JP2005338319A - Drum unit and image forming apparatus with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain speed changes of a photoreceptor caused by drive system vibrations or load changes, thereby avoiding degradation in image quality resulting from them. <P>SOLUTION: The drum unit of an image forming apparatus integrally stores at least a photoreceptor drum 10 in a casing 30 and is attachable/detachable to/from the main body of the apparatus. In the drum unit, a ringlike friction static member 50 of a system in which firm contact force is variable is disposed on the internal face of the casing 30 located opposite the side face of the photoreceptor drum 10. The surface of the friction static member 50 is brought into firm contact with the side of the photoreceptor drum 10 so that the side of the photoreceptor drum 10 slides against the surface of the friction static member 50 by the drive of the photoreceptor drum 10. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photosensitive drum of an image forming apparatus that forms an image digitally by an electrophotographic method, and an image forming apparatus including the photosensitive drum.

  In electrophotographic copying machines and printers, a cylindrical photosensitive drum is rotated to form an electrostatic latent image on its running surface, and toner is attached by development to form a toner image, which is transferred. An image is obtained by transferring and fixing on a material.

  In such an image forming apparatus, jitter and image unevenness occur in the output image when a speed fluctuation occurs in the rotating photosensitive drum due to some influence. This is particularly noticeable in digital electrophotographic technology in which writing on the surface of the photosensitive drum is performed by scanning with a semiconductor laser, and fluctuations in the rotational speed of the photosensitive drum are caused by speed fluctuations in the sub-scanning direction of the writing system. As a result, a slight shift occurs in the interval between the write lines, which causes a significant deterioration in image quality.

  Various factors can be cited as factors that deteriorate the driving accuracy of the photosensitive drum. As for the photosensitive member drive system that is responsible for driving the photosensitive member itself, there are main motor drive unevenness, motor shaft flutter, characteristic frequency components inherent in motor-specific structural problems, and the like. With respect to the gear train constituting the drive system, there is a gear one-tooth or one-turn fluctuation due to gear accuracy, in particular, tooth profile accuracy, tooth trace accuracy, and gear flutter accuracy (such as eccentricity). Even when the drive system is composed of motors, gears, etc., the positional relationship between the motor shaft and gear shaft, especially the distance between the shafts, directly affects the backlash amount of the gear. It is a factor that generates vibration at the meshing part.

  Further, the driving accuracy of the photosensitive drum is affected not only by the driving system of the photosensitive drum but also when the peripheral units are operated. That is, since the developing unit, the cleaning unit, the transfer unit and the transport unit, or the transfer / transport unit in which these units are integrated also include the movable portion, vibration is always generated. These vibrations are transmitted to the photosensitive drum through the drum unit or the photosensitive drum frame, and the main body skeleton, and give a fluctuation in the frequency of each vibration to the photosensitive drum or the driving system of the photosensitive drum. Deteriorating the driving accuracy of the photosensitive drum.

  Therefore, in order to prevent such a decrease in image quality, Patent Document 1 discloses, as shown in FIG. 9, a photosensitive drum 10, a casing 30 that houses the photosensitive drum 10, and a drive to the photosensitive drum 10. A ring-shaped member having a drive unit (not shown) for transmitting force and formed on the side surface of the photosensitive drum 10 from a viscoelastic layer 142 and a surface layer 141 protecting the viscoelastic layer 142. It is disclosed that the sliding member 140 is rubbed against the inner surface of the casing 30 facing the sliding member 140 by driving the photosensitive drum 10.

