Abstract:
The present invention relates to a separation member in contact with a sheet for separating the sheet with frictional force, comprising plurality of protrusion members, each structured of a supporting portion upright from an operation surface for the sheet and a distal end portion formed at a distal end of the supporting portion capable of contacting to the sheet. The supporting portion of the protrusion member is inclined toward a downstream side in a sheet feeding direction with respect to a direction perpendicular to the operation surface of the sheet.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Intention  
           [0002]    This invention relates to a roller member for conveying sheets by frictional force thereof in contact with the sheets and, more particularly, to a roller member capable of accurately conveying and separating the sheets even for the sheets in any size, and a sheet conveyance apparatus as well as an image forming apparatus such as a photocopier, a printer, a word processor, a facsimile machine, using this member.  
           [0003]    2. Related Background Art  
           [0004]    An example of a laser beam printer equipped with a conventional sheet feeding apparatus is shown in FIG. 10. This printer separately feeds one by one the sheets P contained in a sheet cassette  101  in a stacking manner by a feeding roller  102   a  as a sheet feeding apparatus and a roller  102   b  rotating integral with the feeding roller  102   a , and a separation pad  108  capable of contacting to the feeding roller  102   a  or the roller  102   b . The sheet is conveyed to the image forming section  106  including, e.g., a photosensitive drum  106   a  and a developing unit  106   b  by conveyance rollers  104   a ,  104   b  and registration rollers  105   a ,  105   b , and the toner image formed at the image forming section  106  is transferred to be formed as image. The sheet P after the toner image is transferred is conveyed to a fixing unit  107  to fix thermally the toner image, and is delivered to A delivery portion  108 .  
           [0005]    The separation pad  103  is structured of an elastic member such as a rubber or the like in contact with the feeding roller  102   a , and a surface  106  thereof is furnished with polishing processing or slicing processing in a direction perpendicular to the sheet feeding direction, thereby separating the recording sheet P with frictional characteristics.  
           [0006]    The conventional sheet feeding apparatus described above however, raises the following problems. For example, where feeding force is set largely in aiming at a thick sheet of about 200 g/m 2 , if a thin sheet of about 60 g/m 2  is tried to be fed, the sheets in a plural number are inevitably fed at the same time. To separate the sheets, some plans, are used such that pushing force exerted to the feeding roller  102   a  of the separation pad  103  is largely set to raise nipping pressure or that the separation pad  103  is made in use of a material having a higher frictional coefficient.  
           [0007]    Even where the pushing force of the separation pad  103  is increased as described above, no effect is given except the nipping portion, so that considerably large pushing force is needed to operate separation function only by the nipping portion. Large drive force is therefore required for the feeding roller  102   a , so that the drive motor is needed to have a large capacity, and so that this may raise a problem that extraordinary noises called as “screaming” tend to occur where the frictional force among the separation pad  103 , the feeding roller  102   a , and the roller  102   b  is strong.  
           [0008]    In a case that a material having a high frictional coefficient is used for the separation pad  103 , the fictional coefficient may be changed from wearing due to durable situation or the like, and therefore, this raises a problem that the feeding property may be dropped.  
           [0009]    In addition, in a case of the separation pad  103  having a high frictional coefficient, a thin sheet fed from the feeding roller  102   a  way hit the separation pad  103  during conveyance of the thin sheet, thereby raising a problem that the sheet front end receives damages, or namely, “front edge folding” may occur.  
           [0010]    Substantially the same phenomenon may occur in sheets being left under a high humidity circumstance and absorbing moisture during a sheet conveyance period for the sheets other than the thin sheets.  
           [0011]    Moreover, there raises a problem that the separation performance may be dropped due to reduction of the frictional coefficient from attachments of paper powder.  
         SUMMARY OF THE INVENTION  
         [0012]    This invention is accomplished in consideration of the problem described above It is an object of the invention to provide a separation member having a good separation performance for a long period about various sheet materials from a thin sheet to a thick sheet including such as OHT, gross paper, and the like, ad a sheet feeding apparatus and an image forming apparatus having this separation member.  
