Abstract:
A two-component developing apparatus includes a developer carrier, a first regulating member, a developer container, and a toner container. The developer carrier is configured to carry and transfer the two-component developer including a magnetic carrier. The first regulating member is configured to regulate an amount of the two-component developer carried and transferred by the developer carrier. The developer container is configured to receive the developer removed by the first, regulating member. The toner container is configured to supply toner to the developer carrier. The developer stirring member is configured to carry and stir the developer between the first regulating member and the second regulating member. The second regulating member includes a support member on one end side of the second regulating member in its longitudinal direction to which greater amount of the developer is supplied than to another end side of the second regulating member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This patent specification is based on Japanese patent application, No. 2002-376250 filed on Dec. 26, 2002 and No. 2003-027904 filed on Feb. 5, 2003 in the Japanese Patent Office, which are hereby incorporated by reference in its entirety.  
         FIELD OF THE INVENTION  
         [0002]    The present invention relates to a two-component development apparatus and a process cartridge for using toner as a developer for developing an electrostatic image in electrophotography, electrostatic recording and electrostatic printing and the like, and an electrophotographic developing apparatus which uses toner. More particularly, the present invention relates to a two-component development apparatus and a process cartridge used in an image forming apparatus for use in copiers, laser printers and plain-paper facsimile machines and so on which use a direct or indirect electrophotographic development method.  
         BACKGROUND OF THE INVENTION  
         [0003]    In electrophotography, an image forming method typically uses a photoconductive substance to form an electrostatic latent image on an electrostatic image carrying member using various means. The electrostatic latent image is then developed with toner and is transferred on a recording sheet and the like as desired. Subsequently, the toner is fixed by heating or solvent vapor so that copy images or printed images can be obtained. For developing latent electrostatic images formed on an electrophotographic image carrier such as a photoconductor to visible toner images, there are conventionally proposed two methods: a wet-type developing method using a liquid type developer, and a dry-type developing method using a dory-type developer. The dry-type developer includes a one-component dry-type developer comprising a toner obtained by dispersing a coloring agent such as a colorant in a binder resin; and a two-component dry-type developer obtained by mixing the above-mentioned toner and carrier particles. Although these methods individually have their own advantages and shortcomings, the dry-type developing method is more prevalent than the wet-type developing method.  
           [0004]    Since in the two-component developing method it is relatively easy to increase operation speed and lengthen lifetime as compared with the one-component developing method, the two component developing method is widely used for medium and high speed copiers and printers.  
           [0005]    For carrying out the above-mentioned developing method, the developing device employs the two-component developing method for controlling toner concentration using two developer regulating members and a developer carrier. This system eliminates a sensor and a toner supply controlling device, thereby making a device relatively inexpensive and compact.  
           [0006]    The above-mentioned developing device, however, has several disadvantages. One disadvantage is that it prevents a compulsive toner supplying control. As a result, a toner concentration control depends on a gap between a regulating member and the developer carrier, a gap between a developer stirring member and the developer carrier, and magnetic flux density caused by a magnet of the developer carrier, and a peak magnetic flux density and a position of one half band width (i.e., angle) of the developer carrier.  
           [0007]    However, assembling deviations caused by a regulation gap of the two regulating members (i.e., first and second regulating members), manufacturing precision and tolerances of parts, and magnetic flux density deviation caused by a magnet of the developer carrier cause an amount of the developer regulating deviation. Therefore, the developer tends to be axially located in a longitudinal direction of the developer carrier. This causes the developer to be nearer one end of a development region. An increase in the developer at one end decreases toner, thereby causing a loss in image concentration. A decrease in the developer at one end increases toner, thereby causing a soiling of background.  
           [0008]    Further, the two-component developing device with a toner concentration controlling function can be downsized so that it can be utilized for a compact printer and the like. The compact printer is often placed on a desk so that the printer tends to be operated in an inclined position as compared to a large printer placed on a floor. Such an inclined printer tends to make the developer move to one end. This leads to a loss in latent image concentration and a soiling of background at one end.  
           [0009]    Therefore, a high parts tolerance and assembly precision are demanded in this system. Utilizing a machine in a horizontal position is required. As long as the above-mentioned condition is not satisfied, unusual images such as uneven image concentration and a soiling of background tend to be generated.  
