JP2005350244A - Paper feeding device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper feeding device capable of restricting the occurrence of paper feeding error by adjusting upward energizing force of a push-up plate in response to operation of a paper feeding roller. <P>SOLUTION: A crank means (disk) 16 is fixed to a driving shaft 7a of the paper feeding roller 7 for cooperative rotation, and a tensile spring 17 is stretched between the crank means 16 and a rocking side of the push-up plate 9. Lock position of the tensile spring 17 in relation to the crank means 16 is set so that the tensile spring 17 has the maximum tensile force and energizes the push-up plate 9 upward when delivering/separating a paper sheet with rotation of the paper feeding roller 7 and so that a front end of a paper sheet bundle P is strongly pushed to the paper feeding roller 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a complex machine thereof, and separates recording sheets or documents one by one and feeds them to an image forming unit (recording unit or image reading unit). The present invention relates to a sheet feeding device.

  In the image forming apparatus, an image forming unit (recording unit or image reading unit), a paper feeding device for feeding recording paper or a document to the image forming unit, and paper from the paper feeding device are sequentially fed. A paper conveying means is provided for this purpose. As the paper feeding device, a paper feeding cassette that accommodates a large number of sheets and is detachably attached to the main body of the image forming apparatus, and a paper sheet that is brought into contact with the center of the upper surface of the front end of the accommodated paper bundle and rotates. Examples thereof include a feeding roller for feeding out and a separating unit for preventing double feeding of the fed paper. In particular, such a cassette system is widely used in recording paper feeding devices. Patent Document 1 and Patent Document 2 show examples of an image forming apparatus provided with such a sheet feeding device.

  In the recording paper feeding device disclosed in Patent Document 1, a push-up plate is installed on the bottom of a cassette in an upwardly biased state by a compression spring, and the recording paper is placed on the push-up plate against the elasticity of the compression spring. Detained. The central portion of the front end of the recording paper bundle biased upward by the push-up plate is pressed against the paper feed roller, and the corners at both ends of the front end are regulated by a separation claw (snubber) as separation means. ing. Thus, when the paper feed roller rotates, a conveying force is applied to the center of the upper surface of the front end of the recording paper bundle, and the corner portion is regulated by the separation claw, so that the recording paper is separated and fed out one by one. In addition to the separation claw method, a separation pad installed so as to be pressed by the paper feed roller, a device using a retard roller, and the like are often used as the separation means.

In addition, the recording paper feeding device disclosed in Patent Document 2 incorporates a mechanism for moving the push-up plate up and down in accordance with the feeding state (amount of recording paper bundle), and the recording paper is fed when the cassette is loaded. The impact sound when coming into contact with the roller is reduced.
Japanese Patent Laid-Open No. 8-59008 JP 2001-72255 A

  In the paper feeding device as described above, the recording paper bundle accommodated and placed in the cassette is always biased upward by the push-up plate, so that the central portion of the recording paper is rotated by rotating the paper feeding roller. Is applied. However, while the paper feeding operation is performed, both sides of the recording paper are in a state where a transport load is applied such that the recording paper is pulled from the center. However, if the transport load is large, the resistance of the paper guide unit and other mechanism units is reduced. In some cases, the sheet may be warped up, causing a paper feed error. In particular, in order to reduce the size of the image forming apparatus, a sheet conveyance path having a layout structure in which the recording sheet fed from the sheet feeding device is turned approximately 180 ° and turned toward the recording unit has come to be used in many cases. However, such a U-turn-shaped conveyance path has a large degree of bending, so that the resistance received from the conveyance path is large, and a paper feeding error due to the conveyance load is likely to occur. Further, in Patent Document 2, the push-up plate is moved up and down in accordance with the amount of recording paper bundles, and the urging force of the push-up plate is variable. However, the mechanism is extremely complicated, and depending on the state of paper feed. It is not intended to alleviate the resistance experienced by recording paper.

  The present invention has been made in view of the above circumstances, and allows the upward biasing force of the push-up plate to be adjusted in conjunction with the paper feed roller, thereby reducing the resistance received by the paper and generating a paper feed error. It is an object of the present invention to provide a paper feeding device that can reduce the amount of paper.