           [0013]    A representative structure according to the invention to accomplish the above object is a separation member in contact with a sheet for separating the sheet with frictional force, including a plurality of protrusion members, each structured of a supporting portion upright from an operation surface for the sheer and a distal end portion formed at a distal end of the supporting portion capable of contacting to the sheet, wherein the supporting portion of the protrusion member is inclined toward a downstream side in a sheet feeding direction with aspect to a direction perpendicular to the operation surface of the sheet. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a cross section showing an essential portion of an image forming apparatus equipped with a feeding apparatus according to a first embodiment;  
         [0015]    [0015]FIG. 2 is a substantially front view of the feeding apparatus according to the first embodiment;  
         [0016]    [0016]FIG. 3 is a cross section showing an essential portion of the feeding apparatus according to the first embodiment;  
         [0017]    [0017]FIG. 4 is an illustration showing feeding operation in the feeding apparatus according to the first embodiment;  
         [0018]    [0018]FIG. 5 is an illustration showing a separation pad of tho feeding apparatus according to the first embodiment;  
         [0019]    [0019]FIG. 6 is an illustration showing the separation pad of the feeding apparatus according to the first embodiment;  
         [0020]    [0020]FIG. 7 is an illustration showing the separation pad of the feeding apparatus during the feeding operation according to the first embodiment;  
         [0021]    [0021]FIG. 8 is an illustration showing a separation pad of the feeding apparatus according to a second embodiment;  
         [0022]    [0022]FIG. 9 is an illustration showing the separation pad of the feeding apparatus during the feeding operation according to the second embodiment; and  
         [0023]    [0023]FIG. 10 is a cross section showing essential portion of an image forming apparatus equipped with a feeding apparatus as a prior art. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    [First Embodiment] 
         [0025]    Hereinafter, an embodiment of a feeding apparatus according to this invention is described with an example of a laser beam printer serving as an image forming apparatus in use of an electrophotographic method in which laser beam is scanned on a photosensitive drum to make recording.  
         [0026]    [The Whole Structure] 
         [0027]    [0027]FIG. 1 is a cross section showing an essential portion of an image forming apparatus  1  equipped with a feeding apparatus according to a first embodiment; FIG. 2 is a substantially front view of the feeding apparatus  2  according to the first embodiment.  
         [0028]    An outlined structure of the laser beam printer of the embodiment is described as below.  
         [0029]    In the drawings, numeral  3  is a feeding tray seam as a sheet staking means for stacking sheets P serving as sheets fed in the image forming apparatus, and sheets P are stacked on a sheet stacking surface  3   a  of the feeding tray  3 . The sheet P its pushed by a pressure plate  5  as a pushing member to a feeding roller  4  as a feeding means disposed on an upper front end side e)f the feeding tray  3 , and is picked up. The sheets P me separated and fed one by one with a separation pad unit  6  structuring the separating means and with the feeding roller  4 , and are conveyed to a transfer section with the conveyance rollers  7   a ,  7   b  as a conveying means.  
         [0030]    Numeral  8  is a registration server, which synchronizes emission timing of a laser scanner  9  as an exposure light source to the front end position of the sheet P, thereby depicting the images from a prescribed position on the sheet P. Numeral  10  is a returning mirror.  
         [0031]    Numeral  11  is a process cartridge  11  as image forming means made of, e.g., a photosensitive drum  12 , a developing unit, a cleaner, a charging roller; numeral  13  is a transfer roller for transferring emerged images on the photosensitive drum  12  to the sheet P; numeral  14  is a conveyance guide for guiding the transferred sheet P to the fixing unit  15 ; and the fixing unit  15  thermally fixes the emerged images on the sheet P. The sheet P is delivered onto a delivery tray  18  formed integral with an outer cover  17  by a delivery roller  16 .  
         [0032]    [About Sheet Conveyance Angle] 
         [0033]    As shown in FIG. 1, the feeding apparatus  2  having the feeding roller  4 , the pressure plate  5 , and the separation pad unit  6 , the transferring means for transferring the emerged images on the photosensitive drum  12  by the transfer roller  13  onto the sheet P, and the fixing unit  15  for thermally fixing the toner images on the sheet P are disposed substantially linearly as extending obliquely upward where the fixing unit  15  is located at the topmost position.  
         [0034]    The sheet P stacked an the feeding tray  3  is conveyed to the transfer unit by the conveyance roller  7  along the substantially straight conveyance route after fed by the feeding roller  4 , and is thereafter conveyed to the fixing unit  15  concurrently with the toner image transfer by the photosensitive drum  12  and the transfer roller  13  in a sandwiching manner. Because the conveyance route during this for the sheet P is substantially straight, frictional noises between the sheet P and the guide member during the sheet conveyance can be reduced, and the sheet P can be conveyed stably, so that the apparatus has a structure that reliability on the sheet conveyance can be improved.  