         SUMMARY OF THE INVENTION  
         [0010]    Accordingly, the present invention advantageously provides a process cartridge including a housing, at least one of a latent image carrier, a charging mechanism, and a cleaning mechanism, and a developing mechanism configured to have a two-component developing apparatus for use in an image forming apparatus.  
           [0011]    The developer apparatus of the present invention advantageously includes a developer carrier configured to carry and transfer a two-component developer including a magnetic carrier. The developer apparatus also includes a first regulating member configured to regulate an amount of the two-component developer carried and transferred by the developer carrier, and a developer container including a second regulating member positioned upstream of the first regulating member in a direction of developer conveyance of the developer carrier and configured to receive the developer removed by the first regulating member. The developer apparatus further includes a toner container formed adjacent to the developer container and configured to supply toner to the developer carrier, and a developer stirring member configured to carry and stir the developer between the first regulating member and the second regulating member. The second regulating member includes a support member on one end side of the second regulating member in a longitudinal direction thereof to which greater amount of the developer is supplied than to another end side of the second regulating member. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which:  
         [0013]    [0013]FIG. 1 is a schematic drawing illustrating an exemplary developing unit of an image forming apparatus using a preferred embodiment of a two-component development apparatus according to the present invention;  
         [0014]    [0014]FIG. 2A is a simplified schematic drawing illustrating a flow and accumulation of a developer in a direction of an end of a second regulating member;  
         [0015]    [0015]FIG. 2B is a simplified schematic drawing illustrating a curved surface of a support member in accordance with a shape of the developer stirring member;  
         [0016]    [0016]FIG. 3A illustrates an example of measurement results according to a preferred embodiment of the present invention;  
         [0017]    [0017]FIG. 3B illustrates an exemplary structure of a support member according to a preferred embodiment of the present invention;  
         [0018]    [0018]FIG. 4A is a perspective view of an example of a second regulating member seen from the right end in a sheet moving direction according to a preferred embodiment of the present invention;  
         [0019]    [0019]FIG. 4B is a perspective view of a support member provided on both ends of a second regulating member;  
         [0020]    [0020]FIG. 4C is a perspective view of a support member provided on both ends and an intermediate section of the second regulating member;  
         [0021]    [0021]FIG. 5 is a drawing illustrating an example of developer weight measurement result according to a preferred embodiment of the present invention;  
         [0022]    [0022]FIG. 6 is a simplified schematic drawing illustrating an example of positional relationship between a developer stirring member and a support member according to a preferred embodiment of the present invention;  
         [0023]    [0023]FIG. 7 is a drawing illustrating an example of developer weight measurement result according to a preferred embodiment of the present invention;  
         [0024]    [0024]FIG. 8 illustrates an exemplary structure of a support member according to a preferred embodiment of the present invention;  
         [0025]    [0025]FIG. 9 is a drawing illustrating an exemplary image concentration measurement result according to a preferred embodiment of the present invention;  
         [0026]    [0026]FIG. 10 is a simplified schematic drawing illustrating an example of positional relationship between a support member and a second regulating member according to a preferred embodiment of the present invention;  
         [0027]    [0027]FIG. 11 is a drawing illustrating an example of a developer weight measurement result according to a preferred embodiment of the present invention;  
         [0028]    [0028]FIG. 12 is a simplified schematic drawing illustrating an example of positional relationship between a support member and a second regulating member according to a preferred embodiment of the present invention;  
         [0029]    [0029]FIG. 13 is a drawing illustrating an exemplary image concentration measurement result according to a preferred embodiment of the present invention;  
         [0030]    [0030]FIG. 14 is a drawing illustrating an exemplary image concentration measurement result according to a preferred embodiment of the present invention;  
         [0031]    [0031]FIG. 15 is a schematic drawing illustrating an exemplary developing unit  300  of an image forming apparatus using another preferred embodiment of a two-component development apparatus according to the present invention; and  
         [0032]    [0032]FIG. 16 is a schematic cross sectional view of a process cartridge configured to integrally combine a preferred embodiment of a two-component development apparatus with a photoconductor and the like according to the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0033]    In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner. Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, particularly to FIG. 1, an exemplary developing unit  200  of an image forming apparatus using a two-component development apparatus according to a preferred embodiment of the present invention is now described.  
         [0034]    As shown in FIG. 1, a development unit  13  arranged close to a photosensitive drum  1 , which is a latent image carrier, mainly includes a support case  14 , a developing sleeve  15  serving as a developer carrier, a developer containing member  16   a,  a first regulating member  17  serving as a developer regulating member, and a second regulating member  23 .  