  The present invention is a sheet feeding device for feeding sheets one by one toward an image forming unit in an image forming apparatus, the sheet placing unit for placing a bundle of sheets, and the sheet placing A push-up plate pivotally attached to the section so as to be able to push up the sheet bundle, a paper feed roller abutting on a substantially central portion in the width direction of the upper surface of the front end of the paper bundle, and a paper feed operation of the paper feed roller Separating means for preventing double feeding of paper accompanying the above, a crank means is fixed to the drive shaft of the paper feed roller so as to be cooperatively rotatable, and between the crank means and the swinging side of the push-up plate The tension spring holds the maximum tension and urges the push-up plate upward when the paper is fed and separated as the paper feed roller rotates. The locking position of the tension spring with respect to the crank means is set to apply To.

  In the paper feeding device of the present invention, as in the second aspect of the invention, the separating means is installed so as to be pressed by the paper feeding roller in the vicinity of the front end of the paper bundle placed on the paper placement section. It can consist of a separate pad. According to a third aspect of the present invention, the sheet placing portion is composed of a sheet feeding cassette that is detachably attached to the image forming apparatus, and the push-up plate, the sheet feeding roller, and the separating unit are the sheet feeding unit. It can also be incorporated into a cassette and configured as a cassette unit. In this case, when the cassette unit is mounted in the image forming apparatus, the drive shaft of the paper feed roller is connected to a drive source installed in the image forming apparatus. It is desirable that it is made.

  According to the paper feeding device of the present invention, the crank means cooperates with the rotation of the paper feeding roller, and when the paper is fed and separated, the tension spring holds the maximum tension and urges the push-up plate upward, Since the locking position of the tension spring with respect to the crank means is set so that the front end of the sheet bundle is strongly pressed against the sheet feeding roller, the sheet is smoothly fed out and separated by the rotation action of the sheet feeding roller. After the feeding and separation of the paper, the paper feed roller continues to rotate. However, the tension of the tension spring is weakened due to the displacement of the crank means accompanying the cooperative rotation. The power is weakened. Accordingly, the conveyance load on both sides of the sheet is reduced, the resistance at the guide section as described above is also reduced, and the occurrence frequency of sheet feeding errors is reduced.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view showing an example of an image forming apparatus in which the paper feeding device of the present invention is adopted, FIG. 2 is a perspective view of the main part of the paper feeding device, and FIGS. (C) is explanatory drawing which shows the operation state.

  The image forming apparatus 1 shown in the figure is applied to a so-called multi-function machine having a facsimile function, a copying function, and a printer function, and an automatic document feeder (ADF) 2, an image reading unit 3, The recording unit 4 and the recording paper feeding unit 5 are stacked. The ADF 2 feeds and separates the originals deposited and placed on the original tray 2a one by one by a pickup roller 2b and a separating means (a pair of separating roller and retard roller) 2c. Then, while transporting the curved transport path 2g by the transport roller pairs 2d, 2e, and 2f, the image is read by the stationary scanning scanning device (described later) 3a at the scanning point p of the ADF document halfway, and the discharge roller The pair 2h functions so as to be sequentially discharged onto the document discharge tray 2i.

  The image reading unit 3 includes an ADF reading unit 3b and a flat plate reading scanning unit (FBS) 3c. In FIG. 1, the reading scanning device 3a is in a standby / stationary state on the ADF reading unit 3b immediately below the ADF reading point p. In addition, a state in which an image of a document sequentially fed automatically by the ADF 2 is read is illustrated. When performing image reading in the FBS 3c, the reading scanning device 3a moves to the FBS 3c, and reads an image of a document placed downward on the platen glass 3d while reciprocating left and right under the platen glass 3d. A series of mechanisms constituting the ADF 2 also serves as a platen cover (document pressing plate) and can be opened and closed up and down with the back side of the paper surface as a hinge portion.

