the registration roller pair 12 for image feed formation. Thereafter, the sheet S subjected to the fixing process is fed to the intermediate transfer belt 13 after the skew state is corrected by the registration roller unit 12. Then, the second image formation is performed based on the image data stored in the image memory (not shown) that has been subjected to the magnification correction in the main scanning direction and the sub-scanning direction. Thereafter, the same process as the one-sided image formation is performed. Then it is discharged out of the machine.

  2 is a diagram showing a schematic configuration of each of the paper feeding units 1 to 3. In FIG. 2, reference numeral 101 denotes a first drive motor. The first drive motor 101 causes the pickup roller 7, the feed roller 8A, and the retard. The roller 8B is driven to rotate.

  A pickup roller (not shown) holding the pickup roller 7 is driven in the vertical direction by driving a first drive motor 101 which is a separation drive means for driving the retard roller 8B together with the feed roller 8A. Reference numeral 7 denotes a sheet cassette 4 or 5 serving as a sheet storage unit, or a sheet S stacked on the sheet feed tray 6, which can be brought into contact with or separated from the uppermost one.

  Reference numerals 70A and 70B denote a pair of conveying rollers which are downstream conveying means provided downstream of the feed roller 8A for conveying one sheet S separated by the feed roller 8A and the retard roller 8B to the image forming unit 102. The pair of conveyance rollers 70A and 70B is rotationally driven by a second drive motor 102 which is a downstream conveyance driving unit. Reference numeral 70C denotes a conveyance sensor that detects that a sheet has reached the nip portion of the conveyance roller pair 70A, 70B. Based on a detection signal from the conveyance sensor 70C, a control unit (not shown) will be described later. In addition, the rotational speeds of the first and second drive motors 101 and 102 are changed (controlled).

Here, the driving force of the first drive motor 101 is transmitted to the feed roller 8A in the _Nf direction via the one-way clutch 103. The driving force of the driving motor 101 transmitted to the feed roller 8A is transmitted to the pickup roller 7 in the _Nr1 direction by the timing belt 104 and the pulleys 105 and 106. Further, the driving force of the driving motor 101 transmitted to the feed roller 8A is transmitted to the retard roller 8B via the timing belt 107, the pulleys 108 and 109, and the torque limiter 110.

  The torque limiter 110, which is a torque transmission means, is rotated by the first drive motor 101 to transmit a predetermined amount of rotational torque to the retard roller 8B, and has a predetermined size to the retard roller 8B by the feed roller 8A. It rotates with the retard roller 8B until a reverse rotational torque exceeding the rotational torque is applied.

Thus, the retard roller 8B rotates in the _Nr2 direction following the feed roller 8A during a normal paper feeding operation, but the torque limiter 110 provided between the drive motor 101 and the retard roller 8B and the one-way. Only the driving force is transmitted to the retard roller 8B by the gear 111.

  Next, the sheet feeding operation of each of the sheet feeding units 1 to 3 having such a configuration will be described with reference to FIG.

The uppermost sheet S1 among the sheets S stored in the sheet feeding cassette or the like is picked up by the pickup roller 7, the feed roller 8A, and the retard roller 8B driven by the first drive motor 101 as shown in FIG. It is fed at a speed V _1. The rotation speed _{N t} corresponding to the rotation torque of the torque limiter 110 in this case, a feed roller 8A, the roller diameter of the retard roller 8B and _D f, _{D r,} gear number _T f pulleys 108 and 109, When T _r and the rotation speed of the feed roller 8A are N _f , the following results.

Here, _assuming that the maximum rotation speed of the torque limiter 110 is N _tmax , the rotation speed N _f of the feed roller 8A and the sheet conveyance speed so as not to exceed the maximum rotation speed N _tmax (maximum torque) of the torque limiter 110. setting range of V ₁ is as follows.

In this way, the rotational speed N _f of the feed roller 8A and the conveying speed V ₁ of the sheet S1 are set so that the rotational speed of the torque limiter 110 does not exceed the maximum rotational speed N _tmax corresponding to a predetermined rotational torque. By setting to a small value, heat generation of the torque limiter 110 can be reduced, and idling torque fluctuation during operation of the torque limiter 110 can be suppressed, and stable separation and feeding can be performed.

Further, after this, when the leading end of the sheet S1, which is conveyed at the speed V ₁ is detected by the conveyance sensor 70C, the control means (not shown) is so as to increase the rotational speed of the second driving motor 102, thereby as shown in FIG. 3 (b), the sheet S1 is to increase withdrawn at a speed _{V 2} speed by the conveying roller pairs 70A, 70B. At this time, the pickup roller 7 is raised to reduce the load on the conveying roller pair 70A, 70B.

