JP3867693B2 - Paper feeder - Google Patents

Description

  The present invention relates to a sheet feeder such as an automatic document feeder (hereinafter referred to as an ADF apparatus), and more particularly, a pickup roller that feeds a sheet (document) set on a sheet feed (document) tray from an uppermost layer. The drive mechanism.

  In general, an electrophotographic copying machine and a facsimile apparatus are provided with an ADF apparatus for separating originals set on an original tray one by one and feeding them to a reading unit. In such an ADF apparatus, a pickup roller for feeding out the original set on the original tray, a separation roller for separating and feeding the fed original one by one, and a downstream side of the separation roller are provided. A conveyance roller that conveys the document toward the reading unit is provided.

  As an example of the ADF apparatus provided with the pickup roller as described above, a paper feeding apparatus disclosed in Patent Document 1 described later can be given. In the sheet feeding device, a pickup arm is attached to the drive shaft of the separation roller so as to be swingable up and down. A pickup roller is pivotally supported on the front side of the pickup arm, and the drive is transmitted from the drive shaft to the pickup roller. In addition, a torque limiter is interposed at the connection between the pickup arm and the drive shaft, and when the drive shaft rotates, torque is not applied to the front side of the pickup arm when a load exceeding the load torque of the torque limiter is not applied. The pickup arm swings in the same direction in conjunction with the rotation of the drive shaft by the action of the limiter. On the other hand, when a load exceeding the load torque of the torque limiter is applied during this swinging, that is, on the document tray When the pickup arm is pressed onto the deposited document, the pickup arm is prevented from swinging. Even when the pickup arm is prevented from swinging, the rotation of the drive shaft is continued, so that the original is fed out from the uppermost layer portion of the accumulated original by the rotation of the pickup roller transmitted from the drive shaft. The

  In the sheet feeding device as described above, the circumferential speed of conveyance by the conveyance roller is slightly larger than the circumferential speeds of the pickup roller and the separation roller. This is to secure the interval between pages of the continuously supplied document. Therefore, due to the length of the conveyance path between the separation roller and the conveyance roller, when the leading edge of the document being fed reaches the conveyance roller, the latter half is restrained by the separation roller and the pickup roller, and the peripheral speed difference As a result, a transport load (tensile force) is applied to the document. In order to reduce this conveyance load, a one-way clutch is interposed between the separation roller and the pickup roller and the respective drive transmission systems, and when the pulling force is applied, the separation roller and the pickup roller transmit each drive transmission. It is cut off from the system and is idle.

By the way, the pick-up roller is not substantially involved in the feeding of the original when it is idling, so it is not necessary to press it onto the accumulated original. Thus, from this point of view, in the above conventional example, the pickup arm is always urged in the direction opposite to the swing by the tension spring, and the separation roller is idly rotated by the action of the one-way clutch. Is configured to cut off power transmission from the drive shaft to the pickup arm. Therefore, when the separating roller is idling, the pickup arm is flipped upward by the restoring action of the tension spring, and the pickup roller is held in a standby position that is not in contact with the accumulated original until the next original is fed out. (For example, see Patent Document 1).
JP 7-157115 A

  In the conventional paper feeder, the pickup roller does not press against the accumulated original while the latter half of the original being fed is on the original tray, so that the pickup roller resists the original being fed. It does not become, and smooth feeding is made. However, while the documents accumulated on the document tray are sequentially fed out and fed, the pickup arm swings up and down for each document. Therefore, depending on the number of documents, the repeated pickup arm swings. The impact sound that accompanies the movement can be annoying. Further, such repeated swinging also promotes wear and tear of the surrounding mechanism portion. Therefore, it has been tried again to configure the pick-up roller so that it keeps pressing on the stacked document until the tension spring is stopped and all the documents placed on the document tray are fed. Yes.