         [0035]    The support case  14  having an opening near the photosensitive drum  1  includes a toner hopper  19 . The toner hopper  19  serves as a toner container for containing a toner  18  therein. The developer containing member  16   a  is formed integrally with the support case  14  near the photosensitive drum  1  to the opposite side of the toner hopper  19 . The developer containing member  16   a  forms a developer container  16  for containing a developer  22  including a carrier made of the toner  18  and magnetic particles. The support case  14 , positioned below the developer container  16 , includes a protrusion  14   a  having an opposing face  14   b.  The support case  14  also includes a toner supply opening  20  for supplying the toner  18  through a space between the bottom of the developer container  16  and the opposing face  14   b.    
         [0036]    Disposed inside the toner hopper  19  is a toner agitator  21  which serves as a toner supplying mechanism rotated by a driving mechanism (not shown). The toner agitator  21  rotates in a direction of an arrow (c) as shown to agitatedly convey the toner  18  contained in the toner hopper  19  toward the toner supply opening  20 .  
         [0037]    The photosensitive drum  1  rotates in a direction of an arrow (a) as shown using a driving mechanism (not shown). The developing sleeve  15 , disposed between the photosensitive drum  1  and the toner hopper  19 , is opposed to the photosensitive drum  1  with a development gap (i.e., a processing gap). The developing sleeve  15  rotates in a direction of an arrow (b) as shown using a driving mechanism (not shown). The developing sleeve  15  includes therein a magnet (not shown) which serves as a magnetic field generator. The magnet is fixed in a relative position of magnetic pole with respect to the development unit  13 .  
         [0038]    The first regulating member  17  is disposed on one end of the developer containing member  16   a  and over the top of the developing sleeve  15 . The first regulating member  17  is disposed between one end of the first regulating member  17  and an outer circumferential surface of the developing sleeve  15  with a fixed gap. On the other hand, the second regulating member  23  is arranged near the toner supply opening  20  of the developer container  16 . The second regulating member  23  has one end integrally disposed on the developer container  16   a  with the other end arranged with a fixed gap to the outer circumferential surface of the developing sleeve  15  (i.e., toward the center of the developing sleeve  15 ). That is, the second regulating member  23  is disposed in a direction against a flow of the developer  22  formed on a surface of the developing sleeve  15 .  
         [0039]    Disposed at an upstream side of the first regulating member  17  on the developer container  16   a  and at a downstream side of the second regulating member  23  is a cylindrical developer stirring member  30 . The developer stirring member  30  is driven to rotate in a similar direction of the developing sleeve  15  (i.e., in a direction of an arrow (d)) by a driving mechanism (not shown). The developer stirring member  30 , made of ferromagnet, is magnetized by the magnet in the developing sleeve  15  so that it can attract and convey a magnetic developer. The developer container  16  is configured to have sufficient spaces to circularly move the developer  22  within a range of magnetic force of the developing sleeve  15 .  
         [0040]    The opposing face  14   b  of the support case  14  is formed over a predetermined length so as to slope downward from the toner hopper  19  toward the developing sleeve  15 . When vibration, magnetic force variation of the magnet (not shown) disposed in the developing sleeve  15 , and a partial increase, in toner concentration in the developer  22  are generated to drop the carrier in the developer container  16  between the second regulating member  23  and a circumferential surface of the developing sleeve  15 , the dropped carrier is received by the opposing face  14   b  to move toward the developing sleeve  15 . Then, the carrier is attracted to the developing sleeve  15  with a magnetic force and is replenished to the developer container  16 . This structure prevents a decrease in an amount of carrier in the developer container  16 . This structure also prevents uneven image concentration of the developing sleeve  15  in the axial direction at a time of image formation. An inclination angle α of the opposing face  14   b  is preferably about at 5 degrees, for example. A length of the opposing face  14   b  is about 2 to 20 mm, for example, preferably about 3 to 10 mm.  
         [0041]    With the above-mentioned structure, the toner  18 , which is conveyed by the agitator  21  from the inside of the toner hopper  19 , is fed to the developer  22  carried by the developing sleeve  15  through the toner supply opening  20  and is conveyed to the developer container  16 . The developer  22  in the developer container  16  is separated with two flows. One is to pass through a gap (i.e., a doctor gap) between the developing sleeve  15  and the developer stirring member  30 . The other is to be attracted to the developer stirring member  30  and is conveyed on the developer stirring member  30  in a direction of an arrow (d). Since the latter is agitated before reaching the first regulating member  17 , the replenished toner is sufficiently dispersed. Then, the developer passes through a gap between the first regulating member  17  and the developing sleeve  15  and is conveyed to a position opposed to an outer circumferential surface of the photosensitive drum  1 . Only toner  18  is electrostatically connected to an electrostatic image on the photosensitive drum  1 , thereby forming a toner image on the photosensitive drum  1 .  
