JP2007254092A - Paper feeding/separating mechanism and image forming device applied with the paper feeding/separating mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To securely prevent double feeding while suppressing chattering during paper feeding. <P>SOLUTION: This paper feeding/separating mechanism 40 is provided with a paper feeding roller 311 of which peripheral face is pressed against and abuts on an upper surface of an uppermost paper sheet P1 at a downstream end of a paper sheet bundle P placed on an energizing plate 37 of a paper sheet cassette 31, and with a friction pad 70 arranged in a lower part opposing to the paper feeding roller 311 via the uppermost paper sheet P1. The friction pad 70 is energized toward a direction opposite to the paper carrying direction by the energizing force of a coil spring 80. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is provided in an apparatus that performs a predetermined process on paper, and feeds the paper bundles separated from each other and fed out one by one from a paper stack stored in a stacked state in a predetermined paper storage unit. The present invention relates to a paper separation mechanism and an image forming apparatus to which the paper feed separation mechanism is applied.

  Conventionally, a sheet feeding / separating mechanism as described in Patent Documents 1 and 2 is known. First, the paper feeding / separating mechanism described in Patent Document 1 is provided corresponding to a paper feeding container (paper tray) of an image forming apparatus such as a copying machine or a facsimile machine, and a plurality of sheets stored in the paper tray. Each sheet is fed out one by one from a sheet bundle formed by stacking sheets of paper and fed toward the image forming apparatus.

  Such a paper feed separating mechanism includes a paper feed roller made of a material having a large friction coefficient such as rubber that is driven and rotated around an axis disposed on the downstream end side in the paper transport direction in the paper tray, and a lower portion of the paper feed roller. And a friction pad made of a material having a large friction coefficient such as rubber, which is in contact with the peripheral surface of the paper feed roller. The friction pad presses the peripheral surface of the paper feed roller with the biasing force of the spring.

  The sheet bundle stored in the sheet tray is urged upward by a predetermined urging unit in a state where the upper surface of the uppermost sheet is in contact with the lower peripheral surface of the sheet feeding roller, and the downstream side The upper surface of the edge is in contact with the friction pad.

  In this state, when the paper feed roller is driven and rotated in the direction in which the paper is pulled out from the paper tray, the uppermost paper is guided to the peripheral surface of the paper feed roller having a large friction coefficient and pulled out of the paper tray, Paper is fed toward the forming apparatus.

  In such a paper feed separation mechanism, for example, when two sheets of paper are pulled out of the paper tray due to the driving rotation of the paper feeding roller, these two sheets of paper are separated from the paper feeding roller that is driving and rotating. It is sandwiched between the peripheral surface and the top surface of the friction pad. In this state, the frictional force between the uppermost sheet and the second sheet is not only smaller than the frictional force between the uppermost sheet and the peripheral surface of the paper feed roller, but also with the second sheet and the friction. Since the frictional force between the upper surface of the pad and the upper surface of the pad is smaller, the uppermost sheet is guided by the driving rotation of the paper feed roller and pulled out, while the second sheet is blocked by the friction pad and pulled out. In the end, so-called two-sheet feeding, in which two sheets are fed at once, is suppressed.

  Next, the paper feeding / separating mechanism described in Patent Document 2 is provided on a document tray of a copying machine, a facsimile machine, or the like, and a document bundle formed by stacking a plurality of documents placed on the document tray. Each original is fed out and fed to the original reading unit.

  This separation mechanism is basically similar to that of Patent Document 1 as well, a paper feed roller that rotates around an axis disposed at an end of the original tray on the side of the original reading unit, and a lower portion of the paper supply roller. And a friction pad that is in contact with the peripheral surface of the paper feed roller, and is designed to prevent the feeding of two originals by the same action as that of Patent Document 1. Is different from that of Patent Document 1 in which the friction pad does not swing, in that the pad is configured to be swingable in the vertical direction.

In Patent Document 2, it is possible to suppress the vibration of the document by swinging the friction pad when the document is fed, and a so-called chatter sound generated when the document is vibrated finely when the document is fed. It is stated that it will not occur.
JP-A-4-354740 JP 2005-67784 A

  However, in the paper separation structures described in Patent Documents 1 and 2, it is difficult for each paper to be peeled off at the edge of the paper bundle depending on the type of paper or the cutting process. In a situation where it is difficult to separate the second sheet, there is a problem that two sheets may be fed.

  The present invention has been made in view of such a situation, and is capable of reliably preventing two sheets from being fed while suppressing the occurrence of chatter noise during feeding and the sheet feeding. An object of the present invention is to provide an image forming apparatus to which a separation mechanism is applied.

  According to the first aspect of the present invention, there is provided a paper feed roller whose peripheral surface is pressed against the upper surface of the uppermost paper at the downstream end in the paper feeding direction of the paper stack placed on the paper tray, the paper feed roller, A sheet feeding / separating mechanism including a friction pad disposed oppositely at a lower portion through the uppermost sheet, wherein the friction pad is configured to have a feeding direction of the sheet from the sheet tray by a biasing force of a biasing unit. It is biased toward the opposite direction.

  According to such a configuration, even if a plurality of sheets are simultaneously fed out from the sheet bundle, the uppermost sheet in the sheet bundle is guided by the driving rotation of the sheet feeding roller to be able to feed the second sheet. Is pushed back toward the rear by the friction pad to which the urging force is applied by the urging means, so that a plurality of sheets can be fed simultaneously at the same time as compared to the case where no urging force is applied to the friction pad as in the prior art. The occurrence of inconvenience such as paper feeding toward the printer is reliably prevented.