  In this case, as described above, while the drive shaft of the separation roller is rotating forward, the pickup roller is always pressed against the uppermost layer portion of the document, and the drive transmission system from the drive shaft to the pickup roller is always maintained. It is operating. Accordingly, when the trailing edge of the preceding document comes off from the pickup roller and the pulling force by the preceding document does not act on the pickup roller, the drive transmission to the pickup roller via the one-way clutch is resumed and the next document is fed out. . If the next document is fed immediately after the tension of the preceding document is removed, the trailing edge of the preceding document and the leading edge of the next document are simultaneously introduced into the separation roller. Is prevented from entering. Therefore, the front portion of the next original is curved between the separation roller and the pickup roller, and when the next original is fed as it is, an original jam occurs.

  The present invention has been made in view of the above situation, and the feeding of the succeeding sheet is delayed so that the trailing edge of the preceding sheet and the leading edge of the succeeding sheet are not simultaneously introduced into the separation roller. The present invention provides a paper feeding device that can smoothly feed a large number of sheets.

The present invention includes a pickup roller that feeds out the paper placed on the paper placement unit, a separation roller that separates and feeds the fed paper one by one,
The present invention relates to a sheet feeding device including a conveying roller disposed downstream of the separation roller and having a peripheral speed greater than that of the separation roller and the pickup roller.
According to the first aspect of the present invention, the pickup roller is connected to the drive transmission system via the one-way clutch and the differential clutch means, and is always pressed and maintained on the accumulated paper during the paper feeding operation. ,
The differential clutch means delays a predetermined time after the preceding sheet comes out of the pickup roller during conveyance of the preceding sheet in a state in which a conveyance load is applied by the conveyance roller. It is configured to establish a drive connection relationship.

According to a second aspect of the present invention, the pickup roller is pivotally supported on the front side of a frame that is swingably mounted around the drive shaft of the separation roller, and the drive transmission system is supported by the drive shaft. Drive is transmitted through,
A torque limiter is interposed at the connecting portion of the frame and the drive shaft, and the frame is in the same direction in conjunction with the rotation of the drive shaft in a state where a load exceeding the load torque of the torque limiter is not applied to the front side. The frame is prevented from swinging and the drive shaft continues to rotate in a state in which the load is greater than the load torque of the torque limiter.

According to a third aspect of the present invention, the differential clutch means includes a clutch member that is driven and transmitted from the drive transmission system via the one-way clutch, a clutch pawl in the thrust direction formed on the clutch member, and an end face of the pickup roller. It consists of clutch claws protruding on the
Both claws are aligned in a thrust manner in the thrust direction and arranged with a predetermined play space in the radial direction, and the predetermined time is determined by the size of the play space.

  According to the first aspect of the present invention, after the preceding paper in a state in which the conveyance load is applied by the conveyance roller has come out of the pickup roller, the differential clutch means is used to delay and drive the pickup roller and the drive transmission system. Since the connection relationship is established, if the delay interval is set as appropriate, the trailing edge of the preceding sheet and the leading edge of the succeeding sheet can be prevented from being simultaneously introduced into the separation roller. That is, the pickup roller is stopped from the time when the trailing edge of the preceding sheet is removed from the pickup roller until the drive connection relationship is established. Until the paper is pulled out, the pickup roller stops and the subsequent paper is not fed out, so that the trailing edge of the preceding paper and the leading edge of the succeeding paper are not fed simultaneously. Will not occur.

  According to the invention of claim 2, when the drive shaft of the separation roller starts to rotate, the frame swings by the action of the torque limiter. This swinging is continued until a load exceeding the load torque of the torque limiter is applied to the front side. Therefore, when the pickup roller is pressed onto the paper placed on the paper placement portion, this swinging is prevented. At this time, since the rotation of the drive shaft is continued, the rotational power of the drive shaft is transmitted to the pickup roller via the drive transmission system, and the paper placed on the paper placement portion is sequentially from the uppermost layer portion. It goes out. This continuous feeding reduces the layer thickness of the accumulated paper. However, since the above-mentioned swinging force is always applied to the frame by the action of the torque limiter, the pickup roller is pushed onto the accumulated paper. This state is maintained and the paper is fed out without delay.