  The recording unit 4 shown in the figure is composed of an electrophotographic recording apparatus, and is composed of a drum unit 41 including a photosensitive drum 41a and a charger 41b, a light (LED or laser) writing unit 42, a toner container and a developing roller. A unit unit (developing unit) 43, a transfer unit 44 and a fixing unit 45. A discharge roller pair 4a and a discharge tray 4b are connected to the downstream side of the fixing device 45. In this electrophotographic recording apparatus, image information read by the image reading unit 3 or image information transmitted from an external terminal such as a facsimile or a personal computer is uniformly charged by a charger 41b. Optical information is written on the surface of 41a as optical information by the optical writing unit 42, and an electrostatic latent image based on the optical information is formed on the surface of the photosensitive drum 41a.

  The electrostatic latent image is developed by the developing device 43 and is sequentially transferred as a toner image by the transfer device 44 onto a recording sheet conveyed on the curved conveyance path 12 described later. The toner image transferred to the recording paper is fixed as a permanent image by the fixing device 45, and the recording paper on which the permanent image is formed is discharged and accumulated on the discharge tray 4b by the discharge roller pair 4a. The recording unit 4 is not limited to the electrophotographic recording apparatus as shown in the figure, and a known recording apparatus such as an ink ribbon recording apparatus, an ink jet recording apparatus, or various color recording apparatuses is adopted. It goes without saying that it is possible.

  The drum unit 41 is a unit in which a photosensitive drum 41a, a charger 41b, a toner cleaner (not shown), and a drum rotation transmission mechanism and other mechanisms (not shown) are set. As an integral process member, it is detachably mounted at a predetermined position of the apparatus. The developing unit 43 is integrally unitized with a toner container, a developing roller, a stirring member, and a mechanism portion (not shown), and is detachably mounted at a predetermined position of the apparatus as an integrated process member as described above. Is.

  The paper feed unit 5 includes a recording paper cassette (paper placement unit) 6 that can be taken in and out in the direction perpendicular to the paper surface. A paper feed roller 7 is disposed on the front end of the recording paper cassette 6. The separation pad (separating means) 8 is pressed toward the paper feed roller 7, and the recording paper P stored in the recording paper cassette 6 is fed out from the uppermost layer portion with the rotation of the paper feed roller 7, and the separation pad. Under the action of 8, the sheets are separated one by one and sent out. In the recording paper cassette 6, there are a push-up plate 9 for placing a recording paper that can be swung up and down with a pivot pin 9a as a fulcrum, and a regulating plate 6a for adjusting the position for regulating the rear end of the recording paper. Is provided. The push-up plate 9 is urged upward by a tension spring 17 described later. In addition, although illustration and description are omitted, it goes without saying that additional members necessary as the recording paper cassette 6 are also provided. Note that an optional cassette (not shown) may be disposed below the recording paper cassette 6 to constitute a multi-cassette system having two or more stages.

  Near the recording paper discharge side of the recording paper cassette 6, a guide member 10 capable of tilting back and forth is installed, and further behind it, a jam access cover (with an interval through which recording paper from the lower cassette can pass) A maintenance opening / closing cover 11 is attached, and the jam access cover 11 is attached to the right side wall portion of the box-shaped housing 1a in the image forming apparatus 1 so as to be openable and closable with the hinge pin 11a as a fulcrum. The upper part of the inner surface of the jam access cover 11 is curved toward the recording paper cassette 6 to form a part of the curved conveyance path 12 described later.

  Inside the jam access cover 11 is attached a press roller 13a that mates with the conveying roller 13 installed in the box-shaped housing 1a. If the jam access cover 11 is opened with the hinge pin 11a as a fulcrum, The pairing of the transport roller 13 and the press roller 13a is released, and the recording paper (jam paper) stopped in the vicinity can be taken out. The curved conveyance path 12 changes the direction of the recording paper fed from the recording paper cassette 6 by approximately 180 degrees, conveys it in a U-turn shape, and directs it toward the recording unit 4. A registration roller pair 14 is disposed in the curved conveyance path 12 in the vicinity of the upstream side of the recording unit 4, and is stopped (registered) while the leading edge of the recording paper enters the nip portion of the registration roller pair 14. The registration roller pair is driven in synchronization with the toner image formed on the photosensitive drum, and is fed toward the image transfer position between the photosensitive drum 41a and the transfer device (transfer roller) 44. The A recording paper conveying means for feeding the recording paper fed from the recording paper cassette 6 to the recording unit is constituted by a conveying roller 13, a curved conveying path 12 and a registration roller pair 14.

