JP2014185000A - Sheet feed device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet feed device that can efficiently release a separation nip portion with a small number of components and an image formation device.SOLUTION: A retard pressurized link 17, which is provided rotatably in a retard drive shaft 5 provided in parallel with a retard roller shaft 4 and supports rotatably the retard roller shaft 4, is energized by first energizing means so that a retard roller 1 pressure contacts a feed roller 2. Further in the retard drive shaft 5 is rotatably provided a retard pressure releasing link 15. When the paper feed cassette 6 is not installed, the retard roller shaft 4 is pressurized by the retard pressure releasing link 15 to separate the retard roller 1 from the feed roller 2. When the paper feed cassette 6 is installed, the retard pressure releasing link 15 is rotated so as to move the retard roller shaft 4 in a direction of pressure contacting the retard roller 1 with the feed roller 2.

Description

  The present invention relates to a sheet feeding apparatus and an image forming apparatus, and more particularly to a configuration of a separation unit that separates sheets one by one using a retard roller.

  Conventional image forming apparatuses such as printers, copiers, and facsimiles include a sheet feeding apparatus that feeds a sheet set in a sheet feeding cassette by a feeding roller and supplies the sheet to an image forming unit. The sheet feeding apparatus includes a separation unit that separates the sheets one by one in order to prevent double feeding of two or more sheets when the sheets are fed by a feeding roller.

  A retard roller separation type having a feed roller that rotates in the same direction as the feed roller and a retard roller that presses the feed roller with a predetermined pressure (hereinafter referred to as retard pressure) as the separation unit. There is. The retard roller is driven at a constant torque (hereinafter referred to as rotational torque) with respect to the rotation in the reverse direction (hereinafter referred to as reverse feed direction) to the rotation of the sheet feeding direction in which the sheet is fed via the torque limiter. The sheet can be rotated in both the sheet feeding direction and the reverse feeding direction. When two or more sheets enter the nip portion (hereinafter referred to as a separation nip portion) between the feed roller and the retard roller, the retard roller rotates in the reverse feeding direction, thereby preventing the double feeding of the sheets. Send out one by one.

  By the way, when the sheet feeding apparatus is not feeding a sheet, the leading edge of the sheet may be held between the separation nip portion of the retard roller and the feed roller. If the paper feeding cassette is pulled out from the apparatus main body in this state, the sheet may remain in the transport path and cause sheet jamming. In particular, this problem occurs remarkably in the case where the sheet feeding cassette is pulled out from the apparatus main body in a direction orthogonal to the sheet feeding direction.

  Therefore, in a sheet feeding apparatus having a conventional retard roller separation type separation unit, a separation mechanism that separates the retard roller from the feed roller by a link mechanism when the sheet feeding cassette is pulled out (Patent) Reference 1). FIG. 10 is a view showing a separation mechanism provided in such a conventional sheet feeding apparatus, and the separation mechanism includes a retard pressure press / release link 10, a first retard pressure link 11, and a second retard pressure link. 12 etc.

  When a paper feed cassette (not shown) is attached, the contact portion 23 of the second retard pressure link 12 shown in FIG. 10A is pressed by the paper feed cassette. When the second retard pressure link 12 is pressed, the first retard pressure link 11 moves in the direction of arrow a shown in FIG. 10B while resisting the retard pressure release spring 14. Along with this movement, the retard pressure pressurizing / releasing link 10 biased in the direction of arrow a by the retard pressurizing spring 13 rotates about the fulcrum 22 in the direction of arrow b. As a result, the pressing piece 21 provided on the retard pressure pressurizing / releasing link 10 comes into pressure contact with the retard roller shaft 4, and the retard roller 1 rises and comes into pressure contact with a feed roller (not shown).

  On the other hand, when the paper feed cassette is pulled out from the apparatus main body, the pressure on the contact portion 23 of the second retard pressure link 12 by the paper feed cassette is released, and the second retard pressure link 12 is moved by the retard pressure release spring 14 as shown in FIG. Move as shown in (c) of FIG. As a result, as shown in FIG. 10 (d), the first retard pressure link 11 moves in the direction of the arrow c, and the retard pressure pressurizing / releasing link 10 moves against the retard pressurizing spring 13 along with this. It rotates around the fulcrum 22 in the d direction. As a result, the pressing piece 21 provided on the retard pressure pressurizing / releasing link 10 is separated from the retard roller shaft 4, the retard roller 1 is separated from a feed roller (not shown), and the separation nip portion is released.