  In addition, when the paper fed out from the paper bundle moves while the paper feed roller is driven and rotated while being sandwiched between the paper feed roller and the friction pad, vibration is generated due to the paper sliding on the friction pad. Since it is absorbed by the biasing means, the generation of the so-called chatter noise generated by the sheet due to vibration is reliably prevented.

  Furthermore, since the amount of movement of the friction pad against the urging force of the urging means differs depending on the type of paper, the difference in the amount of movement of the friction pad makes it possible to cope with the type of paper. Occurrence of inconvenience that causes a problem in sheet feeding depending on the type is prevented.

  According to a second aspect of the present invention, in the first aspect of the present invention, a pad holder that supports the friction pad in a state where the upper portion is exposed is provided, and the pad holder is held so as to be movable forward and backward with respect to a paper feeding direction. The pedestal to be provided is provided.

  According to this configuration, the friction pad is movably attached to the gantry member in a stable state via the pad support movable member.

  According to a third aspect of the present invention, in the second aspect of the present invention, a storage recess for movably storing the pad holder is provided on the upper surface of the pedestal.

  According to such a configuration, the mounting state of the friction pad with respect to the pedestal is stabilized by mounting the friction pad in the mounting recess through the pad holder.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the biasing means is one of a coil spring, a plate spring, and an elastomer. .

  According to such a configuration, the optimum biasing means is selected from among the coil spring, the plate spring, and the elastomer depending on the situation.

  The invention according to claim 5 is an image forming apparatus for forming an image based on image information, and includes a document tray on which a bundle of documents having an image to be read is placed and a bundle of sheets on which the image is to be transferred. 2. One or both of transfer paper trays to be placed are provided, and the paper tray is one or both of the document tray and the transfer paper tray. 4 is an image forming apparatus to which the sheet feeding / separating mechanism according to any one of 4 is applied.

  According to this configuration, the image forming apparatus can enjoy the functions and effects provided by the sheet feeding and separating mechanism according to claims 1 to 4 applied to the image forming apparatus.

  According to the first aspect of the present invention, even if a plurality of sheets are simultaneously fed out from the sheet bundle, the uppermost sheet in the sheet bundle is guided by the driving rotation of the sheet feeding roller and can be fed. The first sheet is pushed back by the friction pad to which the urging force is applied by the urging means, so that a plurality of sheets are compared with the case where the urging force is not applied to the friction pad as in the conventional case. At the same time, it is possible to reliably prevent the occurrence of inconveniences such as feeding to the paper feed destination.

  In addition, when the paper fed out from the paper bundle moves while the paper feed roller is driven and rotated while being sandwiched between the paper feed roller and the friction pad, vibration is generated due to the paper sliding on the friction pad. Since it is absorbed by the biasing means, it is possible to reliably prevent the occurrence of the so-called chatter sound generated by the sheet due to vibration.

  Furthermore, since the amount of movement of the friction pad against the urging force of the urging means differs depending on the type of paper, the difference in the amount of movement of the friction pad makes it possible to cope with the type of paper. It is possible to reliably prevent the occurrence of inconveniences that cause problems in paper feeding depending on the type.

  According to the second aspect of the present invention, there is provided a pad holder that supports the friction pad with the upper portion exposed, and a pedestal that holds the pad holder movably in the paper transport direction is provided. The friction pad can be movably attached to the gantry member in a stable state via the pad support movable member.

  According to the third aspect of the present invention, since the storage recess for movably storing the pad holder is provided on the upper surface of the pedestal, the friction pad is attached to the mounting recess via the pad holder. The mounting state of the friction pad on the pedestal can be stabilized.

  According to the fourth aspect of the present invention, the optimum biasing means can be selected from among the coil spring, the plate spring and the elastomer according to the situation.

  According to the fifth aspect of the present invention, the image forming apparatus can enjoy the effects of the sheet feeding / separating mechanism according to the first to fourth aspects applied to the image forming apparatus.

  FIG. 1 is an explanatory diagram of a side sectional view showing an outline of an internal structure of an example of a printer 10 to which an embodiment of a paper feeding / separating mechanism according to the present invention is applied. FIG. Is stored in the storage position T1, and FIG. 1B shows a state in which the paper cassette 31 is pulled out to the pull-out position T2. In FIG. 1, the Y-Y direction is referred to as the front-rear direction, in particular, the -Y direction is referred to as the front, and the + Y direction is referred to as the rear.

  As shown in FIG. 1, the printer 10 stores sheets P1 to be subjected to printing processing, and also feeds out sheets P1 one by one from the stored bundle of sheets P1 (sheet bundle P) or manually feeds the sheets P1. The image forming unit 20 that performs image transfer processing on the paper P1 supplied from the sheet feeding device 30, and the image forming unit 20 performs transfer processing. A fixing unit 27 that performs a fixing process on the applied paper P <b> 1 is configured to be installed above the partition plate 115 in the apparatus main body 11. The paper P1 subjected to the fixing process by the fixing unit 27 is discharged to a paper discharge tray 117 formed on the top of the apparatus main body 11.