  The paper feeding device of the present invention will be described in more detail with reference to FIG. In the figure, the paper feed roller 7 is mounted on a drive shaft 7a via a one-way clutch 7b. When the drive shaft 7a rotates in the direction of the arrow in the figure, the one-way clutch 7b is locked and the paper feed roller 7 is the same. It is designed to rotate in the direction. A coupling portion 7c is fixed to one end of the drive shaft 7a, and the paper feed roller 7 is attached to the recording paper cassette 6 together with the drive shaft 7a and the coupling portion 7c so as to be rotatable. When the recording paper cassette 6 is mounted on the paper feed unit 5 of the image forming apparatus 1, the cup is connected to the coupling unit 15a of the rotation control actuator (drive source) 15 including a motor and a transmission mechanism installed in the image forming apparatus 1. The ring portion 7c is meshed and connected so that the drive shaft 7a rotates with the driving force of the rotation control actuator 15 being obtained.

  A disk 16 as a crank means is fixed to the other end of the drive shaft 7a. Further, a connecting bar 9b is fixed to the swinging side of the push-up plate 9, and this connecting pin 9b extends through the circular groove 6b formed in the side wall of the recording paper cassette 6. ing. A tension spring 17 is stretched so as to connect a locking pin (locking position) 16 a attached to the disk surface of the disk 16 and the connecting bar 9 b, and the push-up plate 9 is pulled by the tension applied by the tension spring 17. The oscillating side is in an upward biased state.

  The operation of the sheet feeding apparatus configured as described above will be described with reference to FIGS. 3 (a), 3 (b), and 3 (c). FIG. 3A shows a standby state in which the locking pin 16a of the disk (crank means) 16 is positioned below (near the bottom dead center). In this state, the recording paper bundle P is set in a recording paper cassette 6 as a paper placing portion. The push-up plate 9 is in an upward biased state by the tension spring 17, but since the locking pin 16 a is positioned below, the pull force of the tension spring 17 is weak, and the push-up plate 9 depends on the weight of the recording paper bundle P and the push-up plate 9. Is set to sink to the bottom of the recording paper cassette 6. Accordingly, the upper surface of the front end of the recording paper bundle P does not come into contact with the paper feed roller 7 or is in a state of being touched lightly depending on the amount of the recording paper bundle P.

  When the drive shaft 7a starts to rotate from the state of FIG. 3A and the disk 16 also rotates cooperatively, the locking pin 16a is moved along with the rotation of the disk 16 as shown by the arrow in FIG. When it is displaced upward and reaches its top dead center, the tension force of the tension spring 17 becomes maximum. During this time, the swinging side of the push-up plate 9 is lifted by the tensile force of the tension spring 17, and the upper surface of the front end of the recording paper bundle P is in strong contact with the paper feed roller 7. By this contact, the rotational force of the paper feed roller 7 acts on the upper surface of the front end of the recording paper bundle P, and the uppermost recording paper P1 is fed out. Then, due to the action of the separation pad 8, the double feeding of the recording paper is prevented and separated one by one and fed toward the downstream conveying roller pair 13, 13a.

  The rotation of the drive shaft 7a continues and the leading edge of the recording paper P1 is nipped by the transport roller pair 13, 13a, but the peripheral speed of the transport roller pair 13, 13a is set slightly faster than the peripheral speed of the paper feed roller 7. Therefore, the feed roller 7 is unlocked with respect to the drive shaft 7a by the one-way clutch 7b by the force acting to pull the recording paper P1, and is relatively idle. Then, as the disk 16 continues to rotate, as shown in FIG. 3C, the locking pin 16a is displaced downward from the top dead center. As a result, the tensile force of the tension spring 17 becomes weaker, and the push-up plate 9 Is swung down by the weight of the recording paper bundle P or the like. Accordingly, the contact between the sheet feeding roller 7 and the recording sheet bundle P is eliminated, and the conveyance load by the sheet feeding roller 7 on both sides of the recording sheet P1 is not applied.