JP 2000-16618 A

  However, in such a conventional sheet feeding apparatus, the contact portion 23 of the second retard pressure link 12 serving as the power point shown in FIG. 10, the fulcrum 22, and the tip of the pressing piece 21 serving as the action point are separated from each other. The number of places where operating resistance is generated by the link increases. Moreover, since it is necessary to change the force transmission direction at a plurality of fulcrums, the transmission efficiency as a mechanism is deteriorated. Furthermore, when a plurality of links are used, there is a problem that the number of parts increases and the required space becomes wide.

  Accordingly, the present invention has been made in view of such a current situation, and an object of the present invention is to provide a sheet feeding device and an image forming apparatus that can efficiently release the separation nip portion with a small number of parts. Is.

  The present invention relates to a sheet feeding device, in which a sheet storage unit that is detachably attached to the apparatus main body, a feeding roller that feeds a sheet stored in the sheet storage unit, and a sheet fed by the feeding roller. A conveying roller that conveys, a separation roller that presses and contacts the conveying roller so as to separate the sheet together with the conveying roller, a separation roller shaft to which the separation roller is attached, and an apparatus main body. An arm member that is rotatably provided and rotatably supports the separation roller shaft, and a first urging member that urges the arm member to rotate in a direction in which the separation roller is pressed against the transport roller. Means, a rotating member that is rotatably provided in the apparatus main body, and has a contact portion that can contact the sheet storage portion and a pressing portion that can press the separation roller shaft, and the rotating member. The member is urged to press the separation roller shaft via the pressing portion so as to rotate in a direction in which the separation roller is separated from the transport roller, and acts on the separation roller shaft from the pressing portion. A biasing force that opposes the biasing force of the first biasing means that acts on the separation roller shaft by the arm member and that is larger than the biasing force; Is not attached to the apparatus main body, the rotating member is rotated by the second urging means, the separating roller shaft is pressed by the pressing portion, and the separating roller is separated from the conveying roller. When the sheet storage portion is attached to the apparatus main body, the rotation member is rotated in a direction to release the pressing of the separation roller shaft by the pressing portion by the pressing of the contact portion by the sheet storage portion. By the first biasing means, it is characterized in that for pressing the separation roller to the conveyance roller.

  As in the present invention, when the sheet storage unit is not mounted, the separation roller is separated from the transport roller by the rotating member, and when the sheet storage unit is mounted, the separation roller is pressed against the transport roller. The separation nip can be efficiently released with a small number of parts.

1 is a diagram illustrating a schematic configuration of a full-color laser beam printer which is an example of an image forming apparatus including a sheet feeding device according to a first embodiment of the present invention. The figure explaining the structure of the said sheet feeding apparatus. FIG. 4 is a diagram illustrating a configuration of a retard roller separation mechanism provided in the sheet feeding device. FIG. 6 is a first diagram illustrating an operation when the retard roller separation mechanism is mounted with a paper feed cassette. FIG. 10 is a second diagram illustrating an operation when the retard roller separation mechanism is mounted with a paper feed cassette. The figure explaining the state when the paper feed cassette of the said retard roller separation mechanism is taken out. The figure explaining the structure of the sheet feeding apparatus which concerns on the 2nd Embodiment of this invention. FIG. 4 is a diagram illustrating a configuration of a retard roller separation mechanism provided in the sheet feeding device. The figure explaining the state when the paper feed cassette of the said retard roller separation mechanism is taken out. FIG. 6 is a diagram illustrating a separation mechanism provided in a conventional sheet feeding apparatus.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a full-color laser beam printer which is an example of an image forming apparatus provided with a sheet feeding apparatus according to the first embodiment of the present invention.

