Abstract:
A cleaning device comprising a cleaning member contactable to a moving image bearing member to clean a surface of the image bearing member; holding means for holding the cleaning member; vibrating means which is vibratable; wherein the holding means this movable toward and away from the image bearing member, and wherein the vibrating means is supported on the holding means.

Description:
FIELD OF THE INVENTION AND RELATED ART  
         [0001]    The present invention relates to a cleaning device cleaning a surface of an image bearing member in an image forming apparatus such as a printer, a copying machine, a facsimile or the like and an image forming apparatus provided with the same.  
           [0002]    A cleaning blade is known as a cleaning member for cleaning an image bearing member in an image forming apparatus such as a printer, a copying machine, a facsimile or the like.  
           [0003]    For example, in an image forming apparatus of an electrophotographic type, a toner image is formed on a photosensitive drum (image bearing member) through image forming processes including a charging process, an exposure process and a developing process, and the toner image is transferred onto a recording material (paper, for example) from a photosensitive drum by a transfer process. In the transfer process, the toner constituting the toner image on the photosensitive drum are not entirely transferred onto the recording material, but a small amount of the toner remains on the surface of the photosensitive drum. The toner was remaining on the surface of photosensitive drum (residual toner) is removed from the surface of photosensitive drum by the cleaning blade.  
           [0004]    As shown in FIG. 6, an edge  61   a  of a cleaning blade  61  is contacted to the surface of the photosensitive drum  11 , by which the residual toner deposited on the surface of the photosensitive drum  11  is scraped off the drum surface.  
           [0005]    However, the conventional example involves following problems.  
           [0006]    As shown in FIG. 6, in the neighborhood of the edge  61   a  of the cleaning blade  61  contacted to the photosensitive drum  11 , the residual toner scraped off the surface of the photosensitive drum  11  is accumulated. Normally, the accumulated residual toner falls into a cleaner container (unshown) of the cleaning device when the residual toner becomes large to a certain extent.  
           [0007]    However, since the recent demand for the high-speed operation of the image forming apparatus results in an increased peripheral speed (process speed) of the photosensitive drum  11 , the residual toner does not fall but continuous becoming larger, depending on the ambient conditions, and the residual toner may passes through the nip N formed between the edge  61   a  of the cleaning blade  61  and a surface of the photosensitive drum  11 . The problem with this is that residual toner having passed through the nip is transferred onto the recording material (sheet material) in the next image forming process with result of stripes produced on the resultant image.  
           [0008]    As for a means for improving the cleaning property of the cleaning blade, Japanese Laid-open Patent Application Hei 6-4014 and Japanese Laid-open Patent Application Hei 11-174922 propose imparting vibration to the cleaning blade using a piezoelectric element. The piezoelectric element is mounted on the cleaning blade. The cleaning blade is deteriorated with use, and therefore, the piezoelectric element is replaced when the cleaning blade is replaced. This increases the cost. Additionally, it is difficult to impart such a vibration as is sufficient to remove the residual toner. A method as proposed in Japanese Laid-open Patent Application Hei 9-160455 in which the cleaning blade is imparted with collision vibration, may create such a vibration as is enough to remove the coagulated and grown toner. However, depending on the behavior of the cleaning blade when the collision vibration is imparted, the residual toner may passes through the nip.  
         SUMMARY OF THE INVENTION  
         [0009]    Accordingly, it is a principal object of the present invention to provide a cleaning device and an image forming apparatus in which coagulation of the toner is effectively prevented in the neighborhood of the cleaning member, thus properly removing the toner image from the image bearing member.  
           [0010]    According to an aspect of the present invention, there is provided a cleaning device comprising a cleaning member contactable to a moving image bearing member to clean a surface of the image bearing member; holding means for holding said cleaning member; vibrating means which is vibratable; wherein said holding means this movable toward and away from said image bearing member, and wherein said vibrating means is supported on said holding means.  
           [0011]    According to another aspect of the present invention, there is provided an image forming apparatus comprises a movable image bearing member; image forming means for forming an image on said image bearing member; a cleaning member contacted to said image bearing member to clean a surface of said image bearing member; holding means for holding said cleaning member; vibrating means which is vibratable; wherein said holding means this movable toward and away from said image bearing member, and wherein said vibrating means is supported on said holding means.  
           [0012]    These and other objects, features, and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a schematic longitudinal sectional view of an image forming apparatus according to an embodiment of the present invention.  
         [0014]    [0014]FIG. 2 is a schematic longitudinal sectional view of a cleaning device according to an embodiment of the present invention.  
         [0015]    [0015]FIG. 3 (( a )-( d )) is enlarged views illustrating removal of the coagulated toner adjacent the edge of cleaning blade by vibration.  
         [0016]    [0016]FIG. 4 is a perspective view of a motor and a case constituting the vibrating means.  
         [0017]    [0017]FIG. 5 is a perspective view of a frame provided with two vibrating means.  
         [0018]    [0018]FIG. 6 is an enlarged view showing coagulation of the toner in the neighborhood of the edge of the cleaning blade.  