According to this, a load due to friction of the sliding member 140 is generated with respect to the rotation of the photosensitive drum 10 to increase the torque value, and as a result, the sensitivity to the speed variation of the rotation of the photosensitive drum 10 becomes dull. Is eliminated, and the image is rotated at a stable speed, and a high-quality image is obtained.
JP 2002-357987 (summary, FIG. 9)

  As described above, when the torque value of the photosensitive drum is increased, the image quality is improved. However, if the torque value is increased too much, a large load is applied to the drive unit, and in some cases, the gear may be damaged. Further, in the above-described conventional configuration, a low torque (for example, 1 kgf · cm or less) is not so much a problem. However, if the viscoelastic layer 142 is increased in hardness or thickness in order to produce a high torque (for example, 2 kgf · cm or more). There is a problem that the compression ratio changes due to the individual difference between the length of the photosensitive drum 10 and the width of the casing 30 and the torque value varies and is not stable.

  The present invention has been made in view of the above-described conventional problems, and includes a drum unit capable of efficiently reducing fluctuations in the speed of the photosensitive drum and thereby driving the photosensitive drum at a stable rotational speed at all times. The purpose is to provide an image forming apparatus.

  In order to achieve the above object, a drum unit of the present invention is a drum unit of an image forming apparatus in which at least a photosensitive drum is housed and integrated in a casing and configured to be detachable from the apparatus main body. A ring-shaped frictional stationary member with a variable pressure contact force is provided on the inner surface of the casing facing the side surface, and the surface is pressed against the side surface of the photosensitive drum, and the side surface of the photosensitive drum and the side surface of the photosensitive drum are driven by driving the photosensitive drum. The friction stationary member is rubbed against the surface.

  Specifically, the friction stationary member includes a substrate and a viscoelastic layer fixed to the substrate. The friction stationary member includes a surface layer fixed on the viscoelastic layer.

  Further, the substrate is provided so as to be rotatable with respect to the inner surface of the casing, and between the surface of the substrate facing the inner surface of the casing and the inner surface of the casing, depending on a relative position in the rotation direction of the substrate with respect to the inner surface of the casing. An uneven fitting mechanism having different fitting depths is provided.

  Further, a pressing means capable of adjusting a force for pressing the substrate is provided on the surface side of the substrate facing the inner surface of the casing.

  Further, the substrate is formed in a shape having a cylindrical portion, and a screw is cut around the cylindrical portion to process it into a bolt shape, and the substrate is screwed to the inner surface of the casing.

  According to another aspect of the present invention, there is provided an image forming apparatus including the drum unit and a driving unit that rotationally drives the photosensitive drum.

  According to the present invention, it is possible to adjust the force that presses the frictional stationary member provided on the inner surface of the casing of the drum unit toward the side surface of the photosensitive drum, and the photosensitive drum due to the individual difference between the length of the photosensitive drum and the casing width of the drum unit. Variations in torque values during the driving of the body drum can be eliminated, and the photosensitive drum is always driven and rotated at a constant peripheral speed even when subjected to vibration inherent in the drive system and fluctuations in the load during image formation. As a result, it is possible to provide a drum unit and an image forming apparatus capable of recording a high-quality image with markedly improved image density unevenness and color unevenness that occur particularly in the sub-scanning direction of the writing system.

  A first embodiment of the present invention will be described with reference to the drawings. First, the configuration and operation of the image forming apparatus of the present invention will be described with reference to FIGS.

  In FIG. 1, reference numeral 10 denotes a photosensitive drum as an image bearing member, which is an OPC photosensitive member coated on a drum, which is grounded and rotated clockwise. In FIG. 1, reference numeral 12 denotes a scorotron charger, which gives a uniform charge of VH to the circumferential surface of the photosensitive drum 10 by a corona discharge using a grid held by VG and a corona discharge wire. Prior to the charging by the scorotron charger 12, in order to eliminate the history of the photoconductor up to the previous print, exposure by the PCL 11 using a light emitting diode or the like is performed to neutralize the peripheral surface of the photoconductor.

  As shown in FIG. 2, the photosensitive drum 10 is attached to and detached from the apparatus main body as a drum unit that is housed in a casing 30 together with the charger 12, the transfer roller 18, and the cleaning device 22. The photosensitive drum 10 has an integral rotating shaft 102 supported on both side walls of the casing 30 by bearings 31. When the drum unit is mounted, the photosensitive drum 10 is connected to a helical gear G using a motor m shown in FIG. And is rotated at a predetermined speed in the clockwise direction while receiving thrust.