  In FIG. 1, reference numeral 31 denotes a full-color laser beam printer (hereinafter referred to as a printer), 31A denotes a printer main body that is an image forming apparatus main body, and 31B denotes an image forming unit that forms an image on a sheet. Reference numeral 32 denotes an image reading apparatus installed substantially horizontally above the printer main body 31A. A sheet discharge space S for discharging sheets is formed between the image reading apparatus 32 and the printer main body 31A. Reference numeral 31 </ b> C denotes a sheet feeding device that feeds the sheet P from the sheet feeding cassette 6 that is a sheet storage unit that stores the sheet P. The paper feed cassette 6 is detachably attached to a printer main body 31A that also serves as a sheet feeding apparatus main body.

  The image forming unit 31B is of a four-drum full-color system, and forms four toner images of the laser scanner 28 and four colors of yellow (Y), magenta (M), cyan (C), and black (K). The process cartridge 36 is provided. Here, each process cartridge 36 includes a photosensitive drum 41, a charger 39 as a charging unit, and a developing unit 40 as a developing unit.

  In addition, the image forming unit 31B includes an intermediate transfer unit 31D disposed above the process cartridge 36 and a fixing unit 35. Reference numeral 43 denotes a toner cartridge for supplying toner to the developing device 40. The intermediate transfer unit 31D is provided inside the intermediate transfer belt 29 wound around the drive roller 29a and the tension roller 29b, and contacts the intermediate transfer belt 29 at a position facing the photosensitive drum 41. A primary transfer roller 42 is provided. Here, the intermediate transfer belt 29 is rotated in the direction of an arrow by a driving roller 29a driven by a driving unit (not shown).

  Then, by applying a positive transfer bias to the intermediate transfer belt 29 by the primary transfer roller 42, each color toner image having a negative polarity on the photosensitive drum is sequentially transferred to the intermediate transfer belt 29 in a multiple transfer manner. A secondary transfer roller 37 constituting a secondary transfer unit that transfers a color image formed on the intermediate transfer belt to the sheet P is provided at a position facing the driving roller 29a of the intermediate transfer unit 31D.

  Further, a fixing unit 35 is disposed above the secondary transfer roller 37, and a first discharge roller pair 34, a second discharge roller pair 34a, and a double-side reversing unit 31E are disposed at the upper left part of the fixing unit 35. . A control unit 31F controls the image forming operation of the image forming unit 31B and the sheet feeding operation of the sheet feeding device 31C.

  Next, an image forming operation of the printer 31 configured as described above will be described. First, when image information of a document is read by the image reading device 32, the image information is subjected to image processing, converted into an electrical signal, and transmitted to the laser scanner 28 of the image forming unit 31B. In the image forming unit 31B, the surface of the photosensitive drum 41 of each process cartridge 36 is scanned by the laser light emitted from the laser scanner 28. As a result, the surface of the photosensitive drum 41 whose surface is uniformly charged to a predetermined polarity and potential by the charger 39 is sequentially exposed, and yellow, magenta, cyan on the photosensitive drum of each process cartridge 36, respectively. And an electrostatic latent image of black are sequentially formed.

  Thereafter, the electrostatic latent image is developed and visualized with each color toner of yellow, magenta, cyan and black, and each color toner image on each photoconductive drum by the primary transfer bias applied to the primary transfer roller 42. Are sequentially superimposed on the intermediate transfer belt 29 and transferred. As a result, a toner image is formed on the intermediate transfer belt 29.

  In parallel with the toner image forming operation, the sheet P is fed from the sheet feeding device 31C, and the fed sheet P is conveyed to the registration roller pair 38. Thereafter, the sheet P is transported to the secondary transfer section after the skew is corrected by the registration roller pair 38. In this secondary transfer portion, the toner images are collectively transferred onto the sheet P by the secondary transfer bias applied to the secondary transfer roller 37.

  Next, the sheet P onto which the toner image has been transferred in this manner is conveyed to the fixing unit 35, and is fixed to the sheet P as a color image by receiving heat and pressure in the fixing unit 35. Thereafter, the sheet P on which the image has been fixed is discharged into the paper discharge space S by the first discharge roller pair 34 or the second discharge roller pair 34 a provided downstream of the fixing unit 35, and is formed on the bottom surface of the paper discharge space S. It is loaded on the protruding loading unit 45.