         [0035]    The fixing unit  15  is disposed at the topmost location in the sheet conveyance route, and therefore, heats generated from the fixing unit  15 , even where the printing operation is made successively, are discharged to the exterior of the apparatus out of the louver portion, not shown, formed in the outer cover  17 , so that the apparatus can obtain always good output images without receiving any influence from the heats generated from the fixing unit  15  because the process cartridge  11  and the laser scanner  9  are disposed below or on a side of the fixing unit  15 .  
         [0036]    [Arrangement of the Laser Scanner] 
         [0037]    The laser scanner  9  as shown in FIG. 1 is disposed on an upper left side with respect to a scanner polygon  9   a  as a unit location. To make compact the size of the image forming apparatus as much as possible, it is most effective to render the laser beam incident to the photosensitive drum  12  in a direction perpendicular to the sheet conveyance route from the feeding apparatus  2  via the transferring means to the fixing unit  15  as shown in FIG. 1. With such a structure, the depth and height of The image forming apparatus can be designed to the minimum size.  
         [0038]    Because a scanner motor  9   b  rotating the scanner polygon mirror  9   a  is held substantially in a horizontal state, no load is exerted to a bearing of the scanner motor, so that any problem such that wearing of the bearing renders the duration of the scanner motor  9   b  short may not occur, so that the apparatus can be used for a long time.  
         [0039]    With a structure shown in FIG. 1, the process cartridge  11  is detachably attached horizontally in a direction toward the feeding tray  3 , and the jamming recovery in the image forming apparatus and replacement of the process cartridge  11  can be done in the same direction, so that the usability is much improved.  
         [0040]    [About Electronic Equipment System Layout] 
         [0041]    An electronic equipment unit  19  made of an AC power source, a DC, power source, and a high voltage power source is disposed below the sheet Conveyance route directing an obliquely upper side from the feeding apparatus  2  to the bring unit  15  as shown in FIG. 1, and the space in the electronic equipment unit is structured to be wider from the feeding area to the fixing area. With this structure, a route of air flow generated by heats generated front the electronic equipment unit  19  is ensured.  
         [0042]    Heats generated from the fixing unit  15  disposed at a top of the electronic equipment Sit  19  is exhausted to the exterior of the apparatus through a louver portion, not shown, formed in the outer cover  17 . At that time, a space is formed between the rear surface of the fixing unit  15  and the outer cover  17 , thereby producing air flow thereat form waste heats out of the fixing unit  15 .  
         [0043]    Accordingly, in forming the large space below the fixing unit  15  as described above, arranging the electronic equipment unit  19 , and forming the space on the rear surface side of the fixing unit  15 , air flow may be generated for waste heats from the electronic equipment unit  19  to the fixing unit  15  even where no fan or the like is provided for cooling purpose, so that heat remaining inside the image forming apparatus is cut out, and so that the apparatus prevents the temperature from increasing.  
         [0044]    [About Arrangement of the Drive Source] 
         [0045]    A motor  20  as a drive source is directly mounted on an inner side of a side wall as a part of the frame of the image forming apparatus as shown in FIG. 1, and attached with screws. The motor  20  is disposed below the sheet conveyance surface for feeding, transferring, and fixing.  
         [0046]    Where the motor is disposed below the sheet conveyance portion this allows corresponding flexibly to larger motors and changes from a stepping motor to a DC motor when corresponding to faster operation of the image forming apparatus. This can accomplish easily a faster operation from, e.g., 10 ppm to 20 ppm.  
         [0047]    Herein, the outline structure of the laser printer is described. Subsequently, the structure of the feeding apparatus  2  in this embodiment is described.  
         [0048]    [About the Feeding Apparatus] 
         [0049]    Next, a structure of the sheet feeding apparatus is described in detail. FIG. 3 is a cross section showing an essential portion of the feeding apparatus according to the first embodiment; FIG. 4 is a schematic part cross Portion showing the feeding apparatus  2 .  
         [0050]    As shown in FIG. 2, FIG. 3, the feeding roller  4  as a feeding meals is constituted of a half moon shape roller having a cross section in a letter D and a shaft  21 . Rollers  22  ( 22   a ,  22   b  ) held rotatably at the shaft  21  are formed at respective sides of the feeding roller  4 . The rollers  22  is in a circular shape and has a diameter slightly smaller than the maximum outer shape of the feeding roller  4 . A gear  23  exists on one end of the shaft  21 . The feeding roller  4  rotates in reception of drive via the gear  23  from the motor  20 .  
