JP2010202311A - Paper feeder and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a space-saving paper feeder preventing a residual of paper when a tray is pulled out. <P>SOLUTION: When a separation driving shaft 59 is driven in the paper conveyance direction (direction opposite to paper feed) by a separation driving motor 57 until a paper front end is detected by a detection means 73 after completion of paper feeding operation, a press-contact force is resolved due to the occurrence of a reaction force in the direction opposite to a tangential force between rollers. When pressurization is released, a separation roller 52 is dropped by its own weight, and nip with a paper feeding roller 51 is resolved. That is, the separation roller 52 is reversed until the front end of the paper is detected by a detection means 73 to allow the separation roller 52 to be dropped by its own weight after completion of feeding operation, thereby achieving the space-saving paper feeder preventing the residual of paper when the paper tray is pulled out. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a paper feeding device that picks up the paper stored in a paper tray one by one and supplies it to a desired location, and image forming such as a printer, a facsimile, a copying machine, and a multifunction machine including these paper feeding devices. Relates to the device.

  In an image forming apparatus such as an electrophotographic copying machine, a laser beam printer, a facsimile, or an apparatus called a multi-function machine having a plurality of these functions, a paper feeding device that feeds paper one by one from a paper tray Friction separation roller system having a sheet feeding roller that rotates in the feeding direction, and a separation roller that is in pressure contact with the sheet feeding roller and that is applied with a driving force in a direction opposite to the feeding direction via a torque limiter A sheet feeding apparatus (hereinafter referred to as an FRR system) is well known.

  In this FRR type paper feeding device, the paper feeding roller and the separation roller are always in pressure contact. Therefore, when the paper tray is pulled out with the paper held in the nip between the two rollers, the paper is brought into the image forming apparatus. It remains, causing a paper jam (paper jam).

  Thus, for example, it is conceivable to use a mechanism that forcibly releases the separation roller disclosed in Patent Document 1. However, in recent printers and copiers, the paper feed roller and separation roller have become smaller in diameter due to space saving and multi-stage paper trays, so even with slight deviation of the rollers, the change in the contact angle between the rollers with respect to the pressure contact direction Increases and the biting force of the rollers also increases. In order to forcibly release this, a mechanism having a considerably large releasing force must be formed, which hinders space saving of the apparatus.

  In response to this problem, for example, in Patent Document 2, the feed roller shaft is reversed by a reverse rotation preventing member, so that the tangential force remaining even when the roller driving is stopped due to a slight deviation of the roller is eliminated. An invention is disclosed in which falling and nip are released by its own weight.

  However, the conventional measures as described above are based on the premise that the paper feed roller shaft rotates idly (the electromagnetic clutch is used in the above-described patent document embodiment). Since the idling torque of all the rows is large, it is difficult to reverse the feed roller shaft with the anti-reverse member.

  The present invention has been made in view of the drawbacks of the prior art, and in the friction separation roller paper feeding device that always applies a driving force to the separation roller during feeding, regardless of the type of drive source of the paper feed roller, An object of the present invention is to provide a space-saving paper feeding device that prevents paper remaining when a tray is pulled out with a simple configuration.

  According to a first aspect of the present invention, there is provided a sheet feeding device that feeds a sheet picked up from a sheet container and a driving force in a direction opposite to the sheet feeding roller via a torque limiter. When there is no sheet and when there is one sheet, the sheet is rotated with the sheet feeding roller, and when there are a plurality of sheets, the separating roller is rotated in the direction in which the sheet separating roller is pressed against the sheet feeding roller. An urging means for urging, a releasing means for releasing the pressure contact force of the separating roller against the paper feeding roller against the urging force of the urging means, and In the paper feeding device including the reverse rotation preventing means for preventing the reverse rotation and the detection means for detecting the paper downstream in the transport direction of the paper feed roller, the separation is performed until the detection means detects the paper after the completion of the feeding operation. Roller in the same direction as the feed roller Characterized by applying the driving force.

  According to a second aspect of the present invention, in the paper feeding device according to the first aspect of the present invention, the paper feeding device includes an opening / closing portion that can be opened and closed when removing jammed paper in the device, and a detection unit that detects an open / closed state of the opening / closing portion Immediately after the detection means changes from the open state to the closed state when a jam occurs, the separation roller is applied with a driving force in the same direction as the paper feed roller until the detection means detects the paper.

  According to a third aspect of the present invention, in the paper feeding device according to the first or second aspect, the separation roller is driven in the same direction as the paper feeding roller until the detection means detects the paper immediately after the power is turned on. It is characterized by giving.