         [0019]    [0019]FIG. 7 is a longitudinal view of a frame provided with two vibrating means.  
         [0020]    [0020]FIG. 8 shows another example of supporting the frame. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings. In the accompanying drawings, the same reference numerals are assigned to the elements having the corresponding functions, and redundant detailed description is omitted for simplicity.  
         [0022]    [0022]FIG. 1 shows an example of the image forming apparatus according to an embodiment of the present invention. The image forming apparatus is a laser beam printer, and FIG. 1 is a schematic longitudinal section thereof. In this example, the member to be cleaned by the cleaning device  17  according to this invention is a photosensitive drum  11 .  
         [0023]    The laser beam printer (image forming apparatus) shown in this Figure comprises a printer station (image formation station) and a reader portion (image reading station).  
         [0024]    The printer station  1  has an image bearing member in the form of an electrophotographic photosensitive member (photosensitive drum). Around the circumference of the photosensitive drum  11 , there are provided a primary charger (primary charging means)  12 , an exposure device (exposure means)  13 , a developing device (developing means)  14 , a transfer charger  15 , a separation charger  16 , and a cleaning device (cleaning means)  17  in the order named. There are sheet feeding cassettes  18   a,    18   b,  sheet feeding rollers  19   a,    19   b,  registration rollers  20 , a conveyer belt  21 , a fixing device (fixing means)  22  having a fixing roller  22   a  and a pressing roller  22   b,  discharging rollers  23  in the order named along the feeding direction of the recording material (paper for example) from the upstream side.  
         [0025]    On the other hand, the reader portion  2  comprises a platen glass  31 , an original pressing plate  32 , a light source  33 , reflection mirror  34   a,    34   b,    34   c,  a lens  35 , a CCD (photoelectric conversion element)  36 , an image processor  37  and so on.  
         [0026]    In the print portion  1  of the image forming apparatus, the photosensitive drum  11  is located by a driving means (unshown) in the direction indicated by an arrow at a predetermined process speed (peripheral speed), and during the rotation, the surface of the photosensitive drum  11  is uniformly charged to a predetermined potential of a predetermined polarity by the primary charger  12 . On the other hand, in the reader portion  2 , the original (unshown) pressed on the platen glass  31  by the original pressing plate  32  is eliminated at the bottom surface (image surface) by the light source  33 . The light reflected by the original is reflected by the reflection mirrors  34   a,    34   b,    34   c  and is passed through the lens  35  and is incident on the CCD 36 . The light incident on the CCD 36  is subjected to a known image processing by the image processor  37 , and is converted to an electric signal  38 , and is supplied to the exposure device  13  of the printer station  1  as image information to be printed.  
         [0027]    The laser scanner  13   a  of the exposure device  13  projects the light modurated in accordance with the image information onto the surface of the electrically charged photosensitive drum  11  by way of the reflection mirror  13   b.  By the exposure of the surface of photosensitive drum  11 , an electrostatic latent image is formed on the surface thereof.  
         [0028]    The electrostatic plated image is developed by the developing device  14 . The developing device  14  contains a developer (toner), which is transferred onto the electrostatic latent image on the surface of the photosensitive drum  11  by applying a developing bias voltage to the developing sleeve  14   a,  by which the electrostatic latent image is visualized into a toner image.  
         [0029]    The toner image formed on the photosensitive drum  11  in this manner is then transfer onto a recording material P. The recording material P is fed out of the sheet feeding cassette  18   a  or the sheet feeding cassette  18   b  by the sheet feeding roller  19   a  or the sheet feeding roller  19   b,  and is fed into the transfer portion formed between the photosensitive drum  11  and the transfer charger  15  with timed relation with the toner image on the photosensitive drum  11  by the registration rollers  20 . The toner image on the photosensitive drum  11  is transferred onto the recording material P by application of a transfer bias to the transfer charger  15 .  
         [0030]    The recording material P, after the toner image transfer, is separated from the surface of the photosensitive drum  11  by the separation charger  16 , is supplied into the fixing device  22  by the conveyer belt  21 . In the fixing device  22 , the recording material P is heated and pressed by the fixing roller  22   a  and the pressing roller  22   b,  by which the toner image is fixed on the surface of the recording material P. Then, the recording material P is discharged to an outside of the main assembly of image forming apparatus by the discharging rollers  23 .  
         [0031]    On the other hand, the photosensitive drum  11 , after the toner image transfer, the cleaning device  17  removes from the photosensitive drum  11  the residual toner (deposited matter) not having been transferred but remaining on the surface thereof, so that photosensitive drum  11  is prepared for the next image forming operation. The cleaning device  17  will be described in detail hereinafter.  
         [0032]    In FIG. 1, an automatic original feeding device  39  is indicated by chain lines. The automatic original feeding device  39  is disposed above the original pressing plate  32  and functions to automatically supplies the originals onto the platen glass  31  and of optically discharge the original from the platen glass  31 .  
         [0033]    Referring to FIG. 2, the cleaning apparatus  17  in accordance with the present invention will be described in detail. FIG. 2 is a vertical sectional view of the cleaning apparatus  17 , at a plane perpendicular to the lengthwise direction (axial direction) of the photoconductive drum  11 .  