  The paper feeding device 30 includes a paper cassette (paper tray, transfer paper tray) 31 for storing a paper bundle P that is detachably attached to the apparatus main body 11, and a front end portion of the paper cassette 31. And a manual paper feed unit 38 provided. The apparatus body 11 is provided with a large-diameter paper feed roller 311 that feeds out one sheet P1 from the sheet bundle P at a position corresponding to the upstream side (front side) of the sheet cassette 31. A small-diameter conveying roller 312 is provided at a position directly above the paper roller. Then, the sheet P1 fed out from the sheet cassette 31 by driving the sheet feeding roller 311 passes through the sheet feeding roller 312 and the sheet feeding / conveying path 313 and the registration roller pair 314 provided at the downstream end thereof, and the image forming unit 20. The paper is fed into the printer. The paper cassette 31 will be described later with reference to FIG.

  The image forming unit 20 performs a transfer process on the paper P1 based on image information transmitted from a computer or the like, and is provided so as to be rotatable around a drum core extending in the left-right direction (direction orthogonal to the paper surface of FIG. 1). A charger 22, an exposure device 23, a developing device 24, a transfer roller 25, and a cleaning device 26 are arranged in a clockwise direction from a position immediately above the photosensitive drum 21 along the peripheral surface of the photosensitive drum 21 thus formed. It is formed by being.

  The photosensitive drum 21 is for forming an electrostatic latent image and a toner image along the electrostatic latent image on the peripheral surface, and a smooth and tough amorphous silicon layer is laminated on the peripheral surface. It is suitable for forming these images.

  The charger 22 forms a uniform charge on the peripheral surface of the photosensitive drum 21 rotating clockwise around the drum center. In this embodiment, the photosensitive member is subjected to corona discharge from a wire. A corona discharge type that applies a charge to the peripheral surface of the drum 21 is employed. Instead, the peripheral surface of the photoconductive drum 21 rotates while being driven while being in contact with the peripheral surface of the photoconductive drum 21. You may employ | adopt the charging roller system which provides an electric charge to a surrounding surface.

  The exposure device 23 irradiates the peripheral surface of the rotating photosensitive drum 21 with laser light to which intensity is applied based on image data transmitted from an external device such as a computer, and the photosensitive drum 21 is thereby radiated. An electrostatic latent image is formed on the peripheral surface of the photosensitive drum 21 by erasing the electric charge in the portion where the laser light on the peripheral surface is checked.

  The developing device 24 supplies the toner in the developer to the peripheral surface of the photosensitive drum 21 to attach the toner to the portion where the electrostatic latent image is formed on the peripheral surface. A toner image is formed on the peripheral surface. In the present invention, a so-called two-component system composed of toner and carrier is used as the developer. The toner is a fine powder having a particle diameter of 6 to 12 μm in which additives such as a colorant, a charge control agent and wax are dispersed in a binder resin.

The carrier is magnetic particles having a particle size of 60 to 200 μm such as magnetite (Fe ₃ O ₄ ), and is used for charging the toner. The toner is a consumable that is appropriately replenished from the toner cartridge 241 to the developing device 24, whereas a predetermined amount of the carrier is loaded in the developing device 24 in advance, and is circulated and used without being consumed. In the present invention, the toner cartridge 241 is loaded with toner and a carrier (that is, a developer), and both the toner and the carrier are supplied to the developing device 24 at the same time.

  The transfer roller 25 transfers a positively charged toner image formed on the peripheral surface of the photosensitive drum 21 to the paper P1 with respect to the paper P1 sent to a position immediately below the photosensitive drum 21. A negative charge having a polarity opposite to that of the toner image is applied to the paper P1.

  Accordingly, the sheet P1 that has reached the position immediately below the photosensitive drum 21 is pressed and sandwiched between the transfer roller 25 and the photosensitive drum 21, and the toner image on the circumferential surface of the photosensitive drum 21 that is positively charged is negatively charged. It is peeled off toward the surface of P1, and a transfer process is performed.

  The cleaning device 26 is for removing the toner remaining on the peripheral surface of the photosensitive drum 21 after the transfer process to the paper P1 and cleaning it. The peripheral surface of the photosensitive drum 21 cleaned by the cleaning device 26 is again directed to the charger 22 for the next image forming process.

  The fixing unit 27 performs a fixing process by heating the toner image of the paper P1 that has been subjected to the transfer process in the image forming unit 20, and includes a heat roller 271 in which an energizing heating element such as a halogen lamp is mounted. And a pressure roller 272 having a peripheral surface opposed to the lower portion of the heat roller 271. Then, the paper P1 after the transfer process is composed of a heat roller 271 that is driven to rotate clockwise around the roller center and a pressure roller 272 that is driven to rotate counterclockwise around the roller center. By passing through the nip portion between them, the heat from the heat roller 271 is obtained and the fixing process is performed. The sheet P1 subjected to the fixing process is discharged to the discharge tray 117 through the discharge conveyance path 273.

  The manual paper feed unit 38 is supported by a front wall 381 whose rear edge extends from the lowest position to the position directly above the conveyance roller 312 on the upstream end side of the image forming unit 20, and the front wall 381. And a manual feed tray 382.

  Hereinafter, the sheet feeder 30 will be described in detail with reference to FIG. FIG. 2 is a perspective view showing an embodiment of the paper feeding device 30. In FIG. 2, the XX direction is referred to as the left-right direction, and the YY direction is referred to as the front-rear direction. In particular, the -X direction is referred to as the left, the + X direction is referred to as the right, the -Y direction is referred to as the front, and the + Y direction is referred to as the rear. As shown in FIG. 2, the paper feeding device 30 includes a paper cassette 31 and a manual paper feeding unit 38 formed at the front end position of the paper cassette 31. A sheet cassette 31 which is one component of the sheet feeding device 30 includes an arc-shaped front plate 32 whose front surface is expanded in an arc shape outward (forward) in a plan view, and the arc-shaped front plate 32. A bottom plate 33 extending rearward from the lower edge portion on the back surface (rear surface) side, and a pair of side plates 34 projecting upward from the left and right side portions of the bottom plate 33 and extending in the front-rear direction. And has a rectangular box shape in plan view with an upper surface opened.