  According to the third aspect of the present invention, the pickup roller rotates idly by the action of the one-way clutch while the conveyance load (tensile force) is applied to the paper by the conveyance roller, so that the pickup roller protrudes from the end surface of the pickup roller. The clutch pawl is rotated in advance relative to the clutch pawl of the clutch member. Therefore, in this state, the play space is formed on the anti-rotation side of the pickup roller side clutch pawl, and the clutch member side clutch pawl continues to rotate following the pickup roller side clutch pawl with a delay of the play space. Will be.

  When the paper subjected to the transport load is removed from the pickup roller, the tensile force does not act on the pickup roller, so that the idle rotation of the roller is stopped. Since the clutch member continues to rotate, the clutch member-side clutch pawl rotates and moves in the play space and comes into contact with the pickup roller-side clutch pawl, so that the drive connection relationship between the pickup roller and the drive transmission system is again established. Established. Since the pickup roller does not rotate during the rotational movement of the clutch member side clutch pawl in the play space, the succeeding sheet is not fed out, and this delay causes the succeeding sheet to pass after the separating roller passes. Since the sheet can be set so as to be introduced into the separation roller, there is no concern that the sheet jam due to the overlap feeding as described above.

  As described above, according to the present invention, the preceding sheet in a state in which the conveying load is applied by the conveying roller is configured so that the pickup roller does not rotate immediately after it has come out of the pickup roller. The feeding is delayed so that the trailing edge of the preceding sheet and the leading edge of the succeeding sheet are not simultaneously introduced into the separation roller. Therefore, the separating roller is configured to introduce the succeeding sheet after the preceding sheet is pulled out. The continuous feeding and feeding of a large number of sheets placed on the sheet placing portion can be performed very smoothly. In addition, since such a function is achieved by simple differential clutch means associated with the transmission mechanism including the up-and-down swing mechanism of the pickup roller and the one-way clutch as in the inventions of claims 2 and 3, the electromagnetic clutch The cost of the apparatus can be reduced and the practical value can be increased without using expensive electrical components such as the above.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a longitudinal sectional view of a main part of an ADF 1 in a facsimile machine, a copying machine, or a so-called multi-function machine having both facsimile and copying functions (including a printer function).

  The ADF 1 shown in the figure is configured as a document feeder for reading an image while conveying a sheet document D one by one and outputting it as a digital signal. A document tray 2b is detachably attached to the document supply port 2a of the ADF 1 so that the document tray 2b is inclined downward toward the document supply port 2a, and a document placement unit is formed by the document supply port 2a and the document tray 2b. A (paper placing portion) 2 is configured. A pickup roller 3 for feeding out the original (paper) D deposited on the original placing portion 2 from the upper layer portion is disposed on the original supply port portion 2a. A document separation device 4 for separating and feeding the sheets one by one is provided. The document separation device 4 includes a separation roller 4a and a separation pad 4b urged so as to elastically contact the peripheral body of the separation roller 4a. The document fed out by the pickup roller 3 is introduced between the separation roller 4a and the separation pad 4b, and is separated one by one due to the difference in friction coefficient with respect to the two papers as the separation roller 4a rotates, and is fed downstream. Sent. 4c is a compression spring for elastically bringing the separation pad 4b into contact with the periphery of the separation roller 4a.

  The originals separated one by one by the original separating device 4 reach the conveying roller 6 through the curved conveying path 5, are nipped and conveyed by the pressure roller 6 a, pass over the platen 7, and are discharged by the discharging roller 8. It is discharged onto the tray 9. When the document passes over the platen 7, the image information on the document is sequentially read by the reading and scanning device 10 waiting under the platen 7 and is output as a digital signal as described above. The reading scanning device 10 includes a light source 10a formed of a fluorescent lamp or a cold cathode tube, a plurality of mirrors 10b, a condensing lens 10c, and a CCD (charge coupled device) 10d. 10e. Irradiation light from the light source 10a is reflected by the original passing through the reading point P on the platen 7, and then repeatedly reflected by the four mirrors 10b, is condensed by the condenser lens 10c, and enters the CCD 10d ( (Refer to the light path of the one-dot chain line). In the CCD 10d, image information drawn on the document is converted into an electric signal and output as a digital signal.