Here, when the conveyance speed of the sheet S1 is increased in this way, a reverse rotational torque exceeding a predetermined magnitude is applied to the retard roller 8B. In this case, the rotation of the feed roller 8A is also performed. In order to prevent the number N _f (or the conveyance speed) from exceeding the set range, that is, to keep the rotational speed of the torque limiter 110 below a certain value, the control means increases the rotational speed of the second drive motor 102. At the same time, the rotational speed of the first drive motor 101 is decreased. Thus, the pickup roller 7, a feed roller 8A, the conveying speed of the retard roller 8B is decelerated, it becomes _{V 0.}

  Then, the sheet S1 is pulled and accelerated by the pair of conveying rollers 70A and 70B in this way, thereby achieving a high speed, and the rotation of the torque limiter 110 is reduced by decelerating the feed roller 8A and the retard roller 8B. The number can be controlled below a certain number of revolutions.

The rotation speed _{N t} is conveying roller pair 70A of the torque limiter 110 in this case, 70B rotational speed of when the _{N h} is as follows.

Accordingly, _assuming that the maximum rotation speed of the torque limiter 110 is N _tmax , the rotation speed N _f of the feed roller 8A, the sheet conveyance speed V ₀ , the rotation speed N _h of the conveyance roller 70B, the sheet conveyance speed V ₂ , and each The setting range is as follows.

  And it becomes possible to achieve high speed by performing the conveyance control of (a)-(c) of FIG. 3 within the speed setting range of (1)-(3).

  Further, when such a sheet feeding operation is performed, if the reverse rotation torque exceeding a predetermined magnitude is applied to the retard roller 8B as the conveyance speed of the sheet S increases, the rotation speed of the torque limiter 110 is increased. Thus, the heat generation of the torque limiter 110 can be reduced, and the stable separation and feeding of the sheet S can be achieved. As a result, even if the conveyance speed (image forming apparatus) is increased, fluctuations in idling torque during operation of the torque limiter 110 are suppressed, and stable separation and feeding are possible.

  In the present embodiment, the feed roller 8A and the retard roller 8B are driven in the same manner and pulled out by the pair of conveyance rollers 70A and 70B. However, for simplification, the conveyance rollers 70A and 70B are eliminated, and the feed roller 8A and The same control is possible even if a separate drive motor is attached to the retard roller 8B and the rotational speed of the retard roller drive motor is decreased simultaneously with the increase of the rotational speed of the feed roller drive motor.

  Next, a second embodiment of the present invention will be described.

  FIG. 4 is a diagram illustrating the configuration of the sheet feeding apparatus according to the present embodiment. In FIG. 4, the same reference numerals as those in FIG. 2 indicate the same or corresponding parts.

  In FIG. 4, reference numeral 121 denotes a first drive motor capable of forward and reverse rotation, which is a separate drive means. The drive of the first drive motor 121 is transmitted to the drive input stage gears 112, 113 and transmitted to the drive input stage gear 112. The driving force of the driving motor 121 transmitted to the one-way gears 114 and 115 and the idler 116, and the driving force of the driving motor 121 transmitted to the driving input stage gear 113 is transmitted to the one-way gears 117 and 118 and the idlers 119 and 120, respectively. After that, it is transmitted to the feed roller 8A and the retard roller 8B.

  The drive input stage gears 112 and 113, the one-way gears 114 and 115, the idler 116, the one-way gears 117 and 118, and the idlers 119 and 12 are provided between the first drive motor 121 and the torque limiter 110. Transmission ratio switching means for switching the drive transmission ratio from the drive motor 121 to the retard roller 8B is configured.

Here, in the present embodiment, for example, when the first driving motor 121 is rotated in the arrow a direction, _{N f} direction to the feed roller 8A by the one-way gear 114, driving the _{N r} direction to retard roller 8B Is transmitted. At this time, the one-way gears 117 and 118 rotate in reverse and do not transmit drive. Meanwhile, when the drive motor 121 is rotated in the arrow b direction, _{N f} direction to the feed roller 8A, it is driven in the _{N r} direction to retard roller 8B is transmitted by the one-way gear 117, 118. At this time, the one-way gears 114 and 115 rotate in reverse and do not transmit drive.