  A pair of guided projecting pieces 341 projecting in opposite directions are provided at appropriate positions of the side plates 34, while the pair of side plates 111 (FIG. 1B) of the apparatus main body 11 are provided. The guide grooves 111a extending in the front-rear direction corresponding to the guided protrusions 341 are respectively recessed, and the sheet cassette 31 is guided by the guided protrusions 341 in these guide grooves 111a (FIG. 1B). While moving forward and backward, the storage position T1 (FIG. 1 (A)) stored in the apparatus main body 11 and the pull-out position T2 (FIG. 1 (B)) protruding outward from the apparatus main body 11 are used. The position can be changed.

  The bottom plate 33 is provided with a longitudinally moving guide recess 331 extending in the longitudinal direction at a central position in the lateral direction on the upper surface side, and can be moved back and forth while being guided by the longitudinally guiding guide recess 331. A position regulating member 35 is provided. The front / rear position restricting member 35 is for restricting the rear end position of the sheet bundle P (FIG. 1) placed on the bottom plate 33, and a horizontal plate 351 that slides in the front / rear movement guide recess 331. And a vertical plate 352 erected from the rear end portion of the horizontal plate 351. Then, the vertical plate 352 can be moved in accordance with the paper size to be brought into contact with the rear end of the paper bundle P.

  In addition, the bottom plate 33 is provided with a pair of left and right movement guide recesses 332 at a front position on the upper surface thereof, and a pair of left and right movement guide recesses 332 that are movable in the left and right directions while being guided by the left and right movement guide recesses 332. A left-right position restricting member 36 is provided. These left and right position restricting members 36 are for restricting the left and right positions of the sheet bundle P (FIG. 1) placed on the bottom plate 33, and include a horizontal plate 361 that slides in the left and right motion guide recess 332. The horizontal plate 361 has a vertical plate 362 erected from opposite edges in the left-right direction. Then, the sheet bundle P can be held between the pair of vertical plates 362 by moving these left and right position regulating members 36 in the opposite direction by the same amount according to the sheet size.

  Accordingly, the sheet bundle P placed on the bottom plate 33 of the sheet cassette 31 is sandwiched between the front / rear position restricting member 35 and the pair of left / right position restricting members 36 so that the front end is in contact with the front wall 381. It will be positioned in the cassette 31.

  Further, at the position of the front half of the bottom plate 33, an urging plate 37 that urges the front half of the sheet bundle P placed without interfering with the left-right position regulating member 36 upward is provided. . The urging plate 37 is pivotally supported around a support shaft 371 (FIG. 1) extending in the left-right direction at the rear end side, and is urged upward by a coil spring 372 (FIG. 1). Thus, the uppermost sheet P1 of the sheet bundle P loaded in the sheet cassette 31 comes into contact with the sheet feed roller 311 in a state where the sheet cassette 31 is stored in the apparatus main body 11 (FIG. 1A). Yes. Therefore, the uppermost sheet P1 of the sheet bundle P is driven and rotated by the sheet feed roller 311 to the image forming unit 20 via the sheet feed roller 311, the conveyance roller 312, the sheet conveyance path 313 and the registration roller pair 314. It will be sent out sequentially.

  In the sheet feeding device 30 configured as described above, a sheet feeding separation mechanism 40 according to the present invention is provided on the front wall 381. Hereinafter, the sheet feeding / separating mechanism 40 will be described with reference to FIGS. FIG. 3 is an exploded perspective view showing an embodiment of the paper feed separation mechanism 40, and FIG. 4 is an assembled perspective view thereof. 5 is a cross-sectional view taken along the line I-I of the sheet feeding / separating mechanism 40 shown in FIG. 4. FIG. 5A shows a state where the friction pad 70 is located at the home position S1, and FIG. The state where the friction pad 70 is located at the urging force application position S2 is shown. 3 to 5 are the same as those shown in FIG. 2 (X is the left-right direction (-X: leftward, + X: rightward), Y is the front-rear direction (-Y: forward, + Y: backward)).

  First, as shown in FIG. 3, the sheet feeding / separating mechanism 40 includes a gantry member (pedestal) 50 that is fitted in the center position in the left-right direction on the front wall 381 (FIG. 2) of the manual sheet feeding unit 38, and the gantry member 50. A pad support movable member (pad holder) 60 that is mounted so as to be movable forward and backward relative to the sheet transport direction, a friction pad 70 mounted on the pad support movable member 60, and the pad support movable member 60 in the sheet transport direction. The coil spring 80 is configured to be biased so as to be pressed toward the downstream side.

  The gantry member 50 is set in a shape bent in a “<” shape in a side view so as to correspond to the rear surface of the front wall 381. The gantry member 50 is a pad that is laid between a pair of left and right leg posts 51 and the upper edge portions of the pair of leg posts 51 and is inclined approximately 30 ° toward the front with respect to the extending direction of the leg posts 51. The holding part 52 is provided.