  The reading scanning device 10 in the figure is configured to be used also as a flat bed scanner (FBS). That is, although a part of the illustration is omitted, the FBS portion 11 is coupled to the right side of the broken portion in FIG. Although the carriage 10e is stationary at the reading position of the ADF document in the illustrated example, when reading the FBS document, the carriage 10e moves into the FBS unit 11 and reciprocates in the FBS unit 11 along the lower surface of the platen glass 12. During this reciprocation, the image information of the document placed on the platen glass 12 is read by the reading scanning device 10 as described above. The ADF 1, the document tray 2b, and the discharge tray 9 are integrated to form a platen cover, and can be opened and closed up and down with the back side of the paper surface as a hinge portion (not shown). Therefore, when the FBS unit 11 reads a document, the platen cover is opened and the document is placed on the exposed platen glass 12.

  The separation roller 4a, the transport roller 6 and the discharge roller 8 are configured such that one motor (not shown) is used as a drive source and drive transmission is appropriately performed via a transmission means (same as above) such as a gear or a belt. . The pickup roller 3 is configured to be transmitted from the drive transmission system of the separation roller 4a, which will be described in detail below. 2 is a perspective view of the drive mechanism in which the pickup roller 3 and the separation roller 4a are unitized, as viewed from below, FIG. 3 is an exploded perspective view thereof, and FIG. 4 is a longitudinal sectional view of a main part of the drive mechanism. is there.

  Reference numeral 4d denotes a drive shaft for the separation roller 4a, which rotates with the driving force of the motor. The drive shaft 4d is fitted with a pulley 4e that rotates integrally with the drive shaft 4d by engagement via a pin 4g. Further, a separation roller 4a is fitted on the drive shaft 4d so as to be freely rotatable, and a coil spring 4f that conjugates both is fitted on the pulley 4e and the small diameter cylindrical portions 4e1 and 4a1 of the separation roller 4a. . The coil spring 4f functions as a spring clutch (one-way clutch), and when the drive shaft 4d rotates forward (in the direction of arrow A in FIG. 2), this rotational force causes the coil spring 4f to be tightened. Embedded in. Therefore, when the drive shaft 4d rotates forward and the pulley 4e rotates integrally, the coil spring 4f is tightened, and the small-diameter cylindrical portions 4e1 and 4a1 are engaged with each other via the coil spring 4f. As a result, the pulley 4e rotates. The separation roller 4a is transmitted to the separation roller 4a, and the separation roller 4a rotates in the normal direction (the direction in which the document is fed), that is, the A direction.

  The rotation of the pulley 4e is also transmitted to the pickup roller 3. That is, the drive shaft 4d is attached with a frame 3a that can swing up and down with the axis of the drive shaft 4d as a fulcrum. The support shaft 3b is supported on the front side of the frame 3a so that the shaft can rotate. The pickup roller 3 is fitted so as to be freely rotatable. Further, a pulley 3c is fitted on the support shaft 3b so as to be freely rotatable. A belt 3d is stretched between the pulley 3c and a pulley 4e on the separation roller 4a side, and a pulley 4e on the separation roller 4a side is stretched. The rotation is transmitted to the pulley 3c on the pickup roller 3 side.