         [0051]    The pressure plate  5  is urged by pressure spring  24 ,  25  and pushes the sheet P to the feeding roller  4  during feeding of the sheet P. The separation pad  26  is formed at a portion where the pressure plate  5  pushes the sheet P to the feeding roller  4 . The separation sheet  26  is made of a caulk or synthetic word surface and has a frictional coefficient with respect to the sheet P of about 0.5 to 1.0, thereby contributing prevention of doubly feeding of the bottom most sheet in rho sheets P on the pressure plate  5 .  
         [0052]    The separation pad  6  is structured of a separation pad  6   a  made of an elastic body for separating the fed sheets P to one sheet and a holder  6   b  for holding the separation pad  6   a . The separation pad  6  is in contact with the feeding roller  22  with a pad spring  27  during the apparatus is in a waiting state.  
         [0053]    Width regulating plates  28 ,  29  formed at the pressure plate  5  are movable in a sheet width direction in matching with the sheet size on the pressure plate Lo regulate the sheet width of the sheet P.  
         [0054]    Cams  30 ,  31  are secured around the opposite ends of the sheet  21  and are in contact with cam portions  5   a ,  5   b  of the pressure plate  5 . The cams  30 ,  31  while in an apparatus waiting state, urges the pressure plate  5  in opposing to the pressure spring  24 ,  25  so as not to render the sheet in contact with the feeding roller  4 . The shaft  21  and the pressure plate  5  are rotatably held to the frame  32 . Numeral  33  is a sheet guide from the feeding roller  4  to the conveyance roller  7 .  
         [0055]    [About Feeding Operation and Sheet Separation Property] 
         [0056]    Referring to FIG. 4 through FIG. 7, the feeding operation and the feature of the separation pad unit  6  are described. It is to be noted that: FIG. 4 is a partly cross section during feeding operation of the sheet feeding apparatus; FIG. 5 and FIG. 6 are enlarged views of the separation pad  6   a  used for the sheet feeding apparatus. FIG. 7 is an enlarged operation diagram of the separation pad  6   a  during the feeding operation of the sheet feeding apparatus.  
         [0057]    The feeding roller  4  receives drive force via the gear  23  from the motor  20  and rotates in a direction of arrow D in FIG. 4. The cams  30 ,  31  of the pressure plate  5  arc stopped urging the pressure plate  5  according to the rotation of the feeding roller  4 , and the pressure plate  5  pushes the sheet P with force of the pressure springs  24 ,  25  to the feeding roller  4 . The sheets P in a several number around a top of the sheets P in contact with the feeding roller  4  are conveyed by the feeding roller  4 , and subsequently, are separated to one sheet P in contact with the feeding roller  4  with the separation pad  6   a  of the separation pad unit  6 .  
         [0058]    [0058]FIG. 5 shows a detail of the nipping portion N of the separation pad  6   a  and the separation pad surface  6   c  in a downstream side range W 2  in the sheet feeding direction (hereinafter, simply referred to as “downstream side range”) with respect to the nipping portion N; FIG. 6 shows a detail of the separation pad surface  6   c  in an upstream side range W 1  in the sheet feeding direction (hereinafter, simply referred to as “upstream side range”).  
         [0059]    Numeral  6   d  is a three-dimensional structural body as a fine protrusion member on the separation pad  6   a  and is structured of a supporting portion  62  and a distal cad portion  63 . This three-dimensional structural body  6   d  is made of the cylindrical supporting portion  62  (in this embodiment, having a cylindrical shape of diameter r) upright from an elastic base  61  as a sheet operation surface of the invention, and a spherical distal end portion  63  (in this embodiment, having a spherical shape of diameter R where r&lt;R) formed At a tip of the supporting portion, thereby forming the body in a mushroom shape with a height in a range of 1 to 500 micron meters.  
         [0060]    The supporting portion  62  is formed in a way slant with an angle alpha with respect to the elastic base  61  toward the sheet feeding direction. The distal cad portion  63  is a spherical shape of a diameter R and is formed with a distance L micron meters to the adjacent three-dimensional structural bodies  6   d  as arranged orderly in the sheet feeding direction as well as a direction perpendicular to the sheet feeding direction.  