  As described above, since the conveyance load by the paper feed roller 7 to the both sides of the recording paper P1 is not applied, the resistance in the guide portions and the like on both sides of the recording paper P1 is reduced, and the warping is less likely to occur. In particular, as in the illustrated embodiment, even in the paper conveyance path 12 formed in a U-turn shape having a large degree of bending, smooth conveyance is performed, and the occurrence of paper feeding errors is significantly reduced, so that image formation is performed. This greatly contributes to the compactness of the device 1.

  Thereafter, the drive shaft 7a of the paper feed roller 7 is rotated by approximately one rotation and stopped, but the fed recording paper P1 is continuously conveyed toward the recording unit 4 by the conveying roller pair 13 and 13a. The second half of the recording paper P1 is nipped by the paper feeding roller 7 and the separation pad 8 for a predetermined time. During this time, the one-way clutch 7b is unlocked by the tensile force of the recording paper P1, and the paper feeding roller 7 Spins idle. When the trailing edge of the recording paper P1 is out of the nip position between the paper feed roller 7 and the separation pad 8, the standby state shown in FIG. 3 (a) is entered, but if the paper feed signal is continuously input, the recording paper P1 rotates. The sheet feeding roller 7 is driven to rotate again by the control actuator 15.

  As described above, at the recording paper separation position in FIG. 3B, the tensile force of the tension spring 17 acts most strongly, and the conveyance load accompanying the conveyance action by the paper feed roller 7 increases. In the process of shifting to the standby position shown in FIG. 3A through the state shown in FIG. 3C, the tension force of the tension spring 17 is weakened and the conveying load on both sides of the recording paper P1 is reduced. The frequency of paper errors is reduced. Such a mode of operation is easily realized by appropriately setting the position of the locking pin (locking position) 16a with respect to the disk surface of the disk (crank means) 16, and has a simple structure. The practical value obtained is extremely large.

  In the above embodiment, an example of a recording paper feeding unit has been described. However, the present invention can also be applied to a document feeding unit. Further, although a so-called multifunction machine has been described as an example of the image forming apparatus, it goes without saying that the present invention can also be applied to other image forming apparatuses having a sheet feeding unit.

1 is a schematic longitudinal sectional view illustrating an example of an image forming apparatus in which a paper feeding device of the present invention is employed. It is a perspective view of the principal part of the paper feeder. FIG. 4A is an explanatory diagram illustrating an operation state of the sheet feeding device, where FIG. 3A illustrates a standby position state, FIG. 3B illustrates a separation position state, and FIG. 3C illustrates a state after separation is completed.

Explanation of symbols

1 Image forming apparatus body 4 Recording unit (image forming unit)
6 Recording paper cassette (paper placement section)
7 Feed roller 7a Drive shaft 8 Separation pad (separation means)
9 Push-up plate 15 Rotation control actuator (drive source)
16 disc (crank means)
16a Locking pin (locking position)
17 Tension spring P Paper bundle

Claims (4)

A sheet feeding device for feeding sheets one by one toward an image forming unit in an image forming apparatus,
A paper placement portion for placing the paper bundle, a push-up plate pivotably mounted on the paper placement portion so as to be able to swing up and down, and an upper surface of the front end of the paper bundle in the width direction. A paper feed roller that contacts the central portion, and a separating means for preventing double feeding of paper accompanying the paper feed operation of the paper feed roller,
Crank means is fixed to the drive shaft of the paper feed roller so as to be cooperatively rotatable, and a tension spring is stretched between the crank means and the oscillating side of the push-up plate. At the time of feeding / separation, the tension spring has the maximum tension and urges the push-up plate upward, and the locking position of the tension spring with respect to the crank means is set so that the front end of the sheet bundle is strongly pressed against the paper feed roller. A paper feeder characterized by.   The sheet feeding device according to claim 1, wherein the separation unit includes a separation pad installed near the front end of the sheet bundle placed on the sheet placing unit so as to be pressed by the sheet feeding roller. apparatus.   The sheet placing portion is composed of a paper feed cassette that is detachably attached to the image forming apparatus, and a push-up plate, a paper feed roller, and a separating unit are incorporated in the paper feed cassette to constitute a cassette unit. The paper feeding device according to claim 1, wherein the paper feeding device is provided.   4. The drive shaft of the paper feed roller is connected to a drive source installed in the image forming apparatus when the cassette unit is mounted on the image forming apparatus. The paper feeder described.

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