         [0034]    The cleaning apparatus  17  comprises a frame  41  (first frame), a frame  42  (second frame), a cleaning blade  43  (cleaning member), a magnetic roller  44 , a conveying screw  4   b,  a sheet  46 , a holder  47 , shafts  48  and  49 , a tension spring  50  (pressure generating means), and a vibration generating means  51 .  
         [0035]    The cleaning blade  43  is formed of elastic plate. It is held to the frame  41 , being sandwiched between the frame  41 , and the holder  47  attached to the frame  41  with the use of screws  61 . One of the lengthwise edges of the cleaning blade  43  is placed in contact with the peripheral surface of the photoconductive drum  11 , with the cleaning blade  43  tilted so that it counters the moving direction (indicated by an arrow mark) of the peripheral surface of the photoconductive drum  11 . The portion  41   a  of the surface of the frame  41 , with which the back side of the cleaning blade  43  is placed in contact, and the portion  47   a  of the surface of the holder  47 , with which the end surface of the cleaning blade  43  is placed in contact, have been processed with high accuracy, and have been positioned also with high accuracy. In other words, the cleaning blade  43  is held to the frame  41 , with a portion of the cleaning blade  43  being placed in contact with the portion  41   a  of the frame  41  and the portion  47   a  of the holder  47 , so that the cleaning blade  43  is highly accurately positioned relative to the photoconductive drum  11 . The frame  41 , which holds the cleaning blade  43 , also holds the vibrating means  50 .  
         [0036]    The frame  41  is pivotally attached to the frame  42 , with the use of the shaft  48 . One end of the tension spring  50  is connected to a part of the frame  42 , and the other end of the tension spring  50  is connected to a part of the frame  41 . Thus, the frame  41  is kept pressed by this tension spring  50  in the direction to pivot counterclockwise about the shaft  48  in the drawing. As a result, the edge  43   a  of the cleaning blade  43  is kept in contact with the peripheral surface of the photoconductive drum  11 , generating a proper amount of contact pressure.  
         [0037]    The frame  42  has a portion, which is vertical when the cleaning apparatus is in the image forming apparatus main assembly, and a portion, which extends toward the photoconductive drum  11  from the bottom end of the vertical portion. The aforementioned magnetic roller  44  and conveying screw  45  are rotationally supported by these two portions of the frame  42 , and are rotationally driven by a driving means (unshown).  
         [0038]    The magnetic roller  44  is disposed below the cleaning blade  43 . Its peripheral surface is covered with a layer of residual toner which has been scraped down from the peripheral surface of the photoconductive drum  11  by the cleaning blade  43 . The thickness of this residual toner layer is regulated by the sheet  46  and shaft  49 . The magnetic roller  44  places its toner layer in contact with the peripheral surface of the photoconductive drum  11 , across the area closest to the magnetic roller  44 , from one lengthwise end of the photoconductive drum  11  to the other (direction parallel to the generatrix of the photoconductive drum  11 ), so that the peripheral surface of the photoconductive drum  11  is coated again with the residual toner. This is for the following reason. That is, if the peripheral surface of the photoconductive drum  11  is not re-coated with the residual toner after the residual toner is completely scraped down from the peripheral surface of the photoconductive drum  11  by the cleaning blade, the friction between the cleaning blade  43  and a portion of the peripheral surface of the photoconductive drum  11  with the residual toner, becomes different from the friction between the cleaning blade  43  and a portion of the peripheral surface of the photoconductive drum  11  with no residual toner, causing the cleaning blade  43  to micrometrically vibrate. Therefore, the peripheral surface of the photoconductive drum  11  is evenly coated with the removed residual toner to make uniform the friction between the cleaning blade  43  and photoconductive drum  11  in terms of the lengthwise direction of the photoconductive drum  11  in order to prevent the cleaning blade  43  from micrometrically vibrating. The “fresh” residual toner on the photoconductive drum  11  is scraped away, along with the “re-coated” residual toner, by the cleaning blade  43 , and is recovered by the magnetic roller  44 .  
         [0039]    The sheet  46  is placed in contact with the shaft  49 . It has the function of conveying to the conveying screw  45  the excessive amount of the residual toner on the peripheral surface of the magnetic roller  44 . The conveying screw  5  conveys the residual toner to an unshown recovered residual toner container.  
         [0040]    FIGS.  3 ( a ),  3 ( b ),  3 ( c ), and  3 ( d ) are enlarged views of the contact area between the peripheral surface of the photoconductive drum  11  and the edge  43   a  of the cleaning blade  43 , and its adjacencies, in this embodiment of the present invention.  
         [0041]    As the edge  43   a  of the cleaning blade  43  in contact with the photoconductive drum  11  scrapes the peripheral surface of the photoconductive drum  11 , the residual toner particles agglomerate at the edge  43   a  as shown in FIG. 3( a ). As the amount of the agglomerate residual toner particles at the edge  43   a  grows as shown in FIG. 3( b ), there arises a possibility that a certain portion of the agglomerate residual particles will pass through the nip N between the edge  43   a,  and adheres to the recording medium P, ruining the image thereon. Therefore, as the residual toner particles agglomerate at the edge  43   a,  they must be removed before the amount of the agglomerate residual toner at the edge  43  grows large enough for the residual particles to pass through the nip N.  