  According to a fourth aspect of the present invention, in the paper feeding device according to any one of the first to third aspects, the detection unit is disposed at a position near the downstream side of the paper feeding roller in the paper transport direction. And

  According to a fifth aspect of the present invention, an image reading apparatus includes the paper feeding device according to any one of the first to fourth aspects.

  According to a sixth aspect of the present invention, there is provided the image forming apparatus according to the fifth aspect, wherein the image forming apparatus is a tandem method capable of simultaneously performing exposure scanning on a plurality of photoconductors and capable of forming images of different colors. It is a device.

  According to the present invention, after the feeding operation is completed, the separating roller is reversed until the leading edge of the sheet is detected by the detecting unit so that the separating roller can be dropped by its own weight. A space-type paper feeding device can be provided.

1 is a schematic central sectional view of a color printer showing an embodiment of the present invention; FIG. 1 is a schematic central sectional view of the image forming unit in FIG. FIG. 1 is a schematic cross-sectional view with a part of the frame opened from FIG. The perspective view which shows a sheet feeding part in the state in which the separation roller was pressed against the sheet feeding roller The perspective view which shows the paper feeding part in the state which canceled the pressure contact state of the separation roller and the paper feeding roller The figure for demonstrating the positional relationship of a separation roller and a paper feeding roller Partial perspective view for explaining the drive system of the paper feed unit (A) and explanatory diagram showing the positional relationship between the detection means and the paper feed roller (B) Explanatory drawing showing the positional relationship between the detection means and the paper feed roller

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, modes for carrying out the present invention will be described with reference to embodiments shown in the drawings. The present invention is not limited to the illustrated image forming apparatus, and can be applied to various apparatuses that perform image formation.

  FIG. 1 shows a central sectional view of a full-color printer employing a so-called tandem system as an example of an image forming apparatus to which the present invention is applied, and FIG. 2 is a central sectional view showing an outline of an image forming unit in this printer. It is.

  First, the internal configuration of the full-color printer 100 will be described with reference to FIGS. The full-color printer 100 includes four latent images as image forming means for forming images of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). Drum-shaped photoconductors 2Y, 2M, 2C, and 2Bk, which are bodies, are arranged in parallel at equal intervals in the left-right direction in the drawing. During operation of the image forming apparatus 100, the image forming apparatus 100 is rotated in the direction of the arrow by a drive source (not shown).

  Around the photoreceptors 2Y, 2M, 2C, and 2Bk, members and devices necessary for an electrophotographic image forming apparatus such as a developing device are provided, and the image forming units 1Y, 1C, 1M, and 1Bk are configured at four locations. However, for the sake of convenience, in order to correspond to the toner color of the image to be imaged, Y (yellow), C (cyan), M (magenta), Bk (representing the color) are displayed after the number indicating each image forming device for convenience. Black) will be attached as a subscript. In the following description, when there is no need to specify a color in the description, it is simply referred to as the photoreceptor 2. Other components will also be described without adding Y to Bk when it is necessary to specify the color, and without adding Y to Bk when it is not necessary to specify the color. The four image forming units 1 have the same configuration.

  Focusing on the image forming unit 1Y including the yellow image photoreceptor 2Y shown in FIG. 2, a charging device 4Y including a charging roller 4aY according to an electrophotographic process, a developing roller 5aY, and a developing blade are disposed around the photoreceptor 2Y. An image forming member such as a developing device 5Y having 5bY, a screw 5cY, etc., a cleaning brush 3aY, a cleaning blade 3bY, a recovery screw 3bY and the like, and a cleaning device 3Y are sequentially arranged.

  The photoreceptor 2Y has a layer structure in which an organic semiconductor layer that is a photoconductive substance is provided on the surface of an aluminum cylinder having a diameter of about 30 to 120 mm, for example. The members arranged around the other photoconductors 2C, 2M, and 2Bk are the same. That is, only the color of the toner used for image formation is different. It is possible to use a belt-like photoconductor.

  As shown in FIG. 1, a laser beam corresponding to image data for each color is scanned on the surface of each photoconductor 2 that has been uniformly charged by a charging means below each photoconductor 2 to form an electrostatic latent image. An exposure device 8 is provided for forming. Between each charging device 4 and each developing device 5, an elongated space is secured in the direction of the rotation axis of the photosensitive member 2 so that the laser light irradiated by the exposure device 8 enters the photosensitive member. .