  FIG. 2 is a diagram illustrating the configuration of the sheet feeding apparatus 31C according to the present embodiment. 2A is a perspective view of the sheet feeding apparatus 31C, and FIG. 2B is a side view of the sheet feeding apparatus 31C. In FIG. 2, reference numeral 3 denotes a pickup roller that is a feeding roller that picks up the sheets stacked on the paper feed cassette 6, and 2 is a feed roller that is a conveying roller that conveys the picked-up roller. Reference numeral 1 denotes a retard roller that is a separation roller that constitutes a separation unit 1a that is in pressure contact with the feed roller 2 and separates a plurality of sheets one by one.

  2a is a feed roller shaft that is rotated by a drive unit (not shown), 4 is a retard roller shaft that is a separation roller shaft, and 5 is provided in parallel to the feed roller shaft 2a and the retard roller shaft 4, and is rotated by a drive unit (not shown). This is the retard drive shaft 5. The rotation of the retard drive shaft 5 is transmitted to the retard roller shaft 4 via the retard gear train 9, and the rotation of the retard roller shaft 4 is attached to one end of the retard roller shaft 4 in the axial direction via the torque limiter 8. Is transmitted to the retard roller 1. The pickup roller 3 rotates in the sheet feeding direction for feeding a sheet by the rotation of the feed roller shaft 2a transmitted through the gear train 3a.

  The retard roller 1 is driven by a constant torque (hereinafter referred to as rotational torque) with respect to the rotation in the direction opposite to the sheet feeding direction (hereinafter referred to as the reverse feeding direction) via the torque limiter 8, and the sheet feeding is performed. It is possible to rotate in either direction or reverse direction. The drive transmission force of the torque limiter 8 (a limit value at which drive transmission is interrupted) is always set to be larger than the friction force generated between the sheets due to the friction coefficient of the used sheet. Further, the drive transmission force (limit value) of the torque limiter 8 is set smaller than the frictional force due to the friction coefficient between the sheet and the feed roller 2.

  For this reason, when the number of sheets entering the nip portion (hereinafter referred to as the separation nip portion) between the feed roller 2 and the retard roller 1 is one or no sheet, the retard roller 1 rotates the feed roller 2. Take around. Further, when two or more sheets enter the separation nip, the retard roller 1 rotates in the reverse feeding direction opposite to the feeding direction to prevent double feeding of the sheets. The retard roller shaft 4 is supported in a cantilever manner by a shaft support portion 24 provided on the paper feed frame 7 and can swing in the vertical direction.

  In FIG. 2, reference numeral 27 denotes a retard roller separation mechanism. As shown in FIG. 3, the retard roller separation mechanism 27 includes a retard pressure release link 15 that is a rotating member that is rotatably supported by a retard drive shaft 5 that is a support shaft. In addition, a retard pressure pressurizing link 17 which is an arm member which is rotatably supported by the retard drive shaft 5 and rotatably supports the retard roller shaft 4 is provided.

  The retard pressure pressurizing link 17 is urged upward by a retard pressurizing spring 16 as a first urging means so as to press the retard roller 1 against the feed roller 2. The retard pressure release link 15 is urged downward by a retard pressure release spring 18 as a second urging means so as to separate the retard roller 1 from the feed roller 2. Here, the urging force of the retard pressure release spring 18 is large enough to press the retard roller shaft 4 against the urging force of the retard pressure spring 16 when the paper feed cassette 6 is not attached to the apparatus main body. Is set to

  FIG. 4 shows a state when the paper feed cassette 6 is mounted. In the present embodiment, the paper feed cassette 6 is mounted from the width direction orthogonal to the sheet feeding direction indicated by the arrow in FIG. When the paper feed cassette 6 is mounted, the inclined surface 6a of the pressing portion 6c provided at the upper end of the paper feed cassette 6 and having the inclined surface 6a and the pressing surface 6b is provided so as to be able to contact the retard pressure release link 15. The contact part 23 is pressed. Then, the paper feed cassette 6 is mounted, and the pressing surface 6b of the pressing portion 6c presses the contact portion 23.

  As a result, as shown in FIG. 5A, the retard pressure release link 15 that has been urged downward by the retard pressure release spring 18 and rotated downward is resisting the retard pressure release spring 18. As shown in FIG. 5B, it rotates upward. The retard pressure release link 15 is formed with a pressing portion 15a that can press the retard roller shaft 4 from above. Until the paper feed cassette 6 is mounted, the retard roller shaft 4 is pressed by the pressing portion 15a of the retard pressure releasing link 15 rotating downward as shown in FIG. The retard roller 1 is held away from the feed roller 2.