         [0042]    Thus, in this embodiment, vibrations are transmitted (FIG. 3( c )) to the cleaning blade  43 , through the frame  41 , by activating the vibration generating means  51  (FIG. 1), so that the residual toner particles, which have agglomerated at the edge  43   a  of the cleaning blade  43 , are removed from the edge  43   a  before formation of unsatisfactory images begins (FIG. 3( d )). However, as the vibration generating means  51  is activated, the vibrations therefrom propagate to the photoconductive drum  11  by way of the cleaning blade  43 . Therefore, it is not desired for the vibration generating means  51  to be activated during image formation. Thus, it is not possible to frequently activate the vibration generating means  51 . However, it was confirmed by experiments that stopping image formation for every 1,000th copy to operate the vibrating apparatus for approximately 0.5 second sufficed to remove the agglomerated residual toner particles. In other words, the effect of the operation of the vibrating means  5  for removing the agglomerated residual toner particles upon the ratio of the actual working time of the image forming apparatus is insignificant. Therefore, it is preferred that the image forming operation is temporarily stopped for every 1,000th copy, for example, to vibrate the cleaning blade  43  while image formation is not carried out.  
         [0043]    [0043]FIG. 4 shows the structure of the vibration generating means  51  in this embodiment.  
         [0044]    The vibration generating means  51  comprises a motor  52 , a weight  53  attached to the output shaft  52   a  of the motor  52 , and a case  54 . The motor  52  is connected to a control circuit (unshown) and is stationarily disposed in the case  54 . The case  54  containing the motor  52  is securely fixed to the frame  41  as shown in FIG. 1. The weight  53  is attached to the output shaft  52   a,  with its center of gravity offset from the output shaft  52   a.  Therefore, as the output shaft  52   a  of the motor  52  is rotationally driven by the control circuit, the motor  52  vibrates. These vibrations of the motor  52  propagate through the case  54  and frame  41 , reaching the cleaning blade  43 . The case  54  is given the function of preventing toner particles from entering the motor  52 , and also, the function of efficiently propagating the vibrations of the motor  52  to the frame  41  by restraining the motor  52 .  
         [0045]    In the aforementioned experiments, the revolution of the motor  52  was set at 9,500 rpm. Incidentally, when the revolution of the motor  52  was kept within a range of 7,000 rpm-12,000 rpm, reasonably good results were obtained.  
         [0046]    As long as vibrations effective to remove the agglomerated residual toner particles from the cleaning blade  43  can be given to the cleaning blade  43 , the structure of the vibration generating means  51  does not need to be limited to the above described one.  
         [0047]    The placement of a single vibration generating means  51  at the center of the frame  41  of the cleaning apparatus  17  in terms of the lengthwise direction of the frame  41  is sufficiently effective. In such a case, however, vibrations must be greater in amplitude in order for the vibrations to efficiently propagate to the lengthwise ends of the cleaning blade  43 . Therefore, a plurality of the vibration generating means  51  may be attached to the frame  41  so that vibrations with a smaller amplitude can be uniformly propagated from one lengthwise end of the cleaning blade  43  to the other. For example, the vibration generating means  51  may be disposed at each lengthwise end of the frame  41 , as shown in FIG. 5. In such a case, it is desired that the vibrating means  5  are symmetrically distributed with respect to the lengthwise center A of the frame  41  in order to minimize the unevenness in the contact pressure between the cleaning blade  43  and photoconductive drum  11 , in terms of the lengthwise direction of the cleaning blade  43  (photoconductive drum  11 ).  
         [0048]    The frame  42  (housing) is for recovering the residual toner after the residual toner is removed from the peripheral surface of the photoconductive drum  11  by the cleaning blade  43 . The housing  43  comprises the top portion  42   a,  back portion  42   b,  and bottom portion  42   c.  It has an opening, which faces the peripheral surface of the photoconductive drum  11 . The top portion  42   a  has a pair of supporting members  56  (only one is shown in the drawing), which are located at the lengthwise ends of the top portion  42   a,  one for one, and project downward, supporting the shaft  48 , which is disposed so that its axial line  48   a  is virtually parallel to the generatrix of the photoconductive drum  11 .  