  An exposure apparatus 8 in the illustrated example is a laser scanning type exposure apparatus using a laser light source, a polygon mirror, and the like. Beam light 8Y, 8C modulated from four semiconductor lasers (not shown) according to image data to be formed. , 8M, 8Bk. The exposure apparatus 8 accommodates optical parts and control parts by a metal or resin casing, and is provided with a light-transmitting dustproof member at the emission port on the upper surface. Although the embodiment is composed of a single housing, a plurality of exposure apparatuses can be individually provided in each image forming unit. In addition to an exposure apparatus that employs the above laser, an exposure apparatus that combines a known LED array and an imaging means can also be employed.

  When the yellow (Y), cyan (C), magenta (M), and black (Bk) toners are consumed by the developing devices 5Y, 5C, 5M, and 5Bk that handle the respective colors, they are detected by a toner detection unit (not shown). The toner cartridges 40Y, 40C, 40M, and 40Bk that store the toners of the respective colors provided in the upper portion of the image forming apparatus 100 are supplied to the developing devices 5 by a supply unit (not shown). The outer shell of each toner cartridge is a container made of resin or paper, and is provided with a discharge port in part, and can be easily attached to and detached from the mounting portion TS of the image forming apparatus 100. Combined with individual toner replenishing means provided on the main body. In order to prevent the toner cartridge 40 of each color from being erroneously mounted and supplying toner to a developing device that handles different colors, the mounting portion TS and the toner cartridge 40 are paired with each other to provide a wrong mounting prevention means. is there.

  The developing device 5 includes two screws 5c for stirring and conveying the toner and the carrier. When the developing device 5 is mounted on the image forming apparatus 100, one end of the toner replenishing means described above is connected to the upper portion of the left screw 5c in the drawing. The toner is supplied to the developing roller 5a rotating in the direction of the arrow by the screw 5c, but the thickness of the toner layer on the surface of the developing roller 5a is regulated to a predetermined thickness by the blade 5b. The developing roller 5a is a cylinder made of stainless steel or aluminum, and is supported by the frame of the developing device so as to be rotatable and a distance from the photosensitive member is properly secured. A predetermined line of magnetic force is formed inside the developing roller 5a. A magnet is provided.

  Then, the electrostatic latent image for each color formed on the surface of each photoconductor 2 by the laser beam is developed by the developing device 5 that handles toner of a predetermined color to become a visible image.

  An intermediate transfer unit 6 is disposed on the top of the photoreceptor 2. The roller 6b rotates so that the intermediate transfer belt 6a as an image carrier supported and stretched by a plurality of rollers 6b, 6c, 6d, and 6e travels in the direction of the arrow. The intermediate transfer belt 6a is endless, and is stretched and arranged so that a part of each photoconductor after the development process comes into contact. Primary transfer rollers 7 </ b> Y, 7 </ b> C, 7 </ b> M, and 7 </ b> K are provided on the inner peripheral portion of the belt so as to face each photoconductor 2.

  A cleaning device 6h is provided on the outer peripheral portion of the intermediate transfer belt 6a at a position facing the roller 6e. The cleaning device 6h wipes off unnecessary toner remaining on the surface of the belt 6a and foreign matters such as paper dust. The roller 6e facing the cleaning device 6h includes a mechanism that applies tension to the belt 6a. Although it always moves to ensure an appropriate belt tension, the opposing cleaning device can also move in conjunction.

  The intermediate transfer belt 6a is, for example, a belt based on a resin film or rubber having a base thickness of 50 to 600 μm, and applies a toner image carried by each photoreceptor 2 to the primary transfer roller 7. It has a resistance value that enables electrostatic transfer to the belt surface by the bias. The members related to the intermediate transfer belt 6 a are configured as the intermediate transfer unit 6 and can be attached to and detached from the image forming apparatus 100.

  As an example, the intermediate transfer belt 6a may be one in which, for example, carbon is dispersed in polyamide and the volume resistance value of which the resistance is adjusted to about 10 6 to 10 12 Ωcm can be used, but is not limited thereto. A belt detent rib for stabilizing the running of the intermediate transfer belt 6a is provided on one side or both ends of the belt.

As an example of the primary transfer roller 8, a metal roller serving as a core metal whose surface is coated with a conductive rubber material can be used, and a bias is applied to the core metal part from a power source (not shown). As the conductive rubber material, carbon is dispersed in urethane rubber, and the resistance is adjusted to about 10 ⁵ Ωcm. A metal roller that does not have a rubber layer can also be used.