  The pad holding unit 52 is set at an installation position so that the surface thereof faces the peripheral surface of the paper feed roller 311 in a state where the paper cassette 31 is set at the storage position T1 (FIG. 1A). . The pad holding portion 52 includes a surface plate 53 whose front side is inclined forward and forward, a substantially vertical back plate 54 opposed to the surface plate 53 at the front, and the back plate 54 and the surface plate. 53, a pair of side plates 55 laid in the left-right direction between the respective end edges of the top plate 53, and a top plate 56 laid between the top edge portions of the back plate 54 and the front plate 53, and the lower surface is open. Has been. Each of the pedestals 51 extends downward from the lower end of the rear end of each side plate 55.

  The surface plate 53 is provided with a rectangular mounting recess 531 for mounting the pad support movable member 60 formed by being recessed over substantially the entire surface. The mounting recess 531 is set so that the amount of recess is slightly deeper than the vertical dimension of the pad support movable member 60 over the whole, whereby the pad support movable member 60 is mounted in the mounting recess 531. The concave portion 531 does not protrude to the outside. The bottom plate 532 of the mounting recess 531 is parallel to the front plate 53.

  The bottom plate 532 is provided with a communication opening 533 that crosses the bottom plate 532 in the width direction at a central position in the left-right direction. The communication opening 533 is provided to transmit the urging force of the coil spring 80 mounted on the back surface side of the bottom plate 532 to the pad support movable member 60. The bottom plate 532 is provided with a pair of left and right guide rails 534 that extend in the width direction of the bottom plate 532 that bulges toward the front side. These guide rails 534 are for guiding the movement of the pad support movable member 60 in the mounting recess 531.

  The mounting recess 531 has a vertical width dimension set to approximately twice the width dimension of the pad support movable member 60 and a horizontal dimension slightly longer than the left and right dimensions of the pad support movable member 60. Thus, the pad support movable member 60 can move forward and backward in the inclination direction while sliding on the bottom plate 532 by an amount of its own width within the mounting recess 531.

  The gantry member 50 configured in this manner has a fulcrum shaft 57 projecting in the opposite direction to each other in the vicinity of the leg column 51 at the lower part of the pair of side plates 55 in the left-right direction, and rotates around the fulcrum shaft 57. While being supported by the front wall 381 (FIG. 2) so as to be movable, the upper portion of the back plate 54 is pressed rearward by the urging force of the pressing spring 58. As a result, the gantry member 50 receives a pressing force counterclockwise around the fulcrum shaft 57 by the pressing spring 58, so that the friction pad 70 is pressed against the peripheral surface of the paper feed roller 311.

  The pad support movable member 60 is for supporting the friction pad 70, and in the present embodiment, press processing is performed so that a pair of side edges of a long rectangular metal plate are bent in the same direction. It is formed by doing. The pad support movable member 60 has a bottom plate 61 whose length in the left-right direction is set slightly shorter than the inner dimension in the left-right direction of the mounting recess 531, and projects upward from both side edges of the bottom plate 61. And a pair of side plates 62 extending in the left-right direction. The height dimension of each side plate 62 is set slightly lower than the amount of depression of the mounting recess 531.

  In the pad support movable member 60, a pair of positions and dimensions are set on the bottom plate 61 so that the bottom plate 61 is fitted to a pair of guide rails 534 provided on the bottom plate 532 of the gantry member 50 in a sliding contact state. A guided groove 611 is formed. When the pad support movable member 60 is mounted in the mounting recess 531, the pair of guided grooves 611 are fitted into the corresponding guide rails 534, whereby the pad support movable member 60 has the guided grooves 611. It is possible to move forward and backward in the width direction of the mounting recess 531 in a stable state while being guided by each guide rail 534.

  In the pad supporting movable member 60, the rear side plate 62 is provided with a protruding piece 621 that protrudes downward from the center position in the left-right direction. In the present embodiment, the protruding piece 621 is formed by cutting and raising the bottom plate 61 downward.

  The protruding piece 621 is for supporting the base end side (lower part) of the coil spring 80. In order to ensure this support, a cylindrical piece 622 having a diameter slightly smaller than the inner diameter of the coil spring 80 is provided on the front side of the protruding piece 621 so as to protrude forward. The coil spring 80 is prevented from being detached from the projecting piece 621 by externally fitting the proximal end side of the coil spring 80.

  The friction pad 70 is provided so as to prevent the sheet P1 from being fed by sandwiching the sheet P1 with the sheet feeding roller 311 and the length dimension of the friction pad 70 is the length of the pad support movable member 60. The width dimension is set to be slightly wider than the inner dimension between the pair of side plates 62 of the pad support movable member 60, and the thickness dimension is the vertical dimension of the side plate 62 of the pad support movable member 60. It is set slightly thicker.

  Therefore, when the friction pad 70 is mounted on the pad support movable member 60 by being fitted between the pair of side plates 62 while being compressed and elastically deformed in the width direction, the friction pad 70 is prevented from being detached from the pad support movable member 60 by its own elastic force. At the same time, the surface side protrudes upward from the upper edge of each side plate 62. When the pad supporting movable member 60 is mounted in the mounting recess 531 in this state, the upper surface of the friction pad 70 slightly protrudes from the mounting recess 531 to the outside.