         [0049]    The entirety of the frame  41  is pivotally supported by the aforementioned shaft  48 . Referring to FIG. 5, the frame  42  is structured so that the dimension of the frame  42  in the lengthwise direction of the cleaning apparatus is greater than the dimension of the frame  42  in the direction perpendicular to the lengthwise direction of the cleaning apparatus. It has the top and bottom portions, and the inclined portion which connects the top and bottom portions. It has an opening, which is on the back side. To the top surface of the bottom portion, the motors  51 , or a vibrating means, are attached. To the front surface of the inclined portion, the holder  47  is secured with the use of the small screws  61 , with a portion of the cleaning blade  43  being sandwiched between the holder  47  and the inclined portion of the frame  41 . The top portion of the frame  41  is provided with a pair of bearing portions  62  (only one is shown in the drawing), which project from the lengthwise ends of the top portion, one for one, and through which the end portions of the aforementioned shaft  48  are inserted, one for one. In other words, the entirety of the frame  41  is pivotally supported by the shaft  48 . The direction in which the frame  41  pivots is the virtually horizontal direction in the drawing, in other words, the direction in which the frame  41  approaches, or moves away from, the peripheral surface of the photoconductive drum  11 . Further, the frame  41  is provided with a spring anchoring portion, which is located on the back side of the frame  41 , and to which one end of the tension spring  50  is anchored.  
         [0050]    The cleaning blade  43  is a member in the form of a piece of plate extending in the generatrix direction (lengthwise direction) of the photoconductive drum  11 . It is formed of, for example, synthetic resin, and is flexible. It is secured to the frame  41 , with its top side being sandwiched between the frame  41  and holder  47 , so that its bottom side projects from the holder, with its edge  43   a  contacting the peripheral surface of the photoconductive drum  11 .  
         [0051]    Referring to FIG. 4, to the output shaft  52   a  of the motor  52 , the weight  53  is attached in such a manner that its center of gravity is offset from the shaft  52   a.  The weight  53  in this embodiment is virtually fan-shaped. However, in principle, as long as the center of gravity of the weight  54  is offset from the output shaft  52   a,  the shape of the weight  53  does not need to be limited to the fan-shape. The motor  52  is disposed within the case  54 . The motor  52  and case  54  together constitute a motor unit  51 .  
         [0052]    Referring to FIG. 7, the motor unit  51 , which constitutes a vibration generating means, is attached to the top surface of each lengthwise end of the bottom portion of the frame  41 . Incidentally, in FIG. 7, each lengthwise end portion of the case  51  is drawn with an imaginary window through which the motor  52  can be seen. The two motor units  51  are positioned so that the distance x from one motor unit  51  to the center C of the frame  41  in terms of the lengthwise direction of the frame  41  becomes the same as the distance x′ from the other motor unit  51  to the center C, and also so that the output shaft  52   a  of each motor  52  becomes virtually parallel to the axial line  48   a  of the shaft  48 . In the drawing, each weight  53  is positioned on the left side of the corresponding motor  51 . However, the weights  53  may be positioned so that both are on the right side of the corresponding motors  51 , or one is on the right side of the corresponding motor  51 , whereas the other is on the left side of the corresponding motor  51 . To both motors  51 , the control circuit (unshown) is connected to control the motors  51  so that the two weights  53  are rotated in the same direction.  
         [0053]    Incidentally, when the two motors  51  and the two weights  53  are positioned as shown in FIG. 7, it is preferable that the two motors  51  are controlled so that the rotational direction of one weight  53  becomes opposite to that of the other weight  53 , because such an arrangement can intensify the vibrations of the frame  41 .  
         [0054]    The tension spring  50  as a pressure generating elastic member is positioned between a part of the housing  42  and the spring anchoring portion of the frame  41 , keeping the entirety of the frame  41 , which is pivotally supported by the shaft  48 , pressured in the direction to rotate counterclockwise, in the drawing, about the shaft  48 . As a result, the edge  43   a  of the cleaning blade  43  is kept in contact with the peripheral surface of the photoconductive drum  11 , generating a predetermined amount of contact pressure. Since the shaft  48  is positioned virtually in parallel to the generatrix of the photoconductive drum  11 , the contact between the peripheral surface of the photoconductive drum  11  and the edge  43   a  the cleaning blade  43  forms the nip N (FIG. 3) between the peripheral surface of the photoconductive drum  11  and the edge  43   a,  which extends in the direction of the generatrix of the photoconductive drum  11 .  
         [0055]    As described above, in this embodiment, the frame  41  which is supporting the cleaning blade  43  is pivotally supported by the shaft  48  virtually in parallel to the generatrix of the photoconductive drum  11 , and also, the output shaft  52   a  of the motor  52  is positioned virtually in parallel to the shaft  48 . Therefore, the micro-vibrations generated by the combination of the motors  52  and weights  53  are efficiently transmitted to the edge  43   a  of the cleaning blade  43 , micrometrically vibrating the edge  43   a  in the direction to cause the edge  43   a  to contact, or move away from, the peripheral surface of the photoconductive drum  11 , in the contact nip N between the peripheral surface of the photoconductive drum  11  and the edge  43   a  of the cleaning blade  43 . As a result, the residual toner particles are satisfactorily removed as they agglomerate at the edge  43   a.    
         [0056]    The above described structure efficiently generates satisfactory vibrations for dislodging the agglomerate residual toner particles, making it possible to accomplish such objects as reducing the size of a vibration generation motor, reducing the power consumption, and the like.  