  After the photoreceptor is uniformly charged, the image exposure unit 13 performs image exposure based on the image signal. The image exposure means 13 is scanned by a polygon mirror 131 rotating with a laser diode (not shown) as an emission light source, an fθ lens, etc., and the optical path is bent by a reflection mirror 132, and the photosensitive drum 10 is rotated (sub-scanning). A latent image is formed. In this embodiment, the character portion is exposed to form an inverted latent image in which the character portion has a lower potential VL.

  At the periphery of the photosensitive drum 10, there are provided developing devices 14 each containing a developer composed of toner such as yellow (Y), magenta (M), cyan (C), and black (K) and a carrier. The development of the first color is performed by a developing sleeve 141 that contains a magnet and rotates while holding the developer. Subsequently, an image forming process similar to that for the first color is performed for the second color, the third color, and the fourth color, and a four-color visible image is formed on the circumferential surface of the photosensitive drum 10. At this time, the neutralization by the PCL 11 performed in the first color image forming process is not performed because the toner adhering to the image portion of the first color scatters due to a rapid decrease in the surrounding potential.

  On the other hand, the recording paper P carried out from a paper feed cassette (not shown) is temporarily stopped and fed to the transfer area by the rotation operation of the paper feed roller 17 when the transfer timing is ready.

  In the transfer area, the transfer roller 18 is pressed against the peripheral surface of the photosensitive drum 10 in synchronism with the transfer timing, and the fed recording paper P is sandwiched to transfer the multicolor images all at once.

  Next, the recording paper P is neutralized by the separation brush 19 brought into a pressure contact state almost simultaneously, separated by the peripheral surface of the photosensitive drum 10 and conveyed to the fixing device 20, and the toner is heated and pressed by the heat roller 201 and the pressure roller 202. Are then discharged to the outside of the apparatus via the paper discharge roller 21. The transfer roller 18 and the separation brush 19 are retracted away from the peripheral surface of the photosensitive drum 10 after the recording paper P has passed to prepare for the next toner image formation.

  On the other hand, the photosensitive drum 10 from which the recording paper P has been separated removes and cleans residual toner by the pressure contact of the blade 221 of the cleaning device 22, and again undergoes charge removal by the PCL 11 and charging by the charger 12 for the next image forming process. enter. The blade 221 moves immediately after cleaning the photoreceptor surface and retracts from the circumferential surface of the photoreceptor drum 10.

  In the present invention, the speed fluctuation of the photosensitive drum 10 is suppressed as follows. FIG. 3 is a cross-sectional view of the support structure for the side surface on the non-driving side of the photosensitive drum 10 according to the first embodiment viewed from the direction A in FIG. The outer surface of the flange 101 that supports the side end of the photosensitive drum 10 is a flat surface, and a ring-shaped pressure contact force variable type is provided on the side surface (inner surface) of the casing 30 that faces the side surface of the flange 101. The friction stationary member 50 is fixed to be rotatable. The friction stationary member 50 is a member in which a viscoelastic layer 52 having a predetermined thickness is fixed on a substrate 51 and a surface layer 53 in contact with the flange 101 is further fixed on the viscoelastic layer 52.

  FIG. 4A is a plan view of the main part of the inner surface of the casing of the drum unit, and FIG. 4B is a plan view of the surface of the substrate facing the inner surface of the casing of the drum unit. FIG. 5 is a supplementary explanatory diagram of FIG. Hereinafter, the configuration of the inner surface of the casing 30 and the surface of the substrate 51 facing the inner surface of the casing 30 will be described in detail based on these drawings.