  The friction pad 70 is formed of an elastomer such as rubber or a flexible synthetic resin material, and applies an appropriate friction force to the paper P1 in a state where the paper P1 is sandwiched between the paper feed roller 311 and the friction pad 70. It is made like that. Such a friction pad 70 is configured so that the frictional force formed between the friction pad 70 and the paper P1 is smaller than the frictional force formed between the paper feed roller 311 and the paper P1. The material P1 is selected and the sheet P1 sandwiched between the sheet feeding roller 311 and the friction pad 70 is rotated from the sheet bundle P according to the rotation of the sheet feeding roller 311 by the rotation of the sheet feeding roller 311. It has come out.

  Incidentally, in the present embodiment, urethane cork rubber among various elastomers is adopted as the material of the friction pad 70, whereas EPDM (Ethylene polypropylene diene terpolymer) is adopted as the material of the paper feed roller 311. However, in the present invention, the elastomer for the friction pad 70 is urethane cork rubber, and the elastomer for the paper feed roller 311 is not limited to EPDM. Various elastomers can be employed as long as the pad 70 satisfies the condition that the frictional force between the pad 70 and the paper P1 is smaller.

  The coil spring 80 applies a biasing force to the pad support movable member 60 so as to set the friction pad 70 at the home position S1 via the pad support movable member 60. As shown in FIG. 5, one end of the coil spring 80 is externally fitted to a columnar piece 622 provided on the protruding piece 621 of the pad support movable member 60 in the compressed state, while the other end is The base plate 50 is stopped by a corner formed by the back plate 54 and the top plate 56 in the pad holding portion 52.

  The urging force of the coil spring 80 is smaller than the frictional force between the paper P1 and the friction pad 70 when the friction pad 70 is set at the home position S1, as shown in FIG. As shown in FIG. 5B, the biasing force of the coil spring 80 is greater than the frictional force between the paper P1 and the friction pad 70 when the friction pad 70 has shifted to the biasing force application position S2. Something like that has been adopted.

  When the paper feed roller 311 is stopped, the friction pad 70 is pressed rearward by the urging force of the coil spring 80 via the pad support movable member 60, and as shown in FIG. Thus, the position is set to the home position S1.

  On the other hand, when the uppermost sheet P1 of the sheet bundle P is in contact with the peripheral surface of the sheet feeding roller 311, the sheet feeding roller 311 is driven and rotated counterclockwise around the axis. 4A, the uppermost sheet P1 is guided by the rotation of the sheet feeding roller 311 and pulled out from the sheet bundle P, and the peripheral surface of the sheet feeding roller 311 and the upper surface of the friction pad 70 are shown. It passes through the nip N between the two.

  At this time, the friction pad 70 moves obliquely upward toward the front while compressing the coil spring 80 against the urging force of the coil spring 80, and the friction pad 70 moves in a state where the frictional force and the urging force are antagonistic. Therefore, it is positioned at the biasing force applying position S2 (FIG. 5B) where the biasing force of the coil spring 80 is applied to the paper P1.

  Then, the sheet P1 is fed out from the sheet bundle P in this state. When the feeding of the uppermost sheet P1 in the sheet bundle P is completed, the friction pad 70 returns to the home position S1 shown in FIG. 5A and is used for feeding the next sheet P1.

  Hereinafter, the operation of the sheet feeding / separating mechanism 40 will be described in more detail with reference to FIG. FIG. 6 is an explanatory diagram for explaining the operation of the paper feed separation mechanism 40. In FIGS. 6A and 6B, only one of the uppermost paper P1 is fed out from the paper bundle P. FIG. FIG. 6C to FIG. 6E show the time-dependent action of the paper feed separation mechanism 40 at the time, and two sheets of the uppermost sheet P1 and the next sheet P1 from the sheet bundle P are simultaneously displayed. The time-dependent operation of the sheet feeding / separating mechanism 40 when the so-called two sheets are fed out is shown. In addition, the direction display by Y in FIG. 6 is the same as that in FIG. 2 (−Y: forward, + Y: backward).

  First, the gantry member 50 is urged counterclockwise around the fulcrum shaft 57 by the urging force of the pressing spring 58, and the friction pad 70 is pressed against the peripheral surface of the paper feed roller 311, thereby the friction pad 70 and the friction pad 70. A nip portion N that nips the paper P <b> 1 is formed between the paper feed roller 311.

  In this state (a state in which the friction pad 70 is set at the home position S1), the paper feed roller 311 is driven and rotated counterclockwise around the shaft center, thereby being urged upward by the urging plate 37. As shown in FIG. 6A, the uppermost sheet P1 of the sheet bundle P that has been fed is fed forward and the leading end of the sheet P1 reaches the nip portion N. When the paper P1 reaches the nip portion N, the friction pad 70 still remains at the home position S1.

  At this time, the driving rotation of the paper feed roller 311 is continued, so that the paper P1 continues to be guided by the rotation of the paper feed roller 311 and moves forward. At this time, the friction pad 70 is guided by the movement of the paper P1 and moves obliquely upward toward the front in the mounting recess 531 against the biasing force of the coil spring 80. As shown in FIG. The position is set to the urging force application position S2.

  The friction pad 70 attempts to return to the rear by the biasing force of the coil spring 80 that is compression-elastically deformed in the state where the friction pad 70 is set at the biasing force applying position S2. Since the frictional force between the friction pad 70 and the paper P1 is smaller than the frictional force between the paper feeding roller 311 and the paper P1, the paper P1 is not pushed back by the friction pad 70 and the paper feeding roller 311 It will be pulled forward according to the rotation.