  The rotation of the pulley 3c is transmitted to the pickup roller 3 through a one-way clutch and a differential clutch. That is, a one-way clutch 3e is fitted to the support shaft 3b, and a coil spring 3f is press-fitted to the outer peripheral portion of the one-way clutch 3e and the pulley 3c in a conjugate manner. This coil spring 3f is incorporated in such a relationship that the forward rotation direction of the pulley 3c, that is, the direction of arrow A (document feeding direction) is the winding loosening direction. When the drive is transmitted to the one-way clutch 3e due to the normal rotation of the pulley 3c in the A direction, the coil spring 3f is not loosened and is transmitted by its tightening force. When an abnormal load (for example, a force pulling the document in the reverse direction) is applied to the pickup roller 3, the coil spring 3f is loosened to reduce the impact on the drive transmission system of the pulley 3c and reduce its wear. Can be prevented.

  As shown in FIG. 4, the one-way clutch 3 e includes an outer ring member 3 e 1 and a one-way clutch structure 3 e 2 that is fitted on the inner periphery thereof. When the rotational force in the direction A shown in FIG. 3 is applied to the outer ring member 3e1 via the coil spring 3f, the one-way clutch 3e locks the outer ring member 3e1 and the support shaft 3b by the one-way clutch structure 3e2. On the contrary, when a force in the anti-A direction acts on the outer ring member 3e1, it functions to unlock. By this lock, the rotational force in the direction A of the pulley 3c is transmitted to the support shaft 3b. As such a one-way clutch 3e, a known one is appropriately selected and adopted as long as it has the above-described function.

  A differential clutch member 3g is fixed to the support shaft 3b adjacent to the one-way clutch 3e, and the differential clutch member 3g is provided with a clutch pawl 3g1 extending in the thrust direction. When the clutch pawls 3g2 are projected and the clutch pawls 3g1 and 3g2 are engaged with each other, mutual rotation transmission is performed. The function of the differential clutch means by the both clutch claws 3g1 and 3g2 will be described later.

  The frame 3a swings up and down in conjunction with forward / reverse rotation of the drive shaft 4d via the torque limit means. That is, one coupling member 3i integrated with the drive shaft 4d via a pin 3h inserted through the drive shaft 4d so as to be orthogonal to the axis thereof, and the other coupling elastically contacted with the outer surface of the frame 3a A compression spring 3k (torque limiter) is elastically mounted between the member 3j. Therefore, when the drive shaft 4d rotates forward in the A direction, the friction due to the restoring elasticity of the compression spring 3k acts between the coupling members 3i and 3j, so that it swings in the B direction with respect to the frame 3a. Force acts. As a result of the frame 3a swinging in the B direction, the pickup roller 3 comes into contact with the uppermost layer portion of the document D deposited on the document tray 2b as shown in FIG.

  If the drive shaft 4d continues to rotate forward even after the pickup roller 3 comes into contact with the uppermost layer portion of the document D, the swing of the frame 3a is prevented by the deposited layer of the document D, but the rotation of the drive shaft 4d is described above. Continued against the friction force. Accordingly, the rotation of the drive shaft 4d is transmitted to the pulley 3c via the pulley 4e and the belt 3d, and further transmitted to the one-way clutch 3e by the tightening force of the coil spring 3f. Then, the support shaft 2b is rotated by locking the one-way clutch 3e, and the pickup roller 3 is rotated in the A direction (forward rotation, that is, the document feeding direction) by the engagement of both clutch claws 3g1 and 3g2. The rotation of the drive shaft 4d is transmitted to the separation roller 4a via the pulley 4e and the spring clutch 4f, and the separation roller 4a also rotates in A (normal rotation, that is, the document feeding direction).

  As a result, the document D on the document tray 2 b is fed out from the uppermost layer, separated one by one, and fed toward the conveyance path 5. Although the accumulated layer thickness of the document D on the document tray 2b is reduced by this feeding and feeding, the force in the B direction is always applied to the frame 3a while the drive shaft 4d rotates in the A direction. Therefore, the pickup roller 3 is always pressed and urged against the uppermost layer portion of the document D, so that the feeding of the document D is not delayed. When the feeding and feeding of all the originals D on the original tray 2b are completed, the drive shaft 4d temporarily stops and then reversely rotates in the anti-A direction. Along with this reverse rotation, the anti-B direction force acts on the frame 3a due to the friction action of the compression spring 3k, and the front side is lifted, and the pickup roller 3 waits above the document tray 2b by the subsequent stop of the drive shaft 4d. Held in position.