         [0061]    The three-dimensional structural body  6   d  in this embodiment is structured of an ether based urethane resin of the same material as the elastic base  61 . It is to be noted that as a usable material for the elastic base  61 , exemplified are natural rubber, ethylene-propylene rubber (EPR), ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber (SBR), butyl rubber (IIR), silicone rubber, urethane rubber, etc., and caulk, butyl-isopropyl-ethylene rubber, etc.  
         [0062]    The supporting portion  62  in the nipping portion N of the separation pad  6   a  and the downstream side range W 2  is in the cylindrical shape of diameter r, and the supporting portion  62  in the upstream side range W 1  is in the cylindrical shape of diameter (r−Δr). Here, a formula r&gt;r−Δr is satisfied. That is, the supporting portion  62  of the upstream side range W 1  is thinner than the supporting portion in the downstream side range W 2 , so that the elastic force is made smaller by that portion.  
         [0063]    [0063]FIG. 7( a ) shows a contact state between the separation pad in the upstream side range W 1  of the separation pad and the recording sheet P. FIG. 7( b ) shows a contact state between the separation pad in the nipping portion N as well as the downstream side range W 2  and the recording sheet P.  
         [0064]    Where the recording sheets P of two sheets or more are conveyed by the conveyance roller  1 , the front and of the recording sheet P first enters in the upstream side range W 1  of the separation pad. At that time, the front and hits the digital and portions of  63  the three-dimensional structural body  6   d  of the separation pad. Because the diameter of the supporting portion  62  is designed to be smaller by Δr than the diameter r of the supporting portion  62  set so as to be obtain necessary separation frictional force at the nipping portion and the downstream side range W 2 , the three-dimensional structural body  6   d  is elastically transformed properly in a sheet feeding direction (arrow C direction) in association with entry of the recording sheet. Because the distal end is in a spherical shape, this does not give abrupt resistance to the front end of the recording sheets, so that the recording sheets can be separated in preventing the recording sheets from receiving damages at the front end such as “front edge folding” or the like.  
         [0065]    With the recording sheet of a plural number conveyed to the downstream side as not separated completely in the upstream side range W 1 , as shown in FIG. 7( b ), the recording sheets in contact with the feeding roller at the nipping portion N are conveyed in arrow C direction, and the recording sheets on the downstream side are held on the separation pad by the friction between the distal end portion  63  of the three-dimensional structural body  6   d  and the recording sheet. At that time, where the frictional coefficient among further overlapping recording sheets is large, the sheets tend to be conveyed in arrow C direction. In such a case, however, the front end of the recording sheet hits the distal end portions  63  of the three-dimensional structural body, and because the supporting portions  62  at the nipping portion and the downstream side range W 2  have the adequate elastic force to separate the sheets, the sheets are prevented from being doubly fed.  
         [0066]    As described above, with the separation pad  6   a  in this embodiment, the distal end  63  of the three-dimensional structural body  6   d  during a series of separation operations always obtains a constant contact area to any recording sheet having any physical property including the weight per unit area, so that the frictional force exerted to the recording sheet P is made stable, thereby improving the separation performance. Thus, the pushing force by the pad spring  27  of the Separation pad unit  6  can be set lower than that of the conventional example, thereby reducing the friction of the separation pad  6   a , and improving the durability. The separation pad  6   a  can be made of a rubber material or the like having a high resistance against wearing, and since the required drive torque for the feeding roller can be made smaller in comparison with the conventional structure, the sheet feeding apparatus having excellent durability and stable separation property can be provided with reduced costs.  
         [0067]    When the sheet is separated, as shown in FIG. 7( b ), even where foreign objects S such as paper powder or the like are attached to the sheet P, the foreign objects may not be attached to the distal end portion  63  because dropping to the elastic base  61 , so that the objects do not affect the sheet separation force. Accordingly, the stable separation feature is maintained for, a long time.  
         [0068]    Where the recording sheet is entered with a deep angle with respect to the surface of the separation pad  6   a , the front end of the recording sheet may not be engaged with the three-dimensional structural body, so that the recording sheet may not receive any damage, and so that the stable separation performance is obtained.  
         [0069]    With this apparatus, the materials can be selected widely regarding the rubber material of the separation means and the rubber material of the pushing portion of the pushing means, so that this apparatus can enjoy a high performance separation operation even in use of an inexpensive, highly durable rubber material, an that the feeding apparatus of such a high performance can be provided with a lower price.  
         [0070]    [Second Embodiment] 
         [0071]    Next, a separation pad of a second embodiment is described. It is to be noted that the differences only from those in the first embodiment are described herein, and others are omitted.  