That is, the first driving motor 121 is a, b feed roller 8A be rotated in any direction N _f direction, although the retard roller 8B is rotated in N _r direction, in this embodiment, the transmission ratio changing means The drive transmission ratio is switched, and the rotation speed of the retard roller 8B relative to the rotation speed of the feed roller 8A is smaller when the drive motor 121 rotates in the arrow b direction than when the drive motor 121 rotates in the arrow a direction. ing.

  Next, the sheet feeding operation of the sheet feeding apparatus (each sheet feeding unit 1 to 3) having such a configuration will be described with reference to FIG.

The uppermost sheet S1 is driven by a motor 101 which rotates in the direction of arrow a in FIG. 4, a pickup roller 7, as shown in (a) of FIG. 5, the feed roller 8A, is fed at a rate V ₁ by retard roller 8B ing. The rotation speed _{N t} of the torque limiter 110 in this case, a feed roller 8A, the roller diameter _D f of the retard roller 8B, and _{D r,} the gear number of the one-way gear 114 and 115 _{T f1, T r1} Then follows become that way.

Here, when the maximum rotational speed of the torque limiter 110 and _{N tmax,} set the conveyance speed _{V 1} of the revolving speed _{N f} and the sheet feed roller 8A to not exceed the maximum rotational speed _{N tmax} of the torque limiter 110 The range is as follows.

In this way, the rotational speed N _f of the feed roller 8A and the conveying speed V ₁ of the sheet S1 are set so that the rotational speed of the torque limiter 110 does not exceed the maximum rotational speed N _tmax corresponding to a predetermined rotational torque. By setting to a small value, heat generation of the torque limiter 110 can be reduced, and idling torque fluctuation during operation of the torque limiter 110 can be suppressed, and stable separation and feeding can be performed.

Further, after this, when the leading end of the sheet S1, which is conveyed at the speed V ₁ is detected by the conveyance sensor 70C, as shown in (b) of FIG. 5, the control means first driving motor 121 and the second drive motor 102 is temporarily stopped, and thereafter, the driving of the motors 102 and 121 once stopped at a predetermined timing is resumed.

At this time, the control means rotates the first drive motor 121 in the direction of arrow b. By rotating in this manner, the sheet S1 is conveyed at high speed to a speed V ₂ as shown in (c) of FIG. When the first drive motor 121 rotates in the direction of the arrow b as described above, the rotational speed of the retard roller 8B with respect to the rotational speed of the feed roller 8A becomes small as described above.

In other words, by rotating the first driving motor 121 in the direction of the arrow b, as well as achieve faster by increasing the conveying speed of the feed roller 8A from V ₁ to V _2, a predetermined size to retard roller 8B Accordingly Even when rotational torque in the reverse direction exceeding the above is applied, the rotational speed of the torque limiter 110 can be controlled to be equal to or lower than a certain rotational speed by reducing the rotational speed of the retard roller 8B.

If the number of gears of the one-way gears 117 and 118 at this time is T _f2 and T _r2 , the rotational speed N _t of the torque limiter 110 is as follows.

Thus, when the maximum rotational speed of the torque limiter 110 and N _tmax, revolving speed N _f and the conveying speed V ₂ and the setting range of the seat of the feed roller 8A is as follows.

  Then, by performing the conveyance control of (a) to (c) of FIG. 5 within the speed setting range of (4) and (5), it is possible to achieve high speed.

  Further, when the rotational speed of the reverse direction exceeding a predetermined magnitude is applied to the retard roller 8B at a predetermined timing as the conveyance speed of the sheet S increases, the rotational speed of the torque limiter 110 is decreased. By switching the transmission ratio of the transmission ratio switching means, the heat generation of the torque limiter 110 is mitigated, and idling torque fluctuation during operation of the torque limiter 110 is suppressed, and stable separation and feeding can be performed. In order to further increase the speed, it is also possible to pull out the conveying roller pair 70A, 70B by rotating at a high speed as in the first embodiment described above.

  Next, a third embodiment of the present invention will be described.

  FIG. 6 is a diagram illustrating the configuration of the sheet feeding apparatus according to the present embodiment. In FIG. 6, the same reference numerals as those in FIG. 2 denote the same or corresponding parts.

  In FIG. 6, reference numeral 122 denotes a variable speed drive motor which is a separate drive means. The drive of the drive motor 122 is transmitted to the drive input gear 123, and the drive force of the drive motor 121 transmitted to the drive input stage gear 123 is These are transmitted to the pair of conveying rollers 70A and 70B by the idler gear 132 and the gear 133, and are transmitted to the feed roller 8A by the clutch gear 124, and the drive is switched ON / OFF by the clutch 125.