  When the feeding process of the uppermost sheet P1 from the sheet bundle P is completed and the drive rotation of the sheet feeding roller 311 is temporarily stopped in preparation for the next sheet P1, the friction pad 70 is moved to the coil spring 80. The urging force is returned from the urging force application position S2 to the home position S1. By repeatedly driving and stopping the paper feed roller 311, the paper P 1 is fed from the paper bundle P one by one toward the image forming unit 20.

  Next, the operation of the friction pad 70 when two sheets P1 are simultaneously fed out from the sheet bundle P by the driving rotation of the sheet feed roller 311 will be described with reference to FIGS. 6C to 6E. . First, when the paper feed roller 311 is driven and rotated counterclockwise around the axis, when two sheets P1 are simultaneously fed out from the sheet bundle P, as shown in FIG. A plurality of sheets P1 (hereinafter, the uppermost sheet P1 is referred to as the uppermost sheet P11 and the uppermost next sheet P1 is referred to as the next sheet P12) simultaneously reach the nip portion N.

  In this state, the drive rotation of the paper feed roller 311 is continued, so that the friction pad 70 is guided to the two sheets P1 that rotate with the paper feed roller 311, as shown in FIG. Once moved to the urging force application position S2. At this time, static friction acts between the uppermost sheet P11 and the next sheet P12.

  However, the frictional force between the uppermost sheet P11 and the paper feed roller 311 is larger than the frictional force between the uppermost sheet P11 and the next sheet P12, and the next sheet P12 is interposed between both via the friction pad 70. Since the urging force toward the rear side of the coil spring 80 is applied by the frictional force, slip occurs between the uppermost sheet P11 and the next sheet P12, and thereby, between the uppermost sheet P11 and the next sheet P12. Dynamic friction comes to act on.

  Since the dynamic friction is smaller than the static friction, the friction pad 70 cannot hold the urging force application position S2 against the urging force of the coil spring 80, whereby the uppermost sheet P11 is moved to the sheet feeding roller 311. The friction pad 70 is moved toward the home position S1 with the next sheet P12 by the urging force of the coil spring 80 as shown in FIG.

  Thus, even if two sheets P1 are simultaneously fed out from the sheet bundle P by the driving rotation of the sheet feeding roller 311, the friction pad 70 in contact with the next sheet P12 is as shown in FIG. In addition, since the next paper P12 is pushed rearward by the urging force of the coil spring 80, it is reliably prevented that the two papers P1 are simultaneously fed toward the image forming unit 20 by the paper feed roller 311. can do.

  Note that, based on FIGS. 6C to 6E, a sheet feeding that prevents feeding of two sheets is taken as an example in which two sheets of paper P1 are simultaneously fed out by driving rotation of the sheet feeding roller 311. Although the operation of the separation mechanism 40 has been described, even when three or more sheets P1 are fed out, the plurality of sheets P1 are separated by the action of the friction pad 70 to which the urging force is applied by the same coil spring 80 as described above. It is possible to reliably prevent the sheet from being fed to the image forming unit 20.

  As described in detail above, the sheet feeding / separating mechanism 40 according to the present invention has a peripheral surface pressed against the upper surface of the uppermost sheet P1 at the downstream end of the sheet bundle P placed on the urging plate 37 of the sheet cassette 31. The sheet feeding roller 311 is in contact with the sheet feeding roller 311, and the friction pad 70 is disposed opposite to the sheet feeding roller 311 with the uppermost sheet P 1 interposed therebetween. The friction pad 70 includes a coil spring 80. Is biased in the direction opposite to the sheet conveying direction by the urging force, even if a plurality of sheets are simultaneously fed out from the sheet bundle P, the uppermost sheet P1 is driven to rotate the sheet feeding roller 311. The friction pad 7 whose second sheet P1 is temporarily moved from the home position S1 to the urging force applying position S2 by the urging force of the coil spring 80 while being able to feed by being guided. There pushed back rearward to accompany the return to the home position S1, whereby the occurrence of inconveniences such as paper P1 of the plurality sheets is fed to the image forming section 20 at the same time can be reliably prevented.

  Furthermore, since the amount of movement of the friction pad 70 varies against the urging force of the coil spring 80 depending on the type of the paper P1, it is possible to cope with the type of paper depending on the difference in the amount of movement of the friction pad 70. In addition, it is possible to reliably prevent the occurrence of inconvenience such as a problem in feeding out the paper P1 (that is, feeding two sheets) depending on the type of the paper P1.

  In addition, when the paper feed roller 311 is driven and rotated while the paper P1 fed out from the paper bundle P is sandwiched between the paper feed roller 311 and the friction pad 70, the paper P1 is rubbed against the friction pad 70. Since the vibration generated by this is absorbed by the expansion and contraction of the coil spring 80, it is possible to reliably prevent the generation of the so-called chatter sound generated by the paper P1 due to the vibration.

  Further, in the above-described embodiment, the pad support movable member 60 that supports the friction pad 70 with the upper portion exposed is provided, and the pad support movable member 60 can be moved in the paper transport direction. Since the holding base member 50 is provided, the friction pad 70 is movably attached to the base member 50 in a stable state via the pad support movable member 60.

  In addition, since the storage concave portion for movably storing the pad support movable member 60 is provided on the upper surface of the gantry member 50, the friction pad 70 is attached to the mounting recess 531 via the pad support movable member 60. The mounting state of the friction pad 70 to the gantry member 50 is stabilized.

  The present invention is not limited to the above embodiment, and includes the following contents.