A secondary transfer roller 14a is provided in the vicinity of the support roller 6b on the outer periphery of the intermediate transfer belt 6a. The secondary transfer roller 14a is formed by coating the surface of a metal roller serving as a metal core with a conductive rubber, and a bias is applied to the metal core part from the power supply 14b. Carbon is dispersed in the rubber, and the volume resistance is adjusted to about 10 ⁷ Ωcm. A toner image carried on the intermediate transfer belt 6a is electrostatically transferred to the sheet S by applying a bias while passing a recording medium (hereinafter referred to as a sheet S) between the intermediate transfer belt 6a and the secondary transfer roller 14a. The

  A plurality of, for example, two-stage sheet feed trays 9A and 9B are arranged below the exposure device 8 so as to be able to be drawn. The paper S stored in these paper feed trays is selectively sent out by the rotation of the corresponding pickup roller 51, and sent to the paper feed transport path P1 by the paper feed roller 52 and the transport roller pair 12A, 12B.

  A pair of registration rollers 13 is provided in the paper feed conveyance path P1 in order to take a feed timing for feeding the paper S to the secondary transfer unit. The sheet S is conveyed from the registration roller pair 13 toward a secondary transfer portion configured by the intermediate transfer belt 6a and the secondary transfer roller 14a.

  The manual paper feeder 25 provided on the right side of the drawing can be rotated and stored in a part of the frame F of the image forming apparatus main body 100 when not in use. The uppermost sheet S stored in the manual sheet feeding device 25 is fed by the sheet feeding roller 26, separated by the separating unit 27 so that only one sheet is reliably conveyed, and conveyed by the conveying roller pair 22, 24. It is sent to the pair of registration rollers 13 via the path P1.

  A fixing device 15 having a heating unit is provided above the secondary transfer unit. In this example, it is composed of rollers 15a and 15b with built-in heaters, but a type employing a belt and a heating method employing IH can also be appropriately employed.

  The switching guide G1 is rotatable, and in the state shown in the figure, the sheet having been fixed is guided to the paper discharge path P3 and discharged to the paper discharge stack T at the top of the image forming apparatus 100 by the pair of paper discharge rollers 16. , Stack.

  The printer 100 in FIG. 1 includes a conveyance path and rollers for reversing and refeeding paper so that images can be automatically formed on both sides of the paper. Specifically, a switchback path P5 and a refeed path P6 are provided inside the frame F, and the switching guides G1 and G2 and the reversible guides can be reversed so that the paper on which image formation has been completed on one side is conveyed to the feed path P1. A roller 18a and a reversible roller 22 are provided. Rollers 23 and 24 are in contact with the reversible drive roller 22, and when the roller 22 rotates in the clockwise direction, the paper is conveyed from the manual paper feeder 25 in cooperation with the roller 24. When rotating clockwise, the paper is fed again in the direction of the registration roller 13 in cooperation with the roller 23.

  When the switching guide G1 is rotated clockwise from the state shown in the drawing, the sheet having been fixed is guided to the transport path P4 by the roller pair 17, and is transported to the rollers 18a and 18b through the switching guide G2, and is temporarily switched back. It is sent to the road P5. As the roller 18a rotates counterclockwise and the switching guide G2 rotates counterclockwise, the sheet is fed to the refeed path P6. The paper conveyed by the roller pairs 15c, 20 and 14c, 21 is further conveyed to the roller pairs 22, 23 and reaches the registration roller pair 13.

  The apparatus shown in FIG. 1 includes another sheet feeding device 50 at the bottom. In this example, the two paper feed cassettes 9C and 9D are provided. However, a type in which the number of paper feed cassettes is further increased can be adopted, and a type having a built-in paper feed tray having a larger number of paper storage may be used.

  The third switching guide G3 above the fixing device 15 and downstream in the conveying direction of the roller pair 17 rotates counterclockwise from the state of FIG. 1, guides the sheet S after fixing, and enters the paper discharge path P8. It can be conveyed and discharged to another paper discharge device (not shown). As this another discharge device, for example, a bin tray having several stages of discharge trays can be cited, but various known devices can be adopted.

  An operation at the time of single-sided printing in which an image is formed on one side of the paper P in the above-described configuration will be described.

  First, an electrostatic latent image is obtained by irradiating the surface of the photoreceptor 2Y uniformly charged by the charging roller 4aY with the laser light 8Y corresponding to the image data for yellow emitted from the semiconductor laser by the operation of the exposure device 4. Is formed.

  This electrostatic latent image is subjected to development processing by the developing roller 5aY and is developed with yellow toner, becomes a visible image, and receives a transfer action by the primary transfer roller 7Y on the surface of the intermediate transfer belt 6a that moves in synchronization with the photoreceptor 2Y. The primary transfer. Such latent image formation, development, and primary transfer operation are performed in the same manner sequentially at the timings of the photoreceptors 2C, 2M, and 2Bk.