  The driving force transmitted to the feed roller 8A is transmitted to the retard roller 8B by the idler gear 130, the clutch gear 127, or the gear 126, the idler gear 131, and the one-way gear 129. The idler gear 130, the clutch gear 127, or the gear 126, the idler gear 131, and the one-way gear 129 are provided between the drive motor 122 and the torque limiter 110 to switch the drive transmission ratio from the drive motor 122 to the retard roller 8B. Transmission ratio switching means is configured.

  Reference numeral 128 denotes a shifting clutch for the retard roller 8B. When the shifting clutch 128 is ON, the retard roller 8B is in a high speed rotation mode by the idler gear 130 and the clutch gear 127, and when the shifting clutch 128 is OFF, The retard roller 8B is in the low speed rotation mode by the gear 126, the idler gear 131, and the one-way gear 129. That is, in the present embodiment, the retard roller 8B rotates at a high speed when the transmission clutch 128 is turned on, and the retard roller 8B rotates at a low speed when the transmission clutch 128 is turned off.

  Next, the sheet feeding operation of the sheet feeding apparatus (each sheet feeding unit 1 to 3) having such a configuration will be described with reference to FIG.

The uppermost sheet S1 is in a state where the clutch 125 is turned ON, as shown in (a) of FIG. 7 by the rotation of the driving motor 122, the pickup roller 7, a feed roller 8A, at the speed _{V 1} by the retard roller 8B Being transported. At this time, the clutch 128 is ON. In this case, assuming that the gear numbers of the clutch gears 124 and 127 are T _f1 and T _r1 and the roller diameters of the feed roller 8A and the retard roller 8B are D _f and D _r , rotational speed _{N t} of the torque limiter 110 is as follows.

Here, when the maximum rotational speed of the torque limiter 110 and _{N tmax,} set the conveyance speed _{V 1} of the revolving speed _{N f} and the sheet feed roller 8A to not exceed the maximum rotational speed _{N tmax} of the torque limiter 110 The range is as follows.

In this way, the rotational speed N _f of the feed roller 8A and the conveying speed V ₁ of the sheet S1 are set so that the rotational speed of the torque limiter 110 does not exceed the maximum rotational speed N _tmax corresponding to a predetermined rotational torque. By setting to a small value, heat generation of the torque limiter 110 can be reduced, and idling torque fluctuation during operation of the torque limiter 110 can be suppressed, and stable separation and feeding can be performed.

Further, after this, when the leading end of the sheet conveyed at the speed V ₁ is detected by the conveyance sensor 70C, the control unit increases the rotational speed of the drive motor 122 is accelerated to the transport speed V _2. At the same time, in order to keep the rotation speed of the torque limiter below a certain value, the speed change clutch 128 is turned OFF, and the retard roller 8B is set to the low speed rotation mode.

When the speed is increased in this way, even when a reverse rotational torque exceeding a predetermined magnitude is applied to the retard roller 8B, the torque limiter is reduced by reducing the rotation of the retard roller 8B. The number of rotations 110 can be controlled below a certain number of rotations. At this time, if the gear numbers of the gear 126 and the one-way gear 129 are T _f2 and T _r2 , the rotational speed N _t of the torque limiter 110 is as follows.

Thus, when the maximum rotational speed of the torque limiter 110 and N _tmax, revolving speed N _f and the conveying speed V ₂ and the setting range of the seat of the feed roller 8A is as follows.

  Then, it is possible to achieve high speed by performing the conveyance control of (a) to (c) of FIG. 7 within the speed setting range of (6) and (7).

  Further, when the rotational speed of the reverse direction exceeding a predetermined magnitude is applied to the retard roller 8B at a predetermined timing as the conveyance speed of the sheet S increases, the rotational speed of the torque limiter 110 is decreased. By switching the transmission ratio of the transmission ratio switching means by the speed change clutch 128, the heat generation of the torque limiter 110 is alleviated, the idling torque fluctuation during operation of the torque limiter 110 is suppressed, and stable separation and feeding can be performed.

  In the above description, the case where the sheet feeding apparatus according to the present invention is applied to an image forming apparatus provided with an image forming unit has been described. However, the present invention is not limited thereto, and the sheet feeding apparatus is not limited thereto. It goes without saying that can be applied to an image reading apparatus having an image reading unit.