         [0057]    As long as vibrations satisfactory for removing the agglomerate residual toner particles can be generated, the number and structure of the motor unit  51  does not need to be limited to those described above. For example, two motor units  51  may be disposed so that the distance from one motor unit  51  to the lengthwise center C of the frame  41  becomes different from the distance from the other motor unit  51  to the center C.  
         [0058]    Embodiment 2  
         [0059]    In the preceding embodiment, the top and bottom halves of the supporting member for supporting the cleaning blade were two integral parts of the supporting member. In this embodiment, however, they are made independent from each other. More specifically, the top half having the shaft  48 , bearings  63 , and pressure generating means anchoring portion is provided with a pin  71 , which projects virtually straight downward, and to which the frame  41  is attached, as shown in FIG. 8. With the provision of this structural arrangement, not only is the frame  41  pivotable in the direction indicated by an arrow mark  73 , but also in the direction indicated by an arrow mark  72 . Otherwise, the vibrating apparatus structure in this embodiment is the same as that in the first embodiment.  
         [0060]    This structural arrangement makes the contact pressure generated between the peripheral surface of the photoconductive drum  11  and the cleaning blade  43  as the cleaning blade  43  is placed in contact with the peripheral surface of the photoconductive drum  11  by the pressure applied to the cleaning blade  43  from the tension spring  50 , by way of the frame  41 , uniform across the contact nip N in terms of the lengthwise direction of the cleaning blade  43 , stabilizing the cleaning apparatus in terms of cleaning performance.  
         [0061]    In the preceding embodiments, two motors  51  were employed. However, three or more motors  51  may be employed. When the number of the motors  51  is even, they should be symmetrically positioned with respect to the lengthwise center C of the frame  41 , whereas when the number of the motors  51  is odd, it is recommended that the central one is placed at the center C, and the rest are symmetrically positioned with respect to the center C.  
         [0062]    &lt;Structure of Cleaning Blade&gt; 
         [0063]    Next, the characteristics required of a cleaning blade in accordance with the present invention will be described.  
         [0064]    As the vibration generating means  51  is activated, the vibrations from the vibration generating means  51  cause the cleaning blade  43  to bounce, in other words, to separate, from the peripheral surface of the photoconductive drum  11  several tens of micrometers to several hundreds of micrometers, at the same frequency as the vibrations generated by the vibration generating means  51 , even while the photoconductive drum  11  is not rotated. As the cleaning blade  43  separates from the peripheral surface of the photoconductive drum  11 , a portion of the agglomerate residual toner particles which had been dammed up by the contact nip N between the cleaning blade  43  and the photoconductive drum  11  is sometimes allowed to migrate onto the downstream side (back side) of the cleaning blade  43  in terms of the moving direction of the peripheral surface of the photoconductive drum  11 . If the distance by which the cleaning blade  43  separates from the peripheral surface of the photoconductive drum  11  is large, a substantial amount of the residual toner particles migrates onto the back side of the cleaning blade  43 , and adheres to the residual latent image remaining on the peripheral surface of the photoconductive drum  11  after image transfer, appearing across the portion of an image formed during the following rotational cycle of the photoconductive drum  11 .  
         [0065]    The inventors of the present invention repeatedly carried out the following studies, discovering that for the efficient removal of the agglomerate residual toner particles from the cleaning blade  43  while preventing the phenomenon that a part of the agglomerate residual toner particles migrates onto the back side of the cleaning blade and effects an unsatisfactory image, it is effective to reduce the coefficient of impact resilience, that is, one of the physical properties of the cleaning blade  43 , to no more than 40%.  
         [0066]    Table 1 shows the results of an experiment in which five groups of elastic cleaning blades  43 , which were different in coefficient of impact resilience, but identical in shape and hardness, were compared in terms of the formation of unsatisfactory images, the imperfections of which were traceable to the aforementioned downstream migration of the agglomerate residual toner particles onto the back side of the cleaning blade.  
                                           TABLE 1                                       Coefficient of   33   37   40   43   48           impact resilience           Defects due to   G   G   G   N   N           back side toner                                              
 
         [0067]    In the experiments, the vibration generating means  51  was activated for one second, with the photoconductive drum  11  kept stationary, and then, a normal image forming operation was carried out. The obtained images were evaluated mainly for soiling. When the amount of the residual toner particles which were allowed to migrate onto the back side of the cleaning blade  43  by the vibrations from the vibration generating means  51  was large, the migrated residual toner particles electrostatically adhered to the residual electrostatic latent image on the photoconductive drum  11 , that is, the residual latent image which remained on the photoconductive drum  11  after toner image transfer, in particular, the distinctive line portions, or the like, of the residual latent image, which were stronger in electric field; in other words, images were soiled.  
         [0068]    Prior to the experiment, it was confirmed that the five groups of cleaning blades different in coefficient of impact resilience were not different in the effectiveness in removing the agglomerate residual toner particles. Then, the images formed after the vibration generating means  51  was activated at the minimum strength for effectively removing the agglomerate residual toner particles, were evaluated for the image defects traceable to the aforementioned downstream migration of residual toner particle migration onto the back side of the cleaning blade.  