  As a result, yellow Y, cyan C, magenta M, and black Bk toner images are carried on the surface of the intermediate transfer belt 6a as sequentially overlapping four-color toner images in the direction of the arrow together with the intermediate transfer belt 6a. Moved. On the other hand, the remaining toner and foreign matter are cleaned on the surface of the photoreceptor 2 by the cleaning device 3.

  The four-color toner image formed on the intermediate transfer belt 6a is transferred onto the sheet S conveyed in synchronization with the intermediate transfer belt 6a by receiving a transfer action by the secondary transfer roller 14a. The surface of the intermediate transfer belt 6a is cleaned by a belt cleaning device 6h to prepare for the next image formation / transfer process.

  The sheet P on which the image has been transferred is subjected to a fixing action by the fixing device 15 and is discharged onto the sheet discharge stack T by the sheet discharge roller 16 with the image surface facing downward (face down).

  An operation at the time of double-sided recording in which an image is formed on both sides of the paper S in such a configuration will be described. By the operation as described above, first, an image is transferred from the intermediate transfer belt 6a to one side of the sheet SP, and the sheet that has passed through the fixing device 15 is guided toward the roller pair 17 by the first switching guide G1. The sheet S traveling above the second switching guide G2 at the rotation position in FIG. 1 through the third switching guide and the conveying path P4 provided downstream of the conveying path of the roller pair 17 is transferred to the conveying path P5 by the roller 18a. 18b, the reversible drive roller 18a rotates in the clockwise direction. The roller pair 19 is also a roller that can be rotated forward and backward, and once the paper S is received in the switchback conveyance path P5, it is reversely rotated to reversely feed the paper S. At that time, the second switching guide G2 rotates counterclockwise from the posture shown in the figure, and the conveyance path P4 is formed by the roller pairs 15c, 20 and 14c, 21 with the rear end of the sheet S as the leading end. Transport toward After that, the sheet S is made to reach the registration roller pair 13 as described above, and the registration roller pair 13 takes timing, and the sheet S having an image on one side is again directed to the secondary transfer portion where the secondary transfer roller 14a is provided. The toner image on the intermediate transfer belt 6a is transferred to the other side of the paper S.

  Images to be formed on the second surface of the sheet S are sequentially formed by an image forming process that is started when the sheet S is conveyed to a predetermined position. The image forming process in this case is also the same as the above-described full-color toner image formation during single-sided printing, and this full-color toner image is carried on the intermediate transfer belt 6a. However, since the front and back of the paper are reversed in the transport path, the creation of the image data emitted from the exposure device is controlled so that the image is formed in the reverse direction in the paper transport direction compared to when the image was first formed. Executed.

  The sheet S on which the full-color toner images are transferred on both sides in this way is again discharged onto the discharge stack portion T by the discharge roller 16 after the fixing process by the fixing device 15. In order to increase the efficiency of double-sided image formation, several sheets of paper can be transported simultaneously on the transport path. The formation timing of the images to be formed on the front and back of the paper is executed by a control means (not shown). Incidentally, if the polarity of the toner image formed on the photosensitive member 2 is negative, the toner image on the photosensitive member 2 is transferred to the surface of the intermediate transfer belt 6a by applying a positive charge to the primary transfer roller 7. Further, the toner image on the surface of the intermediate transfer belt 6a is transferred onto the sheet S by applying a positive charge to the secondary transfer roller 14a.

  The single-sided printing operation and the double-sided printing operation have been described with reference to an example in which full-color printing is performed. However, there are photosensitive members that are not used during black-and-white monochrome printing. In addition to not operating the unused photoreceptors 2Y, 2C, 2M or developing devices 5Y, 5C, 5M, a mechanism is provided for keeping these unused photoreceptors and the intermediate transfer belt 6a in non-contact. In this embodiment, the inner frame 6f that supports the roller 6d and the primary transfer rollers 7Y, 7C, and 7M is supported so as to be rotatable about the shaft 6g, and in a direction away from the photoreceptor 2 (clockwise in FIG. 1). By rotating, only the photoconductor 2Bk comes into contact with the intermediate transfer belt 6a, and an image forming process is executed to create a monochrome image using black toner. This is advantageous in terms of improving the service life.

  When maintenance or parts replacement is required, maintenance is performed by opening an exterior cover (not shown), etc., but the members constituting the image forming unit 1 shown in FIG. It is convenient to exchange.