  Here, when the retard pressure releasing link 15 rotates upward, the pressing of the retard roller shaft 4 by the pressing portion 15a is released. At this time, the retard roller shaft 4 rises because it is urged upward by the retard pressure spring 16 via the retard pressure link 17 as shown in FIG. (B), the retard roller 1 contacts the feed roller 2.

  On the other hand, when the paper feed cassette 6 is taken out, the pressing of the retard pressure release link 15 by the pressing portion 6c provided at the upper end of the paper feed cassette 6 is released as shown in FIG. As a result, the retard pressure release link 15 rotates downward by the action of the retard pressure release spring 18 as shown in FIG. Here, the urging force of the retard pressure release spring 18 acting on the retard roller shaft 4 is opposed to the urging force of the retard pressure spring 16 acting on the retard roller shaft 4 by the retard pressure pressing link 17, and It is larger than its energizing force.

  For this reason, when the retard pressure release link 15 rotates downward, the retard roller shaft 4 is pressed by the pressing portion 15 a, and the retard pressure pressurizing link 17 rotates downward against the retard pressurizing spring 16. As a result, as shown in FIGS. 6A, 6B and 6C, the retard roller 1 moves downward to leave the feed roller 2 and the roller nip is released.

  As described above, in the present embodiment, the retard roller 1 is separated from the feed roller 2 by the retard pressure release link 15 when the paper feed cassette 6 is not attached to the apparatus main body. Further, when the paper feed cassette 6 is mounted on the apparatus main body, the retard roller 1 is pressed against the feed roller 2. With this configuration, in the retard roller separation mechanism, the number of links becomes only the retard pressure release link 15 and is reduced. Therefore, the force point formed by the contact portion 23 of the retard pressure release link 15 and the pressing portion 15 a that presses the retard roller shaft 4. The configured action point is close.

  Further, the rotation center of the retard pressure release link 15, the force point, and the action point are positioned substantially in parallel along the sheet feeding direction. As a result, the number of places where resistance is generated is reduced, and the transmission efficiency is improved. As a result, malfunctions are less likely to occur and the stability of the operation is increased. Further, by using the retard drive shaft 5 as the rotation center of the retard pressure release link 15, the number of parts is reduced, and the separation nip portion can be efficiently released with a small number of parts. Furthermore, space saving and cost reduction can be achieved.

  Next, a second embodiment of the present invention will be described. FIG. 7 is a diagram illustrating the configuration of the sheet feeding apparatus according to the present embodiment. 7A is a perspective view of the sheet feeding apparatus, and FIG. 7B is a side view of the sheet feeding apparatus. In FIG. 7, the same reference numerals as those in FIG. 2 described above indicate the same or corresponding parts.

  In FIG. 7, reference numeral 19 denotes a retard roller holder that holds the retard roller shaft 4, and this retard roller holder 19 has a retard holder shaft 25 provided in parallel to the feed roller shaft 2 a and the retard roller shaft 4 as a rotation center. Rotate. Reference numeral 20 denotes a coupling provided between a drive unit (not shown) and the retard roller shaft 4, and the drive from the drive unit is transmitted to the retard roller shaft 4 via the coupling 20. Further, the rotating end of the retard roller holder 19 is biased upward by the retard pressure spring 16 shown in FIG. 6 described above, whereby the retard roller shaft 4 moves upward, and the retard roller 1 is Press contact with a feed roller (not shown).

  In the sheet feeding apparatus having such a configuration, when the sheet feeding cassette 6 is mounted, as shown in FIG. 5 described above, the retard pressure that has been rotated downward by being biased downward by the retard pressure release spring 18. The release link 15 rotates upward while resisting the retard pressure release spring 18. When the retard pressure release link 15 rotates upward, the pressing of the retard roller shaft 4 by the pressing portion 15a is released. At this time, the retard roller holder 19 holding the retard roller shaft 4 is lifted upward by the retard pressurizing spring 16, and as shown in (a) to (c) of FIG. The retard roller 1 contacts the feed roller 2.