         [0042]    An end of the second regulating member  23 , there is provided a support member  40  on the second regulating member  23 . The support member  40  prevents an increase in developer amount of the developer container  16  at an end of the second regulating member  23  due to deviations and inclinations of a gap (i.e., a predoctor gap) in a longitudinal direction (i.e., in a vertical direction in the drawing) of the second regulating member  23 . The support member  40  also prevents the above-mentioned loss in image concentration and provides sufficient stability for an inclination of the machine. Although the support member  40  is provided on one end of the second regulating member  23  (i.e., on one end side of an increase in the developer) in the above-mentioned example, the support member  40  may be provided on both ends or provided on both ends and an intermediate section of the second regulating member  23 .  
         [0043]    When there is no support member  40  on the second regulating member  23  and a gap between the first regulating member  17  and the second first regulating member  23  is deviated right and left (i.e., in the axial direction), a developer flows from a region B in which the developer  22  flows smoothly in a direction of an end of the second regulating member  23  as show in FIG. 2A. This flow forms a region A in which the developer  22  is accumulated. The region A is a high developer concentration region where the flow of the developer  22  is compressed in a direction of an end of the second regulating member  23 . In the region A, the developer stirring member  30  conveys less toner to a downward direction. This is because the high developer concentration region A in the developer  22  impedes the general downward flow of the developer  22 . In addition, a high triboelectrification of developer particle significantly fractionizes developers, which disrupts the flow of the developer  22  in a downstream direction. Further, when the developer insufficiently flows from the second regulating member  23  in a downstream direction, the developer is increased before passing through the second regulating member  23  so that the developer has difficulty in passing through the second regulating member  23 . As mentioned previously, this decrease in toner feed provides insufficient toner and decreased toner concentration, causing a loss in image concentration. Similarly, when the developing unit is tilted side-to-side, the developer flows downward so that the region A exists at a place where the flow of the developer passing through the second regulating member  23  is accumulated. In this region, since the developer  22  has difficulty in flowing downward, the developer  22  is increased before it passes through the second regulating member  23 , where toner fading is generated due to insufficient toner supply.  
         [0044]    To avoid this problem, the support member  40  is disposed on the end of the second regulating member  23  so that the developer  22 , which passes through the second regulating member  23 , smoothly flows downward by eliminating the developer-accumulated region A. Further, an upper front surface of the support member  40  (i.e., a surface oppose to the developer stirring member  30 ) is formed as a curved surface (see FIG. 2B) in accordance with a shape of the developer stirring member  30  so as to maintain almost constant intervals between the developer stirring member  30  and the support member  40 . This structure enhances feeding property of the developer stirring member  30 . As a result, the second regulating member  23  also has a smoothing development flow like the region B at the end thereof, eliminating a loss in image concentration. Although the upper front surface of the support member  40  is preferably formed as a curved surface in the above-mentioned example, it may be shaped like a flat surface. With such structure, the support member  40  is also inclined downward.  
         [0045]    In the following examples are described several preferred embodiments to illustrate the invention. All examples are explained based on the following conditions.  
         [0046]    (1) Developing sleeve/photosensitive drum linear velocity ratio: 2.  
         [0047]    (2) Doctor gap: 0.32 mm.  
         [0048]    (3) Predoctor gap: 1.12 mm.  
         [0049]    (4) Development gap (Processing gap): 0.33 mm.  
         [0050]    (5) Toner concentration (TC) in equilibrium state based on the above-mentioned gap condition: 8±3 wt %.  
         [0051]    (6) Magnetic ground toner: average particle size 7.2 μm.  
         [0052]    (7) Carrier: average particle size 50 μm.  