  When the image forming unit 1 shown in FIG. 2 is configured as a process cartridge, a guide unit and a handle for mounting on the printer 100 are provided to facilitate attachment and detachment. In addition, it is convenient to provide a storage device (for example, an IC tag) for storing the characteristics and operation status of the process cartridge, which is a guideline for maintenance. Further, when performing maintenance or replacement on the intermediate transfer belt unit 6, the belt and the photosensitive member can be separated and the intermediate transfer belt unit can be pulled out.

  FIG. 3 is a partial view showing a state in which the frame F is opened from the state shown in FIG. The lower rotation axis Fa is the rotation center, and the upper part can be opened. Prior to opening, most of the transport path can be opened by opening a lock lever (not shown), so that the jammed paper can be easily treated. The secondary transfer unit 14 in which the conveyance paths P2 and P5 are formed on both sides has the center of the roller 23 as a rotation center, and when the frame F is opened as shown in FIG. 3, the secondary transfer roller 14a is moved to the intermediate transfer belt 6a. Rotation behavior is given to the secondary transfer unit 14 so that the roller 14c is separated from the roller 21.

  The secondary transfer unit 14 includes a power supply 14b inside, and a unit having a paper transport function outside the case.

  The fixing device 15 also has a conveyance roller 15c and a conveyance guide surface, and a part thereof constitutes a conveyance path P6. The fixing device 15 is supported in the state shown in FIG. 3 so that it can be pulled out to the right in the drawing. Therefore, it is possible to easily handle a paper jam that has occurred inside the fixing device.

  As shown in FIGS. 4 and 5, the principle of paper feeding of the paper feeding unit is that a predetermined return in a direction opposite to the paper transport direction (hereinafter referred to as a paper return direction) is performed by a torque limiter 54 having a predetermined idling torque. The separation roller 52 that generates force is brought into pressure contact with the paper feed roller 51, and when two or more sheets are sandwiched in the nip, the separation roller 52 rotates in the paper return direction, and the paper feed tray 9 starts from the lowermost sheet. When there is no sheet in the nip and when only one sheet is nipped, the idling torque of the torque limiter 54 is exceeded, so only the separation roller 52 is driven by the sheet feed roller 51 in the sheet conveyance direction. Rotating. The paper feed roller 51 is attached to a paper feed shaft 56 to which driving is transmitted from the paper feed drive motor 55, and the separation roller 52 is attached to the separation driven shaft 58 via a torque limiter 54. In addition, a gear 60 is engaged with a gear 61 mounted on a separation driven shaft on a separation drive shaft 59 to which driving is transmitted from the separation drive motor 57. The separation driven shaft 58 is rotatably supported by a bearing 62, and the bearing 62 is engaged with a notch 63a of the support plate 63 so as to be movable in the vertical direction.

  The bearing 62 is placed on an upper side portion 65 a of an urging lever 65 that is swingably attached by a shaft 64. One end of an initial pressure spring 66 is attached to the lower side portion 65c of the urging lever 65, and a projecting portion 65b extending in the horizontal direction is integrally provided in the vicinity of the lower side portion 65c. The other end of the initial pressure spring 66 is attached to the frame 10 schematically shown in FIG. 1, and the biasing lever 65 presses the bearing 62 upward by the action of the initial pressure spring 66, thereby separating. A roller 52 is pressed against the paper feed roller 51.

  In the vicinity of the urging lever 65, a release lever 67 is attached to the frame 10 so as to be slidable in the axial direction of the separating drive shaft. A claw portion 67 a is provided at one end of the release lever 67, and the release lever 67 is biased by a release spring 68 attached at one end to the release lever 67 and at the other end to the frame 30.

  The other end of the release lever 67 is rotatably linked to one end of a link member 70 that is rotatably attached by a shaft 69. In a state where the paper feed tray 9 is set in the apparatus main body, the link member 70 is rotated clockwise by the protrusion 9 a provided on the back surface of the paper feed tray 9. By the action of the link member 70, the release lever 67 slides toward the separation roller 62, and the claw portion 67 a of the release lever 67 is separated from the protruding portion 65 b of the urging lever 65. The roller 51 is pressed. When the paper feed tray 9 is pulled out from the apparatus main body, the release lever 67 is pulled by the release spring 68 and slides in the reverse direction, and the claw portion 67 a pushes the protruding portion 65 b of the biasing lever 65. Here, since the release force of the release spring 68 is set larger than the urging force of the initial pressure spring 66, the pressure applied to the bearing 62 by the urging lever 65 is released.