  In the illustrated example, a felt ring 3m is interposed between the frame 3a and the coupling member 3j. The felt ring 3m maintains the integration of the drive shaft 4a and the frame 3a due to the friction action of the compression spring 3k, and after the pickup roller 3 abuts on the deposited layer of the document and its swing is prevented. It functions to relieve the contact frictional resistance between the coupling member 3j and the frame 3a accompanying the rotation of the drive shaft 4a.

  The document D fed out by the pickup roller 3 and separated one by one by the separation roller 4a reaches the conveyance roller 6, is registered by the conveyance roller 6, and is conveyed toward the reading point P. As described above, the circumferential speed of the conveyance roller 6 is slightly larger than the circumferential speeds of the pickup roller 3 and the separation roller 4a. Accordingly, when the leading end reaches the conveyance roller 6 due to the length of the conveyance path 5, the latter half of the document D is restrained by the separation roller 4a and the pickup roller 3, and therefore the document D is caused by the difference in peripheral speed. A conveyance load (tensile force) is applied to the. The pulling force of the document D acts on the separating roller 4a and the pickup roller 3 in the direction of unlocking the coil spring 4f and the one-way clutch 3e as a spring clutch. Therefore, the separation roller 4a and the pickup roller 3 are disconnected from the respective drive transmission systems, and are idled to reduce the transport load.

  As described above, while the drive shaft 4d is rotating forward, the pickup roller 3 is always pressed against the uppermost layer portion of the document D, and the drive transmission system from the pulley 4e to the pulley 3c is always operating. Accordingly, when the trailing edge of the preceding document is detached from the pickup roller 3 and the tensile force does not act on the pickup roller 3, the drive transmission from the pulley 3c to the pickup roller 3 is resumed, and the next document is fed out. In this case, the drive transmission is established immediately after the action of the tensile force is eliminated, and when the next original is fed out, the trailing edge of the preceding original and the leading edge of the next original are simultaneously introduced into the separation roller 4a. However, the leading edge of the next original is prevented from entering by the separation action of the separation roller 4a and the separation pad 4b. Therefore, the front side portion of the next original is curved between the separation roller 4a and the pickup roller 3, and an original jam occurs when the next original is fed as it is.

  In order to prevent the occurrence of the document jam as described above, in the illustrated mechanism, a differential clutch means is interposed between the one-way clutch 3e and the pickup roller 3. The differential clutch means includes a clutch pawl 3g1 provided on the differential clutch member 3g and a clutch pawl 3g2 provided on the end of the pickup roller 3. Both clutch pawls 3g1 and 3g2 are arranged in a row in a thrust direction and have a predetermined play space (maximum angle of about 300 °) 3g3 in the radial direction. In such a configuration, while the pickup roller 3 is idly rotated in the direction A while being pulled by the document D, the peripheral speed by the tensile force is larger than the peripheral speed by the drive transmission system. The clutch pawl 3g2 on the roller 3 side comes into contact with the clutch pawl 3g1 on the differential clutch member 3g side from the rear side in the same rotation direction A. That is, along the rotation direction A, the clutch pawl 3g1 is positioned behind the clutch pawl 3g2 with a play space (about 300 °) 3g3.

  When the trailing end of the document D is detached from the pickup roller 3, the pulling action by the document D is released, and the idle rotation of the pickup roller 3 is stopped. After that, since the differential clutch member 3g continues to rotate in the A direction, the claw 3g1 on the differential clutch member 3g side rotates and moves (about 300 °) in the play space 3g3, so that the pickup roller 3 side Of the claw 3g2 from the rear side in the same rotation direction A. By this contact, the drive transmission relationship from the differential clutch member 3g to the pickup roller 3 is established, and the pickup roller 3 starts to rotate in the A direction.