         [0053]    In one example, the support member  40  is disposed on a right end of the second regulating member  23  in a sheet moving direction to print 1,000 images on A4 size sheets and then to measure a black image concentration at a right end and a middle portion. As a comparative example, similar printing is performed without disposing the support member  40  to measure image concentration. The center position of measurement is set at the center of an image forming area and the end is measured about 10 mm inside from the image forming area. Measurement results are shown in FIG. 3A. The support member  40  is formed as shown in FIG. 3B. The material of the support member  40  is acrylonatrile butadiene styrene (ABS). FIG. 4A shows the support member  40  disposed on the second regulating member  23 . FIG. 4A is a perspective view of a second regulating member  23  seen from the right end in a sheet moving direction. In FIG. 4A, the developing sleeve  15  is located at the right of the second regulating member  23 . Alternatively, the support member  40  may be provided on both ends (see FIG. 4B) or provided on both ends and an intermediate section of the second regulating member  23  (see FIG. 4C).  
         [0054]    Subsequently, prior to passing through the second regulating member  23 , a developer weight is compared with and without the support member  40 . The developer  22  is placed into the development unit  13 , where the development unit  13  is driven to rotate the photosensitive drum  1  at a linear velocity of 120 mm/minute over 3 minutes before developer weight measurements. The measurement results are shown in FIG. 5. When the developer weight is measured, the developer  22  is sampled from the toner supply opening  20  with a bar magnet before the developer  22  passes through the second regulating member  23 . The developer sample is taken up to 25 mm from a right end of the support member  40  in a sheet moving direction. FIG. 5 shows the developer is decreased about 40 percent before it passes through the second regulating member  23  when the support member  40  is disposed on the second regulating member  23 .  
         [0055]    In another example, the support member  40  is disposed on a right end of the second regulating member  23  in a sheet moving direction and a gap A between the developer stirring member  30  and the support member  40  is changed to measure the developer weight before it passes through the right end of the second regulating member  23 . The support member  40 , formed as shown in FIG. 3B, is different in thickness H. The material of the support member  40  is ABS. FIG. 6 shows a positional relationship between the developer stirring member  30  and the support member  40 . The developer  22  is placed in the developer container  16 ,  16  where the developer container  16  is driven to rotate the photosensitive drum  1  at a linear velocity of  120  mm/minute over 3 minutes before developer weight measurements prior to the developer passing through the second regulating member  23 . The developer sample is taken up to 25 mm from a right end of the support member  40  in a sheet moving direction. FIG. 7 shows a measurement result of the developer weight to a ratio (i.e., A/H) between the gap A and the thickness H of the support member. As can be seen from FIG. 7, a minimum value exists when A/H is 0.6. Moreover, when the support member  40  has the thickness H significantly smaller than the gap A, the A/H has a significantly larger value. However, when H is equal to 0, the developer weighs 0.7 g. As a result, when the developer weighs less than 0.7 g, the support member  40  provides an effective control. The resulting A/H is at least 0.3.  
         [0056]    In still another example, the length B of the support member  40  in a longitudinal direction is varied to print 1,000 images on A4 size sheets and then to measure black image concentration. The support member  40  is formed as shown in FIG. 8. The measurement result is shown in FIG. 9. As can be seen from FIG. 9, the support member  40  having a length of at least 20 mm provides an effective control in comparison with no support member  40  disposed on the second regulating member  23 . More preferably, the support member  40  has a length of at least 25 mm.  
         [0057]    In yet another example, the support member  40  is disposed on a right end of the second regulating member  23  in a sheet moving direction and a gap C between the support member  40  and the second regulating member  23  is changed in the vertical direction to measure the developer before it passes through the second regulating member  23 . FIG. 10 shows a positional relationship between and the support member  40  and the second regulating member  23 . The developer  22  is placed in the development unit  13 , where the development unit  13  is driven to rotate photosensitive drum  1  at a linear velocity of 120 mm/minute over 3 minutes before developer weight measurements. The developer sample is taken up to 25 mm from a right end of the support member  40  in a sheet moving direction. The measurement result is shown in FIG. 11. When the gap C is at least 1.0 mm, the developer weight is saturated before the developer passes through the second regulating member  23 . When the support member  40  is not disposed on the second regulating member  23 , the developer weighs 1.2 g (not shown in FIG. 11), which is substantially similar to saturation as shown in FIG. 11. Thus, the support member  40  having the gap C of no more than about 1.0 mm provides an effective control. More preferably, the gap C is no more than 0.5 mm in length.  