         [0069]    Whether the vibration generating means  51  was effective for removing the agglomerate residual toner particles or not was judged using the following method. First, an ordinary image forming operation was carried out to produce 10,000 A4 size copies, using the test apparatuses, in an ambience in which the temperature was 23° C. and the relative humidity was low at 5%, that is, an ambience in which the residual toner particles easily agglomerated. Then, it was confirmed that the edge of the cleaning blades  43  collected an approximately 1.5 mm-1.8 mm thick layer of agglomerate residual toner particles across its entire lengthwise range. Next, the vibration generating means  51  was activated at a predetermined strength for one second, with the photoconductive drum  11  kept stationary. Then, the cleaning blade  43  was gently separated from the photoconductive drum  11 , and the thickness of the layer of the agglomerate residual toner particles remaining on the cleaning blade  43  was measured. When the thickness of this layer was no more than 0.3 mm, it was judged that the agglomerate residual toner particles had been effectively removed.  
         [0070]    The method used to measure the coefficients of impact resilience of the cleaning blades in this embodiment is compliant to JISK6301. In this embodiment, the values of the coefficients of impact resilience of the cleaning blades were those measured at 40° C., unless specified.  
         [0071]    The reason for measuring the coefficient of impact resilience at 40° C. is as follows. In the hollow of the photoconductive drum  11  in this embodiment, a drum heater (unshown) as a heating means was disposed to keep the temperature of the photoconductive drum  11  at approximately 40° C. (temperature control) in order to prevent the formation of an image with the appearance of flowing water. Thus, the cleaning blade  43  was always used at a temperature of approximately 40° C., or the image formation temperature.  
         [0072]    In this embodiment, the temperature was kept at 40° C. However, as long as the temperature is, within a range of 30° C.-49° C., the formation of images with the appearance of flowing water can be prevented. The application of the present invention is not limited to an image forming apparatus equipped with a temperature control mechanism for the photoconductive drum  11 . Further, the value of the coefficient of impact resilience of the cleaning blade  43  has only to be within a range correspondent to the ordinary temperature range within which an image forming apparatus in accordance with the present invention is used.  
         [0073]    As for the material for the cleaning blade  43 , various conventional rubbers can be used. In particular, urethane rubber is preferable since it is superior in mechanical strength such as wear resistance. For example, polyurethane elastomer manufactured using the chemical reaction between commercially available polyol and polyisocyanate can be used with preferable results. As for the commercially available polyol, there are polyester polyol and polyether polyol. The examples of polyester polyol are polyethylene-adipate-ester polyol, polyethylene-butylene-adipate-ester polyol, or caprolactone-ester polyol, and the like, and the examples of polyether polyol are polyoxy-propylene glycol, and the like.  
         [0074]    It became evident from the results the experiment shown in Table 1 that as long as the cleaning blade  43  was no more than 40% in coefficient of impact resilience, it was possible to prevent the phenomenon that images were soiled by the downstream migration of the residual toner particles onto the back side of the cleaning blade  43 .  
         [0075]    The following theory is not intended to limit the scope of the present invention. But, based on the studies of the above described experiment, the inventors of the present invention theorized that the amount by which the agglomerate residual toner particles migrate downstream onto the back side of the cleaning blade  43 , in other words, the amount of image soiling traceable to the downstream migration of the residual toner particles onto the back side of the cleaning blade  43 , is dependent upon the coefficient of impact resilience of the cleaning blade  43 , for the following reason. That is, the edge (free end) of a cleaning blade  43  higher in coefficient of impact resilience bounces higher from the peripheral surface of the photoconductive drum  11  than the edge of a cleaning blade  43  lower in coefficient of impact resilience. Thus, the amount by which the agglomerate residual toner particles migrate downstream onto the back side of a cleaning blade is smaller when the cleaning blade is lower in coefficient of impact resilience.  
         [0076]    Next, the relationship between the coefficient of impact resilience of the cleaning blade  43  and the cleaning performance of the cleaning apparatus  17  will be described. Table 2 shows the results of the following experiment. That is, 10,000 A4 size copies were made, using the test apparatuses, the cleaning apparatuses of which were different in coefficient of impact resilience within a range of 5%-25% (identical in shape and hardness), in an ambience in which the temperature was 23° C. and the relative humidity was low at 50%. Then, the obtained copies were subjectively evaluated regarding the presence or absence of the image defect traceable to the cleaning failure.  
                                               TABLE 2                                       Coefficient of   5   7   10   14   19   25           impact resilience           Insufficient   N   N   G   G   G   G           cleaning                                              
 
         [0077]    It had been confirmed in advance that under the above described condition, the residual toner particles did not agglomerate. Thus, the cleaning failure indicated in Table 2 means such a cleaning failure that occurs regardless of the agglomeration of the residual toner particles.  
         [0078]    It will be evident from Table 2 that satisfactory cleaning performance can be realized by employing a cleaning member, the coefficient of impact resilience of which is no less than 10%.  