  As shown in FIG. 4A and FIG. 5A, hemispherical depressions (dimples) are provided on the opposing surface (inner surface) of the casing 30. That is, on the inner surface of the casing 30, the position where the first dimple row 33 is shifted by 120 ° in the radial direction about the through hole 32 for passing the shaft 102 of the photosensitive drum 10 (in FIG. 5A). Are provided at three positions at 4 o'clock, 8 o'clock and 12 o'clock), and are shifted by 30 ° in the counterclockwise direction with respect to the respective first dimple rows 33 (in FIG. 3 o'clock, 7 o'clock, and 11 o'clock positions), the second dimple rows 34 are provided at three positions, and the center angle is shifted by 30 ° counterclockwise with respect to each of the second dimple rows 34 (FIG. 5A ), Three third dimples (rows) 35 are provided at 2 o'clock, 6 o'clock, and 10 o'clock positions.

  The first dimple row 33 includes three dimples having different sizes (small dimple 33c, medium dimple 33b, and large dimple 33a) arranged in a row in the order of “small”, “medium”, and “large”. The dimple row 34 includes two dimples having different sizes (medium dimple 34b and large dimple 34a) arranged in a row in the order of “medium” and “large”, and the third dimple row 35 has a size of “large”. One dimple (large dimple 35a) is provided. The large dimples 33a of the first dimple row 33, the large dimples 34a of the second dimple row 34, and the large dimples 35a of the third dimple row 35 are all arranged on the same circle with a large diameter, and the middle dimple 33b of the first dimple row 33 and The middle dimples 34b of the second dimple row 34 are all arranged on the same circle with a medium diameter, and all the small dimples 33c of the first dimple row 33 are arranged on the same circle with a small diameter.

  Further, on the inner surface of the casing 30, each of the dimple rows 33, 34, 35 is arranged in a pair of dimple rows adjacent in the order of the first dimple row 33, the second dimple row 34, and the third dimple row 35 in the counterclockwise direction. On the extended line in the radial direction, square holes 36, 37, and 38 are provided on concentric circles, respectively. Any one of these square holes 36, 37, 38 is engaged with a square protrusion 57 of a locking claw 56 provided on a substrate 51 described later.

  Further, as shown in FIGS. 4B and 5B, a hemispherical protrusion is provided on the surface of the substrate 51 facing the inner surface of the casing 30. That is, on the inner surface of the substrate 51, a position where the projection row 54 is shifted by 120 ° in the radial direction around the through hole 32 for passing the shaft 102 of the photosensitive drum 10 (in FIG. (4 o'clock, 8 o'clock and 12 o'clock positions).

  The projection row 54 includes three hemispherical projections (small projection 54c, middle projection 54b, and large projection 54a) of different sizes arranged in a row in the order of “small”, “medium”, and “large”. . All the large projections 54a of the projection row 54 are arranged on the same circle with the large diameter, all the middle projections 54b of the projection row 54 are arranged on the same circle with the medium diameter, and all the small projections 54c of the projection row 54 are on the same circle with the small diameter. Has been placed. The size and arrangement of the protrusions 54a, 54b, and 54c of the protrusion 54 correspond to the first dimple row 33 (see FIGS. 5A and 5B).

  On the surface side of the peripheral surface of the substrate 51 facing the inner surface of the casing 30, a locking claw 56 is provided on the radial extension line of one protrusion row 54. The locking claw 56 is provided with an angular projection 57 protruding toward the inner surface side of the casing 30.

  For example, as shown in FIG. 3, the square projection 57 is engaged with the square hole 36, but the upper tab of the locking claw 56 is pinched with a finger, and the side surface of the flange 101 as indicated by an arrow X is shown. When a force is applied so as to be tilted to the side, the above engagement is released, so that this locking claw 56 is further rotated clockwise (flange as viewed from the inner surface side of the casing 30 as indicated by arrow Y in FIG. 4B). When viewed from the 101 side, by rotating counterclockwise (see the same arrow Y in FIG. 6A), the entire friction stationary member 50 is rotated together with the substrate 51, so that the angular protrusions 57 are connected to other square holes (corners). Any one of the holes 37 and 38).