  The separation roller 52 is always applied with a driving force in the paper returning direction by the separation driven shaft 58 that rotates in the direction of the arrow R shown in FIG. The pressure contact force of the separation roller 52 against the paper feed roller 51 is the sum of the initial pressure by which the biasing lever 65 presses the bearing 62 upward by the action of the initial pressure spring 66 and the kicking force by the gear 60 and the gear 61. However, this kick-up force is generated only when the torque limiter 54 operates. However, actually, as shown in FIG. 6, there is a slight gap δ in the notch 63a of the bearing 62 and the support plate 63 in order to improve the vertical movement. As a result, the separation roller 52 is displaced from the center line in the pressure contact direction to the paper feed roller 51 by the driving force. Further, due to the elastic deformation of the roller rubber part, the tangential force T between the rubbers has an angle θ from the normal direction of the pressure contact direction. Even if the driving of each roller is stopped, the tangential force T remains because the paper feed roller 51 is prevented from reverse rotation by the reverse rotation preventing member and the separation roller is blocked by the drive system load.

  Even if the urging lever 65 is released in this state, the separation roller 52 is prevented from falling by its own weight due to the frictional force μT ″ between the bearing 62 and the notch 63a of the support plate 63 caused by the horizontal component T ″. The pressure contact state is maintained by the vertical direction component T ′. As the roller diameter decreases, the angle θ increases, so that the pressure contact force tends to increase. Further, the sheet feeding shaft 56 is held so as to be rotatable only in the conveying direction by a bearing 71 incorporating a one-way clutch for preventing reverse rotation, and is configured not to reverse even when the return force of the separation roller 52 is applied. Further, the detection sensor 73 is disposed in the vicinity of the downstream side of the paper feed roller 51.

  The operation of this embodiment will be described with reference to FIGS. In the present embodiment, after the paper feeding operation is completed, if the separation driving shaft 59 is driven in the transport direction (the direction opposite to that during paper feeding) until the detection unit 73 detects the leading edge of the paper by the separation driving motor 57, the tangent line is applied. Since a reaction force in the direction opposite to the force T is generated, the pressure contact force is eliminated. When the pressure on the bearing 62 of the urging lever 65 is released via the release lever 67 (in this embodiment, when the paper feed tray 9 is pulled out from the apparatus), the separation roller 52 falls by its own weight, and the paper feed roller The nip with 51 is eliminated. The drive of the separation drive motor 57 in the transport direction only needs to generate a reaction force in the direction opposite to the tangential force T, and may be a very short time.

  The sheet feeding operation may be completed in a state in which the sheet left in the nip between the sheet feeding roller 51 and the separation roller 52 remains. The sheet is transported by the amount of drive imparted in the transport direction of the separation roller 52. In consideration of the fact that no sheet return force is generated during this period, it is desirable that the drive imparting time be short. Accordingly, the detection sensor 73 is set in the vicinity of the downstream direction in the sheet conveyance direction from the sheet feed roller 51, for example, in a range of less than about 1 mm.

  If the sheet has a small coefficient of friction between the sheets, the sheet is not continuously fed to the upper sheet, and if the sheet does not reach the nip between the sheet feeding roller 51 and the separation roller 52, the separation drive shaft 59 is moved in the conveyance direction (what is the time of sheet feeding)? Even if the drive is applied in the reverse direction, it is not conveyed to the detection means 73.

  Therefore, if the detection means 73 does not detect the leading edge of the sheet even when the separation drive shaft 59 is driven in the conveyance direction (the reverse direction to the time of paper feeding), the conveyance path length from the nip to the detection means 73 is greater than or equal to α. The separation drive motor 57 is stopped. According to the above embodiment, even when the paper tray 9 is pulled out, the nip is released, so that the paper can be prevented from being caught and remaining in the apparatus.

  When a jam occurs, the paper is removed at the time of jam processing in a jam in which even a part of the rear end of the paper remains in the paper feed tray 9, but in the case of a jam that occurs downstream, a paper feed roller In some cases, a sheet of paper left in the nip between 51 and the separation roller 52 remains. After the jam has occurred, when the open / close detection means 72 (for example, sensor) of the open / close section recognizes the closed state and detects that there is no remaining paper in the apparatus by a transport sensor (not shown), the separation drive motor 57 moves in the transport direction. By applying the drive, the nip is released even when the paper tray 9 is pulled out, so that the paper can be prevented from being caught and remaining in the apparatus.

  Immediately after the power is turned on, the state when the power is turned off is unknown. Therefore, when the power is turned off when a jam occurs, it is unclear whether or not the separation drive shaft 59 is driven in the transport direction (the direction opposite to that during paper feeding). Therefore, after the power is turned on, if the detection unit 73 does not detect the paper, the separation drive shaft 59 is driven in the transport direction (the direction opposite to that during paper feeding), so that the paper tray 9 can be pulled out. Since the nip is released, it is possible to prevent the sheet S from being caught and remaining in the apparatus.