         [0079]    The following theory is not intended to limit the scope of the present invention. But, based on the studies of the above described experiment, the inventors of the present invention theorized that the cleaning performance of a cleaning apparatus is dependent upon the coefficient of impact resilience of the cleaning blade  43 , for the following reason. That is, the higher the cleaning blade  43  in coefficient of impact resilience, the superior the cleaning blade  43  in conformity to the peripheral surface of the photoconductive drum  11 , and responsiveness to the micro-vibrations, in the nip N, during the rotation of the photoconductive drum  11 .  
         [0080]    Based on the summarization of the results of the experiments given in Tables 1 and 2, it was evident that the employment of a cleaning blade  43 , the coefficient of impact resilience of which is in a range of 10%-40%, made it possible to efficiently remove the agglomerate residual toner particles, with the use of the vibrations generated by the vibration generating means  51 , while maintaining the cleaning performance of the cleaning apparatus at a preferable level, and also that it reduced the distance a cleaning blade  43  was bounced by the vibrations, preventing the agglomerate residual toner particles from migrate downstream onto the back side of the cleaning blade  43 .  
         [0081]    Thus, in this embodiment, a polyurethane elastomer cleaning blade  43 , the coefficient of impact resilience of which was 30% at 40° C., and the hardness of which was 77 degrees in Hs, was employed.  
         [0082]    Incidentally, the cleaning blade  43  in this embodiment was approximately rectangular in cross section. It was 30 mm in the dimension of its free (unattached) portion in terms of the direction perpendicular to the lengthwise direction of the photoconductive drum  11 , 3 mm in thickness, and 350 mm in the dimension in terms of the direction parallel to the lengthwise direction (axial direction) of the photoconductive drum  11 . Its free edge  43   a  was placed in contact with the peripheral surface of the photoconductive drum  11 . The contact angle, or the angle of the edge  43   a  relative to the tangential line of the photoconductive drum  11  at the contact between the cleaning blade  43  and photoconductive drum  11 , was 27 degrees, and the contact pressure was set to 13 gf/cm.  
         [0083]    Mounting of the cleaning apparatus  17  equipped with the above described cleaning blade  43  in an image forming apparatus in accordance with the present invention confirmed that the cleaning apparatus  17  in accordance with the present invention displayed stable cleaning performance, and that the image defects traceable to the downstream migration of the residual toner particles onto the back side of the cleaning blade  43 , caused by the vibrations generated by the vibration generating means  51 , did not occur.  
         [0084]    As described above, according to this embodiment, in order to prevent the cleaning failure traceable to the phenomenon that the agglomerate residual toner particles migrate downstream onto the back side of the cleaning blade  43 , the residual toner particles agglomerating in the adjacencies of the interface between the photoconductive drum  11  and cleaning blade  43  can be shaken down by vibrating the cleaning blade  43  with the use of the vibration generating means  51 , making it possible to effectively prevent the occurrence of the image defects, or the soiling of the recording medium P, traceable to the cleaning failure.  
         [0085]    Further, the agglomerate residual toner particles can be efficiently removed by the vibrations generated by the vibration generating means  51  while maintaining the cleaning performance at a preferable level. Moreover, the distance the cleaning blade  43  is bounded by the vibrations is smaller. Therefore, virtually no residual toner particle migrates downstream onto the back side of the cleaning blade  43 , preventing the occurrence of the image defects traceable to the downstream migration of the residual toner particles.  
         [0086]    To sum up, according this embodiment, the cleaning performance of the cleaning member can be kept stable at a preferable level by the vibrations generated and transmitted with the use of a simple structural arrangement, without incurring vibration related problems. Therefore, the residual toner particles on the photoconductive drum  11  can be satisfactorily removed without incurring a substantial cost increase.  
         [0087]    As the cumulative length of the usage of the cleaning blade  43  increases, the cleaning blade  43  gradually wears due to friction, declining in cleaning performance. Thus, the cleaning blade  43  must be opportunely replaced. With the provision of the above described structural arrangement, the cleaning blade  43  itself can be simply replaced by removing only the holder  47 , minimizing the cost of the components necessary for the replacement, and the number of steps necessary to be taken for the replacement. Further, the profile irregularity with which the cleaning blade  43  is attached is guaranteed by the profile irregularity of the cleaning blade anchoring surface  41   a  of the frame  41 . Therefore, the replacement cleaning blade can be accurately attached to assure that the manner in which the replacement cleaning blade behaves as vibrations are transmitted thereto by the vibration generating means  51  becomes virtually identical to that of the replaced cleaning blade, which is very important.  
         [0088]    In the preceding description of the embodiments of the present invention, the cleaning apparatus  17  was described as an apparatus for cleaning the peripheral surface of the photoconductive drum  11 ; in other words, the object to be cleaned was the peripheral surface of the photoconductive drum  11 . The application of the present invention, however, is not limited to the above described cleaning apparatus; it is also applicable to a wide range of cleaning apparatuses which clean various objects other than the photoconductive drum  11 . For example, it is applicable to a cleaning apparatus for removing the toner particles adhering to the surface of a photoconductive member in the form of a belt, an intermediary transfer drum, an intermediary transfer belt, or the like, with the results similar to those described above.  
         [0089]    While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following Claims.