  6A and 6B are plan views (a), (c), and (e) showing the rotation angle of the substrate and the relative positional relationship between the dimple row and the projection row, and cross-sectional views (b) and (b) corresponding thereto. d) and (f). The position of the locking claw 56 in the circumferential direction defines the relative position of the projection row 54 and the first to third dimple rows 33 to 35. That is, as shown in FIG. 6A, when the position of the locking claw 56 is at a position where the square protrusion 57 and the square hole 36 are engaged (position at 12 o'clock), The relative position with the first dimple row 33 matches. Further, as shown in FIG. 6C, when the position of the locking claw 56 is at a position where the square protrusion 57 and the square hole 37 are engaged (position at 11 o'clock), The relative position with the second dimple row 34 matches. Alternatively, as shown in FIG. 6 (e), when the position of the locking claw 56 is at a position where the square protrusion 57 and the square hole 38 are engaged (position at 10 o'clock), The relative position with the third dimple row 35 matches. As a result, the pressure contact force of the frictional stationary member 50 can be adjusted as will be described later.

  In this configuration, the surface layer 53 of the friction stationary member 50 on the casing 30 side facing the surface of the flange 101 of the photosensitive drum 10 is pressed by the thrust in the direction of the arrow accompanying the driving of the helical gear G described above. Since the friction stationary member 50 is prevented from rotating in the circumferential direction by the engagement between the angular protrusion 57 and the square hole 36, 37 or 38, the friction stationary member 50 is slid along with the rotation of the photosensitive drum 10. .

  The surface layer 53 protects the viscoelastic layer 52 and secures slipperiness of the surface. When the surface of the flange 101 is rubbed, the braking performance of the member itself and smooth driving of the photosensitive drum 10 are achieved. For this reason, a material having an appropriate hardness and friction coefficient is used.

  The viscoelastic layer 52 absorbs speed fluctuation generated when the photosensitive drum 10 is driven by viscoelasticity and reduces the absolute value of the speed fluctuation. A polymer member having both viscosity and elasticity is used. The When the thickness of the viscoelastic layer 52 is increased, the force for pressing the flange 101 of the photosensitive drum 10 is increased, and a large torque is required to drive the photosensitive drum 10, and a load is applied to the motor m. When the thickness of 52 is small and the pressing force is small, the reduction of the speed fluctuation described above is small and an effect cannot be expected. For this reason, the thickness of the viscoelastic layer 52 is determined after taking these into consideration.

  Specifically, the surface layer 53 includes a wear-resistant resin sheet having a small friction coefficient, such as Teflon (registered trademark) felt, PET film, and the like, and is fixed to the viscoelastic layer 52 via an adhesive. Is done. In particular, Teflon (registered trademark) felt is excellent in adhesive strength to the viscoelastic layer 52.

  Moreover, as said viscoelastic layer 52, foamed resin materials, such as urethane and a silicone, are mentioned, It fixes on the board | substrate 51 through a double-sided tape or an adhesive agent.

  While the photosensitive drum 10 is being rotationally driven, the relative position in the axial direction of the surface of the flange 101 with respect to the casing 30 is defined at a predetermined position within a range where the elastic force of the viscoelastic layer 52 can be obtained by compression. For this reason, the distance (L1 in FIG. 3) between the side surface of the flange 101 and the inner surface of the casing 30 is constant. On the other hand, the distance (L2 in FIG. 3) between the side surface of the flange 101 and the surface of the substrate 51 on the casing 30 side corresponding to the thickness of the entire frictional stationary member 50 is the projection row 54 and the first to third dimple rows. It changes according to the relative positional relationship with 33-35.

  Here, when the relative positions of the projection row 54 and the n-th dimple row (n = 1 to 3) coincide with each other, the latter distance is set to L2 (n), and the friction stationary member 50 at that time is placed on the side surface of the flange 101. The force for pressing (pressing) is defined as F (n). The fact that the distance L2 becomes small means that the compressibility of the viscoelastic layer 52 becomes high and the elastic force becomes large. Therefore, it can be said that the pressure contact force F and the distance L2 are in an inversely proportional relationship.