  (1) In the above embodiment, the printer 10 is described as an example of the image forming apparatus to which the paper feed separation mechanism 40 is applied. However, the present invention is an image forming apparatus to which the paper feed separation mechanism 40 is applied. Is not limited to the printer 10, but may be a copying machine, a facsimile machine, or a scanner that reads a document image and transmits it to another device such as a computer. When the image forming apparatus is a copying machine, a document tray on which a bundle of documents from which images are to be read is placed in addition to the sheet cassette 31 as a sheet tray according to the present invention. When the image forming apparatus is a scanner, the paper cassette 31 is not provided as the paper tray according to the present invention, and only the document tray is provided. Incidentally, when the image forming apparatus is a scanner, it is included in the concept of image formation according to the present invention to prepare image information read from an original so as to be transmitted to an external device such as a computer.

  (2) In the above embodiment, the paper cassette 31 for storing the transfer paper on which the image is transferred is used as the paper tray to which the paper feed separation mechanism 40 is applied. The tray is not limited to the paper cassette 31. When the image forming apparatus is a copying machine or a facsimile machine, a so-called document feed tray for feeding a document toward the image reading unit. It may be.

  (3) In the above embodiment, the coil spring 80 is employed as the urging means for applying the urging force to the friction pad 70 via the pad support movable member 60. However, in the present invention, the urging means is a coil. It is not limited to the spring 80, and an elastomer such as a plate spring or rubber can be employed depending on the situation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side sectional view for explaining an outline of an internal structure of an example of a printer to which an embodiment of a paper feed separation mechanism according to the present invention is applied. FIG. (B) shows a state in which the paper cassette is pulled out to the pulling-out position. It is a perspective view showing one embodiment of a paper feeder. It is a disassembled perspective view which shows one Embodiment of a paper feed separation mechanism. FIG. 4 is an assembly perspective view of the paper feed separation mechanism shown in FIG. 3. FIGS. 5A and 5B are cross-sectional views taken along the line I-I of the paper feed separation mechanism illustrated in FIG. 4, in which FIG. 4A illustrates a state in which the friction pad is positioned at the home position, and FIG. Each is shown. FIGS. 4A and 4B are explanatory diagrams for explaining the operation of a paper feed separation mechanism. FIGS. 4A and 4B are diagrams illustrating a time course of the paper feed separation mechanism when only one of the uppermost paper is fed out from a paper bundle. (C) to (E) show the operation over time of the so-called two-sheet feeding mechanism in which the uppermost sheet and the next sheet are simultaneously fed out from the sheet bundle. Is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printer 11 Apparatus main body 111 Side plate 111a Guide groove 115 Partition plate 117 Paper discharge tray 20 Image forming part 21 Photosensitive drum 22 Charger 23 Exposure device 24 Developing device 241 Toner cartridge 25 Transfer roller 26 Cleaning device 27 Fixing portion 271 Heat roller 272 Pressure roller 273 Paper delivery path 30 Paper feed device 31 Paper cassette (paper tray, transfer paper tray)
311 Paper Feed Roller 312 Transport Roller 313 Paper Feed Transport Path 314 Registration Roller Pair 32 Arc-shaped Front Plate 33 Bottom Plate 331 Front / Rear Motion Guide Concave 332 Left / Right Motion Guide Concave 34 Side Plate 341 Guided Projection Piece 35 Front / Rear Position Restricting Member 351 Horizontal Plate 352 Vertical plate 36 Horizontal position restricting member 361 Horizontal plate 362 Vertical plate 37 Energizing plate 371 Support shaft 372 Coil spring 38 Paper feed unit 381 Front wall 382 Tray 40 Paper feed separation mechanism 50 Mounting member (pedestal)
51 pedestal 52 pad holding portion 53 surface plate 531 mounting recess 532 bottom plate 533 communication opening 534 guide rail 54 back plate 55 side plate 56 top plate 57 fulcrum shaft 58 pressing spring 60 pad support movable member (pad holder)
61 Bottom plate 611 Guided groove 62 Side plate 621 Projection piece 622 Column piece 70 Friction pad 80 Coil spring N Nip part P Paper bundle P1 Paper P11 Topmost paper P12 Next paper S1 Home position S2 Energizing force application position T1 Storage position T2 Pull-out position

Claims (5)

A paper feed roller whose peripheral surface is pressed against and contacted with the upper surface of the uppermost paper at the downstream end in the paper feeding direction of the paper stack placed on the paper tray, and a lower part through the paper supply roller and the uppermost paper A paper feed separation mechanism comprising a friction pad disposed opposite to each other,
The sheet feeding / separating mechanism according to claim 1, wherein the friction pad is biased in a direction opposite to a paper feeding direction from the paper tray by a biasing force of a biasing unit.   2. The pad holder for supporting the friction pad in a state where the upper portion is exposed, and a pedestal for holding the pad holder so that the pad holder can be moved forward and backward with respect to a paper feeding direction is provided. Paper feed separation mechanism.   The sheet feeding / separating mechanism according to claim 2, wherein a storage recess for movably storing the pad holder is provided on an upper surface of the pedestal.   4. The sheet feeding / separating mechanism according to claim 1, wherein the urging means is one of a coil spring, a plate spring, and an elastomer. An image forming apparatus for forming an image based on image information,
One or both of a document tray on which a bundle of documents having images to be read is placed and a transfer paper tray on which a bundle of sheets on which images are to be transferred are provided,
5. The image forming apparatus to which the sheet feeding / separating mechanism according to claim 1 is applied, wherein the sheet tray is one or both of the document tray and the transfer sheet tray. .

Images