  The document feeding operation by the differential clutch means as described above will be described in more detail with reference to FIGS. 5 (a), 5 (b), and 5 (c). FIG. 5A shows a state immediately before the preceding document Dn is detached from the pickup roller 3, and the next document Dn + 1 is taken together when the preceding document Dn is fed out, and enters by the action of the separation roller 4a and the separation pad 4b. Is blocked. In this case, since the preceding document Dn is subjected to a conveyance load by the conveyance roller 6, the one-way clutch 3e is unlocked by the action, so that the pickup roller 3 is relative to the support shaft 3b (differential clutch member 3g). It is idle. Accordingly, the clutch pawl 3g2 on the pickup roller 3 side engages with the clutch pawl 3g1 on the differential clutch member 3g side pushed from behind, and the pickup roller 3 rotates in the A direction together with the differential clutch member 3g and the support shaft 3b. Will be.

  Then, as shown in FIG. 5B, when the preceding document Dn is removed from the pickup roller 3, the transport load of the preceding document Dn is not applied to the pickup roller 3, so that the pickup roller 3 (clutch claw 3g2) is stopped and simultaneously The one-way clutch 3e is locked, and the differential clutch member 3g (clutch pawl 3g1) starts to rotate. However, since the play space 3g3 exists in the rotation direction of the clutch pawl 3g1, the clutch pawl 3g1 and the clutch pawl 3g2 are not yet engaged, and the pickup roller 3 is maintained in a stopped state, and the next document Dn + 1 is fed out. It is not done. During this time, the rotation of the transport roller 6 is continued, so that the feeding of the preceding document Dn is continued.

  When the feeding of the preceding document Dn is continued and the rear end of the preceding document Dn is removed from the separation roller 4a, or immediately after that, the clutch pawl 3g1 rotated and moved in the play space 3g3 comes into contact with and engaged from behind the clutch pawl 3g2. By this engagement, as shown in FIG. 5 (c), the rotation of the differential clutch member 3g, that is, the support shaft 3b is transmitted to the pickup roller 3 via the clutch pawl 3g1 and the clutch pawl 3g2, and the rotation is resumed. The Along with this, the next original Dn + 1 is fed out, and the leading end of the next original Dn + 1 is introduced between the separation roller 4a and the separation pad 4b without overlapping the rear end of the preceding original Dn, and the subsequent next original Dn + 1 is fed. Made. Accordingly, the play space 3g3 is set at an angle such that the clutch pawl 3g1 can come into contact with the back of the clutch pawl 3g2 when the rear end portion of the preceding document Dn is detached from the separation roller 4a.

  Accordingly, since the pickup roller 3 is stopped after the trailing edge of the preceding document Dn is removed from the pickup roller 3 and this drive transmission relationship is established, the trailing edge of the preceding document Dn is the pickup roller. The pickup roller 3 is stopped and the next original is not fed out until it comes off the separation roller 4a from 3 and the trailing edge of the preceding original and the leading edge of the next original Dn + 1 are fed simultaneously. The above-described document jam does not occur. Such a delay function is achieved by a simple mechanism such as the differential clutch means clutch pawls 3g1 and 3g2. Therefore, an expensive electrical component such as an electromagnetic clutch is not required, which greatly contributes to cost reduction of the apparatus.

  In FIG. 1, reference numeral 13 denotes a paper leading edge aligning shutter, which protrudes on the document placing portion 2 and can align the leading edge of the document D set on the document tray 2b in a standby state. The shutter 13 is provided in a link mechanism 14 that swings up and down in conjunction with the rotation of the transport roller 6, and is configured to appear and disappear on the document placement unit 2 by the vertical swing of the link mechanism 14. . That is, a fan-shaped member 15 is coupled to the front side of the link mechanism 14, while a friction pulley 16 is fixed to the drive shaft 6 b of the conveying roller 6, and a fan-shaped member is provided around the friction pulley 16. The relationship is such that the 15 arc surfaces are in frictional contact.