  Under such a premise, as shown in FIG. 6A, when the projection row 54 and the first dimple row 33 coincide, the large projection 54a, the middle projection 54b, and the small projection 54c of the projection row 54 are obtained. Are fitted to the large dimple 33a, the middle dimple 33b, and the small dimple 33c of the corresponding first dimple row 33, and the surface of the substrate 51 and the inner surface of the casing 30 are brought into close contact with each other, so that L2 (1) = L1 (see FIG. 6B). In addition, as shown in FIG. 6C, when the projection row 54 and the second dimple row 34 coincide with each other, the large projection 54a and the middle projection 54b of the projection row 54 are respectively large in the corresponding second dimple row 34. Although the dimple 34a and the middle dimple 34b are fitted, the small protrusion 54c comes into contact with the inner surface of the casing 30. As a result, L2 (2) <L2 (1), F (2)> F (1) ( (Refer FIG.6 (d)). Further, as shown in FIG. 6E, when the projection row 54 and the third dimple row 35 coincide with each other, the large projection 54a of the projection row 54 is fitted with the corresponding large dimple 35a of the third dimple row 35. However, the intermediate protrusion 54b comes into contact with the inner surface of the casing 30. As a result, L2 (3) <L2 (2), F (3)> F (2) (see FIG. 6F). To summarize the above results, L1 = L2 (1)> L2 (2)> L2 (3) and F (1) <F (2) <F (3).

  As described above, the friction stationary member 50 provided on the inner surface of the casing 30 can be obtained simply by rotating the friction stationary member 50 in the circumferential direction and engaging the angular projection 57 with any one of the square holes 36, 37, and 38. The pressing force on the side surface of the photosensitive drum 10 can be adjusted by switching in three stages, and the torque value at the time of driving the photosensitive drum 10 due to the individual difference between the length of the photosensitive drum 10 and the width of the casing 30 can be adjusted. Variations can be eliminated.

  By using the frictional contact member 50 of the pressure contact variable type, the photosensitive drum 10 can be rotated at a stable speed with the speed fluctuation eliminated. Therefore, the photosensitive drum 10 is always driven and rotated at a constant peripheral speed even if it receives vibrations inherent in the driving system and fluctuations in load during image formation, and as a result, an image generated particularly in the sub-scanning direction of the writing system. Density unevenness and color unevenness are remarkably improved, and a high-quality image can be recorded.

  The number and arrangement of the dimple rows and protrusion rows and the number and size of the dimple rows and protrusions are merely examples, and by appropriately changing these, the number of stages at which the pressure contact force can be adjusted is increased or decreased. It goes without saying that it can be done.

  Next, a second embodiment of the present invention will be described. FIG. 7 is a cross-sectional view of the support structure of the side surface on the non-driving side of the photosensitive drum 10 according to the second embodiment as viewed from the direction A in FIG. In this embodiment, parts common to those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. A plurality of key holes 58 are provided on the surface of the substrate 51 opposite to the inner surface of the casing 30 so as to engage the tips of the bolts 39 that are processed into a key shape. A plurality of bolt holes 40 penetrating the side wall are provided. With this configuration, when the bolts 39 are screwed into the respective bolt holes 40 from the outside of the side walls of the casing 30 and the tips of the bolts 39 are engaged with the respective key holes 58 of the substrate 51, the friction stationary member 50 is moved to the inner surface side of the casing 30. Fixed to. In this way, the pressure contact force of the frictional movement member 50 can be adjusted steplessly by tightening or loosening all the bolts 39 at the same rate.