  On the other hand, when the paper feed cassette 6 is taken out, the pressing of the retard pressure release link 15 by the pressing portion 6c provided at the upper end of the paper feed cassette 6 is released as shown in FIG. As a result, the retard pressure release link 15 rotates downward by the action of the retard pressure release spring 18 as shown in FIG. When the retard pressure release link 15 rotates downward as described above, the retard roller shaft 4 is pressed by the pressing portion 15a, and the retard roller holder 19 rotates downward against the retard pressure spring 16. As a result, as shown in FIGS. 9A to 9C, the retard roller 1 moves downward to move away from the feed roller 2, and the roller nip is released.

  As described above, also in the present embodiment, the number of links of the retard roller separation mechanism is as small as only the retard pressure release link 15, and the force point, fulcrum, and action point are positioned substantially linearly in the sheet feeding direction. Can do. For this reason, the number of places where resistance is generated is reduced, and the transmission efficiency is improved.

DESCRIPTION OF SYMBOLS 1 ... Retard roller, 2 ... Feed roller, 2a ... Feed roller shaft, 3 ... Pick-up roller, 4 ... Retard roller shaft, 5 ... Retard drive shaft, 6 ... Paper feed cassette, 6c ... Pressing part, 8 ... Torque limiter, 15 ... retard pressure release link, 16 ... retard pressure spring, 17 ... retard pressure press link, 18 ... retard pressure release spring, 27 ... retard roller separation mechanism, 31 ... full color laser beam printer, 31A ... printer body, 31B ... image Forming unit, 31C ... sheet feeding device, P ... sheet

Claims (8)

A sheet storage unit that is detachably attached to the apparatus body;
A feeding roller for feeding out the sheet stored in the sheet storage unit;
A transport roller for transporting the sheet fed by the feed roller;
A separation roller that constitutes a separation unit that presses and contacts the conveyance roller so as to separate the sheet together with the conveyance roller;
A separation roller shaft to which the separation roller is attached;
An arm member rotatably provided in the apparatus main body, and rotatably supporting the separation roller shaft;
First urging means for urging the arm member so as to rotate in a direction in which the separation roller is pressed against the conveying roller;
A rotating member provided in the apparatus main body so as to be rotatable, and having a contact portion that can contact the sheet storage portion and a pressing portion that can press the separation roller shaft;
The rotating member is urged so as to rotate in a direction in which the separation roller is separated from the transport roller by pressing the separation roller shaft through the pressing portion, and from the pressing portion to the separation roller shaft. A biasing force acting on the separation roller shaft by the arm member, and a biasing force that is opposed to the biasing force of the first biasing means and that is greater than the biasing force.
When the sheet storage unit is not attached to the apparatus main body, the rotation member is rotated by the second urging unit, the separation roller shaft is pressed by the pressing unit, and the separation roller is conveyed. When the sheet storage portion is mounted on the apparatus main body while being separated from the roller, the rotation member is moved in a direction to release the pressing of the separation roller shaft by the pressing portion by the pressing of the contact portion by the sheet storage portion. The sheet feeding device according to claim 1, wherein the sheet feeding device is rotated and the separation roller is pressed against the conveying roller by the first urging unit. A support shaft provided in parallel with the separation roller shaft;
The sheet feeding device according to claim 1, wherein the arm member and the rotating member are rotatably supported by the support shaft.   The rotation member includes the contact portion, a rotation center, and the pressing portion, and the contact portion, the rotation center, and the pressing portion are positioned substantially parallel along the sheet feeding direction. The sheet feeding apparatus according to claim 2, wherein the sheet feeding apparatus is a sheet feeding apparatus.   4. The sheet feeding apparatus according to claim 1, wherein the separation roller shaft is cantilevered by the apparatus main body. 5.   The sheet feeding apparatus according to claim 2, wherein the support shaft is a shaft that transmits driving to the separation roller shaft.   5. The sheet feeding apparatus according to claim 1, wherein driving of the separation roller shaft is transmitted via a coupling. 6.   The sheet feeding apparatus according to claim 1, wherein the separation roller is rotatable in a sheet feeding direction or a reverse feeding direction opposite to the sheet feeding direction.   An image forming apparatus comprising: an image forming unit that forms an image on a sheet; and a sheet feeding device according to claim 1 that feeds the sheet to the image forming unit. apparatus.

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