  As a result, during the forward rotation of the conveying roller 6 (in the document conveying direction), the link mechanism 14 is linked with the rotation of the fan-shaped member 15 accompanying the frictional contact between the peripheral body of the friction pulley 16 and the arcuate surface of the fan-shaped member 15. The shutter 13 swings downward, and the shutter 13 is retracted to the lower part of the document placing portion 2. Further, when the transport roller 6 rotates in the reverse direction, the link mechanism 14 swings upward, and the shutter 13 protrudes onto the document placing portion 2. In this manner, the shutter 13 is caused to appear and retract on the document placement unit 2 mechanically interlocking with the conveyance roller 6, so that it can be easily configured without using expensive electrical components such as a solenoid. it can.

  In FIG. 1, the conveying roller 6 is shown hidden behind the friction pulley 16. Further, instead of an interlocking mechanism based on frictional contact between the friction pulley 16 and the fan-shaped member 15, a mechanism based on meshing of gears may be employed. Further, in the above-described embodiment, an example of ADF has been described. However, it is needless to say that the present invention can be applied to a recording paper feeding device in various image forming apparatuses.

It is a longitudinal cross-sectional view which shows the principal part of ADF and a scanning device. It is the perspective view of the state which looked up at the drive mechanism which united the pick-up roller and the separation roller from the bottom. It is the same exploded perspective view. It is a longitudinal cross-sectional view of the principal part of the drive mechanism. 5A and 5B are diagrams for explaining a document feeding operation by the differential clutch means, where FIG. 5A shows a state immediately before the preceding document is detached from the pickup roller, FIG. 5B shows a state immediately after the removal, and FIG.・ Indicates the state where feeding has started.

Explanation of symbols

1 ADF (paper feeder)
2 Document placement section (paper placement section)
3 Pickup roller 3a Frame 3e One-way clutch 3g Clutch member (differential clutch means)
3g1 clutch pawl (differential clutch means)
3g2 clutch pawl (differential clutch means)
3g3 play space 3k coil spring (torque limiter)
4a Separating roller 4d Drive shaft 6 Conveying roller

Claims (3)

A pickup roller for feeding out the paper placed on the paper placement unit, a separation roller for separating and feeding the fed paper one by one,
A sheet feeding device including a conveying roller disposed downstream of the separation roller and having a peripheral speed greater than that of the separation roller and the pickup roller;
The pickup roller is connected to a drive transmission system through a one-way clutch and a differential clutch means, and is always kept pressed on the stacked paper during the paper feeding operation.
The differential clutch means delays a predetermined time after the preceding sheet comes out of the pickup roller during conveyance of the preceding sheet in a state in which a conveyance load is applied by the conveyance roller. A paper feeding device configured to establish a drive articulation relationship. The pickup roller is pivotally supported on the front side of a frame mounted on the drive shaft of the separation roller so as to be swingable about the axis, and is driven and transmitted by the drive shaft via the drive transmission system. Made,
A torque limiter is interposed at the connecting portion of the frame and the drive shaft, and the frame is in the same direction in conjunction with the rotation of the drive shaft in a state where a load exceeding the load torque of the torque limiter is not applied to the front side. The frame is prevented from swinging and rotation of the drive shaft is continued in a state in which a load exceeding the load torque of the torque limiter is applied. The sheet feeding device according to 1. The differential clutch means includes a clutch member that is driven and transmitted from the drive transmission system via the one-way clutch, a clutch pawl in the thrust direction formed on the clutch member, and a clutch pawl protruding from the end surface of the pickup roller. And more
The both claws are aligned in a thrust manner in the thrust direction and are arranged with a predetermined play space in the radial direction, and the predetermined time is determined by the size of the play space. The sheet feeding device according to 2.

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