  That is, in the paper feeding device of the present invention, after the feeding operation is completed, the separation roller is reversed until the leading edge of the paper is detected by the detection means so that the separation roller can be dropped by its own weight. Can be provided.

  In addition, after the power is turned on, the separation roller is reversed until the leading edge of the paper is detected by the detection means, so that the separation roller can be dropped by its own weight. It can be a device. In addition, the image forming apparatus can be provided with a space-saving paper feeding device that prevents paper remaining when the tray is pulled out.

1: Image forming unit (process cartridge)
2Y, 2C, 2M, 2Bk: Photosensitive drum 3: Cleaning device 3a: Cleaning brush 3b: Cleaning blade 3c: Recovery auger (screw)
4: charging device 4a: charging roller 5: developing device 5a: developing roller 5b: blade 5c: screw 6: intermediate transfer unit 6a: intermediate transfer belts 6b, 6c, 6d, 6e: belt support roller 6f: internal frame 6g: times Driving shaft 6h: belt cleaning device 7: primary transfer roller 8: exposure devices 8Y, 8C, 8M, 8Bk: beam light 9A, 9B: paper feed tray 10: frame 11A, 11B: paper feed roller pair 12A, 12B: transport roller Pair 13: Registration roller pair 14: Secondary transfer unit 14a: Secondary transfer roller 14b: Power supply 14c: Conveying roller 15: Fixing device 15a: Fixing roller 15b: Pressure roller 15c: Conveying roller 16: Discharge roller pair 17 , 18, 19, 20, 21, 22, 23, 24: conveying roller 25: manual sheet feeding device 26: sheet feeding roller 27: Separation means 51: paper feed roller 52: separation roller 53: call roller 54: torque limiter 55: paper feed drive motor 56: paper feed shaft 57: separation drive motor 58: separation driven shaft 59: separation drive shaft 60, 61: gear 62: bearing 63: support plate 64: shaft 65: biasing lever 66: initial pressure spring 67: release lever 68: release spring 69: shaft 70: link member 71: one-way bearing 72: open / close detection means 73: detection means 100: Printer 40: Toner cartridge 50: Paper feeder (bank)
F: Frame Fa: Rotating shaft G1: First switching guide G2: Second switching guide G3: Third switching guide P1: (Paper feed) transport path P2: Transport path P3: Paper discharge transport path P4: Transport path (reversal) Entrance)
P5: Switchback path P6: Refeed path P7: Paper feed path P8: Another paper discharge path S: Paper (recording medium)
T: Paper output section (paper output tray)
ST: Toner cartridge storage

Japanese Patent Laid-Open No. 7-137872 JP 2003-2474 A

Claims (6)

A paper feed roller for feeding the paper picked up from the paper container,
A driving force is applied in a direction opposite to that of the paper feed roller via a torque limiter. When there is no sheet and when there is one sheet, the drive force is accompanied by the sheet feed roller. A separation roller;
Urging means for urging the separation roller in a direction in pressure contact with the sheet feeding roller;
Release means for releasing the pressure contact force of the separation roller to the paper feed roller against the biasing force of the biasing means;
Reversing prevention means for preventing reversal of the paper feed roller accompanying reversal of the separation roller;
In a paper feeding device provided with a detecting means for detecting paper downstream in the conveyance direction of the paper feeding roller,
After the feeding operation is completed, the separation roller is applied with a driving force in the same direction as the paper feed roller until the detection unit detects paper.
A paper feeder characterized by that. The paper feeding device according to claim 1.
An opening / closing part that can be opened and closed when removing jammed paper in the apparatus;
Having a detecting means for detecting an open / closed state of the opening / closing part;
Immediately after the detection means changes from an open state to a closed state when a jam occurs, the separation roller is applied with a driving force in the same direction as the paper feed roller until the detection means detects paper.
A paper feeder characterized by that. The sheet feeding device according to claim 1 or 2,
Immediately after turning on the power, until the detection means detects the paper, the separation roller is applied with a driving force in the same direction as the paper feed roller.
A paper feeder characterized by that. In the paper feeding device according to any one of claims 1 to 3,
The sheet feeding device according to claim 1, wherein the detection unit is arranged at a position near the downstream side of the sheet feeding roller in the sheet conveyance direction. An image forming apparatus comprising the paper feeding device according to claim 1. 6. The image forming apparatus according to claim 5, wherein the image forming apparatus is a tandem apparatus capable of simultaneously performing exposure scanning on a plurality of photoconductors and forming images of different colors. Image forming apparatus.