         [0058]    In another example, the support member  40  is disposed on a right end of the second regulating member  23  in a sheet moving direction and a gap D between the support member  40  and an end of the second regulating member  23  is changed to print 1,000 images on A4 size sheets. Subsequently, black image concentration is measured no more than 10 mm inside from an end of an image forming area. FIG. 12 shows a positional relationship between and the support member  40  and the end of the second regulating member  23 . The measurement results are shown in FIG. 13. As can be seen from FIG. 13, the gap D increases as the image concentration decreases. When the gap D is no more than 1.0 mm, the support member  40  provides an effective control.  
         [0059]    In still another example, as shown in FIG. 6, when a distance A between the developer stirring member  30  and the support member  40  and a ratio of a gap G (i.e., A/G) between the developing sleeve  15  and the developer stirring member  30  are changed, the developer weight is measured before the developer passes through the right end of the second regulating member  23 . The result of, the development weight measurement is shown in FIG. 14. The support member  40 , formed as shown in FIG. 3B, is different in thickness H. The material of the support member  40  is ABS. In addition, the gaps A and G are in millimeter (mm).  
         [0060]    As shown in FIG. 14, changing the gap G between the developing sleeve  15  and the developer stirring member  30  changes A/G curved line. When the support member  40  is not disposed on the second regulating member  23 , the developer weighs 0.7 g as mentioned previously so that the developer no more than 0.7 g is effective. In the A/G curved line which is no more than 0.7 g in the developer weight, a plurality of A/G curved lines are substantially collinear when the gap G is changed in the upper portion. The value is at least A/G=9. In the lower portion, increasing the gap G shifts the A/G curved line to a smaller side. The A/G curved line lies on straight line approximation A/G=6-10G. That is, (6-10×G)≦A/G≦9 is the preferred range.  
         [0061]    Referring to the FIG. 15, another developing unit  300  of an image forming apparatus using a two-component development apparatus according to a preferred embodiment of the present invention is now described. In this embodiment, a surface of a support member  40   a  opposed to the developing sleeve  15  is formed as a curved surface in accordance with a shape of the developing sleeve  15 . Other structure is similar to the above-mentioned embodiment.  
         [0062]    In the present embodiment, a flow of the developer  22  passing through the developing sleeve  15  and the developer stirring member  30  and the developer  22  conveyed by the developer stirring member  30  can be separated. This structure provides sufficient toner supply without affecting the flow of the developer  22  passing through the second regulating member  23 .  
         [0063]    The surface of the support member  40   a  opposed to the developing sleeve  15  can not only be formed as a curved surface as in the present embodiment, but an upper front surface of the support member  40  can also be formed as a curved surface as in the above-mentioned embodiment. Since each embodiment has its own benefit, both structures of embodiments may be preferably combined.  
         [0064]    [0064]FIG. 16 is a schematic cross sectional view of a process cartridge  100  configured to integrally combine a preferred embodiment of a two-component development apparatus with a photoconductor and the like according to the above-mentioned invention. The process cartridge according to the present embodiment is. removably attached to an image forming apparatus such as a copier and a printer. In FIG. 16, a charging mechanism  105 , a developing mechanism  106 , a photosensitive drum  107 , and a cleaning mechanism  108  are unitized as a single package.  
         [0065]    The image forming apparatus using the process cartridge  100  according to the present invention is driven to rotate the photosensitive drum  107  at a predetermined peripheral velocity, where the charging mechanism  105  uniformly charges a circumferential surface of the photosensitive drum  107  at a negative or positive predetermined potential. Image exposure mechanisms (not shown) such as a slit exposure and a laser beam scanning exposure irradiate an image exposing light to sequentially form an electrastatic latent image on the circumferential surface of the photosensitive drum  107 . The resultant electrostatic latent image is developed with toner using the developing mechanism  106  to supply a recording material such as a sheet in synchronism with a rotating of the photoconductor between the photosensitive drum  107  and a transfer unit (not shown) from a sheet supply station (not shown). The transfer unit sequentially transfers a toner image on the recording material. The recording material carrying the transfer image thereon is separated from the circumferential surface of the photosensitive drum  107 . Subsequently, the recording material is introduced to an image fixing unit (not shown) to fix an image with heat pressing and the like. Then, the recording material is printed out as a copy. After image transformation, the cleaning mechanism  108  removes and cleans a residual toner on the surface of the photosensitive drum  107 . Further, a discharge unit (not shown) discharges the photosensitive drum  107  for repeat use in image forming.  
         [0066]    Numerous additional modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure of this patent specification may be practiced otherwise than as specifically described herein.