         [0072]    [0072]FIG. 8 is an structural enlarged view the upstream side range W 1  of the separation pad  6   a  used for the sheet feeding apparatus according to the second embodiment; FIG. 8 is an structural enlarged view the upstream side range W 1  of the separation pad  6   a  during feeding operation of the sheet feeding apparatus.  
         [0073]    Numeral  6   d  is a three-dimensional structural body on the separation pad  6   a  and is made of a supporting portion  62  and a distal end portion  63 . The supporting portion  62  is in a cylindrical shape having a diameter r and is formed as inclined with an angle β in directing the downstream side in the sheet feeding sir with respect to the elastic base  61 . The angle β is set smaller than the inclined angle α in the first embodiment described above (β&gt;α).  
         [0074]    The distal end portion  63  is in a spherical shape having a diameter of R micron meters and is formed with a distance L micron meters to the adjacent three-dimensional structural bodies as arranged orderly in the sheet feeding direction but with a distance L micron meters in a direction perpendicular to the sheet feeding direction su shifted by L/2 in the sheet feeding direction, to form an arrangement of three-dimensional structural bodies in a staggered form.  
         [0075]    It is to be noted that the three-dimensional structural body  6   d  is formed with an ether based urethane rubber as the same material as the elastic base  61  in substantially the same way as in the first embodiment.  
         [0076]    It is to be noted that the shapes of the three-dimensional structural body  6   d  of the nipping portion N of the separation pad  6   a  and of the separation pad  6   a  in the downstream side range W 2  are the same shape as that in the first embodiment, and the arrangement is the same as the staggered arrangement of the three-dimension structural bodies  6   d in the upstream side range W 1 .  
         [0077]    With the separation pad  6   a  of the above structure, where the recording sheets P of two sheets or more arc conveyed by the feeding roller  1 , the front end of the recording sheet first enters in the upstream side range W 1  of the separation pad as shown FIG. 9. At that time, the front end hits the distal end portion  63  of the three-dimensional structural body  6   d  of the separation pad. Because the angle β of the supporting portion  62  is set smaller than the angle a of the supporting portion  62  so designed as to have a necessary separation friction force at the nipping portion, no abrupt resistance is given to the recording sheet front end when the recording sheet P is entered, thereby allowing separation of the recording sheets in preventing surely the recording sheets from receiving damages at the front end such as “front edge folding” or the like.  
         [0078]    Where the entering angle of the recording sheet to the separation pad is changed to a direction extending further, perpendicular to the separation pad surface due to curling at the front end of the recording sheets, a problem such that the recording sheet front end digs into a portion on an upstream side of the three-dimensional structural body, or namely “turning” may not occur, because the three-dimensional structural bodies  6   d  are in the staggered form in the sheet feeding direction, so that the sheets can be guided toward the downstream side.  
         [0079]    [Other Embodiments] 
         [0080]    In the second embodiment, the three-dimensional structural bodies  6   d  are disposed in a staggered manner, but in the first embodiment the three-dimensional structural bodies  6   d  ran be disposed in a staggered manner. In the above embodiments, setting the shape of the supporting portion of the protrusion member to an arbitrary setting value according to kinds of the recording sheets to be fed can do a stable feeding.  
         [0081]    Although in the above embodiments the supporting portion  62  of the three-dimensional structural bodies  6   d  is the cylindrical shape, any of a hollowed cylindrical shape, elliptic cylindrical shape, a polygonal prism shape, a cone shape, a elliptical cone shape, and a polygonal pyramid shape, is useable for the supporting portion. The distal end portion  63  is in the spherical shape, but can be in a shape of a half moon shape, a disc shape, a cone shape, and the like.  
         [0082]    Although in the above embodiment the distance between the adjacent three-dimensional structural bodies  6   d  and the shape of the distal end portion  63  are set constant, those can be formed in various shapes. With such a structure, resonance of vibrations of the respective three-dimensional structural bodies occuring from frictional contacts among the separation pad, the feeding roller, and the recording sheet can be suppressed, and amplification of extraordinary noises can be prevented  
         [0083]    Although in Lie above embodiments the example in which the sheet feeding apparatus is used for the image forming apparatus is shown, this apparatus can be used not only for image forming apparatuses but also for apparatuses having another sheet feeding mechanism, e.g., a reading apparatus such as a scanner having an image reading means for reading information upon conveying an original document.