1 is a diagram illustrating a configuration of a color printer that is an example of an image forming apparatus including a sheet feeding apparatus according to a first embodiment of the present invention. FIG. 3 is a diagram illustrating a schematic configuration of a sheet feeding unit configured by the sheet feeding device. FIG. 6 is a diagram illustrating a sheet feeding operation of the sheet feeding unit. The figure explaining the structure of the sheet feeding apparatus which concerns on the 2nd Embodiment of this invention. FIG. 5 is a diagram illustrating sheet feeding operation of a sheet feeding unit configured by the sheet feeding device. FIG. 6 is a diagram illustrating a configuration of a sheet feeding device according to a third embodiment of the present invention. FIG. 5 is a diagram illustrating sheet feeding operation of a sheet feeding unit configured by the sheet feeding device. Schematic which shows the conventional sheet feeding apparatus. The schematic perspective view which shows the conventional feeding drive transmission part.

Explanation of symbols

1 to 3 Paper feeding units 4 and 5 Cassette paper feeding unit 6 Manual feed tray 7 Pickup roller 8 Separation roller pair 8A Feed roller 8B Retard rollers 70A and 70B Conveying roller pair 100 Color printer 101 First drive motor 102 Second drive motor 103 Sheet Feeder 110 Torque limiter 121 First drive motor 122 Drive motor 128 Shifting clutch S Seat

Claims (9)

A sheet feeding means for feeding a sheet stored in the sheet storage section, a conveying means for conveying the sent sheet provided downstream of the sheet feeding means, and a rotational torque in a direction opposite to the direction of conveying the sheet In a sheet feeding apparatus including a separation unit that transmits the sheet, and a separation feeding unit that separates and feeds the sheet fed by the sheet feeding unit by the transport unit and the separation unit,
Separation drive means for driving the separation means;
A torque transmission means provided between the separation drive means and the separation means, and rotated by the separation drive means to transmit the rotational torque of a predetermined magnitude to the separation means;
With
During sheet feeding by the separation feeding unit, if the reverse rotation torque exceeding the predetermined magnitude is applied to the separation unit, the rotation speed of the torque transmission unit is decreased. apparatus.   The sheet feeding apparatus according to claim 1, wherein the separation driving unit also serves as a driving unit for the conveying unit. A downstream conveying means which is provided on the downstream side of the conveying means and conveys the sheet together with the separation feeding unit;
Downstream transport driving means for driving the downstream transport means;
Control means for controlling the number of rotations of the downstream conveyance drive means and the separation drive means;
With
The control means increases the rotational speed of the downstream conveyance drive means so as to increase the sheet feeding speed at a predetermined timing during sheet feeding, and the separation so as to decrease the rotational speed of the torque transmission means. 2. A sheet feeding apparatus according to claim 1, wherein the rotational speed of the driving means is reduced. Transport driving means for driving the transport means;
Control means for controlling the number of rotations of the transport drive means and the separation drive means;
With
The control means increases the rotation speed of the conveyance drive means so as to increase the sheet feeding speed at a predetermined timing during sheet feeding, and performs the separation driving so as to decrease the rotation speed of the torque transmission means. 2. A sheet feeding apparatus according to claim 1, wherein the number of rotations of the means is reduced. A transmission ratio switching means provided between the separation drive means and the torque transmission means, and for switching a drive transmission ratio from the separation drive means to the separation means;
Control means for controlling the drive transmission ratio switching operation of the transmission ratio switching means;
With
The control means switches the transmission ratio so as to reduce the rotational speed of the torque transmission means when a reverse rotational torque exceeding the predetermined magnitude is applied to the separation means at a predetermined timing during sheet feeding. 2. The sheet feeding apparatus according to claim 1, wherein the transmission ratio of the means is switched.   The separation drive means is a motor capable of forward / reverse rotation, and the transmission ratio switching means switches a drive transmission ratio from the separation drive means to the separation means by switching between normal rotation / reverse rotation of the motor. The sheet feeding apparatus according to claim 5.   6. The sheet feeding apparatus according to claim 5, wherein the transmission ratio switching unit switches a drive transmission ratio from the separation driving unit to the separation unit by switching a clutch.   An image forming apparatus comprising: an image forming unit that forms an image on a sheet; and the sheet feeding device according to any one of claims 1 to 7 that feeds the sheet to the image forming unit. apparatus. An image reading apparatus comprising: an image reading unit that reads an image on a sheet; and the sheet feeding device according to claim 1 that feeds the sheet to the image reading unit. .

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