  Next, a third embodiment of the present invention will be described. FIG. 8 is a cross-sectional view of the support structure of the side surface on the non-driving side of the photosensitive drum 10 according to the third embodiment as viewed from the direction A in FIG. In this embodiment, parts common to those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. The substrate 51 is formed in a shape having a cylindrical bearing portion 51a so that it can also be used as a bearing, and a screw is cut around the bearing portion 51a to process it into a bolt shape. And the bearing hole 41 which penetrated the screw | thread for fitting the bearing part 51a to the side wall of the casing 30 is provided. With this configuration, when the bearing portion 51 a of the substrate 51 is screwed into the bearing hole 41 from the inside of the side wall of the casing 30, the friction stationary member 50 is fixed to the inner surface side of the casing 30. In this way, the pressure contact force of the friction stationary member 50 can be adjusted steplessly by tightening or loosening the bearing portion 51a.

  In this embodiment, the image forming apparatus using the photosensitive drum has been described. However, the present invention is an image forming apparatus using a belt-shaped photosensitive member that is circulated and conveyed between a pair of rotating rollers. In this case, the friction stationary member 50 is provided at the side end of a sliding roller, for example, a rotating roller.

  The present invention relates to the driving of a photosensitive drum of an image forming apparatus that forms an image by a digital method using an electrophotographic method, and in particular, superimposes a single color toner image developed by arranging a plurality of developing devices around the photosensitive drum. By combining them, the image forming apparatus can form a color toner image.

1 is a cross-sectional configuration diagram of an image forming apparatus of the present invention. FIG. 5 is a perspective view showing drive formation of a photosensitive drum. These are principal part sectional drawings of the drum unit which shows the example of installation of a friction stationary member (1st Embodiment). These are the top view (a) of the principal part of the casing inner surface of a drum unit, and the top view (b) of the surface of a board | substrate facing the casing inner surface of a drum unit. FIG. 5 is a supplementary explanatory diagram of FIG. 4. (A), (c), (e) and sectional views (b), (d) corresponding thereto showing the rotation angle of the substrate and the relative positional relationship between the dimple row and the projection row. (F). These are principal part sectional drawings of the drum unit which shows the example of installation of a friction stationary member (2nd Embodiment). These are principal part sectional drawings of the drum unit which shows the example of installation of a friction stationary member (3rd Embodiment). These are the principal part sectional drawings of the conventional drum unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photosensitive drum 30 Casing 50 Friction stationary member 51 Substrate 52 Viscoelastic layer 53 Surface layer 101 Flange

Claims (7)

  In a drum unit of an image forming apparatus in which at least a photosensitive drum is housed and integrated in a casing and configured to be detachable from the apparatus main body, a variable pressure contact force type is applied to the casing inner surface facing the side surface of the photosensitive drum. A ring-shaped frictional stationary member is provided so that the surface thereof is pressed against the side surface of the photosensitive drum, and the side surface of the photosensitive drum and the surface of the frictional stationary member are slid by driving the photosensitive drum. Drum unit featured.   The drum unit according to claim 1, wherein the frictional stationary member includes a substrate and a viscoelastic layer fixed to the substrate.   The drum unit according to claim 2, wherein the friction stationary member includes a surface layer fixed on the viscoelastic layer.   The substrate is provided so as to be rotatable with respect to the inner surface of the casing, and is fitted between the surface of the substrate facing the inner surface of the casing and the inner surface of the casing by a relative position in the rotation direction of the substrate with respect to the inner surface of the casing. The drum unit according to any one of claims 1 to 3, wherein an uneven fitting mechanism having different depths is provided.   The drum unit according to any one of claims 1 to 3, wherein a pressing means capable of adjusting a force for pressing the substrate is provided on a surface side of the substrate facing the inner surface of the casing.   2. The substrate according to claim 1, wherein the substrate is formed into a shape having a cylindrical portion, and a screw is cut around the cylindrical portion to process it into a bolt shape, and the substrate is screwed to the inner surface of the casing. The drum unit in any one of -3.   An image forming apparatus comprising: the drum unit according to claim 1; and a driving unit that rotationally drives the photosensitive drum.

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